Add ALTS code to grpc/core
diff --git a/BUILD b/BUILD
index 4fe3dc6..9c99f95 100644
--- a/BUILD
+++ b/BUILD
@@ -1326,6 +1326,8 @@
         "src/core/lib/security/credentials/oauth2/oauth2_credentials.cc",
         "src/core/lib/security/credentials/plugin/plugin_credentials.cc",
         "src/core/lib/security/credentials/ssl/ssl_credentials.cc",
+        "src/core/lib/security/credentials/alts/alts_credentials.cc",
+        "src/core/lib/security/security_connector/alts_security_connector.cc",
         "src/core/lib/security/security_connector/security_connector.cc",
         "src/core/lib/security/transport/client_auth_filter.cc",
         "src/core/lib/security/transport/secure_endpoint.cc",
@@ -1349,6 +1351,8 @@
         "src/core/lib/security/credentials/oauth2/oauth2_credentials.h",
         "src/core/lib/security/credentials/plugin/plugin_credentials.h",
         "src/core/lib/security/credentials/ssl/ssl_credentials.h",
+        "src/core/lib/security/credentials/alts/alts_credentials.h",
+        "src/core/lib/security/security_connector/alts_security_connector.h",
         "src/core/lib/security/security_connector/security_connector.h",
         "src/core/lib/security/transport/auth_filters.h",
         "src/core/lib/security/transport/secure_endpoint.h",
@@ -1360,6 +1364,7 @@
     language = "c++",
     public_hdrs = GRPC_SECURE_PUBLIC_HDRS,
     deps = [
+        "alts_util",
         "grpc_base",
         "grpc_transport_chttp2_alpn",
         "tsi",
@@ -1583,15 +1588,118 @@
 )
 
 grpc_cc_library(
+    name = "alts_frame_protector",
+    srcs = [
+        "src/core/tsi/alts/crypt/aes_gcm.cc",
+        "src/core/tsi/alts/crypt/gsec.cc",
+        "src/core/tsi/alts/frame_protector/alts_counter.cc",
+        "src/core/tsi/alts/frame_protector/alts_crypter.cc",
+        "src/core/tsi/alts/frame_protector/alts_frame_protector.cc",
+        "src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc",
+        "src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc",
+        "src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc",
+        "src/core/tsi/alts/frame_protector/frame_handler.cc",
+        "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc",
+        "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc",
+        "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc",
+        "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc",
+        "src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc",
+    ],
+    hdrs = [
+        "src/core/tsi/alts/crypt/gsec.h",
+        "src/core/tsi/alts/frame_protector/alts_counter.h",
+        "src/core/tsi/alts/frame_protector/alts_crypter.h",
+        "src/core/tsi/alts/frame_protector/alts_frame_protector.h",
+        "src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h",
+        "src/core/tsi/alts/frame_protector/frame_handler.h",
+        "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h",
+        "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h",
+        "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h",
+        "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h",
+        "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h",
+        "src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h",
+        "src/core/tsi/transport_security_grpc.h",
+    ],
+    external_deps = [
+        "libssl",
+    ],
+    language = "c++",
+    deps = [
+        "gpr",
+        "grpc_base",
+        "tsi_interface",
+    ],
+)
+
+grpc_cc_library(
+    name = "alts_proto",
+    srcs = [
+        "src/core/tsi/alts/handshaker/altscontext.pb.c",
+        "src/core/tsi/alts/handshaker/handshaker.pb.c",
+        "src/core/tsi/alts/handshaker/transport_security_common.pb.c",
+    ],
+    hdrs = [
+        "src/core/tsi/alts/handshaker/altscontext.pb.h",
+        "src/core/tsi/alts/handshaker/handshaker.pb.h",
+        "src/core/tsi/alts/handshaker/transport_security_common.pb.h",
+    ],
+    external_deps = [
+        "nanopb",
+    ],
+    language = "c++",
+)
+
+grpc_cc_library(
+    name = "alts_util",
+    srcs = [
+        "src/core/lib/security/credentials/alts/check_gcp_environment.cc",
+        "src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc",
+        "src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc",
+        "src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc",
+        "src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc",
+        "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc",
+        "src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc",
+        "src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc",
+        "src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc",
+        "src/core/tsi/alts/handshaker/transport_security_common_api.cc",
+    ],
+    hdrs = [
+        "src/core/lib/security/credentials/alts/check_gcp_environment.h",
+        "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h",
+        "src/core/tsi/alts/handshaker/alts_handshaker_service_api.h",
+        "src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h",
+        "src/core/tsi/alts/handshaker/transport_security_common_api.h",
+    ],
+    external_deps = [
+        "nanopb",
+    ],
+    language = "c++",
+    deps = [
+      "alts_proto",
+      "gpr",
+      "grpc_base",
+    ],
+)
+
+grpc_cc_library(
     name = "tsi",
     srcs = [
         "src/core/tsi/alts_transport_security.cc",
+        "src/core/tsi/alts/handshaker/alts_handshaker_client.cc",
+        "src/core/tsi/alts/handshaker/alts_tsi_event.cc",
+        "src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc",
+        "src/core/tsi/alts/handshaker/alts_tsi_utils.cc",
         "src/core/tsi/fake_transport_security.cc",
         "src/core/tsi/ssl_transport_security.cc",
         "src/core/tsi/transport_security_grpc.cc",
     ],
     hdrs = [
         "src/core/tsi/alts_transport_security.h",
+        "src/core/tsi/alts/handshaker/alts_handshaker_client.h",
+        "src/core/tsi/alts/handshaker/alts_tsi_event.h",
+        "src/core/tsi/alts/handshaker/alts_tsi_handshaker.h",
+        "src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h",
+        "src/core/tsi/alts/handshaker/alts_tsi_utils.h",
         "src/core/tsi/fake_transport_security.h",
         "src/core/tsi/ssl_transport_security.h",
         "src/core/tsi/ssl_types.h",
@@ -1602,7 +1710,11 @@
     ],
     language = "c++",
     deps = [
+        "alts_frame_protector",
+        "alts_util",
+        "gpr",
         "grpc_base",
+        "grpc_transport_chttp2_client_insecure",
         "tsi_interface",
     ],
 )
diff --git a/CMakeLists.txt b/CMakeLists.txt
index ab4fa8a..5dfbdcb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -91,6 +91,8 @@
 
 set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)
 
+add_definitions(-DPB_FIELD_16BIT)
+
 if (MSVC)
   include(cmake/msvc_static_runtime.cmake)
   add_definitions(-D_WIN32_WINNT=0x600 -D_SCL_SECURE_NO_WARNINGS -D_CRT_SECURE_NO_WARNINGS -D_WINSOCK_DEPRECATED_NO_WARNINGS)
@@ -469,6 +471,19 @@
 
 add_custom_target(buildtests_cxx)
 add_dependencies(buildtests_cxx alarm_test)
+add_dependencies(buildtests_cxx alts_counter_test)
+add_dependencies(buildtests_cxx alts_crypt_test)
+add_dependencies(buildtests_cxx alts_crypter_test)
+add_dependencies(buildtests_cxx alts_frame_handler_test)
+add_dependencies(buildtests_cxx alts_frame_protector_test)
+add_dependencies(buildtests_cxx alts_grpc_record_protocol_test)
+add_dependencies(buildtests_cxx alts_handshaker_client_test)
+add_dependencies(buildtests_cxx alts_handshaker_service_api_test)
+add_dependencies(buildtests_cxx alts_iovec_record_protocol_test)
+add_dependencies(buildtests_cxx alts_security_connector_test)
+add_dependencies(buildtests_cxx alts_tsi_handshaker_test)
+add_dependencies(buildtests_cxx alts_tsi_utils_test)
+add_dependencies(buildtests_cxx alts_zero_copy_grpc_protector_test)
 add_dependencies(buildtests_cxx async_end2end_test)
 add_dependencies(buildtests_cxx auth_property_iterator_test)
 add_dependencies(buildtests_cxx backoff_test)
@@ -517,6 +532,8 @@
 endif()
 add_dependencies(buildtests_cxx channel_arguments_test)
 add_dependencies(buildtests_cxx channel_filter_test)
+add_dependencies(buildtests_cxx check_gcp_environment_linux_test)
+add_dependencies(buildtests_cxx check_gcp_environment_windows_test)
 add_dependencies(buildtests_cxx chttp2_settings_timeout_test)
 add_dependencies(buildtests_cxx cli_call_test)
 add_dependencies(buildtests_cxx client_channel_stress_test)
@@ -538,6 +555,7 @@
 add_dependencies(buildtests_cxx filter_end2end_test)
 add_dependencies(buildtests_cxx generic_end2end_test)
 add_dependencies(buildtests_cxx golden_file_test)
+add_dependencies(buildtests_cxx grpc_alts_credentials_options_test)
 add_dependencies(buildtests_cxx grpc_cli)
 add_dependencies(buildtests_cxx grpc_tool_test)
 add_dependencies(buildtests_cxx grpclb_api_test)
@@ -611,6 +629,7 @@
 add_dependencies(buildtests_cxx thread_manager_test)
 add_dependencies(buildtests_cxx thread_stress_test)
 add_dependencies(buildtests_cxx transport_pid_controller_test)
+add_dependencies(buildtests_cxx transport_security_common_api_test)
 if(_gRPC_PLATFORM_LINUX OR _gRPC_PLATFORM_MAC OR _gRPC_PLATFORM_POSIX)
 add_dependencies(buildtests_cxx writes_per_rpc_test)
 endif()
@@ -631,6 +650,44 @@
   DEPENDS buildtests_c buildtests_cxx)
 endif (gRPC_BUILD_TESTS)
 
+if (gRPC_BUILD_TESTS)
+
+add_library(alts_test_util
+  test/core/tsi/alts/crypt/gsec_test_util.cc
+  test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.cc
+)
+
+if(WIN32 AND MSVC)
+  set_target_properties(alts_test_util PROPERTIES COMPILE_PDB_NAME "alts_test_util"
+    COMPILE_PDB_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}"
+  )
+  if (gRPC_INSTALL)
+    install(FILES ${CMAKE_CURRENT_BINARY_DIR}/alts_test_util.pdb
+      DESTINATION ${gRPC_INSTALL_LIBDIR} OPTIONAL
+    )
+  endif()
+endif()
+
+
+target_include_directories(alts_test_util
+  PUBLIC $<INSTALL_INTERFACE:${gRPC_INSTALL_INCLUDEDIR}> $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+)
+
+target_link_libraries(alts_test_util
+  ${_gRPC_SSL_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  grpc
+)
+
+
+endif (gRPC_BUILD_TESTS)
 
 add_library(gpr
   src/core/lib/gpr/alloc.cc
@@ -959,6 +1016,7 @@
   src/core/ext/filters/http/server/http_server_filter.cc
   src/core/lib/http/httpcli_security_connector.cc
   src/core/lib/security/context/security_context.cc
+  src/core/lib/security/credentials/alts/alts_credentials.cc
   src/core/lib/security/credentials/composite/composite_credentials.cc
   src/core/lib/security/credentials/credentials.cc
   src/core/lib/security/credentials/credentials_metadata.cc
@@ -972,6 +1030,7 @@
   src/core/lib/security/credentials/oauth2/oauth2_credentials.cc
   src/core/lib/security/credentials/plugin/plugin_credentials.cc
   src/core/lib/security/credentials/ssl/ssl_credentials.cc
+  src/core/lib/security/security_connector/alts_security_connector.cc
   src/core/lib/security/security_connector/security_connector.cc
   src/core/lib/security/transport/client_auth_filter.cc
   src/core/lib/security/transport/secure_endpoint.cc
@@ -981,14 +1040,45 @@
   src/core/lib/security/transport/tsi_error.cc
   src/core/lib/security/util/json_util.cc
   src/core/lib/surface/init_secure.cc
-  src/core/tsi/alts_transport_security.cc
-  src/core/tsi/fake_transport_security.cc
-  src/core/tsi/ssl_transport_security.cc
-  src/core/tsi/transport_security_grpc.cc
+  src/core/tsi/alts/crypt/aes_gcm.cc
+  src/core/tsi/alts/crypt/gsec.cc
+  src/core/tsi/alts/frame_protector/alts_counter.cc
+  src/core/tsi/alts/frame_protector/alts_crypter.cc
+  src/core/tsi/alts/frame_protector/alts_frame_protector.cc
+  src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc
+  src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc
+  src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc
+  src/core/tsi/alts/frame_protector/frame_handler.cc
+  src/core/tsi/alts/handshaker/alts_handshaker_client.cc
+  src/core/tsi/alts/handshaker/alts_tsi_event.cc
+  src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc
+  src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc
+  src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc
+  src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc
+  src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc
+  src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc
+  src/core/lib/security/credentials/alts/check_gcp_environment.cc
+  src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc
+  src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc
+  src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc
+  src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc
+  src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc
+  src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc
+  src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc
+  src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc
+  src/core/tsi/alts/handshaker/alts_tsi_utils.cc
+  src/core/tsi/alts/handshaker/transport_security_common_api.cc
+  src/core/tsi/alts/handshaker/altscontext.pb.c
+  src/core/tsi/alts/handshaker/handshaker.pb.c
+  src/core/tsi/alts/handshaker/transport_security_common.pb.c
+  third_party/nanopb/pb_common.c
+  third_party/nanopb/pb_decode.c
+  third_party/nanopb/pb_encode.c
   src/core/tsi/transport_security.cc
   src/core/tsi/transport_security_adapter.cc
-  src/core/ext/transport/chttp2/server/chttp2_server.cc
-  src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc
+  src/core/ext/transport/chttp2/client/insecure/channel_create.cc
+  src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc
+  src/core/ext/transport/chttp2/client/chttp2_connector.cc
   src/core/ext/filters/client_channel/backup_poller.cc
   src/core/ext/filters/client_channel/channel_connectivity.cc
   src/core/ext/filters/client_channel/client_channel.cc
@@ -1012,11 +1102,14 @@
   src/core/ext/filters/client_channel/subchannel_index.cc
   src/core/ext/filters/client_channel/uri_parser.cc
   src/core/ext/filters/deadline/deadline_filter.cc
-  src/core/ext/transport/chttp2/client/chttp2_connector.cc
+  src/core/tsi/alts_transport_security.cc
+  src/core/tsi/fake_transport_security.cc
+  src/core/tsi/ssl_transport_security.cc
+  src/core/tsi/transport_security_grpc.cc
+  src/core/ext/transport/chttp2/server/chttp2_server.cc
+  src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc
   src/core/ext/transport/chttp2/server/insecure/server_chttp2.cc
   src/core/ext/transport/chttp2/server/insecure/server_chttp2_posix.cc
-  src/core/ext/transport/chttp2/client/insecure/channel_create.cc
-  src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc
   src/core/ext/transport/inproc/inproc_plugin.cc
   src/core/ext/transport/inproc/inproc_transport.cc
   src/core/ext/filters/client_channel/lb_policy/grpclb/client_load_reporting_filter.cc
@@ -1025,9 +1118,6 @@
   src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.cc
   src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.cc
   src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c
-  third_party/nanopb/pb_common.c
-  third_party/nanopb/pb_decode.c
-  third_party/nanopb/pb_encode.c
   src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc
   src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
   src/core/ext/filters/client_channel/lb_policy/subchannel_list.cc
@@ -1327,6 +1417,7 @@
   src/core/ext/filters/deadline/deadline_filter.cc
   src/core/lib/http/httpcli_security_connector.cc
   src/core/lib/security/context/security_context.cc
+  src/core/lib/security/credentials/alts/alts_credentials.cc
   src/core/lib/security/credentials/composite/composite_credentials.cc
   src/core/lib/security/credentials/credentials.cc
   src/core/lib/security/credentials/credentials_metadata.cc
@@ -1340,6 +1431,7 @@
   src/core/lib/security/credentials/oauth2/oauth2_credentials.cc
   src/core/lib/security/credentials/plugin/plugin_credentials.cc
   src/core/lib/security/credentials/ssl/ssl_credentials.cc
+  src/core/lib/security/security_connector/alts_security_connector.cc
   src/core/lib/security/security_connector/security_connector.cc
   src/core/lib/security/transport/client_auth_filter.cc
   src/core/lib/security/transport/secure_endpoint.cc
@@ -1349,13 +1441,49 @@
   src/core/lib/security/transport/tsi_error.cc
   src/core/lib/security/util/json_util.cc
   src/core/lib/surface/init_secure.cc
+  src/core/tsi/alts/crypt/aes_gcm.cc
+  src/core/tsi/alts/crypt/gsec.cc
+  src/core/tsi/alts/frame_protector/alts_counter.cc
+  src/core/tsi/alts/frame_protector/alts_crypter.cc
+  src/core/tsi/alts/frame_protector/alts_frame_protector.cc
+  src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc
+  src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc
+  src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc
+  src/core/tsi/alts/frame_protector/frame_handler.cc
+  src/core/tsi/alts/handshaker/alts_handshaker_client.cc
+  src/core/tsi/alts/handshaker/alts_tsi_event.cc
+  src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc
+  src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc
+  src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc
+  src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc
+  src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc
+  src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc
+  src/core/lib/security/credentials/alts/check_gcp_environment.cc
+  src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc
+  src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc
+  src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc
+  src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc
+  src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc
+  src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc
+  src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc
+  src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc
+  src/core/tsi/alts/handshaker/alts_tsi_utils.cc
+  src/core/tsi/alts/handshaker/transport_security_common_api.cc
+  src/core/tsi/alts/handshaker/altscontext.pb.c
+  src/core/tsi/alts/handshaker/handshaker.pb.c
+  src/core/tsi/alts/handshaker/transport_security_common.pb.c
+  third_party/nanopb/pb_common.c
+  third_party/nanopb/pb_decode.c
+  third_party/nanopb/pb_encode.c
+  src/core/tsi/transport_security.cc
+  src/core/tsi/transport_security_adapter.cc
+  src/core/ext/transport/chttp2/client/insecure/channel_create.cc
+  src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc
+  src/core/ext/transport/chttp2/client/chttp2_connector.cc
   src/core/tsi/alts_transport_security.cc
   src/core/tsi/fake_transport_security.cc
   src/core/tsi/ssl_transport_security.cc
   src/core/tsi/transport_security_grpc.cc
-  src/core/tsi/transport_security.cc
-  src/core/tsi/transport_security_adapter.cc
-  src/core/ext/transport/chttp2/client/chttp2_connector.cc
   src/core/ext/filters/load_reporting/server_load_reporting_filter.cc
   src/core/ext/filters/load_reporting/server_load_reporting_plugin.cc
   src/core/plugin_registry/grpc_cronet_plugin_registry.cc
@@ -8661,6 +8789,462 @@
 endif (gRPC_BUILD_TESTS)
 if (gRPC_BUILD_TESTS)
 
+add_executable(alts_counter_test
+  test/core/tsi/alts/frame_protector/alts_counter_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_counter_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_counter_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_crypt_test
+  test/core/tsi/alts/crypt/aes_gcm_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_crypt_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_crypt_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_crypter_test
+  test/core/tsi/alts/frame_protector/alts_crypter_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_crypter_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_crypter_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_frame_handler_test
+  test/core/tsi/alts/frame_protector/frame_handler_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_frame_handler_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_frame_handler_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_frame_protector_test
+  test/core/tsi/alts/frame_protector/alts_frame_protector_test.cc
+  test/core/tsi/transport_security_test_lib.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_frame_protector_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_frame_protector_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_grpc_record_protocol_test
+  test/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_grpc_record_protocol_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_grpc_record_protocol_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_handshaker_client_test
+  test/core/tsi/alts/handshaker/alts_handshaker_client_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_handshaker_client_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_handshaker_client_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_handshaker_service_api_test
+  test/core/tsi/alts/handshaker/alts_handshaker_service_api_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_handshaker_service_api_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_handshaker_service_api_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_iovec_record_protocol_test
+  test/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_iovec_record_protocol_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_iovec_record_protocol_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_security_connector_test
+  test/core/security/alts_security_connector_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_security_connector_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_security_connector_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_tsi_handshaker_test
+  test/core/tsi/alts/handshaker/alts_tsi_handshaker_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_tsi_handshaker_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_tsi_handshaker_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_tsi_utils_test
+  test/core/tsi/alts/handshaker/alts_tsi_utils_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_tsi_utils_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_tsi_utils_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(alts_zero_copy_grpc_protector_test
+  test/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(alts_zero_copy_grpc_protector_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(alts_zero_copy_grpc_protector_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
 add_executable(async_end2end_test
   test/cpp/end2end/async_end2end_test.cc
   third_party/googletest/googletest/src/gtest-all.cc
@@ -9470,6 +10054,74 @@
 endif (gRPC_BUILD_TESTS)
 if (gRPC_BUILD_TESTS)
 
+add_executable(check_gcp_environment_linux_test
+  test/core/security/check_gcp_environment_linux_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(check_gcp_environment_linux_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(check_gcp_environment_linux_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  grpc
+  gpr
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
+add_executable(check_gcp_environment_windows_test
+  test/core/security/check_gcp_environment_windows_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(check_gcp_environment_windows_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(check_gcp_environment_windows_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  grpc
+  gpr
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
 add_executable(chttp2_settings_timeout_test
   test/core/transport/chttp2/settings_timeout_test.cc
   third_party/googletest/googletest/src/gtest-all.cc
@@ -10263,6 +10915,40 @@
 endif (gRPC_BUILD_TESTS)
 if (gRPC_BUILD_TESTS)
 
+add_executable(grpc_alts_credentials_options_test
+  test/core/security/grpc_alts_credentials_options_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(grpc_alts_credentials_options_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(grpc_alts_credentials_options_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  grpc
+  gpr
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+
 add_executable(grpc_cli
   test/cpp/util/grpc_cli.cc
   third_party/googletest/googletest/src/gtest-all.cc
@@ -12603,6 +13289,41 @@
 
 endif (gRPC_BUILD_TESTS)
 if (gRPC_BUILD_TESTS)
+
+add_executable(transport_security_common_api_test
+  test/core/tsi/alts/handshaker/transport_security_common_api_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+
+target_include_directories(transport_security_common_api_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE third_party/googletest/googletest/include
+  PRIVATE third_party/googletest/googletest
+  PRIVATE third_party/googletest/googlemock/include
+  PRIVATE third_party/googletest/googlemock
+  PRIVATE ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(transport_security_common_api_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  alts_test_util
+  gpr
+  grpc
+  ${_gRPC_GFLAGS_LIBRARIES}
+)
+
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
 if(_gRPC_PLATFORM_LINUX OR _gRPC_PLATFORM_MAC OR _gRPC_PLATFORM_POSIX)
 
 add_executable(writes_per_rpc_test
diff --git a/Makefile b/Makefile
index b090b9f..7bc2c82 100644
--- a/Makefile
+++ b/Makefile
@@ -338,6 +338,8 @@
 COREFLAGS += -fno-rtti -fno-exceptions
 LDFLAGS += -g
 
+DEFINES += PB_FIELD_16BIT
+
 CPPFLAGS += $(CPPFLAGS_$(CONFIG))
 CFLAGS += $(CFLAGS_$(CONFIG))
 CXXFLAGS += $(CXXFLAGS_$(CONFIG))
@@ -1094,6 +1096,19 @@
 uri_parser_test: $(BINDIR)/$(CONFIG)/uri_parser_test
 wakeup_fd_cv_test: $(BINDIR)/$(CONFIG)/wakeup_fd_cv_test
 alarm_test: $(BINDIR)/$(CONFIG)/alarm_test
+alts_counter_test: $(BINDIR)/$(CONFIG)/alts_counter_test
+alts_crypt_test: $(BINDIR)/$(CONFIG)/alts_crypt_test
+alts_crypter_test: $(BINDIR)/$(CONFIG)/alts_crypter_test
+alts_frame_handler_test: $(BINDIR)/$(CONFIG)/alts_frame_handler_test
+alts_frame_protector_test: $(BINDIR)/$(CONFIG)/alts_frame_protector_test
+alts_grpc_record_protocol_test: $(BINDIR)/$(CONFIG)/alts_grpc_record_protocol_test
+alts_handshaker_client_test: $(BINDIR)/$(CONFIG)/alts_handshaker_client_test
+alts_handshaker_service_api_test: $(BINDIR)/$(CONFIG)/alts_handshaker_service_api_test
+alts_iovec_record_protocol_test: $(BINDIR)/$(CONFIG)/alts_iovec_record_protocol_test
+alts_security_connector_test: $(BINDIR)/$(CONFIG)/alts_security_connector_test
+alts_tsi_handshaker_test: $(BINDIR)/$(CONFIG)/alts_tsi_handshaker_test
+alts_tsi_utils_test: $(BINDIR)/$(CONFIG)/alts_tsi_utils_test
+alts_zero_copy_grpc_protector_test: $(BINDIR)/$(CONFIG)/alts_zero_copy_grpc_protector_test
 async_end2end_test: $(BINDIR)/$(CONFIG)/async_end2end_test
 auth_property_iterator_test: $(BINDIR)/$(CONFIG)/auth_property_iterator_test
 backoff_test: $(BINDIR)/$(CONFIG)/backoff_test
@@ -1114,6 +1129,8 @@
 bm_pollset: $(BINDIR)/$(CONFIG)/bm_pollset
 channel_arguments_test: $(BINDIR)/$(CONFIG)/channel_arguments_test
 channel_filter_test: $(BINDIR)/$(CONFIG)/channel_filter_test
+check_gcp_environment_linux_test: $(BINDIR)/$(CONFIG)/check_gcp_environment_linux_test
+check_gcp_environment_windows_test: $(BINDIR)/$(CONFIG)/check_gcp_environment_windows_test
 chttp2_settings_timeout_test: $(BINDIR)/$(CONFIG)/chttp2_settings_timeout_test
 cli_call_test: $(BINDIR)/$(CONFIG)/cli_call_test
 client_channel_stress_test: $(BINDIR)/$(CONFIG)/client_channel_stress_test
@@ -1133,6 +1150,7 @@
 filter_end2end_test: $(BINDIR)/$(CONFIG)/filter_end2end_test
 generic_end2end_test: $(BINDIR)/$(CONFIG)/generic_end2end_test
 golden_file_test: $(BINDIR)/$(CONFIG)/golden_file_test
+grpc_alts_credentials_options_test: $(BINDIR)/$(CONFIG)/grpc_alts_credentials_options_test
 grpc_cli: $(BINDIR)/$(CONFIG)/grpc_cli
 grpc_cpp_plugin: $(BINDIR)/$(CONFIG)/grpc_cpp_plugin
 grpc_csharp_plugin: $(BINDIR)/$(CONFIG)/grpc_csharp_plugin
@@ -1191,6 +1209,7 @@
 thread_manager_test: $(BINDIR)/$(CONFIG)/thread_manager_test
 thread_stress_test: $(BINDIR)/$(CONFIG)/thread_stress_test
 transport_pid_controller_test: $(BINDIR)/$(CONFIG)/transport_pid_controller_test
+transport_security_common_api_test: $(BINDIR)/$(CONFIG)/transport_security_common_api_test
 writes_per_rpc_test: $(BINDIR)/$(CONFIG)/writes_per_rpc_test
 public_headers_must_be_c89: $(BINDIR)/$(CONFIG)/public_headers_must_be_c89
 gen_hpack_tables: $(BINDIR)/$(CONFIG)/gen_hpack_tables
@@ -1352,7 +1371,7 @@
 
 privatelibs: privatelibs_c privatelibs_cxx
 
-privatelibs_c:  $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libreconnect_server.a $(LIBDIR)/$(CONFIG)/libtest_tcp_server.a $(LIBDIR)/$(CONFIG)/libz.a $(LIBDIR)/$(CONFIG)/libares.a $(LIBDIR)/$(CONFIG)/libbad_client_test.a $(LIBDIR)/$(CONFIG)/libbad_ssl_test_server.a $(LIBDIR)/$(CONFIG)/libend2end_tests.a $(LIBDIR)/$(CONFIG)/libend2end_nosec_tests.a
+privatelibs_c:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc_test_util_unsecure.a $(LIBDIR)/$(CONFIG)/libreconnect_server.a $(LIBDIR)/$(CONFIG)/libtest_tcp_server.a $(LIBDIR)/$(CONFIG)/libz.a $(LIBDIR)/$(CONFIG)/libares.a $(LIBDIR)/$(CONFIG)/libbad_client_test.a $(LIBDIR)/$(CONFIG)/libbad_ssl_test_server.a $(LIBDIR)/$(CONFIG)/libend2end_tests.a $(LIBDIR)/$(CONFIG)/libend2end_nosec_tests.a
 pc_c: $(LIBDIR)/$(CONFIG)/pkgconfig/grpc.pc
 
 pc_c_unsecure: $(LIBDIR)/$(CONFIG)/pkgconfig/grpc_unsecure.pc
@@ -1562,6 +1581,19 @@
 ifeq ($(EMBED_OPENSSL),true)
 buildtests_cxx: privatelibs_cxx \
   $(BINDIR)/$(CONFIG)/alarm_test \
+  $(BINDIR)/$(CONFIG)/alts_counter_test \
+  $(BINDIR)/$(CONFIG)/alts_crypt_test \
+  $(BINDIR)/$(CONFIG)/alts_crypter_test \
+  $(BINDIR)/$(CONFIG)/alts_frame_handler_test \
+  $(BINDIR)/$(CONFIG)/alts_frame_protector_test \
+  $(BINDIR)/$(CONFIG)/alts_grpc_record_protocol_test \
+  $(BINDIR)/$(CONFIG)/alts_handshaker_client_test \
+  $(BINDIR)/$(CONFIG)/alts_handshaker_service_api_test \
+  $(BINDIR)/$(CONFIG)/alts_iovec_record_protocol_test \
+  $(BINDIR)/$(CONFIG)/alts_security_connector_test \
+  $(BINDIR)/$(CONFIG)/alts_tsi_handshaker_test \
+  $(BINDIR)/$(CONFIG)/alts_tsi_utils_test \
+  $(BINDIR)/$(CONFIG)/alts_zero_copy_grpc_protector_test \
   $(BINDIR)/$(CONFIG)/async_end2end_test \
   $(BINDIR)/$(CONFIG)/auth_property_iterator_test \
   $(BINDIR)/$(CONFIG)/backoff_test \
@@ -1582,6 +1614,8 @@
   $(BINDIR)/$(CONFIG)/bm_pollset \
   $(BINDIR)/$(CONFIG)/channel_arguments_test \
   $(BINDIR)/$(CONFIG)/channel_filter_test \
+  $(BINDIR)/$(CONFIG)/check_gcp_environment_linux_test \
+  $(BINDIR)/$(CONFIG)/check_gcp_environment_windows_test \
   $(BINDIR)/$(CONFIG)/chttp2_settings_timeout_test \
   $(BINDIR)/$(CONFIG)/cli_call_test \
   $(BINDIR)/$(CONFIG)/client_channel_stress_test \
@@ -1601,6 +1635,7 @@
   $(BINDIR)/$(CONFIG)/filter_end2end_test \
   $(BINDIR)/$(CONFIG)/generic_end2end_test \
   $(BINDIR)/$(CONFIG)/golden_file_test \
+  $(BINDIR)/$(CONFIG)/grpc_alts_credentials_options_test \
   $(BINDIR)/$(CONFIG)/grpc_cli \
   $(BINDIR)/$(CONFIG)/grpc_tool_test \
   $(BINDIR)/$(CONFIG)/grpclb_api_test \
@@ -1652,6 +1687,7 @@
   $(BINDIR)/$(CONFIG)/thread_manager_test \
   $(BINDIR)/$(CONFIG)/thread_stress_test \
   $(BINDIR)/$(CONFIG)/transport_pid_controller_test \
+  $(BINDIR)/$(CONFIG)/transport_security_common_api_test \
   $(BINDIR)/$(CONFIG)/writes_per_rpc_test \
   $(BINDIR)/$(CONFIG)/boringssl_crypto_test_data \
   $(BINDIR)/$(CONFIG)/boringssl_asn1_test \
@@ -1710,6 +1746,19 @@
 else
 buildtests_cxx: privatelibs_cxx \
   $(BINDIR)/$(CONFIG)/alarm_test \
+  $(BINDIR)/$(CONFIG)/alts_counter_test \
+  $(BINDIR)/$(CONFIG)/alts_crypt_test \
+  $(BINDIR)/$(CONFIG)/alts_crypter_test \
+  $(BINDIR)/$(CONFIG)/alts_frame_handler_test \
+  $(BINDIR)/$(CONFIG)/alts_frame_protector_test \
+  $(BINDIR)/$(CONFIG)/alts_grpc_record_protocol_test \
+  $(BINDIR)/$(CONFIG)/alts_handshaker_client_test \
+  $(BINDIR)/$(CONFIG)/alts_handshaker_service_api_test \
+  $(BINDIR)/$(CONFIG)/alts_iovec_record_protocol_test \
+  $(BINDIR)/$(CONFIG)/alts_security_connector_test \
+  $(BINDIR)/$(CONFIG)/alts_tsi_handshaker_test \
+  $(BINDIR)/$(CONFIG)/alts_tsi_utils_test \
+  $(BINDIR)/$(CONFIG)/alts_zero_copy_grpc_protector_test \
   $(BINDIR)/$(CONFIG)/async_end2end_test \
   $(BINDIR)/$(CONFIG)/auth_property_iterator_test \
   $(BINDIR)/$(CONFIG)/backoff_test \
@@ -1730,6 +1779,8 @@
   $(BINDIR)/$(CONFIG)/bm_pollset \
   $(BINDIR)/$(CONFIG)/channel_arguments_test \
   $(BINDIR)/$(CONFIG)/channel_filter_test \
+  $(BINDIR)/$(CONFIG)/check_gcp_environment_linux_test \
+  $(BINDIR)/$(CONFIG)/check_gcp_environment_windows_test \
   $(BINDIR)/$(CONFIG)/chttp2_settings_timeout_test \
   $(BINDIR)/$(CONFIG)/cli_call_test \
   $(BINDIR)/$(CONFIG)/client_channel_stress_test \
@@ -1749,6 +1800,7 @@
   $(BINDIR)/$(CONFIG)/filter_end2end_test \
   $(BINDIR)/$(CONFIG)/generic_end2end_test \
   $(BINDIR)/$(CONFIG)/golden_file_test \
+  $(BINDIR)/$(CONFIG)/grpc_alts_credentials_options_test \
   $(BINDIR)/$(CONFIG)/grpc_cli \
   $(BINDIR)/$(CONFIG)/grpc_tool_test \
   $(BINDIR)/$(CONFIG)/grpclb_api_test \
@@ -1800,6 +1852,7 @@
   $(BINDIR)/$(CONFIG)/thread_manager_test \
   $(BINDIR)/$(CONFIG)/thread_stress_test \
   $(BINDIR)/$(CONFIG)/transport_pid_controller_test \
+  $(BINDIR)/$(CONFIG)/transport_security_common_api_test \
   $(BINDIR)/$(CONFIG)/writes_per_rpc_test \
   $(BINDIR)/$(CONFIG)/resolver_component_test_unsecure \
   $(BINDIR)/$(CONFIG)/resolver_component_test \
@@ -2086,6 +2139,32 @@
 test_cxx: buildtests_cxx
 	$(E) "[RUN]     Testing alarm_test"
 	$(Q) $(BINDIR)/$(CONFIG)/alarm_test || ( echo test alarm_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_counter_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_counter_test || ( echo test alts_counter_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_crypt_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_crypt_test || ( echo test alts_crypt_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_crypter_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_crypter_test || ( echo test alts_crypter_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_frame_handler_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_frame_handler_test || ( echo test alts_frame_handler_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_frame_protector_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_frame_protector_test || ( echo test alts_frame_protector_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_grpc_record_protocol_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_grpc_record_protocol_test || ( echo test alts_grpc_record_protocol_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_handshaker_client_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_handshaker_client_test || ( echo test alts_handshaker_client_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_handshaker_service_api_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_handshaker_service_api_test || ( echo test alts_handshaker_service_api_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_iovec_record_protocol_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_iovec_record_protocol_test || ( echo test alts_iovec_record_protocol_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_security_connector_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_security_connector_test || ( echo test alts_security_connector_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_tsi_handshaker_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_tsi_handshaker_test || ( echo test alts_tsi_handshaker_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_tsi_utils_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_tsi_utils_test || ( echo test alts_tsi_utils_test failed ; exit 1 )
+	$(E) "[RUN]     Testing alts_zero_copy_grpc_protector_test"
+	$(Q) $(BINDIR)/$(CONFIG)/alts_zero_copy_grpc_protector_test || ( echo test alts_zero_copy_grpc_protector_test failed ; exit 1 )
 	$(E) "[RUN]     Testing async_end2end_test"
 	$(Q) $(BINDIR)/$(CONFIG)/async_end2end_test || ( echo test async_end2end_test failed ; exit 1 )
 	$(E) "[RUN]     Testing auth_property_iterator_test"
@@ -2126,6 +2205,10 @@
 	$(Q) $(BINDIR)/$(CONFIG)/channel_arguments_test || ( echo test channel_arguments_test failed ; exit 1 )
 	$(E) "[RUN]     Testing channel_filter_test"
 	$(Q) $(BINDIR)/$(CONFIG)/channel_filter_test || ( echo test channel_filter_test failed ; exit 1 )
+	$(E) "[RUN]     Testing check_gcp_environment_linux_test"
+	$(Q) $(BINDIR)/$(CONFIG)/check_gcp_environment_linux_test || ( echo test check_gcp_environment_linux_test failed ; exit 1 )
+	$(E) "[RUN]     Testing check_gcp_environment_windows_test"
+	$(Q) $(BINDIR)/$(CONFIG)/check_gcp_environment_windows_test || ( echo test check_gcp_environment_windows_test failed ; exit 1 )
 	$(E) "[RUN]     Testing chttp2_settings_timeout_test"
 	$(Q) $(BINDIR)/$(CONFIG)/chttp2_settings_timeout_test || ( echo test chttp2_settings_timeout_test failed ; exit 1 )
 	$(E) "[RUN]     Testing cli_call_test"
@@ -2162,6 +2245,8 @@
 	$(Q) $(BINDIR)/$(CONFIG)/generic_end2end_test || ( echo test generic_end2end_test failed ; exit 1 )
 	$(E) "[RUN]     Testing golden_file_test"
 	$(Q) $(BINDIR)/$(CONFIG)/golden_file_test || ( echo test golden_file_test failed ; exit 1 )
+	$(E) "[RUN]     Testing grpc_alts_credentials_options_test"
+	$(Q) $(BINDIR)/$(CONFIG)/grpc_alts_credentials_options_test || ( echo test grpc_alts_credentials_options_test failed ; exit 1 )
 	$(E) "[RUN]     Testing grpc_tool_test"
 	$(Q) $(BINDIR)/$(CONFIG)/grpc_tool_test || ( echo test grpc_tool_test failed ; exit 1 )
 	$(E) "[RUN]     Testing grpclb_api_test"
@@ -2236,6 +2321,8 @@
 	$(Q) $(BINDIR)/$(CONFIG)/thread_stress_test || ( echo test thread_stress_test failed ; exit 1 )
 	$(E) "[RUN]     Testing transport_pid_controller_test"
 	$(Q) $(BINDIR)/$(CONFIG)/transport_pid_controller_test || ( echo test transport_pid_controller_test failed ; exit 1 )
+	$(E) "[RUN]     Testing transport_security_common_api_test"
+	$(Q) $(BINDIR)/$(CONFIG)/transport_security_common_api_test || ( echo test transport_security_common_api_test failed ; exit 1 )
 	$(E) "[RUN]     Testing writes_per_rpc_test"
 	$(Q) $(BINDIR)/$(CONFIG)/writes_per_rpc_test || ( echo test writes_per_rpc_test failed ; exit 1 )
 	$(E) "[RUN]     Testing resolver_component_tests_runner_invoker_unsecure"
@@ -2893,6 +2980,46 @@
 # The various libraries
 
 
+LIBALTS_TEST_UTIL_SRC = \
+    test/core/tsi/alts/crypt/gsec_test_util.cc \
+    test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.cc \
+
+PUBLIC_HEADERS_C += \
+
+LIBALTS_TEST_UTIL_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(LIBALTS_TEST_UTIL_SRC))))
+
+
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure libraries if you don't have OpenSSL.
+
+$(LIBDIR)/$(CONFIG)/libalts_test_util.a: openssl_dep_error
+
+
+else
+
+
+$(LIBDIR)/$(CONFIG)/libalts_test_util.a: $(ZLIB_DEP) $(OPENSSL_DEP) $(CARES_DEP) $(LIBALTS_TEST_UTIL_OBJS) 
+	$(E) "[AR]      Creating $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) rm -f $(LIBDIR)/$(CONFIG)/libalts_test_util.a
+	$(Q) $(AR) $(AROPTS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBALTS_TEST_UTIL_OBJS) 
+ifeq ($(SYSTEM),Darwin)
+	$(Q) ranlib -no_warning_for_no_symbols $(LIBDIR)/$(CONFIG)/libalts_test_util.a
+endif
+
+
+
+
+endif
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(LIBALTS_TEST_UTIL_OBJS:.o=.dep)
+endif
+endif
+
+
 LIBGPR_SRC = \
     src/core/lib/gpr/alloc.cc \
     src/core/lib/gpr/arena.cc \
@@ -3195,6 +3322,7 @@
     src/core/ext/filters/http/server/http_server_filter.cc \
     src/core/lib/http/httpcli_security_connector.cc \
     src/core/lib/security/context/security_context.cc \
+    src/core/lib/security/credentials/alts/alts_credentials.cc \
     src/core/lib/security/credentials/composite/composite_credentials.cc \
     src/core/lib/security/credentials/credentials.cc \
     src/core/lib/security/credentials/credentials_metadata.cc \
@@ -3208,6 +3336,7 @@
     src/core/lib/security/credentials/oauth2/oauth2_credentials.cc \
     src/core/lib/security/credentials/plugin/plugin_credentials.cc \
     src/core/lib/security/credentials/ssl/ssl_credentials.cc \
+    src/core/lib/security/security_connector/alts_security_connector.cc \
     src/core/lib/security/security_connector/security_connector.cc \
     src/core/lib/security/transport/client_auth_filter.cc \
     src/core/lib/security/transport/secure_endpoint.cc \
@@ -3217,14 +3346,45 @@
     src/core/lib/security/transport/tsi_error.cc \
     src/core/lib/security/util/json_util.cc \
     src/core/lib/surface/init_secure.cc \
-    src/core/tsi/alts_transport_security.cc \
-    src/core/tsi/fake_transport_security.cc \
-    src/core/tsi/ssl_transport_security.cc \
-    src/core/tsi/transport_security_grpc.cc \
+    src/core/tsi/alts/crypt/aes_gcm.cc \
+    src/core/tsi/alts/crypt/gsec.cc \
+    src/core/tsi/alts/frame_protector/alts_counter.cc \
+    src/core/tsi/alts/frame_protector/alts_crypter.cc \
+    src/core/tsi/alts/frame_protector/alts_frame_protector.cc \
+    src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc \
+    src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc \
+    src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc \
+    src/core/tsi/alts/frame_protector/frame_handler.cc \
+    src/core/tsi/alts/handshaker/alts_handshaker_client.cc \
+    src/core/tsi/alts/handshaker/alts_tsi_event.cc \
+    src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc \
+    src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc \
+    src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc \
+    src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc \
+    src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc \
+    src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc \
+    src/core/tsi/alts/handshaker/alts_tsi_utils.cc \
+    src/core/tsi/alts/handshaker/transport_security_common_api.cc \
+    src/core/tsi/alts/handshaker/altscontext.pb.c \
+    src/core/tsi/alts/handshaker/handshaker.pb.c \
+    src/core/tsi/alts/handshaker/transport_security_common.pb.c \
+    third_party/nanopb/pb_common.c \
+    third_party/nanopb/pb_decode.c \
+    third_party/nanopb/pb_encode.c \
     src/core/tsi/transport_security.cc \
     src/core/tsi/transport_security_adapter.cc \
-    src/core/ext/transport/chttp2/server/chttp2_server.cc \
-    src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc \
+    src/core/ext/transport/chttp2/client/insecure/channel_create.cc \
+    src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc \
+    src/core/ext/transport/chttp2/client/chttp2_connector.cc \
     src/core/ext/filters/client_channel/backup_poller.cc \
     src/core/ext/filters/client_channel/channel_connectivity.cc \
     src/core/ext/filters/client_channel/client_channel.cc \
@@ -3248,11 +3408,14 @@
     src/core/ext/filters/client_channel/subchannel_index.cc \
     src/core/ext/filters/client_channel/uri_parser.cc \
     src/core/ext/filters/deadline/deadline_filter.cc \
-    src/core/ext/transport/chttp2/client/chttp2_connector.cc \
+    src/core/tsi/alts_transport_security.cc \
+    src/core/tsi/fake_transport_security.cc \
+    src/core/tsi/ssl_transport_security.cc \
+    src/core/tsi/transport_security_grpc.cc \
+    src/core/ext/transport/chttp2/server/chttp2_server.cc \
+    src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc \
     src/core/ext/transport/chttp2/server/insecure/server_chttp2.cc \
     src/core/ext/transport/chttp2/server/insecure/server_chttp2_posix.cc \
-    src/core/ext/transport/chttp2/client/insecure/channel_create.cc \
-    src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc \
     src/core/ext/transport/inproc/inproc_plugin.cc \
     src/core/ext/transport/inproc/inproc_transport.cc \
     src/core/ext/filters/client_channel/lb_policy/grpclb/client_load_reporting_filter.cc \
@@ -3261,9 +3424,6 @@
     src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.cc \
     src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.cc \
     src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c \
-    third_party/nanopb/pb_common.c \
-    third_party/nanopb/pb_decode.c \
-    third_party/nanopb/pb_encode.c \
     src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc \
     src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc \
     src/core/ext/filters/client_channel/lb_policy/subchannel_list.cc \
@@ -3565,6 +3725,7 @@
     src/core/ext/filters/deadline/deadline_filter.cc \
     src/core/lib/http/httpcli_security_connector.cc \
     src/core/lib/security/context/security_context.cc \
+    src/core/lib/security/credentials/alts/alts_credentials.cc \
     src/core/lib/security/credentials/composite/composite_credentials.cc \
     src/core/lib/security/credentials/credentials.cc \
     src/core/lib/security/credentials/credentials_metadata.cc \
@@ -3578,6 +3739,7 @@
     src/core/lib/security/credentials/oauth2/oauth2_credentials.cc \
     src/core/lib/security/credentials/plugin/plugin_credentials.cc \
     src/core/lib/security/credentials/ssl/ssl_credentials.cc \
+    src/core/lib/security/security_connector/alts_security_connector.cc \
     src/core/lib/security/security_connector/security_connector.cc \
     src/core/lib/security/transport/client_auth_filter.cc \
     src/core/lib/security/transport/secure_endpoint.cc \
@@ -3587,13 +3749,49 @@
     src/core/lib/security/transport/tsi_error.cc \
     src/core/lib/security/util/json_util.cc \
     src/core/lib/surface/init_secure.cc \
+    src/core/tsi/alts/crypt/aes_gcm.cc \
+    src/core/tsi/alts/crypt/gsec.cc \
+    src/core/tsi/alts/frame_protector/alts_counter.cc \
+    src/core/tsi/alts/frame_protector/alts_crypter.cc \
+    src/core/tsi/alts/frame_protector/alts_frame_protector.cc \
+    src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc \
+    src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc \
+    src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc \
+    src/core/tsi/alts/frame_protector/frame_handler.cc \
+    src/core/tsi/alts/handshaker/alts_handshaker_client.cc \
+    src/core/tsi/alts/handshaker/alts_tsi_event.cc \
+    src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc \
+    src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc \
+    src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc \
+    src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc \
+    src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc \
+    src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc \
+    src/core/tsi/alts/handshaker/alts_tsi_utils.cc \
+    src/core/tsi/alts/handshaker/transport_security_common_api.cc \
+    src/core/tsi/alts/handshaker/altscontext.pb.c \
+    src/core/tsi/alts/handshaker/handshaker.pb.c \
+    src/core/tsi/alts/handshaker/transport_security_common.pb.c \
+    third_party/nanopb/pb_common.c \
+    third_party/nanopb/pb_decode.c \
+    third_party/nanopb/pb_encode.c \
+    src/core/tsi/transport_security.cc \
+    src/core/tsi/transport_security_adapter.cc \
+    src/core/ext/transport/chttp2/client/insecure/channel_create.cc \
+    src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc \
+    src/core/ext/transport/chttp2/client/chttp2_connector.cc \
     src/core/tsi/alts_transport_security.cc \
     src/core/tsi/fake_transport_security.cc \
     src/core/tsi/ssl_transport_security.cc \
     src/core/tsi/transport_security_grpc.cc \
-    src/core/tsi/transport_security.cc \
-    src/core/tsi/transport_security_adapter.cc \
-    src/core/ext/transport/chttp2/client/chttp2_connector.cc \
     src/core/ext/filters/load_reporting/server_load_reporting_filter.cc \
     src/core/ext/filters/load_reporting/server_load_reporting_plugin.cc \
     src/core/plugin_registry/grpc_cronet_plugin_registry.cc \
@@ -14241,6 +14439,568 @@
 endif
 
 
+ALTS_COUNTER_TEST_SRC = \
+    test/core/tsi/alts/frame_protector/alts_counter_test.cc \
+
+ALTS_COUNTER_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_COUNTER_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_counter_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_counter_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_counter_test: $(PROTOBUF_DEP) $(ALTS_COUNTER_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_COUNTER_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_counter_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/frame_protector/alts_counter_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_counter_test: $(ALTS_COUNTER_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_COUNTER_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_CRYPT_TEST_SRC = \
+    test/core/tsi/alts/crypt/aes_gcm_test.cc \
+
+ALTS_CRYPT_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_CRYPT_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_crypt_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_crypt_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_crypt_test: $(PROTOBUF_DEP) $(ALTS_CRYPT_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_CRYPT_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_crypt_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/crypt/aes_gcm_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_crypt_test: $(ALTS_CRYPT_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_CRYPT_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_CRYPTER_TEST_SRC = \
+    test/core/tsi/alts/frame_protector/alts_crypter_test.cc \
+
+ALTS_CRYPTER_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_CRYPTER_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_crypter_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_crypter_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_crypter_test: $(PROTOBUF_DEP) $(ALTS_CRYPTER_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_CRYPTER_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_crypter_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/frame_protector/alts_crypter_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_crypter_test: $(ALTS_CRYPTER_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_CRYPTER_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_FRAME_HANDLER_TEST_SRC = \
+    test/core/tsi/alts/frame_protector/frame_handler_test.cc \
+
+ALTS_FRAME_HANDLER_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_FRAME_HANDLER_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_frame_handler_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_frame_handler_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_frame_handler_test: $(PROTOBUF_DEP) $(ALTS_FRAME_HANDLER_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_FRAME_HANDLER_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_frame_handler_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/frame_protector/frame_handler_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_frame_handler_test: $(ALTS_FRAME_HANDLER_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_FRAME_HANDLER_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_FRAME_PROTECTOR_TEST_SRC = \
+    test/core/tsi/alts/frame_protector/alts_frame_protector_test.cc \
+    test/core/tsi/transport_security_test_lib.cc \
+
+ALTS_FRAME_PROTECTOR_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_FRAME_PROTECTOR_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_frame_protector_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_frame_protector_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_frame_protector_test: $(PROTOBUF_DEP) $(ALTS_FRAME_PROTECTOR_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_FRAME_PROTECTOR_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_frame_protector_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/frame_protector/alts_frame_protector_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/transport_security_test_lib.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_frame_protector_test: $(ALTS_FRAME_PROTECTOR_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_FRAME_PROTECTOR_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_GRPC_RECORD_PROTOCOL_TEST_SRC = \
+    test/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_test.cc \
+
+ALTS_GRPC_RECORD_PROTOCOL_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_GRPC_RECORD_PROTOCOL_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_grpc_record_protocol_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_grpc_record_protocol_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_grpc_record_protocol_test: $(PROTOBUF_DEP) $(ALTS_GRPC_RECORD_PROTOCOL_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_GRPC_RECORD_PROTOCOL_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_grpc_record_protocol_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_grpc_record_protocol_test: $(ALTS_GRPC_RECORD_PROTOCOL_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_GRPC_RECORD_PROTOCOL_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_HANDSHAKER_CLIENT_TEST_SRC = \
+    test/core/tsi/alts/handshaker/alts_handshaker_client_test.cc \
+
+ALTS_HANDSHAKER_CLIENT_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_HANDSHAKER_CLIENT_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_handshaker_client_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_handshaker_client_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_handshaker_client_test: $(PROTOBUF_DEP) $(ALTS_HANDSHAKER_CLIENT_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_HANDSHAKER_CLIENT_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_handshaker_client_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/handshaker/alts_handshaker_client_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_handshaker_client_test: $(ALTS_HANDSHAKER_CLIENT_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_HANDSHAKER_CLIENT_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_HANDSHAKER_SERVICE_API_TEST_SRC = \
+    test/core/tsi/alts/handshaker/alts_handshaker_service_api_test.cc \
+
+ALTS_HANDSHAKER_SERVICE_API_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_HANDSHAKER_SERVICE_API_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_handshaker_service_api_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_handshaker_service_api_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_handshaker_service_api_test: $(PROTOBUF_DEP) $(ALTS_HANDSHAKER_SERVICE_API_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_HANDSHAKER_SERVICE_API_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_handshaker_service_api_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/handshaker/alts_handshaker_service_api_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_handshaker_service_api_test: $(ALTS_HANDSHAKER_SERVICE_API_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_HANDSHAKER_SERVICE_API_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_IOVEC_RECORD_PROTOCOL_TEST_SRC = \
+    test/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol_test.cc \
+
+ALTS_IOVEC_RECORD_PROTOCOL_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_IOVEC_RECORD_PROTOCOL_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_iovec_record_protocol_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_iovec_record_protocol_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_iovec_record_protocol_test: $(PROTOBUF_DEP) $(ALTS_IOVEC_RECORD_PROTOCOL_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_IOVEC_RECORD_PROTOCOL_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_iovec_record_protocol_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_iovec_record_protocol_test: $(ALTS_IOVEC_RECORD_PROTOCOL_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_IOVEC_RECORD_PROTOCOL_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_SECURITY_CONNECTOR_TEST_SRC = \
+    test/core/security/alts_security_connector_test.cc \
+
+ALTS_SECURITY_CONNECTOR_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_SECURITY_CONNECTOR_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_security_connector_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_security_connector_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_security_connector_test: $(PROTOBUF_DEP) $(ALTS_SECURITY_CONNECTOR_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_SECURITY_CONNECTOR_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_security_connector_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/security/alts_security_connector_test.o:  $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_security_connector_test: $(ALTS_SECURITY_CONNECTOR_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_SECURITY_CONNECTOR_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_TSI_HANDSHAKER_TEST_SRC = \
+    test/core/tsi/alts/handshaker/alts_tsi_handshaker_test.cc \
+
+ALTS_TSI_HANDSHAKER_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_TSI_HANDSHAKER_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_tsi_handshaker_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_tsi_handshaker_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_tsi_handshaker_test: $(PROTOBUF_DEP) $(ALTS_TSI_HANDSHAKER_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_TSI_HANDSHAKER_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_tsi_handshaker_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/handshaker/alts_tsi_handshaker_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_tsi_handshaker_test: $(ALTS_TSI_HANDSHAKER_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_TSI_HANDSHAKER_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_TSI_UTILS_TEST_SRC = \
+    test/core/tsi/alts/handshaker/alts_tsi_utils_test.cc \
+
+ALTS_TSI_UTILS_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_TSI_UTILS_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_tsi_utils_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_tsi_utils_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_tsi_utils_test: $(PROTOBUF_DEP) $(ALTS_TSI_UTILS_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_TSI_UTILS_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_tsi_utils_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/handshaker/alts_tsi_utils_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_tsi_utils_test: $(ALTS_TSI_UTILS_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_TSI_UTILS_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+ALTS_ZERO_COPY_GRPC_PROTECTOR_TEST_SRC = \
+    test/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector_test.cc \
+
+ALTS_ZERO_COPY_GRPC_PROTECTOR_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(ALTS_ZERO_COPY_GRPC_PROTECTOR_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/alts_zero_copy_grpc_protector_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/alts_zero_copy_grpc_protector_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/alts_zero_copy_grpc_protector_test: $(PROTOBUF_DEP) $(ALTS_ZERO_COPY_GRPC_PROTECTOR_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(ALTS_ZERO_COPY_GRPC_PROTECTOR_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/alts_zero_copy_grpc_protector_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_alts_zero_copy_grpc_protector_test: $(ALTS_ZERO_COPY_GRPC_PROTECTOR_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(ALTS_ZERO_COPY_GRPC_PROTECTOR_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
 ASYNC_END2END_TEST_SRC = \
     test/cpp/end2end/async_end2end_test.cc \
 
@@ -15115,6 +15875,92 @@
 endif
 
 
+CHECK_GCP_ENVIRONMENT_LINUX_TEST_SRC = \
+    test/core/security/check_gcp_environment_linux_test.cc \
+
+CHECK_GCP_ENVIRONMENT_LINUX_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(CHECK_GCP_ENVIRONMENT_LINUX_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/check_gcp_environment_linux_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/check_gcp_environment_linux_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/check_gcp_environment_linux_test: $(PROTOBUF_DEP) $(CHECK_GCP_ENVIRONMENT_LINUX_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(CHECK_GCP_ENVIRONMENT_LINUX_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/check_gcp_environment_linux_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/security/check_gcp_environment_linux_test.o:  $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr.a
+
+deps_check_gcp_environment_linux_test: $(CHECK_GCP_ENVIRONMENT_LINUX_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(CHECK_GCP_ENVIRONMENT_LINUX_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
+CHECK_GCP_ENVIRONMENT_WINDOWS_TEST_SRC = \
+    test/core/security/check_gcp_environment_windows_test.cc \
+
+CHECK_GCP_ENVIRONMENT_WINDOWS_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(CHECK_GCP_ENVIRONMENT_WINDOWS_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/check_gcp_environment_windows_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/check_gcp_environment_windows_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/check_gcp_environment_windows_test: $(PROTOBUF_DEP) $(CHECK_GCP_ENVIRONMENT_WINDOWS_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(CHECK_GCP_ENVIRONMENT_WINDOWS_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/check_gcp_environment_windows_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/security/check_gcp_environment_windows_test.o:  $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr.a
+
+deps_check_gcp_environment_windows_test: $(CHECK_GCP_ENVIRONMENT_WINDOWS_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(CHECK_GCP_ENVIRONMENT_WINDOWS_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
 CHTTP2_SETTINGS_TIMEOUT_TEST_SRC = \
     test/core/transport/chttp2/settings_timeout_test.cc \
 
@@ -15980,6 +16826,49 @@
 $(OBJDIR)/$(CONFIG)/test/cpp/codegen/golden_file_test.o: $(GENDIR)/src/proto/grpc/testing/compiler_test.pb.cc $(GENDIR)/src/proto/grpc/testing/compiler_test.grpc.pb.cc
 
 
+GRPC_ALTS_CREDENTIALS_OPTIONS_TEST_SRC = \
+    test/core/security/grpc_alts_credentials_options_test.cc \
+
+GRPC_ALTS_CREDENTIALS_OPTIONS_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(GRPC_ALTS_CREDENTIALS_OPTIONS_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/grpc_alts_credentials_options_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/grpc_alts_credentials_options_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/grpc_alts_credentials_options_test: $(PROTOBUF_DEP) $(GRPC_ALTS_CREDENTIALS_OPTIONS_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(GRPC_ALTS_CREDENTIALS_OPTIONS_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/grpc_alts_credentials_options_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/security/grpc_alts_credentials_options_test.o:  $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr.a
+
+deps_grpc_alts_credentials_options_test: $(GRPC_ALTS_CREDENTIALS_OPTIONS_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(GRPC_ALTS_CREDENTIALS_OPTIONS_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
 GRPC_CLI_SRC = \
     test/cpp/util/grpc_cli.cc \
 
@@ -18433,6 +19322,49 @@
 endif
 
 
+TRANSPORT_SECURITY_COMMON_API_TEST_SRC = \
+    test/core/tsi/alts/handshaker/transport_security_common_api_test.cc \
+
+TRANSPORT_SECURITY_COMMON_API_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(TRANSPORT_SECURITY_COMMON_API_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/transport_security_common_api_test: openssl_dep_error
+
+else
+
+
+
+
+ifeq ($(NO_PROTOBUF),true)
+
+# You can't build the protoc plugins or protobuf-enabled targets if you don't have protobuf 3.0.0+.
+
+$(BINDIR)/$(CONFIG)/transport_security_common_api_test: protobuf_dep_error
+
+else
+
+$(BINDIR)/$(CONFIG)/transport_security_common_api_test: $(PROTOBUF_DEP) $(TRANSPORT_SECURITY_COMMON_API_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LDXX) $(LDFLAGS) $(TRANSPORT_SECURITY_COMMON_API_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LDLIBSXX) $(LDLIBS_PROTOBUF) $(LDLIBS) $(LDLIBS_SECURE) $(GTEST_LIB) -o $(BINDIR)/$(CONFIG)/transport_security_common_api_test
+
+endif
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/tsi/alts/handshaker/transport_security_common_api_test.o:  $(LIBDIR)/$(CONFIG)/libalts_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LIBDIR)/$(CONFIG)/libgrpc.a
+
+deps_transport_security_common_api_test: $(TRANSPORT_SECURITY_COMMON_API_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(TRANSPORT_SECURITY_COMMON_API_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
 WRITES_PER_RPC_TEST_SRC = \
     test/cpp/performance/writes_per_rpc_test.cc \
 
@@ -22403,6 +23335,14 @@
 src/core/ext/transport/cronet/transport/cronet_transport.cc: $(OPENSSL_DEP)
 src/core/lib/http/httpcli_security_connector.cc: $(OPENSSL_DEP)
 src/core/lib/security/context/security_context.cc: $(OPENSSL_DEP)
+src/core/lib/security/credentials/alts/alts_credentials.cc: $(OPENSSL_DEP)
+src/core/lib/security/credentials/alts/check_gcp_environment.cc: $(OPENSSL_DEP)
+src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc: $(OPENSSL_DEP)
+src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc: $(OPENSSL_DEP)
+src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc: $(OPENSSL_DEP)
+src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc: $(OPENSSL_DEP)
+src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc: $(OPENSSL_DEP)
+src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc: $(OPENSSL_DEP)
 src/core/lib/security/credentials/composite/composite_credentials.cc: $(OPENSSL_DEP)
 src/core/lib/security/credentials/credentials.cc: $(OPENSSL_DEP)
 src/core/lib/security/credentials/credentials_metadata.cc: $(OPENSSL_DEP)
@@ -22416,6 +23356,7 @@
 src/core/lib/security/credentials/oauth2/oauth2_credentials.cc: $(OPENSSL_DEP)
 src/core/lib/security/credentials/plugin/plugin_credentials.cc: $(OPENSSL_DEP)
 src/core/lib/security/credentials/ssl/ssl_credentials.cc: $(OPENSSL_DEP)
+src/core/lib/security/security_connector/alts_security_connector.cc: $(OPENSSL_DEP)
 src/core/lib/security/security_connector/security_connector.cc: $(OPENSSL_DEP)
 src/core/lib/security/transport/client_auth_filter.cc: $(OPENSSL_DEP)
 src/core/lib/security/transport/secure_endpoint.cc: $(OPENSSL_DEP)
@@ -22427,6 +23368,30 @@
 src/core/lib/surface/init_secure.cc: $(OPENSSL_DEP)
 src/core/plugin_registry/grpc_cronet_plugin_registry.cc: $(OPENSSL_DEP)
 src/core/plugin_registry/grpc_plugin_registry.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/crypt/aes_gcm.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/crypt/gsec.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/frame_protector/alts_counter.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/frame_protector/alts_crypter.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/frame_protector/alts_frame_protector.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/frame_protector/frame_handler.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/handshaker/alts_handshaker_client.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/handshaker/alts_tsi_event.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/handshaker/alts_tsi_utils.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/handshaker/altscontext.pb.c: $(OPENSSL_DEP)
+src/core/tsi/alts/handshaker/handshaker.pb.c: $(OPENSSL_DEP)
+src/core/tsi/alts/handshaker/transport_security_common.pb.c: $(OPENSSL_DEP)
+src/core/tsi/alts/handshaker/transport_security_common_api.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc: $(OPENSSL_DEP)
+src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc: $(OPENSSL_DEP)
 src/core/tsi/alts_transport_security.cc: $(OPENSSL_DEP)
 src/core/tsi/fake_transport_security.cc: $(OPENSSL_DEP)
 src/core/tsi/ssl_transport_security.cc: $(OPENSSL_DEP)
@@ -22454,6 +23419,8 @@
 test/core/end2end/end2end_tests.cc: $(OPENSSL_DEP)
 test/core/end2end/tests/call_creds.cc: $(OPENSSL_DEP)
 test/core/security/oauth2_utils.cc: $(OPENSSL_DEP)
+test/core/tsi/alts/crypt/gsec_test_util.cc: $(OPENSSL_DEP)
+test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.cc: $(OPENSSL_DEP)
 test/core/util/reconnect_server.cc: $(OPENSSL_DEP)
 test/core/util/test_tcp_server.cc: $(OPENSSL_DEP)
 test/cpp/end2end/test_service_impl.cc: $(OPENSSL_DEP)
diff --git a/bazel/grpc_build_system.bzl b/bazel/grpc_build_system.bzl
index 7bc1862..662068a 100644
--- a/bazel/grpc_build_system.bzl
+++ b/bazel/grpc_build_system.bzl
@@ -57,6 +57,12 @@
       ret.append(h)
   return ret
 
+def _maybe_update_cc_library_defines(name):
+  ret = []
+  if name == "alts_proto":
+    ret += ["PB_FIELD_16BIT=1"]
+  return ret
+
 def grpc_cc_library(name, srcs = [], public_hdrs = [], hdrs = [],
                     external_deps = [], deps = [], standalone = False,
                     language = "C++", testonly = False, visibility = None,
@@ -64,10 +70,11 @@
   copts = []
   if language.upper() == "C":
     copts = if_not_windows(["-std=c99"])
+  defines = _maybe_update_cc_library_defines(name)
   native.cc_library(
     name = name,
     srcs = srcs,
-    defines = select({"//:grpc_no_ares": ["GRPC_ARES=0"],
+    defines = defines + select({"//:grpc_no_ares": ["GRPC_ARES=0"],
                       "//conditions:default": [],}) +
               select({"//:remote_execution":  ["GRPC_PORT_ISOLATED_RUNTIME=1"],
                       "//conditions:default": [],}) +
diff --git a/build.yaml b/build.yaml
index e2d1940..e2bb8bf 100644
--- a/build.yaml
+++ b/build.yaml
@@ -16,6 +16,84 @@
   g_stands_for: gorgeous
   version: 1.11.0-dev
 filegroups:
+- name: alts_proto
+  headers:
+  - src/core/tsi/alts/handshaker/altscontext.pb.h
+  - src/core/tsi/alts/handshaker/handshaker.pb.h
+  - src/core/tsi/alts/handshaker/transport_security_common.pb.h
+  src:
+  - src/core/tsi/alts/handshaker/altscontext.pb.c
+  - src/core/tsi/alts/handshaker/handshaker.pb.c
+  - src/core/tsi/alts/handshaker/transport_security_common.pb.c
+  uses:
+  - nanopb
+- name: alts_tsi
+  headers:
+  - src/core/tsi/alts/crypt/gsec.h
+  - src/core/tsi/alts/frame_protector/alts_counter.h
+  - src/core/tsi/alts/frame_protector/alts_crypter.h
+  - src/core/tsi/alts/frame_protector/alts_frame_protector.h
+  - src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h
+  - src/core/tsi/alts/frame_protector/frame_handler.h
+  - src/core/tsi/alts/handshaker/alts_handshaker_client.h
+  - src/core/tsi/alts/handshaker/alts_tsi_event.h
+  - src/core/tsi/alts/handshaker/alts_tsi_handshaker.h
+  - src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h
+  - src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h
+  - src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h
+  - src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h
+  - src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h
+  - src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h
+  - src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h
+  src:
+  - src/core/tsi/alts/crypt/aes_gcm.cc
+  - src/core/tsi/alts/crypt/gsec.cc
+  - src/core/tsi/alts/frame_protector/alts_counter.cc
+  - src/core/tsi/alts/frame_protector/alts_crypter.cc
+  - src/core/tsi/alts/frame_protector/alts_frame_protector.cc
+  - src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc
+  - src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc
+  - src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc
+  - src/core/tsi/alts/frame_protector/frame_handler.cc
+  - src/core/tsi/alts/handshaker/alts_handshaker_client.cc
+  - src/core/tsi/alts/handshaker/alts_tsi_event.cc
+  - src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc
+  - src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc
+  - src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc
+  - src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc
+  - src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc
+  - src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc
+  uses:
+  - alts_util
+  - grpc_base
+  - grpc_transport_chttp2_client_insecure
+  - tsi_interface
+  - tsi
+- name: alts_util
+  headers:
+  - src/core/lib/security/credentials/alts/check_gcp_environment.h
+  - src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h
+  - src/core/tsi/alts/handshaker/alts_handshaker_service_api.h
+  - src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h
+  - src/core/tsi/alts/handshaker/alts_tsi_utils.h
+  - src/core/tsi/alts/handshaker/transport_security_common_api.h
+  src:
+  - src/core/lib/security/credentials/alts/check_gcp_environment.cc
+  - src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc
+  - src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc
+  - src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc
+  - src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc
+  - src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc
+  - src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc
+  - src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc
+  - src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc
+  - src/core/tsi/alts/handshaker/alts_tsi_utils.cc
+  - src/core/tsi/alts/handshaker/transport_security_common_api.cc
+  uses:
+  - alts_proto
+  - grpc_base
+  - tsi_interface
+  - nanopb
 - name: census
   public_headers:
   - include/grpc/census.h
@@ -642,6 +720,7 @@
   - include/grpc/grpc_security.h
   headers:
   - src/core/lib/security/context/security_context.h
+  - src/core/lib/security/credentials/alts/alts_credentials.h
   - src/core/lib/security/credentials/composite/composite_credentials.h
   - src/core/lib/security/credentials/credentials.h
   - src/core/lib/security/credentials/fake/fake_credentials.h
@@ -653,6 +732,7 @@
   - src/core/lib/security/credentials/oauth2/oauth2_credentials.h
   - src/core/lib/security/credentials/plugin/plugin_credentials.h
   - src/core/lib/security/credentials/ssl/ssl_credentials.h
+  - src/core/lib/security/security_connector/alts_security_connector.h
   - src/core/lib/security/security_connector/security_connector.h
   - src/core/lib/security/transport/auth_filters.h
   - src/core/lib/security/transport/secure_endpoint.h
@@ -663,6 +743,7 @@
   src:
   - src/core/lib/http/httpcli_security_connector.cc
   - src/core/lib/security/context/security_context.cc
+  - src/core/lib/security/credentials/alts/alts_credentials.cc
   - src/core/lib/security/credentials/composite/composite_credentials.cc
   - src/core/lib/security/credentials/credentials.cc
   - src/core/lib/security/credentials/credentials_metadata.cc
@@ -676,6 +757,7 @@
   - src/core/lib/security/credentials/oauth2/oauth2_credentials.cc
   - src/core/lib/security/credentials/plugin/plugin_credentials.cc
   - src/core/lib/security/credentials/ssl/ssl_credentials.cc
+  - src/core/lib/security/security_connector/alts_security_connector.cc
   - src/core/lib/security/security_connector/security_connector.cc
   - src/core/lib/security/transport/client_auth_filter.cc
   - src/core/lib/security/transport/secure_endpoint.cc
@@ -687,6 +769,7 @@
   - src/core/lib/surface/init_secure.cc
   secure: true
   uses:
+  - alts_tsi
   - grpc_base
   - grpc_transport_chttp2_alpn
   - tsi
@@ -1211,6 +1294,18 @@
   - grpc++
   - grpc
 libs:
+- name: alts_test_util
+  build: private
+  language: c
+  headers:
+  - test/core/tsi/alts/crypt/gsec_test_util.h
+  - test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.h
+  src:
+  - test/core/tsi/alts/crypt/gsec_test_util.cc
+  - test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.cc
+  deps:
+  - grpc
+  secure: true
 - name: gpr
   build: all
   language: c
@@ -3496,6 +3591,125 @@
   - grpc_unsecure
   - gpr_test_util
   - gpr
+- name: alts_counter_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/frame_protector/alts_counter_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
+- name: alts_crypt_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/crypt/aes_gcm_test.cc
+  deps:
+  - alts_test_util
+  - gpr_test_util
+  - gpr
+  - grpc
+- name: alts_crypter_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/frame_protector/alts_crypter_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
+- name: alts_frame_handler_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/frame_protector/frame_handler_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
+- name: alts_frame_protector_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/frame_protector/alts_frame_protector_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
+  filegroups:
+  - transport_security_test_lib
+- name: alts_grpc_record_protocol_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
+- name: alts_handshaker_client_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/handshaker/alts_handshaker_client_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
+- name: alts_handshaker_service_api_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/handshaker/alts_handshaker_service_api_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
+- name: alts_iovec_record_protocol_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
+- name: alts_security_connector_test
+  build: test
+  language: c++
+  src:
+  - test/core/security/alts_security_connector_test.cc
+  deps:
+  - gpr
+  - grpc
+- name: alts_tsi_handshaker_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/handshaker/alts_tsi_handshaker_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
+- name: alts_tsi_utils_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/handshaker/alts_tsi_utils_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
+- name: alts_zero_copy_grpc_protector_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
 - name: async_end2end_test
   gtest: true
   build: test
@@ -3879,6 +4093,22 @@
   - grpc
   - gpr
   uses_polling: false
+- name: check_gcp_environment_linux_test
+  build: test
+  language: c++
+  src:
+  - test/core/security/check_gcp_environment_linux_test.cc
+  deps:
+  - grpc
+  - gpr
+- name: check_gcp_environment_windows_test
+  build: test
+  language: c++
+  src:
+  - test/core/security/check_gcp_environment_windows_test.cc
+  deps:
+  - grpc
+  - gpr
 - name: chttp2_settings_timeout_test
   gtest: true
   build: test
@@ -4137,6 +4367,14 @@
   args:
   - --generated_file_path=gens/src/proto/grpc/testing/
   uses_polling: false
+- name: grpc_alts_credentials_options_test
+  build: test
+  language: c++
+  src:
+  - test/core/security/grpc_alts_credentials_options_test.cc
+  deps:
+  - grpc
+  - gpr
 - name: grpc_cli
   build: test
   run: false
@@ -4972,6 +5210,15 @@
   - grpc
   - gpr_test_util
   - gpr
+- name: transport_security_common_api_test
+  build: test
+  language: c++
+  src:
+  - test/core/tsi/alts/handshaker/transport_security_common_api_test.cc
+  deps:
+  - alts_test_util
+  - gpr
+  - grpc
 - name: writes_per_rpc_test
   gtest: true
   cpu_cost: 0.5
diff --git a/config.m4 b/config.m4
index 1a05584..57fc2db 100644
--- a/config.m4
+++ b/config.m4
@@ -244,6 +244,7 @@
     src/core/ext/filters/http/server/http_server_filter.cc \
     src/core/lib/http/httpcli_security_connector.cc \
     src/core/lib/security/context/security_context.cc \
+    src/core/lib/security/credentials/alts/alts_credentials.cc \
     src/core/lib/security/credentials/composite/composite_credentials.cc \
     src/core/lib/security/credentials/credentials.cc \
     src/core/lib/security/credentials/credentials_metadata.cc \
@@ -257,6 +258,7 @@
     src/core/lib/security/credentials/oauth2/oauth2_credentials.cc \
     src/core/lib/security/credentials/plugin/plugin_credentials.cc \
     src/core/lib/security/credentials/ssl/ssl_credentials.cc \
+    src/core/lib/security/security_connector/alts_security_connector.cc \
     src/core/lib/security/security_connector/security_connector.cc \
     src/core/lib/security/transport/client_auth_filter.cc \
     src/core/lib/security/transport/secure_endpoint.cc \
@@ -266,14 +268,45 @@
     src/core/lib/security/transport/tsi_error.cc \
     src/core/lib/security/util/json_util.cc \
     src/core/lib/surface/init_secure.cc \
-    src/core/tsi/alts_transport_security.cc \
-    src/core/tsi/fake_transport_security.cc \
-    src/core/tsi/ssl_transport_security.cc \
-    src/core/tsi/transport_security_grpc.cc \
+    src/core/tsi/alts/crypt/aes_gcm.cc \
+    src/core/tsi/alts/crypt/gsec.cc \
+    src/core/tsi/alts/frame_protector/alts_counter.cc \
+    src/core/tsi/alts/frame_protector/alts_crypter.cc \
+    src/core/tsi/alts/frame_protector/alts_frame_protector.cc \
+    src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc \
+    src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc \
+    src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc \
+    src/core/tsi/alts/frame_protector/frame_handler.cc \
+    src/core/tsi/alts/handshaker/alts_handshaker_client.cc \
+    src/core/tsi/alts/handshaker/alts_tsi_event.cc \
+    src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc \
+    src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc \
+    src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc \
+    src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc \
+    src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc \
+    src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc \
+    src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc \
+    src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc \
+    src/core/tsi/alts/handshaker/alts_tsi_utils.cc \
+    src/core/tsi/alts/handshaker/transport_security_common_api.cc \
+    src/core/tsi/alts/handshaker/altscontext.pb.c \
+    src/core/tsi/alts/handshaker/handshaker.pb.c \
+    src/core/tsi/alts/handshaker/transport_security_common.pb.c \
+    third_party/nanopb/pb_common.c \
+    third_party/nanopb/pb_decode.c \
+    third_party/nanopb/pb_encode.c \
     src/core/tsi/transport_security.cc \
     src/core/tsi/transport_security_adapter.cc \
-    src/core/ext/transport/chttp2/server/chttp2_server.cc \
-    src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc \
+    src/core/ext/transport/chttp2/client/insecure/channel_create.cc \
+    src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc \
+    src/core/ext/transport/chttp2/client/chttp2_connector.cc \
     src/core/ext/filters/client_channel/backup_poller.cc \
     src/core/ext/filters/client_channel/channel_connectivity.cc \
     src/core/ext/filters/client_channel/client_channel.cc \
@@ -297,11 +330,14 @@
     src/core/ext/filters/client_channel/subchannel_index.cc \
     src/core/ext/filters/client_channel/uri_parser.cc \
     src/core/ext/filters/deadline/deadline_filter.cc \
-    src/core/ext/transport/chttp2/client/chttp2_connector.cc \
+    src/core/tsi/alts_transport_security.cc \
+    src/core/tsi/fake_transport_security.cc \
+    src/core/tsi/ssl_transport_security.cc \
+    src/core/tsi/transport_security_grpc.cc \
+    src/core/ext/transport/chttp2/server/chttp2_server.cc \
+    src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc \
     src/core/ext/transport/chttp2/server/insecure/server_chttp2.cc \
     src/core/ext/transport/chttp2/server/insecure/server_chttp2_posix.cc \
-    src/core/ext/transport/chttp2/client/insecure/channel_create.cc \
-    src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc \
     src/core/ext/transport/inproc/inproc_plugin.cc \
     src/core/ext/transport/inproc/inproc_transport.cc \
     src/core/ext/filters/client_channel/lb_policy/grpclb/client_load_reporting_filter.cc \
@@ -310,9 +346,6 @@
     src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.cc \
     src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.cc \
     src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c \
-    third_party/nanopb/pb_common.c \
-    third_party/nanopb/pb_decode.c \
-    third_party/nanopb/pb_encode.c \
     src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc \
     src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc \
     src/core/ext/filters/client_channel/lb_policy/subchannel_list.cc \
@@ -635,6 +668,7 @@
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/lib/profiling)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/lib/security/context)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/lib/security/credentials)
+  PHP_ADD_BUILD_DIR($ext_builddir/src/core/lib/security/credentials/alts)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/lib/security/credentials/composite)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/lib/security/credentials/fake)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/lib/security/credentials/google_default)
@@ -651,6 +685,10 @@
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/lib/transport)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/plugin_registry)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/tsi)
+  PHP_ADD_BUILD_DIR($ext_builddir/src/core/tsi/alts/crypt)
+  PHP_ADD_BUILD_DIR($ext_builddir/src/core/tsi/alts/frame_protector)
+  PHP_ADD_BUILD_DIR($ext_builddir/src/core/tsi/alts/handshaker)
+  PHP_ADD_BUILD_DIR($ext_builddir/src/core/tsi/alts/zero_copy_frame_protector)
   PHP_ADD_BUILD_DIR($ext_builddir/third_party/boringssl/crypto)
   PHP_ADD_BUILD_DIR($ext_builddir/third_party/boringssl/crypto/asn1)
   PHP_ADD_BUILD_DIR($ext_builddir/third_party/boringssl/crypto/base64)
diff --git a/config.w32 b/config.w32
index 5e41295..580607d 100644
--- a/config.w32
+++ b/config.w32
@@ -221,6 +221,7 @@
     "src\\core\\ext\\filters\\http\\server\\http_server_filter.cc " +
     "src\\core\\lib\\http\\httpcli_security_connector.cc " +
     "src\\core\\lib\\security\\context\\security_context.cc " +
+    "src\\core\\lib\\security\\credentials\\alts\\alts_credentials.cc " +
     "src\\core\\lib\\security\\credentials\\composite\\composite_credentials.cc " +
     "src\\core\\lib\\security\\credentials\\credentials.cc " +
     "src\\core\\lib\\security\\credentials\\credentials_metadata.cc " +
@@ -234,6 +235,7 @@
     "src\\core\\lib\\security\\credentials\\oauth2\\oauth2_credentials.cc " +
     "src\\core\\lib\\security\\credentials\\plugin\\plugin_credentials.cc " +
     "src\\core\\lib\\security\\credentials\\ssl\\ssl_credentials.cc " +
+    "src\\core\\lib\\security\\security_connector\\alts_security_connector.cc " +
     "src\\core\\lib\\security\\security_connector\\security_connector.cc " +
     "src\\core\\lib\\security\\transport\\client_auth_filter.cc " +
     "src\\core\\lib\\security\\transport\\secure_endpoint.cc " +
@@ -243,14 +245,45 @@
     "src\\core\\lib\\security\\transport\\tsi_error.cc " +
     "src\\core\\lib\\security\\util\\json_util.cc " +
     "src\\core\\lib\\surface\\init_secure.cc " +
-    "src\\core\\tsi\\alts_transport_security.cc " +
-    "src\\core\\tsi\\fake_transport_security.cc " +
-    "src\\core\\tsi\\ssl_transport_security.cc " +
-    "src\\core\\tsi\\transport_security_grpc.cc " +
+    "src\\core\\tsi\\alts\\crypt\\aes_gcm.cc " +
+    "src\\core\\tsi\\alts\\crypt\\gsec.cc " +
+    "src\\core\\tsi\\alts\\frame_protector\\alts_counter.cc " +
+    "src\\core\\tsi\\alts\\frame_protector\\alts_crypter.cc " +
+    "src\\core\\tsi\\alts\\frame_protector\\alts_frame_protector.cc " +
+    "src\\core\\tsi\\alts\\frame_protector\\alts_record_protocol_crypter_common.cc " +
+    "src\\core\\tsi\\alts\\frame_protector\\alts_seal_privacy_integrity_crypter.cc " +
+    "src\\core\\tsi\\alts\\frame_protector\\alts_unseal_privacy_integrity_crypter.cc " +
+    "src\\core\\tsi\\alts\\frame_protector\\frame_handler.cc " +
+    "src\\core\\tsi\\alts\\handshaker\\alts_handshaker_client.cc " +
+    "src\\core\\tsi\\alts\\handshaker\\alts_tsi_event.cc " +
+    "src\\core\\tsi\\alts\\handshaker\\alts_tsi_handshaker.cc " +
+    "src\\core\\tsi\\alts\\zero_copy_frame_protector\\alts_grpc_integrity_only_record_protocol.cc " +
+    "src\\core\\tsi\\alts\\zero_copy_frame_protector\\alts_grpc_privacy_integrity_record_protocol.cc " +
+    "src\\core\\tsi\\alts\\zero_copy_frame_protector\\alts_grpc_record_protocol_common.cc " +
+    "src\\core\\tsi\\alts\\zero_copy_frame_protector\\alts_iovec_record_protocol.cc " +
+    "src\\core\\tsi\\alts\\zero_copy_frame_protector\\alts_zero_copy_grpc_protector.cc " +
+    "src\\core\\lib\\security\\credentials\\alts\\check_gcp_environment.cc " +
+    "src\\core\\lib\\security\\credentials\\alts\\check_gcp_environment_linux.cc " +
+    "src\\core\\lib\\security\\credentials\\alts\\check_gcp_environment_no_op.cc " +
+    "src\\core\\lib\\security\\credentials\\alts\\check_gcp_environment_windows.cc " +
+    "src\\core\\lib\\security\\credentials\\alts\\grpc_alts_credentials_client_options.cc " +
+    "src\\core\\lib\\security\\credentials\\alts\\grpc_alts_credentials_options.cc " +
+    "src\\core\\lib\\security\\credentials\\alts\\grpc_alts_credentials_server_options.cc " +
+    "src\\core\\tsi\\alts\\handshaker\\alts_handshaker_service_api.cc " +
+    "src\\core\\tsi\\alts\\handshaker\\alts_handshaker_service_api_util.cc " +
+    "src\\core\\tsi\\alts\\handshaker\\alts_tsi_utils.cc " +
+    "src\\core\\tsi\\alts\\handshaker\\transport_security_common_api.cc " +
+    "src\\core\\tsi\\alts\\handshaker\\altscontext.pb.c " +
+    "src\\core\\tsi\\alts\\handshaker\\handshaker.pb.c " +
+    "src\\core\\tsi\\alts\\handshaker\\transport_security_common.pb.c " +
+    "third_party\\nanopb\\pb_common.c " +
+    "third_party\\nanopb\\pb_decode.c " +
+    "third_party\\nanopb\\pb_encode.c " +
     "src\\core\\tsi\\transport_security.cc " +
     "src\\core\\tsi\\transport_security_adapter.cc " +
-    "src\\core\\ext\\transport\\chttp2\\server\\chttp2_server.cc " +
-    "src\\core\\ext\\transport\\chttp2\\client\\secure\\secure_channel_create.cc " +
+    "src\\core\\ext\\transport\\chttp2\\client\\insecure\\channel_create.cc " +
+    "src\\core\\ext\\transport\\chttp2\\client\\insecure\\channel_create_posix.cc " +
+    "src\\core\\ext\\transport\\chttp2\\client\\chttp2_connector.cc " +
     "src\\core\\ext\\filters\\client_channel\\backup_poller.cc " +
     "src\\core\\ext\\filters\\client_channel\\channel_connectivity.cc " +
     "src\\core\\ext\\filters\\client_channel\\client_channel.cc " +
@@ -274,11 +307,14 @@
     "src\\core\\ext\\filters\\client_channel\\subchannel_index.cc " +
     "src\\core\\ext\\filters\\client_channel\\uri_parser.cc " +
     "src\\core\\ext\\filters\\deadline\\deadline_filter.cc " +
-    "src\\core\\ext\\transport\\chttp2\\client\\chttp2_connector.cc " +
+    "src\\core\\tsi\\alts_transport_security.cc " +
+    "src\\core\\tsi\\fake_transport_security.cc " +
+    "src\\core\\tsi\\ssl_transport_security.cc " +
+    "src\\core\\tsi\\transport_security_grpc.cc " +
+    "src\\core\\ext\\transport\\chttp2\\server\\chttp2_server.cc " +
+    "src\\core\\ext\\transport\\chttp2\\client\\secure\\secure_channel_create.cc " +
     "src\\core\\ext\\transport\\chttp2\\server\\insecure\\server_chttp2.cc " +
     "src\\core\\ext\\transport\\chttp2\\server\\insecure\\server_chttp2_posix.cc " +
-    "src\\core\\ext\\transport\\chttp2\\client\\insecure\\channel_create.cc " +
-    "src\\core\\ext\\transport\\chttp2\\client\\insecure\\channel_create_posix.cc " +
     "src\\core\\ext\\transport\\inproc\\inproc_plugin.cc " +
     "src\\core\\ext\\transport\\inproc\\inproc_transport.cc " +
     "src\\core\\ext\\filters\\client_channel\\lb_policy\\grpclb\\client_load_reporting_filter.cc " +
@@ -287,9 +323,6 @@
     "src\\core\\ext\\filters\\client_channel\\lb_policy\\grpclb\\grpclb_client_stats.cc " +
     "src\\core\\ext\\filters\\client_channel\\lb_policy\\grpclb\\load_balancer_api.cc " +
     "src\\core\\ext\\filters\\client_channel\\lb_policy\\grpclb\\proto\\grpc\\lb\\v1\\load_balancer.pb.c " +
-    "third_party\\nanopb\\pb_common.c " +
-    "third_party\\nanopb\\pb_decode.c " +
-    "third_party\\nanopb\\pb_encode.c " +
     "src\\core\\ext\\filters\\client_channel\\resolver\\fake\\fake_resolver.cc " +
     "src\\core\\ext\\filters\\client_channel\\lb_policy\\pick_first\\pick_first.cc " +
     "src\\core\\ext\\filters\\client_channel\\lb_policy\\subchannel_list.cc " +
@@ -648,6 +681,7 @@
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\lib\\security");
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\lib\\security\\context");
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\lib\\security\\credentials");
+  FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\lib\\security\\credentials\\alts");
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\lib\\security\\credentials\\composite");
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\lib\\security\\credentials\\fake");
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\lib\\security\\credentials\\google_default");
@@ -664,6 +698,11 @@
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\lib\\transport");
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\plugin_registry");
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\tsi");
+  FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\tsi\\alts");
+  FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\tsi\\alts\\crypt");
+  FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\tsi\\alts\\frame_protector");
+  FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\tsi\\alts\\handshaker");
+  FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\core\\tsi\\alts\\zero_copy_frame_protector");
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\php");
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\php\\ext");
   FSO.CreateFolder(base_dir+"\\ext\\grpc\\src\\php\\ext\\grpc");
diff --git a/gRPC-C++.podspec b/gRPC-C++.podspec
index 821c16d..65a5dc6 100644
--- a/gRPC-C++.podspec
+++ b/gRPC-C++.podspec
@@ -260,6 +260,7 @@
                       'src/core/ext/filters/http/message_compress/message_compress_filter.h',
                       'src/core/ext/filters/http/server/http_server_filter.h',
                       'src/core/lib/security/context/security_context.h',
+                      'src/core/lib/security/credentials/alts/alts_credentials.h',
                       'src/core/lib/security/credentials/composite/composite_credentials.h',
                       'src/core/lib/security/credentials/credentials.h',
                       'src/core/lib/security/credentials/fake/fake_credentials.h',
@@ -271,6 +272,7 @@
                       'src/core/lib/security/credentials/oauth2/oauth2_credentials.h',
                       'src/core/lib/security/credentials/plugin/plugin_credentials.h',
                       'src/core/lib/security/credentials/ssl/ssl_credentials.h',
+                      'src/core/lib/security/security_connector/alts_security_connector.h',
                       'src/core/lib/security/security_connector/security_connector.h',
                       'src/core/lib/security/transport/auth_filters.h',
                       'src/core/lib/security/transport/secure_endpoint.h',
@@ -278,15 +280,35 @@
                       'src/core/lib/security/transport/target_authority_table.h',
                       'src/core/lib/security/transport/tsi_error.h',
                       'src/core/lib/security/util/json_util.h',
-                      'src/core/tsi/alts_transport_security.h',
-                      'src/core/tsi/fake_transport_security.h',
-                      'src/core/tsi/ssl_transport_security.h',
-                      'src/core/tsi/ssl_types.h',
-                      'src/core/tsi/transport_security_grpc.h',
+                      'src/core/tsi/alts/crypt/gsec.h',
+                      'src/core/tsi/alts/frame_protector/alts_counter.h',
+                      'src/core/tsi/alts/frame_protector/alts_crypter.h',
+                      'src/core/tsi/alts/frame_protector/alts_frame_protector.h',
+                      'src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h',
+                      'src/core/tsi/alts/frame_protector/frame_handler.h',
+                      'src/core/tsi/alts/handshaker/alts_handshaker_client.h',
+                      'src/core/tsi/alts/handshaker/alts_tsi_event.h',
+                      'src/core/tsi/alts/handshaker/alts_tsi_handshaker.h',
+                      'src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h',
+                      'src/core/lib/security/credentials/alts/check_gcp_environment.h',
+                      'src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h',
+                      'src/core/tsi/alts/handshaker/alts_handshaker_service_api.h',
+                      'src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h',
+                      'src/core/tsi/alts/handshaker/alts_tsi_utils.h',
+                      'src/core/tsi/alts/handshaker/transport_security_common_api.h',
+                      'src/core/tsi/alts/handshaker/altscontext.pb.h',
+                      'src/core/tsi/alts/handshaker/handshaker.pb.h',
+                      'src/core/tsi/alts/handshaker/transport_security_common.pb.h',
                       'src/core/tsi/transport_security.h',
                       'src/core/tsi/transport_security_adapter.h',
                       'src/core/tsi/transport_security_interface.h',
-                      'src/core/ext/transport/chttp2/server/chttp2_server.h',
+                      'src/core/ext/transport/chttp2/client/chttp2_connector.h',
                       'src/core/ext/filters/client_channel/backup_poller.h',
                       'src/core/ext/filters/client_channel/client_channel.h',
                       'src/core/ext/filters/client_channel/client_channel_factory.h',
@@ -309,7 +331,12 @@
                       'src/core/ext/filters/client_channel/subchannel_index.h',
                       'src/core/ext/filters/client_channel/uri_parser.h',
                       'src/core/ext/filters/deadline/deadline_filter.h',
-                      'src/core/ext/transport/chttp2/client/chttp2_connector.h',
+                      'src/core/tsi/alts_transport_security.h',
+                      'src/core/tsi/fake_transport_security.h',
+                      'src/core/tsi/ssl_transport_security.h',
+                      'src/core/tsi/ssl_types.h',
+                      'src/core/tsi/transport_security_grpc.h',
+                      'src/core/ext/transport/chttp2/server/chttp2_server.h',
                       'src/core/ext/transport/inproc/inproc_transport.h',
                       'src/core/lib/avl/avl.h',
                       'src/core/lib/backoff/backoff.h',
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index 6c6c769..7f61719 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -93,7 +93,7 @@
   }
 
   s.default_subspecs = 'Interface', 'Implementation'
-  s.compiler_flags = '-DGRPC_ARES=0'
+  s.compiler_flags = '-DGRPC_ARES=0', '-DPB_FIELD_16BIT'
   s.libraries = 'c++'
 
   # Like many other C libraries, gRPC-Core has its public headers under `include/<libname>/` and its
@@ -271,6 +271,7 @@
                       'src/core/ext/filters/http/message_compress/message_compress_filter.h',
                       'src/core/ext/filters/http/server/http_server_filter.h',
                       'src/core/lib/security/context/security_context.h',
+                      'src/core/lib/security/credentials/alts/alts_credentials.h',
                       'src/core/lib/security/credentials/composite/composite_credentials.h',
                       'src/core/lib/security/credentials/credentials.h',
                       'src/core/lib/security/credentials/fake/fake_credentials.h',
@@ -282,6 +283,7 @@
                       'src/core/lib/security/credentials/oauth2/oauth2_credentials.h',
                       'src/core/lib/security/credentials/plugin/plugin_credentials.h',
                       'src/core/lib/security/credentials/ssl/ssl_credentials.h',
+                      'src/core/lib/security/security_connector/alts_security_connector.h',
                       'src/core/lib/security/security_connector/security_connector.h',
                       'src/core/lib/security/transport/auth_filters.h',
                       'src/core/lib/security/transport/secure_endpoint.h',
@@ -289,15 +291,35 @@
                       'src/core/lib/security/transport/target_authority_table.h',
                       'src/core/lib/security/transport/tsi_error.h',
                       'src/core/lib/security/util/json_util.h',
-                      'src/core/tsi/alts_transport_security.h',
-                      'src/core/tsi/fake_transport_security.h',
-                      'src/core/tsi/ssl_transport_security.h',
-                      'src/core/tsi/ssl_types.h',
-                      'src/core/tsi/transport_security_grpc.h',
+                      'src/core/tsi/alts/crypt/gsec.h',
+                      'src/core/tsi/alts/frame_protector/alts_counter.h',
+                      'src/core/tsi/alts/frame_protector/alts_crypter.h',
+                      'src/core/tsi/alts/frame_protector/alts_frame_protector.h',
+                      'src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h',
+                      'src/core/tsi/alts/frame_protector/frame_handler.h',
+                      'src/core/tsi/alts/handshaker/alts_handshaker_client.h',
+                      'src/core/tsi/alts/handshaker/alts_tsi_event.h',
+                      'src/core/tsi/alts/handshaker/alts_tsi_handshaker.h',
+                      'src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h',
+                      'src/core/lib/security/credentials/alts/check_gcp_environment.h',
+                      'src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h',
+                      'src/core/tsi/alts/handshaker/alts_handshaker_service_api.h',
+                      'src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h',
+                      'src/core/tsi/alts/handshaker/alts_tsi_utils.h',
+                      'src/core/tsi/alts/handshaker/transport_security_common_api.h',
+                      'src/core/tsi/alts/handshaker/altscontext.pb.h',
+                      'src/core/tsi/alts/handshaker/handshaker.pb.h',
+                      'src/core/tsi/alts/handshaker/transport_security_common.pb.h',
                       'src/core/tsi/transport_security.h',
                       'src/core/tsi/transport_security_adapter.h',
                       'src/core/tsi/transport_security_interface.h',
-                      'src/core/ext/transport/chttp2/server/chttp2_server.h',
+                      'src/core/ext/transport/chttp2/client/chttp2_connector.h',
                       'src/core/ext/filters/client_channel/backup_poller.h',
                       'src/core/ext/filters/client_channel/client_channel.h',
                       'src/core/ext/filters/client_channel/client_channel_factory.h',
@@ -320,7 +342,12 @@
                       'src/core/ext/filters/client_channel/subchannel_index.h',
                       'src/core/ext/filters/client_channel/uri_parser.h',
                       'src/core/ext/filters/deadline/deadline_filter.h',
-                      'src/core/ext/transport/chttp2/client/chttp2_connector.h',
+                      'src/core/tsi/alts_transport_security.h',
+                      'src/core/tsi/fake_transport_security.h',
+                      'src/core/tsi/ssl_transport_security.h',
+                      'src/core/tsi/ssl_types.h',
+                      'src/core/tsi/transport_security_grpc.h',
+                      'src/core/ext/transport/chttp2/server/chttp2_server.h',
                       'src/core/ext/transport/inproc/inproc_transport.h',
                       'src/core/lib/avl/avl.h',
                       'src/core/lib/backoff/backoff.h',
@@ -631,6 +658,7 @@
                       'src/core/ext/filters/http/server/http_server_filter.cc',
                       'src/core/lib/http/httpcli_security_connector.cc',
                       'src/core/lib/security/context/security_context.cc',
+                      'src/core/lib/security/credentials/alts/alts_credentials.cc',
                       'src/core/lib/security/credentials/composite/composite_credentials.cc',
                       'src/core/lib/security/credentials/credentials.cc',
                       'src/core/lib/security/credentials/credentials_metadata.cc',
@@ -644,6 +672,7 @@
                       'src/core/lib/security/credentials/oauth2/oauth2_credentials.cc',
                       'src/core/lib/security/credentials/plugin/plugin_credentials.cc',
                       'src/core/lib/security/credentials/ssl/ssl_credentials.cc',
+                      'src/core/lib/security/security_connector/alts_security_connector.cc',
                       'src/core/lib/security/security_connector/security_connector.cc',
                       'src/core/lib/security/transport/client_auth_filter.cc',
                       'src/core/lib/security/transport/secure_endpoint.cc',
@@ -653,14 +682,42 @@
                       'src/core/lib/security/transport/tsi_error.cc',
                       'src/core/lib/security/util/json_util.cc',
                       'src/core/lib/surface/init_secure.cc',
-                      'src/core/tsi/alts_transport_security.cc',
-                      'src/core/tsi/fake_transport_security.cc',
-                      'src/core/tsi/ssl_transport_security.cc',
-                      'src/core/tsi/transport_security_grpc.cc',
+                      'src/core/tsi/alts/crypt/aes_gcm.cc',
+                      'src/core/tsi/alts/crypt/gsec.cc',
+                      'src/core/tsi/alts/frame_protector/alts_counter.cc',
+                      'src/core/tsi/alts/frame_protector/alts_crypter.cc',
+                      'src/core/tsi/alts/frame_protector/alts_frame_protector.cc',
+                      'src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc',
+                      'src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc',
+                      'src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc',
+                      'src/core/tsi/alts/frame_protector/frame_handler.cc',
+                      'src/core/tsi/alts/handshaker/alts_handshaker_client.cc',
+                      'src/core/tsi/alts/handshaker/alts_tsi_event.cc',
+                      'src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc',
+                      'src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc',
+                      'src/core/lib/security/credentials/alts/check_gcp_environment.cc',
+                      'src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc',
+                      'src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc',
+                      'src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc',
+                      'src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc',
+                      'src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc',
+                      'src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc',
+                      'src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc',
+                      'src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc',
+                      'src/core/tsi/alts/handshaker/alts_tsi_utils.cc',
+                      'src/core/tsi/alts/handshaker/transport_security_common_api.cc',
+                      'src/core/tsi/alts/handshaker/altscontext.pb.c',
+                      'src/core/tsi/alts/handshaker/handshaker.pb.c',
+                      'src/core/tsi/alts/handshaker/transport_security_common.pb.c',
                       'src/core/tsi/transport_security.cc',
                       'src/core/tsi/transport_security_adapter.cc',
-                      'src/core/ext/transport/chttp2/server/chttp2_server.cc',
-                      'src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc',
+                      'src/core/ext/transport/chttp2/client/insecure/channel_create.cc',
+                      'src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc',
+                      'src/core/ext/transport/chttp2/client/chttp2_connector.cc',
                       'src/core/ext/filters/client_channel/backup_poller.cc',
                       'src/core/ext/filters/client_channel/channel_connectivity.cc',
                       'src/core/ext/filters/client_channel/client_channel.cc',
@@ -684,11 +741,14 @@
                       'src/core/ext/filters/client_channel/subchannel_index.cc',
                       'src/core/ext/filters/client_channel/uri_parser.cc',
                       'src/core/ext/filters/deadline/deadline_filter.cc',
-                      'src/core/ext/transport/chttp2/client/chttp2_connector.cc',
+                      'src/core/tsi/alts_transport_security.cc',
+                      'src/core/tsi/fake_transport_security.cc',
+                      'src/core/tsi/ssl_transport_security.cc',
+                      'src/core/tsi/transport_security_grpc.cc',
+                      'src/core/ext/transport/chttp2/server/chttp2_server.cc',
+                      'src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc',
                       'src/core/ext/transport/chttp2/server/insecure/server_chttp2.cc',
                       'src/core/ext/transport/chttp2/server/insecure/server_chttp2_posix.cc',
-                      'src/core/ext/transport/chttp2/client/insecure/channel_create.cc',
-                      'src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc',
                       'src/core/ext/transport/inproc/inproc_plugin.cc',
                       'src/core/ext/transport/inproc/inproc_transport.cc',
                       'src/core/ext/filters/client_channel/lb_policy/grpclb/client_load_reporting_filter.cc',
@@ -765,6 +825,7 @@
                               'src/core/ext/filters/http/message_compress/message_compress_filter.h',
                               'src/core/ext/filters/http/server/http_server_filter.h',
                               'src/core/lib/security/context/security_context.h',
+                              'src/core/lib/security/credentials/alts/alts_credentials.h',
                               'src/core/lib/security/credentials/composite/composite_credentials.h',
                               'src/core/lib/security/credentials/credentials.h',
                               'src/core/lib/security/credentials/fake/fake_credentials.h',
@@ -776,6 +837,7 @@
                               'src/core/lib/security/credentials/oauth2/oauth2_credentials.h',
                               'src/core/lib/security/credentials/plugin/plugin_credentials.h',
                               'src/core/lib/security/credentials/ssl/ssl_credentials.h',
+                              'src/core/lib/security/security_connector/alts_security_connector.h',
                               'src/core/lib/security/security_connector/security_connector.h',
                               'src/core/lib/security/transport/auth_filters.h',
                               'src/core/lib/security/transport/secure_endpoint.h',
@@ -783,15 +845,35 @@
                               'src/core/lib/security/transport/target_authority_table.h',
                               'src/core/lib/security/transport/tsi_error.h',
                               'src/core/lib/security/util/json_util.h',
-                              'src/core/tsi/alts_transport_security.h',
-                              'src/core/tsi/fake_transport_security.h',
-                              'src/core/tsi/ssl_transport_security.h',
-                              'src/core/tsi/ssl_types.h',
-                              'src/core/tsi/transport_security_grpc.h',
+                              'src/core/tsi/alts/crypt/gsec.h',
+                              'src/core/tsi/alts/frame_protector/alts_counter.h',
+                              'src/core/tsi/alts/frame_protector/alts_crypter.h',
+                              'src/core/tsi/alts/frame_protector/alts_frame_protector.h',
+                              'src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h',
+                              'src/core/tsi/alts/frame_protector/frame_handler.h',
+                              'src/core/tsi/alts/handshaker/alts_handshaker_client.h',
+                              'src/core/tsi/alts/handshaker/alts_tsi_event.h',
+                              'src/core/tsi/alts/handshaker/alts_tsi_handshaker.h',
+                              'src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h',
+                              'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h',
+                              'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h',
+                              'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h',
+                              'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h',
+                              'src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h',
+                              'src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h',
+                              'src/core/lib/security/credentials/alts/check_gcp_environment.h',
+                              'src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h',
+                              'src/core/tsi/alts/handshaker/alts_handshaker_service_api.h',
+                              'src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h',
+                              'src/core/tsi/alts/handshaker/alts_tsi_utils.h',
+                              'src/core/tsi/alts/handshaker/transport_security_common_api.h',
+                              'src/core/tsi/alts/handshaker/altscontext.pb.h',
+                              'src/core/tsi/alts/handshaker/handshaker.pb.h',
+                              'src/core/tsi/alts/handshaker/transport_security_common.pb.h',
                               'src/core/tsi/transport_security.h',
                               'src/core/tsi/transport_security_adapter.h',
                               'src/core/tsi/transport_security_interface.h',
-                              'src/core/ext/transport/chttp2/server/chttp2_server.h',
+                              'src/core/ext/transport/chttp2/client/chttp2_connector.h',
                               'src/core/ext/filters/client_channel/backup_poller.h',
                               'src/core/ext/filters/client_channel/client_channel.h',
                               'src/core/ext/filters/client_channel/client_channel_factory.h',
@@ -814,7 +896,12 @@
                               'src/core/ext/filters/client_channel/subchannel_index.h',
                               'src/core/ext/filters/client_channel/uri_parser.h',
                               'src/core/ext/filters/deadline/deadline_filter.h',
-                              'src/core/ext/transport/chttp2/client/chttp2_connector.h',
+                              'src/core/tsi/alts_transport_security.h',
+                              'src/core/tsi/fake_transport_security.h',
+                              'src/core/tsi/ssl_transport_security.h',
+                              'src/core/tsi/ssl_types.h',
+                              'src/core/tsi/transport_security_grpc.h',
+                              'src/core/ext/transport/chttp2/server/chttp2_server.h',
                               'src/core/ext/transport/inproc/inproc_transport.h',
                               'src/core/lib/avl/avl.h',
                               'src/core/lib/backoff/backoff.h',
@@ -975,8 +1062,15 @@
 
     ss.source_files = 'src/core/ext/transport/cronet/client/secure/cronet_channel_create.cc',
                       'src/core/ext/transport/cronet/transport/cronet_transport.cc',
+                      'third_party/nanopb/pb_common.c',
+                      'third_party/nanopb/pb_decode.c',
+                      'third_party/nanopb/pb_encode.c',
                       'src/core/ext/transport/cronet/transport/cronet_transport.h',
-                      'third_party/objective_c/Cronet/bidirectional_stream_c.h'
+                      'third_party/objective_c/Cronet/bidirectional_stream_c.h',
+                      'third_party/nanopb/pb.h',
+                      'third_party/nanopb/pb_common.h',
+                      'third_party/nanopb/pb_decode.h',
+                      'third_party/nanopb/pb_encode.h'
   end
 
   s.subspec 'Tests' do |ss|
diff --git a/grpc.gemspec b/grpc.gemspec
index fbe70aa..3df7cea 100644
--- a/grpc.gemspec
+++ b/grpc.gemspec
@@ -197,6 +197,7 @@
   s.files += %w( src/core/ext/filters/http/message_compress/message_compress_filter.h )
   s.files += %w( src/core/ext/filters/http/server/http_server_filter.h )
   s.files += %w( src/core/lib/security/context/security_context.h )
+  s.files += %w( src/core/lib/security/credentials/alts/alts_credentials.h )
   s.files += %w( src/core/lib/security/credentials/composite/composite_credentials.h )
   s.files += %w( src/core/lib/security/credentials/credentials.h )
   s.files += %w( src/core/lib/security/credentials/fake/fake_credentials.h )
@@ -208,6 +209,7 @@
   s.files += %w( src/core/lib/security/credentials/oauth2/oauth2_credentials.h )
   s.files += %w( src/core/lib/security/credentials/plugin/plugin_credentials.h )
   s.files += %w( src/core/lib/security/credentials/ssl/ssl_credentials.h )
+  s.files += %w( src/core/lib/security/security_connector/alts_security_connector.h )
   s.files += %w( src/core/lib/security/security_connector/security_connector.h )
   s.files += %w( src/core/lib/security/transport/auth_filters.h )
   s.files += %w( src/core/lib/security/transport/secure_endpoint.h )
@@ -215,15 +217,39 @@
   s.files += %w( src/core/lib/security/transport/target_authority_table.h )
   s.files += %w( src/core/lib/security/transport/tsi_error.h )
   s.files += %w( src/core/lib/security/util/json_util.h )
-  s.files += %w( src/core/tsi/alts_transport_security.h )
-  s.files += %w( src/core/tsi/fake_transport_security.h )
-  s.files += %w( src/core/tsi/ssl_transport_security.h )
-  s.files += %w( src/core/tsi/ssl_types.h )
-  s.files += %w( src/core/tsi/transport_security_grpc.h )
+  s.files += %w( src/core/tsi/alts/crypt/gsec.h )
+  s.files += %w( src/core/tsi/alts/frame_protector/alts_counter.h )
+  s.files += %w( src/core/tsi/alts/frame_protector/alts_crypter.h )
+  s.files += %w( src/core/tsi/alts/frame_protector/alts_frame_protector.h )
+  s.files += %w( src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h )
+  s.files += %w( src/core/tsi/alts/frame_protector/frame_handler.h )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_handshaker_client.h )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_tsi_event.h )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_tsi_handshaker.h )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h )
+  s.files += %w( src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h )
+  s.files += %w( src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h )
+  s.files += %w( src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h )
+  s.files += %w( src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h )
+  s.files += %w( src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h )
+  s.files += %w( src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h )
+  s.files += %w( src/core/lib/security/credentials/alts/check_gcp_environment.h )
+  s.files += %w( src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_handshaker_service_api.h )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_tsi_utils.h )
+  s.files += %w( src/core/tsi/alts/handshaker/transport_security_common_api.h )
+  s.files += %w( src/core/tsi/alts/handshaker/altscontext.pb.h )
+  s.files += %w( src/core/tsi/alts/handshaker/handshaker.pb.h )
+  s.files += %w( src/core/tsi/alts/handshaker/transport_security_common.pb.h )
+  s.files += %w( third_party/nanopb/pb.h )
+  s.files += %w( third_party/nanopb/pb_common.h )
+  s.files += %w( third_party/nanopb/pb_decode.h )
+  s.files += %w( third_party/nanopb/pb_encode.h )
   s.files += %w( src/core/tsi/transport_security.h )
   s.files += %w( src/core/tsi/transport_security_adapter.h )
   s.files += %w( src/core/tsi/transport_security_interface.h )
-  s.files += %w( src/core/ext/transport/chttp2/server/chttp2_server.h )
+  s.files += %w( src/core/ext/transport/chttp2/client/chttp2_connector.h )
   s.files += %w( src/core/ext/filters/client_channel/backup_poller.h )
   s.files += %w( src/core/ext/filters/client_channel/client_channel.h )
   s.files += %w( src/core/ext/filters/client_channel/client_channel_factory.h )
@@ -246,7 +272,12 @@
   s.files += %w( src/core/ext/filters/client_channel/subchannel_index.h )
   s.files += %w( src/core/ext/filters/client_channel/uri_parser.h )
   s.files += %w( src/core/ext/filters/deadline/deadline_filter.h )
-  s.files += %w( src/core/ext/transport/chttp2/client/chttp2_connector.h )
+  s.files += %w( src/core/tsi/alts_transport_security.h )
+  s.files += %w( src/core/tsi/fake_transport_security.h )
+  s.files += %w( src/core/tsi/ssl_transport_security.h )
+  s.files += %w( src/core/tsi/ssl_types.h )
+  s.files += %w( src/core/tsi/transport_security_grpc.h )
+  s.files += %w( src/core/ext/transport/chttp2/server/chttp2_server.h )
   s.files += %w( src/core/ext/transport/inproc/inproc_transport.h )
   s.files += %w( src/core/lib/avl/avl.h )
   s.files += %w( src/core/lib/backoff/backoff.h )
@@ -381,10 +412,6 @@
   s.files += %w( src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.h )
   s.files += %w( src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.h )
   s.files += %w( src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h )
-  s.files += %w( third_party/nanopb/pb.h )
-  s.files += %w( third_party/nanopb/pb_common.h )
-  s.files += %w( third_party/nanopb/pb_decode.h )
-  s.files += %w( third_party/nanopb/pb_encode.h )
   s.files += %w( src/core/ext/filters/client_channel/resolver/fake/fake_resolver.h )
   s.files += %w( src/core/ext/filters/client_channel/lb_policy/subchannel_list.h )
   s.files += %w( src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h )
@@ -561,6 +588,7 @@
   s.files += %w( src/core/ext/filters/http/server/http_server_filter.cc )
   s.files += %w( src/core/lib/http/httpcli_security_connector.cc )
   s.files += %w( src/core/lib/security/context/security_context.cc )
+  s.files += %w( src/core/lib/security/credentials/alts/alts_credentials.cc )
   s.files += %w( src/core/lib/security/credentials/composite/composite_credentials.cc )
   s.files += %w( src/core/lib/security/credentials/credentials.cc )
   s.files += %w( src/core/lib/security/credentials/credentials_metadata.cc )
@@ -574,6 +602,7 @@
   s.files += %w( src/core/lib/security/credentials/oauth2/oauth2_credentials.cc )
   s.files += %w( src/core/lib/security/credentials/plugin/plugin_credentials.cc )
   s.files += %w( src/core/lib/security/credentials/ssl/ssl_credentials.cc )
+  s.files += %w( src/core/lib/security/security_connector/alts_security_connector.cc )
   s.files += %w( src/core/lib/security/security_connector/security_connector.cc )
   s.files += %w( src/core/lib/security/transport/client_auth_filter.cc )
   s.files += %w( src/core/lib/security/transport/secure_endpoint.cc )
@@ -583,14 +612,45 @@
   s.files += %w( src/core/lib/security/transport/tsi_error.cc )
   s.files += %w( src/core/lib/security/util/json_util.cc )
   s.files += %w( src/core/lib/surface/init_secure.cc )
-  s.files += %w( src/core/tsi/alts_transport_security.cc )
-  s.files += %w( src/core/tsi/fake_transport_security.cc )
-  s.files += %w( src/core/tsi/ssl_transport_security.cc )
-  s.files += %w( src/core/tsi/transport_security_grpc.cc )
+  s.files += %w( src/core/tsi/alts/crypt/aes_gcm.cc )
+  s.files += %w( src/core/tsi/alts/crypt/gsec.cc )
+  s.files += %w( src/core/tsi/alts/frame_protector/alts_counter.cc )
+  s.files += %w( src/core/tsi/alts/frame_protector/alts_crypter.cc )
+  s.files += %w( src/core/tsi/alts/frame_protector/alts_frame_protector.cc )
+  s.files += %w( src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc )
+  s.files += %w( src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc )
+  s.files += %w( src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc )
+  s.files += %w( src/core/tsi/alts/frame_protector/frame_handler.cc )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_handshaker_client.cc )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_tsi_event.cc )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc )
+  s.files += %w( src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc )
+  s.files += %w( src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc )
+  s.files += %w( src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc )
+  s.files += %w( src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc )
+  s.files += %w( src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc )
+  s.files += %w( src/core/lib/security/credentials/alts/check_gcp_environment.cc )
+  s.files += %w( src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc )
+  s.files += %w( src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc )
+  s.files += %w( src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc )
+  s.files += %w( src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc )
+  s.files += %w( src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc )
+  s.files += %w( src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc )
+  s.files += %w( src/core/tsi/alts/handshaker/alts_tsi_utils.cc )
+  s.files += %w( src/core/tsi/alts/handshaker/transport_security_common_api.cc )
+  s.files += %w( src/core/tsi/alts/handshaker/altscontext.pb.c )
+  s.files += %w( src/core/tsi/alts/handshaker/handshaker.pb.c )
+  s.files += %w( src/core/tsi/alts/handshaker/transport_security_common.pb.c )
+  s.files += %w( third_party/nanopb/pb_common.c )
+  s.files += %w( third_party/nanopb/pb_decode.c )
+  s.files += %w( third_party/nanopb/pb_encode.c )
   s.files += %w( src/core/tsi/transport_security.cc )
   s.files += %w( src/core/tsi/transport_security_adapter.cc )
-  s.files += %w( src/core/ext/transport/chttp2/server/chttp2_server.cc )
-  s.files += %w( src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc )
+  s.files += %w( src/core/ext/transport/chttp2/client/insecure/channel_create.cc )
+  s.files += %w( src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc )
+  s.files += %w( src/core/ext/transport/chttp2/client/chttp2_connector.cc )
   s.files += %w( src/core/ext/filters/client_channel/backup_poller.cc )
   s.files += %w( src/core/ext/filters/client_channel/channel_connectivity.cc )
   s.files += %w( src/core/ext/filters/client_channel/client_channel.cc )
@@ -614,11 +674,14 @@
   s.files += %w( src/core/ext/filters/client_channel/subchannel_index.cc )
   s.files += %w( src/core/ext/filters/client_channel/uri_parser.cc )
   s.files += %w( src/core/ext/filters/deadline/deadline_filter.cc )
-  s.files += %w( src/core/ext/transport/chttp2/client/chttp2_connector.cc )
+  s.files += %w( src/core/tsi/alts_transport_security.cc )
+  s.files += %w( src/core/tsi/fake_transport_security.cc )
+  s.files += %w( src/core/tsi/ssl_transport_security.cc )
+  s.files += %w( src/core/tsi/transport_security_grpc.cc )
+  s.files += %w( src/core/ext/transport/chttp2/server/chttp2_server.cc )
+  s.files += %w( src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc )
   s.files += %w( src/core/ext/transport/chttp2/server/insecure/server_chttp2.cc )
   s.files += %w( src/core/ext/transport/chttp2/server/insecure/server_chttp2_posix.cc )
-  s.files += %w( src/core/ext/transport/chttp2/client/insecure/channel_create.cc )
-  s.files += %w( src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc )
   s.files += %w( src/core/ext/transport/inproc/inproc_plugin.cc )
   s.files += %w( src/core/ext/transport/inproc/inproc_transport.cc )
   s.files += %w( src/core/ext/filters/client_channel/lb_policy/grpclb/client_load_reporting_filter.cc )
@@ -627,9 +690,6 @@
   s.files += %w( src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.cc )
   s.files += %w( src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.cc )
   s.files += %w( src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c )
-  s.files += %w( third_party/nanopb/pb_common.c )
-  s.files += %w( third_party/nanopb/pb_decode.c )
-  s.files += %w( third_party/nanopb/pb_encode.c )
   s.files += %w( src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc )
   s.files += %w( src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc )
   s.files += %w( src/core/ext/filters/client_channel/lb_policy/subchannel_list.cc )
diff --git a/grpc.gyp b/grpc.gyp
index cd3dedd..38597a5 100644
--- a/grpc.gyp
+++ b/grpc.gyp
@@ -64,11 +64,11 @@
     ],
     'cflags_c': [
       '-Werror',
-      '-std=c99'
+      '-std=c99',
     ],
     'cflags_cc': [
       '-Werror',
-      '-std=c++11'
+      '-std=c++11',
     ],
     'include_dirs': [
       '.',
@@ -148,7 +148,7 @@
             '-Wno-deprecated-declarations',
             '-stdlib=libc++',
             '-std=c++11',
-            '-Wno-error=deprecated-declarations'
+            '-Wno-error=deprecated-declarations',
           ],
         },
       }]
@@ -156,6 +156,17 @@
   },
   'targets': [
     {
+      'target_name': 'alts_test_util',
+      'type': 'static_library',
+      'dependencies': [
+        'grpc',
+      ],
+      'sources': [
+        'test/core/tsi/alts/crypt/gsec_test_util.cc',
+        'test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.cc',
+      ],
+    },
+    {
       'target_name': 'gpr',
       'type': 'static_library',
       'dependencies': [
@@ -385,6 +396,7 @@
         'src/core/ext/filters/http/server/http_server_filter.cc',
         'src/core/lib/http/httpcli_security_connector.cc',
         'src/core/lib/security/context/security_context.cc',
+        'src/core/lib/security/credentials/alts/alts_credentials.cc',
         'src/core/lib/security/credentials/composite/composite_credentials.cc',
         'src/core/lib/security/credentials/credentials.cc',
         'src/core/lib/security/credentials/credentials_metadata.cc',
@@ -398,6 +410,7 @@
         'src/core/lib/security/credentials/oauth2/oauth2_credentials.cc',
         'src/core/lib/security/credentials/plugin/plugin_credentials.cc',
         'src/core/lib/security/credentials/ssl/ssl_credentials.cc',
+        'src/core/lib/security/security_connector/alts_security_connector.cc',
         'src/core/lib/security/security_connector/security_connector.cc',
         'src/core/lib/security/transport/client_auth_filter.cc',
         'src/core/lib/security/transport/secure_endpoint.cc',
@@ -407,14 +420,45 @@
         'src/core/lib/security/transport/tsi_error.cc',
         'src/core/lib/security/util/json_util.cc',
         'src/core/lib/surface/init_secure.cc',
-        'src/core/tsi/alts_transport_security.cc',
-        'src/core/tsi/fake_transport_security.cc',
-        'src/core/tsi/ssl_transport_security.cc',
-        'src/core/tsi/transport_security_grpc.cc',
+        'src/core/tsi/alts/crypt/aes_gcm.cc',
+        'src/core/tsi/alts/crypt/gsec.cc',
+        'src/core/tsi/alts/frame_protector/alts_counter.cc',
+        'src/core/tsi/alts/frame_protector/alts_crypter.cc',
+        'src/core/tsi/alts/frame_protector/alts_frame_protector.cc',
+        'src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc',
+        'src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc',
+        'src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc',
+        'src/core/tsi/alts/frame_protector/frame_handler.cc',
+        'src/core/tsi/alts/handshaker/alts_handshaker_client.cc',
+        'src/core/tsi/alts/handshaker/alts_tsi_event.cc',
+        'src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc',
+        'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc',
+        'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc',
+        'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc',
+        'src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc',
+        'src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc',
+        'src/core/lib/security/credentials/alts/check_gcp_environment.cc',
+        'src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc',
+        'src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc',
+        'src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc',
+        'src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc',
+        'src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc',
+        'src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc',
+        'src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc',
+        'src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc',
+        'src/core/tsi/alts/handshaker/alts_tsi_utils.cc',
+        'src/core/tsi/alts/handshaker/transport_security_common_api.cc',
+        'src/core/tsi/alts/handshaker/altscontext.pb.c',
+        'src/core/tsi/alts/handshaker/handshaker.pb.c',
+        'src/core/tsi/alts/handshaker/transport_security_common.pb.c',
+        'third_party/nanopb/pb_common.c',
+        'third_party/nanopb/pb_decode.c',
+        'third_party/nanopb/pb_encode.c',
         'src/core/tsi/transport_security.cc',
         'src/core/tsi/transport_security_adapter.cc',
-        'src/core/ext/transport/chttp2/server/chttp2_server.cc',
-        'src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc',
+        'src/core/ext/transport/chttp2/client/insecure/channel_create.cc',
+        'src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc',
+        'src/core/ext/transport/chttp2/client/chttp2_connector.cc',
         'src/core/ext/filters/client_channel/backup_poller.cc',
         'src/core/ext/filters/client_channel/channel_connectivity.cc',
         'src/core/ext/filters/client_channel/client_channel.cc',
@@ -438,11 +482,14 @@
         'src/core/ext/filters/client_channel/subchannel_index.cc',
         'src/core/ext/filters/client_channel/uri_parser.cc',
         'src/core/ext/filters/deadline/deadline_filter.cc',
-        'src/core/ext/transport/chttp2/client/chttp2_connector.cc',
+        'src/core/tsi/alts_transport_security.cc',
+        'src/core/tsi/fake_transport_security.cc',
+        'src/core/tsi/ssl_transport_security.cc',
+        'src/core/tsi/transport_security_grpc.cc',
+        'src/core/ext/transport/chttp2/server/chttp2_server.cc',
+        'src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc',
         'src/core/ext/transport/chttp2/server/insecure/server_chttp2.cc',
         'src/core/ext/transport/chttp2/server/insecure/server_chttp2_posix.cc',
-        'src/core/ext/transport/chttp2/client/insecure/channel_create.cc',
-        'src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc',
         'src/core/ext/transport/inproc/inproc_plugin.cc',
         'src/core/ext/transport/inproc/inproc_transport.cc',
         'src/core/ext/filters/client_channel/lb_policy/grpclb/client_load_reporting_filter.cc',
@@ -451,9 +498,6 @@
         'src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.cc',
         'src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.cc',
         'src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c',
-        'third_party/nanopb/pb_common.c',
-        'third_party/nanopb/pb_decode.c',
-        'third_party/nanopb/pb_encode.c',
         'src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc',
         'src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc',
         'src/core/ext/filters/client_channel/lb_policy/subchannel_list.cc',
diff --git a/package.xml b/package.xml
index db03230..c4a6f6f 100644
--- a/package.xml
+++ b/package.xml
@@ -204,6 +204,7 @@
     <file baseinstalldir="/" name="src/core/ext/filters/http/message_compress/message_compress_filter.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/http/server/http_server_filter.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/context/security_context.h" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/credentials/alts/alts_credentials.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/credentials/composite/composite_credentials.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/credentials/credentials.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/credentials/fake/fake_credentials.h" role="src" />
@@ -215,6 +216,7 @@
     <file baseinstalldir="/" name="src/core/lib/security/credentials/oauth2/oauth2_credentials.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/credentials/plugin/plugin_credentials.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/credentials/ssl/ssl_credentials.h" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/security_connector/alts_security_connector.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/security_connector/security_connector.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/transport/auth_filters.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/transport/secure_endpoint.h" role="src" />
@@ -222,15 +224,39 @@
     <file baseinstalldir="/" name="src/core/lib/security/transport/target_authority_table.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/transport/tsi_error.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/util/json_util.h" role="src" />
-    <file baseinstalldir="/" name="src/core/tsi/alts_transport_security.h" role="src" />
-    <file baseinstalldir="/" name="src/core/tsi/fake_transport_security.h" role="src" />
-    <file baseinstalldir="/" name="src/core/tsi/ssl_transport_security.h" role="src" />
-    <file baseinstalldir="/" name="src/core/tsi/ssl_types.h" role="src" />
-    <file baseinstalldir="/" name="src/core/tsi/transport_security_grpc.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/crypt/gsec.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/alts_counter.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/alts_crypter.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/alts_frame_protector.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/frame_handler.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_handshaker_client.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_tsi_event.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_tsi_handshaker.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/credentials/alts/check_gcp_environment.h" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_handshaker_service_api.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_tsi_utils.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/transport_security_common_api.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/altscontext.pb.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/handshaker.pb.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/transport_security_common.pb.h" role="src" />
+    <file baseinstalldir="/" name="third_party/nanopb/pb.h" role="src" />
+    <file baseinstalldir="/" name="third_party/nanopb/pb_common.h" role="src" />
+    <file baseinstalldir="/" name="third_party/nanopb/pb_decode.h" role="src" />
+    <file baseinstalldir="/" name="third_party/nanopb/pb_encode.h" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/transport_security.h" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/transport_security_adapter.h" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/transport_security_interface.h" role="src" />
-    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/server/chttp2_server.h" role="src" />
+    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/client/chttp2_connector.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/backup_poller.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/client_channel.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/client_channel_factory.h" role="src" />
@@ -253,7 +279,12 @@
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/subchannel_index.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/uri_parser.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/deadline/deadline_filter.h" role="src" />
-    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/client/chttp2_connector.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts_transport_security.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/fake_transport_security.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/ssl_transport_security.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/ssl_types.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/transport_security_grpc.h" role="src" />
+    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/server/chttp2_server.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/transport/inproc/inproc_transport.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/avl/avl.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/backoff/backoff.h" role="src" />
@@ -388,10 +419,6 @@
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h" role="src" />
-    <file baseinstalldir="/" name="third_party/nanopb/pb.h" role="src" />
-    <file baseinstalldir="/" name="third_party/nanopb/pb_common.h" role="src" />
-    <file baseinstalldir="/" name="third_party/nanopb/pb_decode.h" role="src" />
-    <file baseinstalldir="/" name="third_party/nanopb/pb_encode.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/fake/fake_resolver.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/subchannel_list.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h" role="src" />
@@ -568,6 +595,7 @@
     <file baseinstalldir="/" name="src/core/ext/filters/http/server/http_server_filter.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/http/httpcli_security_connector.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/context/security_context.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/credentials/alts/alts_credentials.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/credentials/composite/composite_credentials.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/credentials/credentials.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/credentials/credentials_metadata.cc" role="src" />
@@ -581,6 +609,7 @@
     <file baseinstalldir="/" name="src/core/lib/security/credentials/oauth2/oauth2_credentials.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/credentials/plugin/plugin_credentials.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/credentials/ssl/ssl_credentials.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/security_connector/alts_security_connector.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/security_connector/security_connector.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/transport/client_auth_filter.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/transport/secure_endpoint.cc" role="src" />
@@ -590,14 +619,45 @@
     <file baseinstalldir="/" name="src/core/lib/security/transport/tsi_error.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/security/util/json_util.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/surface/init_secure.cc" role="src" />
-    <file baseinstalldir="/" name="src/core/tsi/alts_transport_security.cc" role="src" />
-    <file baseinstalldir="/" name="src/core/tsi/fake_transport_security.cc" role="src" />
-    <file baseinstalldir="/" name="src/core/tsi/ssl_transport_security.cc" role="src" />
-    <file baseinstalldir="/" name="src/core/tsi/transport_security_grpc.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/crypt/aes_gcm.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/crypt/gsec.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/alts_counter.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/alts_crypter.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/alts_frame_protector.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/frame_protector/frame_handler.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_handshaker_client.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_tsi_event.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/credentials/alts/check_gcp_environment.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/alts_tsi_utils.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/transport_security_common_api.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/altscontext.pb.c" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/handshaker.pb.c" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts/handshaker/transport_security_common.pb.c" role="src" />
+    <file baseinstalldir="/" name="third_party/nanopb/pb_common.c" role="src" />
+    <file baseinstalldir="/" name="third_party/nanopb/pb_decode.c" role="src" />
+    <file baseinstalldir="/" name="third_party/nanopb/pb_encode.c" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/transport_security.cc" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/transport_security_adapter.cc" role="src" />
-    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/server/chttp2_server.cc" role="src" />
-    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/client/insecure/channel_create.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/client/chttp2_connector.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/backup_poller.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/channel_connectivity.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/client_channel.cc" role="src" />
@@ -621,11 +681,14 @@
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/subchannel_index.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/uri_parser.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/deadline/deadline_filter.cc" role="src" />
-    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/client/chttp2_connector.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/alts_transport_security.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/fake_transport_security.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/ssl_transport_security.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/transport_security_grpc.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/server/chttp2_server.cc" role="src" />
+    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/transport/chttp2/server/insecure/server_chttp2.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/transport/chttp2/server/insecure/server_chttp2_posix.cc" role="src" />
-    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/client/insecure/channel_create.cc" role="src" />
-    <file baseinstalldir="/" name="src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/transport/inproc/inproc_plugin.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/transport/inproc/inproc_transport.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/grpclb/client_load_reporting_filter.cc" role="src" />
@@ -634,9 +697,6 @@
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c" role="src" />
-    <file baseinstalldir="/" name="third_party/nanopb/pb_common.c" role="src" />
-    <file baseinstalldir="/" name="third_party/nanopb/pb_decode.c" role="src" />
-    <file baseinstalldir="/" name="third_party/nanopb/pb_encode.c" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc" role="src" />
     <file baseinstalldir="/" name="src/core/ext/filters/client_channel/lb_policy/subchannel_list.cc" role="src" />
diff --git a/setup.py b/setup.py
index 4f67f82..7c07c56 100644
--- a/setup.py
+++ b/setup.py
@@ -118,6 +118,7 @@
     EXTRA_ENV_COMPILE_ARGS += ' -std=c++11 -std=gnu99 -fvisibility=hidden -fno-wrapv -fno-exceptions'
   elif "darwin" in sys.platform:
     EXTRA_ENV_COMPILE_ARGS += ' -fvisibility=hidden -fno-wrapv -fno-exceptions'
+EXTRA_ENV_COMPILE_ARGS += ' -DPB_FIELD_16BIT'	
 
 if EXTRA_ENV_LINK_ARGS is None:
   EXTRA_ENV_LINK_ARGS = ''
@@ -160,7 +161,7 @@
 
 DEFINE_MACROS = (
     ('OPENSSL_NO_ASM', 1), ('_WIN32_WINNT', 0x600),
-    ('GPR_BACKWARDS_COMPATIBILITY_MODE', 1),)
+    ('GPR_BACKWARDS_COMPATIBILITY_MODE', 1))
 if "win32" in sys.platform:
   # TODO(zyc): Re-enble c-ares on x64 and x86 windows after fixing the
   # ares_library_init compilation issue
diff --git a/src/core/lib/security/credentials/alts/alts_credentials.cc b/src/core/lib/security/credentials/alts/alts_credentials.cc
new file mode 100644
index 0000000..fa05d90
--- /dev/null
+++ b/src/core/lib/security/credentials/alts/alts_credentials.cc
@@ -0,0 +1,119 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/lib/security/credentials/alts/alts_credentials.h"
+
+#include <cstring>
+
+#include <grpc/grpc.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+
+#include "src/core/lib/security/credentials/alts/check_gcp_environment.h"
+#include "src/core/lib/security/security_connector/alts_security_connector.h"
+
+#define GRPC_CREDENTIALS_TYPE_ALTS "Alts"
+#define GRPC_ALTS_HANDSHAKER_SERVICE_URL "metadata.google.internal:8080"
+
+static void alts_credentials_destruct(grpc_channel_credentials* creds) {
+  grpc_alts_credentials* alts_creds =
+      reinterpret_cast<grpc_alts_credentials*>(creds);
+  grpc_alts_credentials_options_destroy(alts_creds->options);
+  gpr_free(alts_creds->handshaker_service_url);
+}
+
+static void alts_server_credentials_destruct(grpc_server_credentials* creds) {
+  grpc_alts_server_credentials* alts_creds =
+      reinterpret_cast<grpc_alts_server_credentials*>(creds);
+  grpc_alts_credentials_options_destroy(alts_creds->options);
+  gpr_free(alts_creds->handshaker_service_url);
+}
+
+static grpc_security_status alts_create_security_connector(
+    grpc_channel_credentials* creds,
+    grpc_call_credentials* request_metadata_creds, const char* target_name,
+    const grpc_channel_args* args, grpc_channel_security_connector** sc,
+    grpc_channel_args** new_args) {
+  return grpc_alts_channel_security_connector_create(
+      creds, request_metadata_creds, target_name, sc);
+}
+
+static grpc_security_status alts_server_create_security_connector(
+    grpc_server_credentials* creds, grpc_server_security_connector** sc) {
+  return grpc_alts_server_security_connector_create(creds, sc);
+}
+
+static const grpc_channel_credentials_vtable alts_credentials_vtable = {
+    alts_credentials_destruct, alts_create_security_connector,
+    /*duplicate_without_call_credentials=*/nullptr};
+
+static const grpc_server_credentials_vtable alts_server_credentials_vtable = {
+    alts_server_credentials_destruct, alts_server_create_security_connector};
+
+grpc_channel_credentials* grpc_alts_credentials_create_customized(
+    const grpc_alts_credentials_options* options,
+    const char* handshaker_service_url, bool enable_untrusted_alts) {
+  if (!enable_untrusted_alts && !grpc_alts_is_running_on_gcp()) {
+    return nullptr;
+  }
+  auto creds = static_cast<grpc_alts_credentials*>(
+      gpr_zalloc(sizeof(grpc_alts_credentials)));
+  creds->options = grpc_alts_credentials_options_copy(options);
+  creds->handshaker_service_url =
+      handshaker_service_url == nullptr
+          ? gpr_strdup(GRPC_ALTS_HANDSHAKER_SERVICE_URL)
+          : gpr_strdup(handshaker_service_url);
+  creds->base.type = GRPC_CREDENTIALS_TYPE_ALTS;
+  creds->base.vtable = &alts_credentials_vtable;
+  gpr_ref_init(&creds->base.refcount, 1);
+  return &creds->base;
+}
+
+grpc_server_credentials* grpc_alts_server_credentials_create_customized(
+    const grpc_alts_credentials_options* options,
+    const char* handshaker_service_url, bool enable_untrusted_alts) {
+  if (!enable_untrusted_alts && !grpc_alts_is_running_on_gcp()) {
+    return nullptr;
+  }
+  auto creds = static_cast<grpc_alts_server_credentials*>(
+      gpr_zalloc(sizeof(grpc_alts_server_credentials)));
+  creds->options = grpc_alts_credentials_options_copy(options);
+  creds->handshaker_service_url =
+      handshaker_service_url == nullptr
+          ? gpr_strdup(GRPC_ALTS_HANDSHAKER_SERVICE_URL)
+          : gpr_strdup(handshaker_service_url);
+  creds->base.type = GRPC_CREDENTIALS_TYPE_ALTS;
+  creds->base.vtable = &alts_server_credentials_vtable;
+  gpr_ref_init(&creds->base.refcount, 1);
+  return &creds->base;
+}
+
+grpc_channel_credentials* grpc_alts_credentials_create(
+    const grpc_alts_credentials_options* options) {
+  return grpc_alts_credentials_create_customized(
+      options, GRPC_ALTS_HANDSHAKER_SERVICE_URL, false);
+}
+
+grpc_server_credentials* grpc_alts_server_credentials_create(
+    const grpc_alts_credentials_options* options) {
+  return grpc_alts_server_credentials_create_customized(
+      options, GRPC_ALTS_HANDSHAKER_SERVICE_URL, false);
+}
diff --git a/src/core/lib/security/credentials/alts/alts_credentials.h b/src/core/lib/security/credentials/alts/alts_credentials.h
new file mode 100644
index 0000000..621789c
--- /dev/null
+++ b/src/core/lib/security/credentials/alts/alts_credentials.h
@@ -0,0 +1,102 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SECURITY_CREDENTIALS_ALTS_ALTS_CREDENTIALS_H
+#define GRPC_CORE_LIB_SECURITY_CREDENTIALS_ALTS_ALTS_CREDENTIALS_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/grpc_security.h>
+
+#include "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h"
+#include "src/core/lib/security/credentials/credentials.h"
+
+/* Main struct for grpc ALTS channel credential. */
+typedef struct grpc_alts_credentials {
+  grpc_channel_credentials base;
+  grpc_alts_credentials_options* options;
+  char* handshaker_service_url;
+} grpc_alts_credentials;
+
+/* Main struct for grpc ALTS server credential. */
+typedef struct grpc_alts_server_credentials {
+  grpc_server_credentials base;
+  grpc_alts_credentials_options* options;
+  char* handshaker_service_url;
+} grpc_alts_server_credentials;
+
+/**
+ * This method creates an ALTS channel credential object.
+ *
+ * - options: grpc ALTS credentials options instance for client.
+ *
+ * It returns the created ALTS channel credential object.
+ */
+grpc_channel_credentials* grpc_alts_credentials_create(
+    const grpc_alts_credentials_options* options);
+
+/**
+ * This method creates an ALTS server credential object.
+ *
+ * - options: grpc ALTS credentials options instance for server.
+ *
+ * It returns the created ALTS server credential object.
+ */
+grpc_server_credentials* grpc_alts_server_credentials_create(
+    const grpc_alts_credentials_options* options);
+
+/**
+ * This method creates an ALTS channel credential object with customized
+ * information provided by caller.
+ *
+ * - options: grpc ALTS credentials options instance for client.
+ * - handshaker_service_url: address of ALTS handshaker service in the format of
+ *   "host:port". If it's nullptr, the address of default metadata server will
+ *   be used.
+ * - enable_untrusted_alts: a boolean flag used to enable ALTS in untrusted
+ *   mode. This mode can be enabled when we are sure ALTS is running on GCP or
+ * for testing purpose.
+ *
+ * It returns nullptr if the flag is disabled AND ALTS is not running on GCP.
+ * Otherwise, it returns the created credential object.
+ */
+
+grpc_channel_credentials* grpc_alts_credentials_create_customized(
+    const grpc_alts_credentials_options* options,
+    const char* handshaker_service_url, bool enable_untrusted_alts);
+
+/**
+ * This method creates an ALTS server credential object with customized
+ * information provided by caller.
+ *
+ * - options: grpc ALTS credentials options instance for server.
+ * - handshaker_service_url: address of ALTS handshaker service in the format of
+ *   "host:port". If it's nullptr, the address of default metadata server will
+ *   be used.
+ * - enable_untrusted_alts: a boolean flag used to enable ALTS in untrusted
+ *   mode. This mode can be enabled when we are sure ALTS is running on GCP or
+ * for testing purpose.
+ *
+ * It returns nullptr if the flag is disabled and ALTS is not running on GCP.
+ * Otherwise, it returns the created credential object.
+ */
+grpc_server_credentials* grpc_alts_server_credentials_create_customized(
+    const grpc_alts_credentials_options* options,
+    const char* handshaker_service_url, bool enable_untrusted_alts);
+
+#endif /* GRPC_CORE_LIB_SECURITY_CREDENTIALS_ALTS_ALTS_CREDENTIALS_H */
diff --git a/src/core/lib/security/credentials/alts/check_gcp_environment.cc b/src/core/lib/security/credentials/alts/check_gcp_environment.cc
new file mode 100644
index 0000000..9680787
--- /dev/null
+++ b/src/core/lib/security/credentials/alts/check_gcp_environment.cc
@@ -0,0 +1,72 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/lib/security/credentials/alts/check_gcp_environment.h"
+
+#include <ctype.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+const size_t kBiosDataBufferSize = 256;
+
+static char* trim(const char* src) {
+  if (src == nullptr) {
+    return nullptr;
+  }
+  char* des = nullptr;
+  size_t start = 0, end = strlen(src) - 1;
+  /* find the last character that is not a whitespace. */
+  while (end != 0 && isspace(src[end])) {
+    end--;
+  }
+  /* find the first character that is not a whitespace. */
+  while (start < strlen(src) && isspace(src[start])) {
+    start++;
+  }
+  if (start <= end) {
+    des = static_cast<char*>(
+        gpr_zalloc(sizeof(char) * (end - start + 2 /* '\0' */)));
+    memcpy(des, src + start, end - start + 1);
+  }
+  return des;
+}
+
+namespace grpc_core {
+namespace internal {
+
+char* read_bios_file(const char* bios_file) {
+  FILE* fp = fopen(bios_file, "r");
+  if (!fp) {
+    gpr_log(GPR_ERROR, "BIOS data file cannot be opened.");
+    return nullptr;
+  }
+  char buf[kBiosDataBufferSize + 1];
+  size_t ret = fread(buf, sizeof(char), kBiosDataBufferSize, fp);
+  buf[ret] = '\0';
+  char* trimmed_buf = trim(buf);
+  fclose(fp);
+  return trimmed_buf;
+}
+
+}  // namespace internal
+}  // namespace grpc_core
diff --git a/src/core/lib/security/credentials/alts/check_gcp_environment.h b/src/core/lib/security/credentials/alts/check_gcp_environment.h
new file mode 100644
index 0000000..aea4cea
--- /dev/null
+++ b/src/core/lib/security/credentials/alts/check_gcp_environment.h
@@ -0,0 +1,57 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SECURITY_CREDENTIALS_ALTS_CHECK_GCP_ENVIRONMENT_H
+#define GRPC_CORE_LIB_SECURITY_CREDENTIALS_ALTS_CHECK_GCP_ENVIRONMENT_H
+
+namespace grpc_core {
+namespace internal {
+
+/**
+ * This method is a helper function that reads a file containing system bios
+ * data. Exposed for testing only.
+ *
+ * - bios_file: a file containing BIOS data used to determine GCE tenancy
+ *   information.
+ *
+ * It returns a buffer containing the data read from the file.
+ */
+char* read_bios_file(const char* bios_file);
+
+/**
+ * This method checks if system BIOS data contains Google-specific phrases.
+ * Exposed for testing only.
+ *
+ * - bios_data: a buffer containing system BIOS data.
+ *
+ * It returns true if the BIOS data contains Google-specific phrases, and false
+ * otherwise.
+ */
+bool check_bios_data(const char* bios_data);
+
+}  // namespace internal
+}  // namespace grpc_core
+
+/**
+ * This method checks if a VM (Windows or Linux) is running within Google
+ * compute Engine (GCE) or not. It returns true if the VM is running in GCE and
+ * false otherwise.
+ */
+bool grpc_alts_is_running_on_gcp();
+
+#endif /* GRPC_CORE_LIB_SECURITY_CREDENTIALS_ALTS_CHECK_GCP_ENVIRONMENT_H */
diff --git a/src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc b/src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc
new file mode 100644
index 0000000..7c4d7a7
--- /dev/null
+++ b/src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc
@@ -0,0 +1,67 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_LINUX
+
+#include "src/core/lib/security/credentials/alts/check_gcp_environment.h"
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/sync.h>
+
+#include <string.h>
+
+#define GRPC_ALTS_EXPECT_NAME_GOOGLE "Google"
+#define GRPC_ALTS_EXPECT_NAME_GCE "Google Compute Engine"
+#define GRPC_ALTS_PRODUCT_NAME_FILE "/sys/class/dmi/id/product_name"
+
+static bool g_compute_engine_detection_done = false;
+static bool g_is_on_compute_engine = false;
+static gpr_mu g_mu;
+static gpr_once g_once = GPR_ONCE_INIT;
+
+namespace grpc_core {
+namespace internal {
+
+bool check_bios_data(const char* bios_data_file) {
+  char* bios_data = read_bios_file(bios_data_file);
+  bool result = (!strcmp(bios_data, GRPC_ALTS_EXPECT_NAME_GOOGLE)) ||
+                (!strcmp(bios_data, GRPC_ALTS_EXPECT_NAME_GCE));
+  gpr_free(bios_data);
+  return result;
+}
+
+}  // namespace internal
+}  // namespace grpc_core
+
+static void init_mu(void) { gpr_mu_init(&g_mu); }
+
+bool grpc_alts_is_running_on_gcp() {
+  gpr_once_init(&g_once, init_mu);
+  gpr_mu_lock(&g_mu);
+  if (!g_compute_engine_detection_done) {
+    g_is_on_compute_engine =
+        grpc_core::internal::check_bios_data(GRPC_ALTS_PRODUCT_NAME_FILE);
+    g_compute_engine_detection_done = true;
+  }
+  gpr_mu_unlock(&g_mu);
+  return g_is_on_compute_engine;
+}
+
+#endif  // GPR_LINUX
diff --git a/src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc b/src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc
new file mode 100644
index 0000000..d97681b
--- /dev/null
+++ b/src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc
@@ -0,0 +1,33 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#if !defined(GPR_LINUX) && !defined(GPR_WINDOWS)
+
+#include "src/core/lib/security/credentials/alts/check_gcp_environment.h"
+
+#include <grpc/support/log.h>
+
+bool grpc_alts_is_running_on_gcp() {
+  gpr_log(GPR_ERROR,
+          "Platforms other than Linux and Windows are not supported");
+  return false;
+}
+
+#endif  // !defined(LINUX) && !defined(GPR_WINDOWS)
diff --git a/src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc b/src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc
new file mode 100644
index 0000000..55efe0e
--- /dev/null
+++ b/src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc
@@ -0,0 +1,114 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WINDOWS
+
+#include "src/core/lib/security/credentials/alts/check_gcp_environment.h"
+
+#include <shellapi.h>
+#include <stdio.h>
+#include <tchar.h>
+#include <windows.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+
+#define GRPC_ALTS_EXPECT_NAME_GOOGLE "Google"
+#define GRPC_ALTS_WINDOWS_CHECK_COMMAND "powershell.exe"
+#define GRPC_ALTS_WINDOWS_CHECK_COMMAND_ARGS \
+  "(Get-WmiObject -Class Win32_BIOS).Manufacturer"
+#define GRPC_ALTS_WINDOWS_CHECK_BIOS_FILE "windows_bios.data"
+
+const size_t kBiosDataBufferSize = 256;
+
+static bool g_compute_engine_detection_done = false;
+static bool g_is_on_compute_engine = false;
+static gpr_mu g_mu;
+static gpr_once g_once = GPR_ONCE_INIT;
+
+namespace grpc_core {
+namespace internal {
+
+bool check_bios_data(const char* bios_data_file) {
+  char* bios_data = read_bios_file(bios_data_file);
+  bool result = !strcmp(bios_data, GRPC_ALTS_EXPECT_NAME_GOOGLE);
+  remove(GRPC_ALTS_WINDOWS_CHECK_BIOS_FILE);
+  gpr_free(bios_data);
+  return result;
+}
+
+}  // namespace internal
+}  // namespace grpc_core
+
+static void init_mu(void) { gpr_mu_init(&g_mu); }
+
+static bool run_powershell() {
+  SECURITY_ATTRIBUTES sa;
+  sa.nLength = sizeof(sa);
+  sa.lpSecurityDescriptor = NULL;
+  sa.bInheritHandle = TRUE;
+  HANDLE h = CreateFile(_T(GRPC_ALTS_WINDOWS_CHECK_BIOS_FILE), GENERIC_WRITE,
+                        FILE_SHARE_WRITE | FILE_SHARE_READ, &sa, OPEN_ALWAYS,
+                        FILE_ATTRIBUTE_NORMAL, NULL);
+  if (h == INVALID_HANDLE_VALUE) {
+    gpr_log(GPR_ERROR, "CreateFile failed (%d).", GetLastError());
+    return false;
+  }
+  PROCESS_INFORMATION pi;
+  STARTUPINFO si;
+  DWORD flags = CREATE_NO_WINDOW;
+  ZeroMemory(&pi, sizeof(pi));
+  ZeroMemory(&si, sizeof(si));
+  si.cb = sizeof(si);
+  si.dwFlags |= STARTF_USESTDHANDLES;
+  si.hStdInput = NULL;
+  si.hStdError = h;
+  si.hStdOutput = h;
+  TCHAR cmd[kBiosDataBufferSize];
+  _sntprintf(cmd, kBiosDataBufferSize, _T("%s %s"),
+             _T(GRPC_ALTS_WINDOWS_CHECK_COMMAND),
+             _T(GRPC_ALTS_WINDOWS_CHECK_COMMAND_ARGS));
+  if (!CreateProcess(NULL, cmd, NULL, NULL, TRUE, flags, NULL, NULL, &si,
+                     &pi)) {
+    gpr_log(GPR_ERROR, "CreateProcess failed (%d).\n", GetLastError());
+    return false;
+  }
+  WaitForSingleObject(pi.hProcess, INFINITE);
+  CloseHandle(pi.hProcess);
+  CloseHandle(pi.hThread);
+  CloseHandle(h);
+  return true;
+}
+
+bool grpc_alts_is_running_on_gcp() {
+  gpr_once_init(&g_once, init_mu);
+  gpr_mu_lock(&g_mu);
+  if (!g_compute_engine_detection_done) {
+    g_is_on_compute_engine =
+        run_powershell() &&
+        grpc_core::internal::check_bios_data(GRPC_ALTS_WINDOWS_CHECK_BIOS_FILE);
+    g_compute_engine_detection_done = true;
+  }
+  gpr_mu_unlock(&g_mu);
+  return g_is_on_compute_engine;
+}
+
+#endif  // GPR_WINDOWS
diff --git a/src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc b/src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc
new file mode 100644
index 0000000..7d54e83
--- /dev/null
+++ b/src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc
@@ -0,0 +1,126 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+
+#include "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h"
+#include "src/core/tsi/alts/handshaker/transport_security_common_api.h"
+
+static grpc_alts_credentials_options* alts_client_options_copy(
+    const grpc_alts_credentials_options* options);
+
+static void alts_client_options_destroy(grpc_alts_credentials_options* options);
+
+static target_service_account* target_service_account_create(
+    const char* service_account) {
+  if (service_account == nullptr) {
+    return nullptr;
+  }
+  auto* sa = static_cast<target_service_account*>(
+      gpr_zalloc(sizeof(target_service_account)));
+  sa->data = gpr_strdup(service_account);
+  return sa;
+}
+
+bool grpc_alts_credentials_client_options_add_target_service_account(
+    grpc_alts_credentials_client_options* options,
+    const char* service_account) {
+  if (options == nullptr || service_account == nullptr) {
+    gpr_log(
+        GPR_ERROR,
+        "Invalid nullptr arguments to "
+        "grpc_alts_credentials_client_options_add_target_service_account()");
+    return false;
+  }
+  target_service_account* node = target_service_account_create(service_account);
+  node->next = options->target_account_list_head;
+  options->target_account_list_head = node;
+  return true;
+}
+
+static void target_service_account_destroy(
+    target_service_account* service_account) {
+  if (service_account == nullptr) {
+    return;
+  }
+  gpr_free(service_account->data);
+  gpr_free(service_account);
+}
+
+static const grpc_alts_credentials_options_vtable vtable = {
+    alts_client_options_copy, alts_client_options_destroy};
+
+grpc_alts_credentials_options* grpc_alts_credentials_client_options_create() {
+  auto client_options = static_cast<grpc_alts_credentials_client_options*>(
+      gpr_zalloc(sizeof(grpc_alts_credentials_client_options)));
+  client_options->base.vtable = &vtable;
+  return &client_options->base;
+}
+
+static grpc_alts_credentials_options* alts_client_options_copy(
+    const grpc_alts_credentials_options* options) {
+  if (options == nullptr) {
+    return nullptr;
+  }
+  grpc_alts_credentials_options* new_options =
+      grpc_alts_credentials_client_options_create();
+  auto new_client_options =
+      reinterpret_cast<grpc_alts_credentials_client_options*>(new_options);
+  /* Copy target service accounts. */
+  target_service_account* prev = nullptr;
+  auto node =
+      (reinterpret_cast<const grpc_alts_credentials_client_options*>(options))
+          ->target_account_list_head;
+  while (node != nullptr) {
+    target_service_account* new_node =
+        target_service_account_create(node->data);
+    if (prev == nullptr) {
+      new_client_options->target_account_list_head = new_node;
+    } else {
+      prev->next = new_node;
+    }
+    prev = new_node;
+    node = node->next;
+  }
+  /* Copy rpc protocol versions. */
+  grpc_gcp_rpc_protocol_versions_copy(&options->rpc_versions,
+                                      &new_options->rpc_versions);
+  return new_options;
+}
+
+static void alts_client_options_destroy(
+    grpc_alts_credentials_options* options) {
+  if (options == nullptr) {
+    return;
+  }
+  auto* client_options =
+      reinterpret_cast<grpc_alts_credentials_client_options*>(options);
+  target_service_account* node = client_options->target_account_list_head;
+  while (node != nullptr) {
+    target_service_account* next_node = node->next;
+    target_service_account_destroy(node);
+    node = next_node;
+  }
+}
diff --git a/src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc b/src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc
new file mode 100644
index 0000000..d428171
--- /dev/null
+++ b/src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc
@@ -0,0 +1,46 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h"
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+grpc_alts_credentials_options* grpc_alts_credentials_options_copy(
+    const grpc_alts_credentials_options* options) {
+  if (options != nullptr && options->vtable != nullptr &&
+      options->vtable->copy != nullptr) {
+    return options->vtable->copy(options);
+  }
+  /* An error occurred. */
+  gpr_log(GPR_ERROR,
+          "Invalid arguments to grpc_alts_credentials_options_copy()");
+  return nullptr;
+}
+
+void grpc_alts_credentials_options_destroy(
+    grpc_alts_credentials_options* options) {
+  if (options != nullptr) {
+    if (options->vtable != nullptr && options->vtable->destruct != nullptr) {
+      options->vtable->destruct(options);
+    }
+    gpr_free(options);
+  }
+}
diff --git a/src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h b/src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h
new file mode 100644
index 0000000..4e46d9f
--- /dev/null
+++ b/src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h
@@ -0,0 +1,112 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SECURITY_CREDENTIALS_ALTS_GRPC_ALTS_CREDENTIALS_OPTIONS_H
+#define GRPC_CORE_LIB_SECURITY_CREDENTIALS_ALTS_GRPC_ALTS_CREDENTIALS_OPTIONS_H
+
+#include <grpc/support/port_platform.h>
+
+#include <stdbool.h>
+
+#include "src/core/tsi/alts/handshaker/transport_security_common_api.h"
+
+/**
+ * Main interface for ALTS credentials options. The options will contain
+ * information that will be passed from grpc to TSI layer such as RPC protocol
+ * versions. ALTS client (channel) and server credentials will have their own
+ * implementation of this interface. The APIs listed in this header are
+ * thread-compatible.
+ */
+typedef struct grpc_alts_credentials_options grpc_alts_credentials_options;
+
+/* V-table for grpc_alts_credentials_options */
+typedef struct grpc_alts_credentials_options_vtable {
+  grpc_alts_credentials_options* (*copy)(
+      const grpc_alts_credentials_options* options);
+  void (*destruct)(grpc_alts_credentials_options* options);
+} grpc_alts_credentials_options_vtable;
+
+struct grpc_alts_credentials_options {
+  const struct grpc_alts_credentials_options_vtable* vtable;
+  grpc_gcp_rpc_protocol_versions rpc_versions;
+};
+
+typedef struct target_service_account {
+  struct target_service_account* next;
+  char* data;
+} target_service_account;
+
+/**
+ * Main struct for ALTS client credentials options. The options contain a
+ * a list of target service accounts (if specified) used for secure naming
+ * check.
+ */
+typedef struct grpc_alts_credentials_client_options {
+  grpc_alts_credentials_options base;
+  target_service_account* target_account_list_head;
+} grpc_alts_credentials_client_options;
+
+/**
+ * Main struct for ALTS server credentials options. The options currently
+ * do not contain any server-specific fields.
+ */
+typedef struct grpc_alts_credentials_server_options {
+  grpc_alts_credentials_options base;
+} grpc_alts_credentials_server_options;
+
+/**
+ * This method performs a deep copy on grpc_alts_credentials_options instance.
+ *
+ * - options: a grpc_alts_credentials_options instance that needs to be copied.
+ *
+ * It returns a new grpc_alts_credentials_options instance on success and NULL
+ * on failure.
+ */
+grpc_alts_credentials_options* grpc_alts_credentials_options_copy(
+    const grpc_alts_credentials_options* options);
+
+/**
+ * This method destroys a grpc_alts_credentials_options instance by
+ * de-allocating all of its occupied memory.
+ *
+ * - options: a grpc_alts_credentials_options instance that needs to be
+ *   destroyed.
+ */
+void grpc_alts_credentials_options_destroy(
+    grpc_alts_credentials_options* options);
+
+/* This method creates a grpc ALTS credentials client options instance. */
+grpc_alts_credentials_options* grpc_alts_credentials_client_options_create();
+
+/* This method creates a grpc ALTS credentials server options instance. */
+grpc_alts_credentials_options* grpc_alts_credentials_server_options_create();
+
+/**
+ * This method adds a target service account to grpc ALTS credentials client
+ * options instance.
+ *
+ * - options: grpc ALTS credentials client options instance.
+ * - service_account: service account of target endpoint.
+ *
+ * It returns true on success and false on failure.
+ */
+bool grpc_alts_credentials_client_options_add_target_service_account(
+    grpc_alts_credentials_client_options* options, const char* service_account);
+
+#endif /* GRPC_CORE_LIB_SECURITY_CREDENTIALS_ALTS_GRPC_ALTS_CREDENTIALS_OPTIONS_H \
+        */
diff --git a/src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc b/src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc
new file mode 100644
index 0000000..62aa7a6
--- /dev/null
+++ b/src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc
@@ -0,0 +1,58 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h"
+#include "src/core/tsi/alts/handshaker/transport_security_common_api.h"
+
+static grpc_alts_credentials_options* alts_server_options_copy(
+    const grpc_alts_credentials_options* options);
+
+static void alts_server_options_destroy(
+    grpc_alts_credentials_options* options) {}
+
+static const grpc_alts_credentials_options_vtable vtable = {
+    alts_server_options_copy, alts_server_options_destroy};
+
+grpc_alts_credentials_options* grpc_alts_credentials_server_options_create() {
+  grpc_alts_credentials_server_options* server_options =
+      static_cast<grpc_alts_credentials_server_options*>(
+          gpr_zalloc(sizeof(*server_options)));
+  server_options->base.vtable = &vtable;
+  return &server_options->base;
+}
+
+static grpc_alts_credentials_options* alts_server_options_copy(
+    const grpc_alts_credentials_options* options) {
+  if (options == nullptr) {
+    return nullptr;
+  }
+  grpc_alts_credentials_options* new_options =
+      grpc_alts_credentials_server_options_create();
+  /* Copy rpc protocol versions. */
+  grpc_gcp_rpc_protocol_versions_copy(&options->rpc_versions,
+                                      &new_options->rpc_versions);
+  return new_options;
+}
diff --git a/src/core/lib/security/security_connector/alts_security_connector.cc b/src/core/lib/security/security_connector/alts_security_connector.cc
new file mode 100644
index 0000000..5ff7d79
--- /dev/null
+++ b/src/core/lib/security/security_connector/alts_security_connector.cc
@@ -0,0 +1,287 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/lib/security/security_connector/alts_security_connector.h"
+
+#include <stdbool.h>
+#include <string.h>
+
+#include <grpc/grpc.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+
+#include "src/core/lib/security/credentials/alts/alts_credentials.h"
+#include "src/core/lib/security/transport/security_handshaker.h"
+#include "src/core/lib/transport/transport.h"
+#include "src/core/tsi/alts/handshaker/alts_tsi_handshaker.h"
+
+typedef struct {
+  grpc_channel_security_connector base;
+  char* target_name;
+} grpc_alts_channel_security_connector;
+
+typedef struct {
+  grpc_server_security_connector base;
+} grpc_alts_server_security_connector;
+
+static void alts_channel_destroy(grpc_security_connector* sc) {
+  if (sc == nullptr) {
+    return;
+  }
+  auto c = reinterpret_cast<grpc_alts_channel_security_connector*>(sc);
+  grpc_call_credentials_unref(c->base.request_metadata_creds);
+  grpc_channel_credentials_unref(c->base.channel_creds);
+  gpr_free(c->target_name);
+  gpr_free(sc);
+}
+
+static void alts_server_destroy(grpc_security_connector* sc) {
+  if (sc == nullptr) {
+    return;
+  }
+  auto c = reinterpret_cast<grpc_alts_server_security_connector*>(sc);
+  grpc_server_credentials_unref(c->base.server_creds);
+  gpr_free(sc);
+}
+
+static void alts_channel_add_handshakers(
+    grpc_channel_security_connector* sc,
+    grpc_handshake_manager* handshake_manager) {
+  tsi_handshaker* handshaker = nullptr;
+  auto c = reinterpret_cast<grpc_alts_channel_security_connector*>(sc);
+  grpc_alts_credentials* creds =
+      reinterpret_cast<grpc_alts_credentials*>(c->base.channel_creds);
+  GPR_ASSERT(alts_tsi_handshaker_create(creds->options, c->target_name,
+                                        creds->handshaker_service_url, true,
+                                        &handshaker) == TSI_OK);
+  grpc_handshake_manager_add(handshake_manager, grpc_security_handshaker_create(
+                                                    handshaker, &sc->base));
+}
+
+static void alts_server_add_handshakers(
+    grpc_server_security_connector* sc,
+    grpc_handshake_manager* handshake_manager) {
+  tsi_handshaker* handshaker = nullptr;
+  auto c = reinterpret_cast<grpc_alts_server_security_connector*>(sc);
+  grpc_alts_server_credentials* creds =
+      reinterpret_cast<grpc_alts_server_credentials*>(c->base.server_creds);
+  GPR_ASSERT(alts_tsi_handshaker_create(creds->options, nullptr,
+                                        creds->handshaker_service_url, false,
+                                        &handshaker) == TSI_OK);
+  grpc_handshake_manager_add(handshake_manager, grpc_security_handshaker_create(
+                                                    handshaker, &sc->base));
+}
+
+static void alts_set_rpc_protocol_versions(
+    grpc_gcp_rpc_protocol_versions* rpc_versions) {
+  grpc_gcp_rpc_protocol_versions_set_max(rpc_versions,
+                                         GRPC_PROTOCOL_VERSION_MAX_MAJOR,
+                                         GRPC_PROTOCOL_VERSION_MAX_MINOR);
+  grpc_gcp_rpc_protocol_versions_set_min(rpc_versions,
+                                         GRPC_PROTOCOL_VERSION_MIN_MAJOR,
+                                         GRPC_PROTOCOL_VERSION_MIN_MINOR);
+}
+
+namespace grpc_core {
+namespace internal {
+
+grpc_security_status grpc_alts_auth_context_from_tsi_peer(
+    const tsi_peer* peer, grpc_auth_context** ctx) {
+  if (peer == nullptr || ctx == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to grpc_alts_auth_context_from_tsi_peer()");
+    return GRPC_SECURITY_ERROR;
+  }
+  *ctx = nullptr;
+  /* Validate certificate type. */
+  const tsi_peer_property* cert_type_prop =
+      tsi_peer_get_property_by_name(peer, TSI_CERTIFICATE_TYPE_PEER_PROPERTY);
+  if (cert_type_prop == nullptr ||
+      strncmp(cert_type_prop->value.data, TSI_ALTS_CERTIFICATE_TYPE,
+              cert_type_prop->value.length) != 0) {
+    gpr_log(GPR_ERROR, "Invalid or missing certificate type property.");
+    return GRPC_SECURITY_ERROR;
+  }
+  /* Validate RPC protocol versions. */
+  const tsi_peer_property* rpc_versions_prop =
+      tsi_peer_get_property_by_name(peer, TSI_ALTS_RPC_VERSIONS);
+  if (rpc_versions_prop == nullptr) {
+    gpr_log(GPR_ERROR, "Missing rpc protocol versions property.");
+    return GRPC_SECURITY_ERROR;
+  }
+  grpc_gcp_rpc_protocol_versions local_versions, peer_versions;
+  alts_set_rpc_protocol_versions(&local_versions);
+  grpc_slice slice = grpc_slice_from_copied_buffer(
+      rpc_versions_prop->value.data, rpc_versions_prop->value.length);
+  bool decode_result =
+      grpc_gcp_rpc_protocol_versions_decode(slice, &peer_versions);
+  grpc_slice_unref(slice);
+  if (!decode_result) {
+    gpr_log(GPR_ERROR, "Invalid peer rpc protocol versions.");
+    return GRPC_SECURITY_ERROR;
+  }
+  /* TODO: Pass highest common rpc protocol version to grpc caller. */
+  bool check_result = grpc_gcp_rpc_protocol_versions_check(
+      &local_versions, &peer_versions, nullptr);
+  if (!check_result) {
+    gpr_log(GPR_ERROR, "Mismatch of local and peer rpc protocol versions.");
+    return GRPC_SECURITY_ERROR;
+  }
+  /* Create auth context. */
+  *ctx = grpc_auth_context_create(nullptr);
+  grpc_auth_context_add_cstring_property(
+      *ctx, GRPC_TRANSPORT_SECURITY_TYPE_PROPERTY_NAME,
+      GRPC_ALTS_TRANSPORT_SECURITY_TYPE);
+  size_t i = 0;
+  for (i = 0; i < peer->property_count; i++) {
+    const tsi_peer_property* tsi_prop = &peer->properties[i];
+    /* Add service account to auth context. */
+    if (strcmp(tsi_prop->name, TSI_ALTS_SERVICE_ACCOUNT_PEER_PROPERTY) == 0) {
+      grpc_auth_context_add_property(
+          *ctx, TSI_ALTS_SERVICE_ACCOUNT_PEER_PROPERTY, tsi_prop->value.data,
+          tsi_prop->value.length);
+      GPR_ASSERT(grpc_auth_context_set_peer_identity_property_name(
+                     *ctx, TSI_ALTS_SERVICE_ACCOUNT_PEER_PROPERTY) == 1);
+    }
+  }
+  if (!grpc_auth_context_peer_is_authenticated(*ctx)) {
+    gpr_log(GPR_ERROR, "Invalid unauthenticated peer.");
+    GRPC_AUTH_CONTEXT_UNREF(*ctx, "test");
+    *ctx = nullptr;
+    return GRPC_SECURITY_ERROR;
+  }
+  return GRPC_SECURITY_OK;
+}
+
+}  // namespace internal
+}  // namespace grpc_core
+
+static void alts_check_peer(grpc_security_connector* sc, tsi_peer peer,
+                            grpc_auth_context** auth_context,
+                            grpc_closure* on_peer_checked) {
+  grpc_security_status status;
+  status = grpc_core::internal::grpc_alts_auth_context_from_tsi_peer(
+      &peer, auth_context);
+  tsi_peer_destruct(&peer);
+  grpc_error* error =
+      status == GRPC_SECURITY_OK
+          ? GRPC_ERROR_NONE
+          : GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+                "Could not get ALTS auth context from TSI peer");
+  GRPC_CLOSURE_SCHED(on_peer_checked, error);
+}
+
+static int alts_channel_cmp(grpc_security_connector* sc1,
+                            grpc_security_connector* sc2) {
+  grpc_alts_channel_security_connector* c1 =
+      reinterpret_cast<grpc_alts_channel_security_connector*>(sc1);
+  grpc_alts_channel_security_connector* c2 =
+      reinterpret_cast<grpc_alts_channel_security_connector*>(sc2);
+  int c = grpc_channel_security_connector_cmp(&c1->base, &c2->base);
+  if (c != 0) return c;
+  return strcmp(c1->target_name, c2->target_name);
+}
+
+static int alts_server_cmp(grpc_security_connector* sc1,
+                           grpc_security_connector* sc2) {
+  grpc_alts_server_security_connector* c1 =
+      reinterpret_cast<grpc_alts_server_security_connector*>(sc1);
+  grpc_alts_server_security_connector* c2 =
+      reinterpret_cast<grpc_alts_server_security_connector*>(sc2);
+  return grpc_server_security_connector_cmp(&c1->base, &c2->base);
+}
+
+static grpc_security_connector_vtable alts_channel_vtable = {
+    alts_channel_destroy, alts_check_peer, alts_channel_cmp};
+
+static grpc_security_connector_vtable alts_server_vtable = {
+    alts_server_destroy, alts_check_peer, alts_server_cmp};
+
+static bool alts_check_call_host(grpc_channel_security_connector* sc,
+                                 const char* host,
+                                 grpc_auth_context* auth_context,
+                                 grpc_closure* on_call_host_checked,
+                                 grpc_error** error) {
+  grpc_alts_channel_security_connector* alts_sc =
+      reinterpret_cast<grpc_alts_channel_security_connector*>(sc);
+  if (host == nullptr || alts_sc == nullptr ||
+      strcmp(host, alts_sc->target_name) != 0) {
+    *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+        "ALTS call host does not match target name");
+  }
+  return true;
+}
+
+static void alts_cancel_check_call_host(grpc_channel_security_connector* sc,
+                                        grpc_closure* on_call_host_checked,
+                                        grpc_error* error) {
+  GRPC_ERROR_UNREF(error);
+}
+
+grpc_security_status grpc_alts_channel_security_connector_create(
+    grpc_channel_credentials* channel_creds,
+    grpc_call_credentials* request_metadata_creds, const char* target_name,
+    grpc_channel_security_connector** sc) {
+  if (channel_creds == nullptr || sc == nullptr || target_name == nullptr) {
+    gpr_log(
+        GPR_ERROR,
+        "Invalid arguments to grpc_alts_channel_security_connector_create()");
+    return GRPC_SECURITY_ERROR;
+  }
+  auto c = static_cast<grpc_alts_channel_security_connector*>(
+      gpr_zalloc(sizeof(grpc_alts_channel_security_connector)));
+  gpr_ref_init(&c->base.base.refcount, 1);
+  c->base.base.vtable = &alts_channel_vtable;
+  c->base.add_handshakers = alts_channel_add_handshakers;
+  c->base.channel_creds = grpc_channel_credentials_ref(channel_creds);
+  c->base.request_metadata_creds =
+      grpc_call_credentials_ref(request_metadata_creds);
+  c->base.check_call_host = alts_check_call_host;
+  c->base.cancel_check_call_host = alts_cancel_check_call_host;
+  grpc_alts_credentials* creds =
+      reinterpret_cast<grpc_alts_credentials*>(c->base.channel_creds);
+  alts_set_rpc_protocol_versions(&creds->options->rpc_versions);
+  c->target_name = gpr_strdup(target_name);
+  *sc = &c->base;
+  return GRPC_SECURITY_OK;
+}
+
+grpc_security_status grpc_alts_server_security_connector_create(
+    grpc_server_credentials* server_creds,
+    grpc_server_security_connector** sc) {
+  if (server_creds == nullptr || sc == nullptr) {
+    gpr_log(
+        GPR_ERROR,
+        "Invalid arguments to grpc_alts_server_security_connector_create()");
+    return GRPC_SECURITY_ERROR;
+  }
+  auto c = static_cast<grpc_alts_server_security_connector*>(
+      gpr_zalloc(sizeof(grpc_alts_server_security_connector)));
+  gpr_ref_init(&c->base.base.refcount, 1);
+  c->base.base.vtable = &alts_server_vtable;
+  c->base.server_creds = grpc_server_credentials_ref(server_creds);
+  c->base.add_handshakers = alts_server_add_handshakers;
+  grpc_alts_server_credentials* creds =
+      reinterpret_cast<grpc_alts_server_credentials*>(c->base.server_creds);
+  alts_set_rpc_protocol_versions(&creds->options->rpc_versions);
+  *sc = &c->base;
+  return GRPC_SECURITY_OK;
+}
diff --git a/src/core/lib/security/security_connector/alts_security_connector.h b/src/core/lib/security/security_connector/alts_security_connector.h
new file mode 100644
index 0000000..e7e4cff
--- /dev/null
+++ b/src/core/lib/security/security_connector/alts_security_connector.h
@@ -0,0 +1,69 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SECURITY_SECURITY_CONNECTOR_ALTS_SECURITY_CONNECTOR_H
+#define GRPC_CORE_LIB_SECURITY_SECURITY_CONNECTOR_ALTS_SECURITY_CONNECTOR_H
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/lib/security/context/security_context.h"
+#include "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h"
+
+#define GRPC_ALTS_TRANSPORT_SECURITY_TYPE "alts"
+
+/**
+ * This method creates an ALTS channel security connector.
+ *
+ * - channel_creds: channel credential instance.
+ * - request_metadata_creds: credential object which will be sent with each
+ *   request. This parameter can be nullptr.
+ * - target_name: the name of the endpoint that the channel is connecting to.
+ * - sc: address of ALTS channel security connector instance to be returned from
+ *   the method.
+ *
+ * It returns GRPC_SECURITY_OK on success, and an error stauts code on failure.
+ */
+grpc_security_status grpc_alts_channel_security_connector_create(
+    grpc_channel_credentials* channel_creds,
+    grpc_call_credentials* request_metadata_creds, const char* target_name,
+    grpc_channel_security_connector** sc);
+
+/**
+ * This method creates an ALTS server security connector.
+ *
+ * - server_creds: server credential instance.
+ * - sc: address of ALTS server security connector instance to be returned from
+ *   the method.
+ *
+ * It returns GRPC_SECURITY_OK on success, and an error status code on failure.
+ */
+grpc_security_status grpc_alts_server_security_connector_create(
+    grpc_server_credentials* server_creds, grpc_server_security_connector** sc);
+
+namespace grpc_core {
+namespace internal {
+
+/* Exposed only for testing. */
+grpc_security_status grpc_alts_auth_context_from_tsi_peer(
+    const tsi_peer* peer, grpc_auth_context** ctx);
+
+}  // namespace internal
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_LIB_SECURITY_SECURITY_CONNECTOR_ALTS_SECURITY_CONNECTOR_H \
+        */
diff --git a/src/core/plugin_registry/grpc_plugin_registry.cc b/src/core/plugin_registry/grpc_plugin_registry.cc
index ccf5f79..6f11e6b 100644
--- a/src/core/plugin_registry/grpc_plugin_registry.cc
+++ b/src/core/plugin_registry/grpc_plugin_registry.cc
@@ -24,12 +24,12 @@
 void grpc_http_filters_shutdown(void);
 void grpc_chttp2_plugin_init(void);
 void grpc_chttp2_plugin_shutdown(void);
-void grpc_tsi_alts_init(void);
-void grpc_tsi_alts_shutdown(void);
 void grpc_deadline_filter_init(void);
 void grpc_deadline_filter_shutdown(void);
 void grpc_client_channel_init(void);
 void grpc_client_channel_shutdown(void);
+void grpc_tsi_alts_init(void);
+void grpc_tsi_alts_shutdown(void);
 void grpc_inproc_plugin_init(void);
 void grpc_inproc_plugin_shutdown(void);
 void grpc_resolver_fake_init(void);
@@ -60,12 +60,12 @@
                        grpc_http_filters_shutdown);
   grpc_register_plugin(grpc_chttp2_plugin_init,
                        grpc_chttp2_plugin_shutdown);
-  grpc_register_plugin(grpc_tsi_alts_init,
-                       grpc_tsi_alts_shutdown);
   grpc_register_plugin(grpc_deadline_filter_init,
                        grpc_deadline_filter_shutdown);
   grpc_register_plugin(grpc_client_channel_init,
                        grpc_client_channel_shutdown);
+  grpc_register_plugin(grpc_tsi_alts_init,
+                       grpc_tsi_alts_shutdown);
   grpc_register_plugin(grpc_inproc_plugin_init,
                        grpc_inproc_plugin_shutdown);
   grpc_register_plugin(grpc_resolver_fake_init,
diff --git a/src/core/tsi/alts/crypt/aes_gcm.cc b/src/core/tsi/alts/crypt/aes_gcm.cc
new file mode 100644
index 0000000..02b1ac4
--- /dev/null
+++ b/src/core/tsi/alts/crypt/aes_gcm.cc
@@ -0,0 +1,687 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/crypt/gsec.h"
+
+#include <openssl/bio.h>
+#include <openssl/buffer.h>
+#include <openssl/err.h>
+#include <openssl/evp.h>
+#include <openssl/hmac.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+
+constexpr size_t kKdfKeyLen = 32;
+constexpr size_t kKdfCounterLen = 6;
+constexpr size_t kKdfCounterOffset = 2;
+constexpr size_t kRekeyAeadKeyLen = kAes128GcmKeyLength;
+
+/* Struct for additional data required if rekeying is enabled. */
+struct gsec_aes_gcm_aead_rekey_data {
+  uint8_t kdf_counter[kKdfCounterLen];
+  uint8_t nonce_mask[kAesGcmNonceLength];
+};
+
+/* Main struct for AES_GCM crypter interface. */
+struct gsec_aes_gcm_aead_crypter {
+  gsec_aead_crypter crypter;
+  size_t key_length;
+  size_t nonce_length;
+  size_t tag_length;
+  uint8_t* key;
+  gsec_aes_gcm_aead_rekey_data* rekey_data;
+  EVP_CIPHER_CTX* ctx;
+};
+
+static char* aes_gcm_get_openssl_errors() {
+  BIO* bio = BIO_new(BIO_s_mem());
+  ERR_print_errors(bio);
+  BUF_MEM* mem = nullptr;
+  char* error_msg = nullptr;
+  BIO_get_mem_ptr(bio, &mem);
+  if (mem != nullptr) {
+    error_msg = static_cast<char*>(gpr_malloc(mem->length + 1));
+    memcpy(error_msg, mem->data, mem->length);
+    error_msg[mem->length] = '\0';
+  }
+  BIO_free_all(bio);
+  return error_msg;
+}
+
+static void aes_gcm_format_errors(const char* error_msg, char** error_details) {
+  if (error_details == nullptr) {
+    return;
+  }
+  unsigned long error = ERR_get_error();
+  if (error == 0 && error_msg != nullptr) {
+    *error_details = static_cast<char*>(gpr_malloc(strlen(error_msg) + 1));
+    memcpy(*error_details, error_msg, strlen(error_msg) + 1);
+    return;
+  }
+  char* openssl_errors = aes_gcm_get_openssl_errors();
+  if (openssl_errors != nullptr && error_msg != nullptr) {
+    size_t len = strlen(error_msg) + strlen(openssl_errors) + 2; /* ", " */
+    *error_details = static_cast<char*>(gpr_malloc(len + 1));
+    snprintf(*error_details, len + 1, "%s, %s", error_msg, openssl_errors);
+    gpr_free(openssl_errors);
+  }
+}
+
+static grpc_status_code gsec_aes_gcm_aead_crypter_max_ciphertext_and_tag_length(
+    const gsec_aead_crypter* crypter, size_t plaintext_length,
+    size_t* max_ciphertext_and_tag_length, char** error_details) {
+  if (max_ciphertext_and_tag_length == nullptr) {
+    aes_gcm_format_errors("max_ciphertext_and_tag_length is nullptr.",
+                          error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  gsec_aes_gcm_aead_crypter* aes_gcm_crypter =
+      reinterpret_cast<gsec_aes_gcm_aead_crypter*>(
+          const_cast<gsec_aead_crypter*>(crypter));
+  *max_ciphertext_and_tag_length =
+      plaintext_length + aes_gcm_crypter->tag_length;
+  return GRPC_STATUS_OK;
+}
+
+static grpc_status_code gsec_aes_gcm_aead_crypter_max_plaintext_length(
+    const gsec_aead_crypter* crypter, size_t ciphertext_and_tag_length,
+    size_t* max_plaintext_length, char** error_details) {
+  if (max_plaintext_length == nullptr) {
+    aes_gcm_format_errors("max_plaintext_length is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  gsec_aes_gcm_aead_crypter* aes_gcm_crypter =
+      reinterpret_cast<gsec_aes_gcm_aead_crypter*>(
+          const_cast<gsec_aead_crypter*>(crypter));
+  if (ciphertext_and_tag_length < aes_gcm_crypter->tag_length) {
+    *max_plaintext_length = 0;
+    aes_gcm_format_errors(
+        "ciphertext_and_tag_length is smaller than tag_length.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  *max_plaintext_length =
+      ciphertext_and_tag_length - aes_gcm_crypter->tag_length;
+  return GRPC_STATUS_OK;
+}
+
+static grpc_status_code gsec_aes_gcm_aead_crypter_nonce_length(
+    const gsec_aead_crypter* crypter, size_t* nonce_length,
+    char** error_details) {
+  if (nonce_length == nullptr) {
+    aes_gcm_format_errors("nonce_length is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  gsec_aes_gcm_aead_crypter* aes_gcm_crypter =
+      reinterpret_cast<gsec_aes_gcm_aead_crypter*>(
+          const_cast<gsec_aead_crypter*>(crypter));
+  *nonce_length = aes_gcm_crypter->nonce_length;
+  return GRPC_STATUS_OK;
+}
+
+static grpc_status_code gsec_aes_gcm_aead_crypter_key_length(
+    const gsec_aead_crypter* crypter, size_t* key_length,
+    char** error_details) {
+  if (key_length == nullptr) {
+    aes_gcm_format_errors("key_length is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  gsec_aes_gcm_aead_crypter* aes_gcm_crypter =
+      reinterpret_cast<gsec_aes_gcm_aead_crypter*>(
+          const_cast<gsec_aead_crypter*>(crypter));
+  *key_length = aes_gcm_crypter->key_length;
+  return GRPC_STATUS_OK;
+}
+
+static grpc_status_code gsec_aes_gcm_aead_crypter_tag_length(
+    const gsec_aead_crypter* crypter, size_t* tag_length,
+    char** error_details) {
+  if (tag_length == nullptr) {
+    aes_gcm_format_errors("tag_length is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  gsec_aes_gcm_aead_crypter* aes_gcm_crypter =
+      reinterpret_cast<gsec_aes_gcm_aead_crypter*>(
+          const_cast<gsec_aead_crypter*>(crypter));
+  *tag_length = aes_gcm_crypter->tag_length;
+  return GRPC_STATUS_OK;
+}
+
+static void aes_gcm_mask_nonce(uint8_t* dst, const uint8_t* nonce,
+                               const uint8_t* mask) {
+  uint64_t mask1;
+  uint32_t mask2;
+  memcpy(&mask1, mask, sizeof(mask1));
+  memcpy(&mask2, mask + sizeof(mask1), sizeof(mask2));
+  uint64_t nonce1;
+  uint32_t nonce2;
+  memcpy(&nonce1, nonce, sizeof(nonce1));
+  memcpy(&nonce2, nonce + sizeof(nonce1), sizeof(nonce2));
+  nonce1 ^= mask1;
+  nonce2 ^= mask2;
+  memcpy(dst, &nonce1, sizeof(nonce1));
+  memcpy(dst + sizeof(nonce1), &nonce2, sizeof(nonce2));
+}
+
+static grpc_status_code aes_gcm_derive_aead_key(uint8_t* dst,
+                                                const uint8_t* kdf_key,
+                                                const uint8_t* kdf_counter) {
+  unsigned char buf[EVP_MAX_MD_SIZE];
+  unsigned char ctr = 1;
+#if OPENSSL_VERSION_NUMBER < 0x10100000L
+  HMAC_CTX hmac;
+  HMAC_CTX_init(&hmac);
+  if (!HMAC_Init_ex(&hmac, kdf_key, kKdfKeyLen, EVP_sha256(), nullptr) ||
+      !HMAC_Update(&hmac, kdf_counter, kKdfCounterLen) ||
+      !HMAC_Update(&hmac, &ctr, 1) || !HMAC_Final(&hmac, buf, nullptr)) {
+    HMAC_CTX_cleanup(&hmac);
+    return GRPC_STATUS_INTERNAL;
+  }
+  HMAC_CTX_cleanup(&hmac);
+#else
+  HMAC_CTX* hmac = HMAC_CTX_new();
+  if (hmac == nullptr) {
+    return GRPC_STATUS_INTERNAL;
+  }
+  if (!HMAC_Init_ex(hmac, kdf_key, kKdfKeyLen, EVP_sha256(), nullptr) ||
+      !HMAC_Update(hmac, kdf_counter, kKdfCounterLen) ||
+      !HMAC_Update(hmac, &ctr, 1) || !HMAC_Final(hmac, buf, nullptr)) {
+    HMAC_CTX_free(hmac);
+    return GRPC_STATUS_INTERNAL;
+  }
+  HMAC_CTX_free(hmac);
+#endif
+  memcpy(dst, buf, kRekeyAeadKeyLen);
+  return GRPC_STATUS_OK;
+}
+
+static grpc_status_code aes_gcm_rekey_if_required(
+    gsec_aes_gcm_aead_crypter* aes_gcm_crypter, const uint8_t* nonce,
+    char** error_details) {
+  // If rekey_data is nullptr, then rekeying is not supported and not required.
+  // If bytes 2-7 of kdf_counter differ from the (per message) nonce, then the
+  // encryption key is recomputed from a new kdf_counter to ensure that we don't
+  // encrypt more than 2^16 messages per encryption key (in each direction).
+  if (aes_gcm_crypter->rekey_data == nullptr ||
+      memcmp(aes_gcm_crypter->rekey_data->kdf_counter,
+             nonce + kKdfCounterOffset, kKdfCounterLen) == 0) {
+    return GRPC_STATUS_OK;
+  }
+  memcpy(aes_gcm_crypter->rekey_data->kdf_counter, nonce + kKdfCounterOffset,
+         kKdfCounterLen);
+  uint8_t aead_key[kRekeyAeadKeyLen];
+  if (aes_gcm_derive_aead_key(aead_key, aes_gcm_crypter->key,
+                              aes_gcm_crypter->rekey_data->kdf_counter) !=
+      GRPC_STATUS_OK) {
+    aes_gcm_format_errors("Rekeying failed in key derivation.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  if (!EVP_DecryptInit_ex(aes_gcm_crypter->ctx, nullptr, nullptr, aead_key,
+                          nullptr)) {
+    aes_gcm_format_errors("Rekeying failed in context update.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  return GRPC_STATUS_OK;
+}
+
+static grpc_status_code gsec_aes_gcm_aead_crypter_encrypt_iovec(
+    gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+    const struct iovec* aad_vec, size_t aad_vec_length,
+    const struct iovec* plaintext_vec, size_t plaintext_vec_length,
+    struct iovec ciphertext_vec, size_t* ciphertext_bytes_written,
+    char** error_details) {
+  gsec_aes_gcm_aead_crypter* aes_gcm_crypter =
+      reinterpret_cast<gsec_aes_gcm_aead_crypter*>(crypter);
+  // Input checks
+  if (nonce == nullptr) {
+    aes_gcm_format_errors("Nonce buffer is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (kAesGcmNonceLength != nonce_length) {
+    aes_gcm_format_errors("Nonce buffer has the wrong length.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (aad_vec_length > 0 && aad_vec == nullptr) {
+    aes_gcm_format_errors("Non-zero aad_vec_length but aad_vec is nullptr.",
+                          error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (plaintext_vec_length > 0 && plaintext_vec == nullptr) {
+    aes_gcm_format_errors(
+        "Non-zero plaintext_vec_length but plaintext_vec is nullptr.",
+        error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (ciphertext_bytes_written == nullptr) {
+    aes_gcm_format_errors("bytes_written is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  *ciphertext_bytes_written = 0;
+  // rekey if required
+  if (aes_gcm_rekey_if_required(aes_gcm_crypter, nonce, error_details) !=
+      GRPC_STATUS_OK) {
+    return GRPC_STATUS_INTERNAL;
+  }
+  // mask nonce if required
+  const uint8_t* nonce_aead = nonce;
+  uint8_t nonce_masked[kAesGcmNonceLength];
+  if (aes_gcm_crypter->rekey_data != nullptr) {
+    aes_gcm_mask_nonce(nonce_masked, aes_gcm_crypter->rekey_data->nonce_mask,
+                       nonce);
+    nonce_aead = nonce_masked;
+  }
+  // init openssl context
+  if (!EVP_EncryptInit_ex(aes_gcm_crypter->ctx, nullptr, nullptr, nullptr,
+                          nonce_aead)) {
+    aes_gcm_format_errors("Initializing nonce failed", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  // process aad
+  size_t i;
+  for (i = 0; i < aad_vec_length; i++) {
+    const uint8_t* aad = static_cast<uint8_t*>(aad_vec[i].iov_base);
+    size_t aad_length = aad_vec[i].iov_len;
+    if (aad_length == 0) {
+      continue;
+    }
+    size_t aad_bytes_read = 0;
+    if (aad == nullptr) {
+      aes_gcm_format_errors("aad is nullptr.", error_details);
+      return GRPC_STATUS_INVALID_ARGUMENT;
+    }
+    if (!EVP_EncryptUpdate(aes_gcm_crypter->ctx, nullptr,
+                           reinterpret_cast<int*>(&aad_bytes_read), aad,
+                           static_cast<int>(aad_length)) ||
+        aad_bytes_read != aad_length) {
+      aes_gcm_format_errors("Setting authenticated associated data failed",
+                            error_details);
+      return GRPC_STATUS_INTERNAL;
+    }
+  }
+  uint8_t* ciphertext = static_cast<uint8_t*>(ciphertext_vec.iov_base);
+  size_t ciphertext_length = ciphertext_vec.iov_len;
+  if (ciphertext == nullptr) {
+    aes_gcm_format_errors("ciphertext is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  // process plaintext
+  for (i = 0; i < plaintext_vec_length; i++) {
+    const uint8_t* plaintext = static_cast<uint8_t*>(plaintext_vec[i].iov_base);
+    size_t plaintext_length = plaintext_vec[i].iov_len;
+    if (plaintext == nullptr) {
+      if (plaintext_length == 0) {
+        continue;
+      }
+      aes_gcm_format_errors("plaintext is nullptr.", error_details);
+      return GRPC_STATUS_INVALID_ARGUMENT;
+    }
+    if (ciphertext_length < plaintext_length) {
+      aes_gcm_format_errors(
+          "ciphertext is not large enough to hold the result.", error_details);
+      return GRPC_STATUS_INVALID_ARGUMENT;
+    }
+    int bytes_written = 0;
+    int bytes_to_write = static_cast<int>(plaintext_length);
+    if (!EVP_EncryptUpdate(aes_gcm_crypter->ctx, ciphertext, &bytes_written,
+                           plaintext, bytes_to_write)) {
+      aes_gcm_format_errors("Encrypting plaintext failed.", error_details);
+      return GRPC_STATUS_INTERNAL;
+    }
+    if (bytes_written > bytes_to_write) {
+      aes_gcm_format_errors("More bytes written than expected.", error_details);
+      return GRPC_STATUS_INTERNAL;
+    }
+    ciphertext += bytes_written;
+    ciphertext_length -= bytes_written;
+  }
+  int bytes_written_temp = 0;
+  if (!EVP_EncryptFinal_ex(aes_gcm_crypter->ctx, nullptr,
+                           &bytes_written_temp)) {
+    aes_gcm_format_errors("Finalizing encryption failed.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  if (bytes_written_temp != 0) {
+    aes_gcm_format_errors("Openssl wrote some unexpected bytes.",
+                          error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  if (ciphertext_length < kAesGcmTagLength) {
+    aes_gcm_format_errors("ciphertext is too small to hold a tag.",
+                          error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+
+  if (!EVP_CIPHER_CTX_ctrl(aes_gcm_crypter->ctx, EVP_CTRL_GCM_GET_TAG,
+                           kAesGcmTagLength, ciphertext)) {
+    aes_gcm_format_errors("Writing tag failed.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  ciphertext += kAesGcmTagLength;
+  ciphertext_length -= kAesGcmTagLength;
+  *ciphertext_bytes_written = ciphertext_vec.iov_len - ciphertext_length;
+  return GRPC_STATUS_OK;
+}
+
+static grpc_status_code gsec_aes_gcm_aead_crypter_decrypt_iovec(
+    gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+    const struct iovec* aad_vec, size_t aad_vec_length,
+    const struct iovec* ciphertext_vec, size_t ciphertext_vec_length,
+    struct iovec plaintext_vec, size_t* plaintext_bytes_written,
+    char** error_details) {
+  gsec_aes_gcm_aead_crypter* aes_gcm_crypter =
+      reinterpret_cast<gsec_aes_gcm_aead_crypter*>(
+          const_cast<gsec_aead_crypter*>(crypter));
+  if (nonce == nullptr) {
+    aes_gcm_format_errors("Nonce buffer is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (kAesGcmNonceLength != nonce_length) {
+    aes_gcm_format_errors("Nonce buffer has the wrong length.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (aad_vec_length > 0 && aad_vec == nullptr) {
+    aes_gcm_format_errors("Non-zero aad_vec_length but aad_vec is nullptr.",
+                          error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (ciphertext_vec_length > 0 && ciphertext_vec == nullptr) {
+    aes_gcm_format_errors(
+        "Non-zero plaintext_vec_length but plaintext_vec is nullptr.",
+        error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  // Compute the total length so we can ensure we don't pass the tag into
+  // EVP_decrypt.
+  size_t total_ciphertext_length = 0;
+  size_t i;
+  for (i = 0; i < ciphertext_vec_length; i++) {
+    total_ciphertext_length += ciphertext_vec[i].iov_len;
+  }
+  if (total_ciphertext_length < kAesGcmTagLength) {
+    aes_gcm_format_errors("ciphertext is too small to hold a tag.",
+                          error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (plaintext_bytes_written == nullptr) {
+    aes_gcm_format_errors("bytes_written is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  *plaintext_bytes_written = 0;
+  // rekey if required
+  if (aes_gcm_rekey_if_required(aes_gcm_crypter, nonce, error_details) !=
+      GRPC_STATUS_OK) {
+    aes_gcm_format_errors("Rekeying failed.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  // mask nonce if required
+  const uint8_t* nonce_aead = nonce;
+  uint8_t nonce_masked[kAesGcmNonceLength];
+  if (aes_gcm_crypter->rekey_data != nullptr) {
+    aes_gcm_mask_nonce(nonce_masked, aes_gcm_crypter->rekey_data->nonce_mask,
+                       nonce);
+    nonce_aead = nonce_masked;
+  }
+  // init openssl context
+  if (!EVP_DecryptInit_ex(aes_gcm_crypter->ctx, nullptr, nullptr, nullptr,
+                          nonce_aead)) {
+    aes_gcm_format_errors("Initializing nonce failed.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  // process aad
+  for (i = 0; i < aad_vec_length; i++) {
+    const uint8_t* aad = static_cast<uint8_t*>(aad_vec[i].iov_base);
+    size_t aad_length = aad_vec[i].iov_len;
+    if (aad_length == 0) {
+      continue;
+    }
+    size_t aad_bytes_read = 0;
+    if (aad == nullptr) {
+      aes_gcm_format_errors("aad is nullptr.", error_details);
+      return GRPC_STATUS_INVALID_ARGUMENT;
+    }
+    if (!EVP_DecryptUpdate(aes_gcm_crypter->ctx, nullptr,
+                           reinterpret_cast<int*>(&aad_bytes_read), aad,
+                           static_cast<int>(aad_length)) ||
+        aad_bytes_read != aad_length) {
+      aes_gcm_format_errors("Setting authenticated associated data failed.",
+                            error_details);
+      return GRPC_STATUS_INTERNAL;
+    }
+  }
+  // process ciphertext
+  uint8_t* plaintext = static_cast<uint8_t*>(plaintext_vec.iov_base);
+  size_t plaintext_length = plaintext_vec.iov_len;
+  if (plaintext_length > 0 && plaintext == nullptr) {
+    aes_gcm_format_errors(
+        "plaintext is nullptr, but plaintext_length is positive.",
+        error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  const uint8_t* ciphertext = nullptr;
+  size_t ciphertext_length = 0;
+  for (i = 0;
+       i < ciphertext_vec_length && total_ciphertext_length > kAesGcmTagLength;
+       i++) {
+    ciphertext = static_cast<uint8_t*>(ciphertext_vec[i].iov_base);
+    ciphertext_length = ciphertext_vec[i].iov_len;
+    if (ciphertext == nullptr) {
+      if (ciphertext_length == 0) {
+        continue;
+      }
+      aes_gcm_format_errors("ciphertext is nullptr.", error_details);
+      memset(plaintext_vec.iov_base, 0x00, plaintext_vec.iov_len);
+      return GRPC_STATUS_INVALID_ARGUMENT;
+    }
+    size_t bytes_written = 0;
+    size_t bytes_to_write = ciphertext_length;
+    // Don't include the tag
+    if (bytes_to_write > total_ciphertext_length - kAesGcmTagLength) {
+      bytes_to_write = total_ciphertext_length - kAesGcmTagLength;
+    }
+    if (plaintext_length < bytes_to_write) {
+      aes_gcm_format_errors(
+          "Not enough plaintext buffer to hold encrypted ciphertext.",
+          error_details);
+      return GRPC_STATUS_INVALID_ARGUMENT;
+    }
+    if (!EVP_DecryptUpdate(aes_gcm_crypter->ctx, plaintext,
+                           reinterpret_cast<int*>(&bytes_written), ciphertext,
+                           static_cast<int>(bytes_to_write))) {
+      aes_gcm_format_errors("Decrypting ciphertext failed.", error_details);
+      memset(plaintext_vec.iov_base, 0x00, plaintext_vec.iov_len);
+      return GRPC_STATUS_INTERNAL;
+    }
+    if (bytes_written > ciphertext_length) {
+      aes_gcm_format_errors("More bytes written than expected.", error_details);
+      memset(plaintext_vec.iov_base, 0x00, plaintext_vec.iov_len);
+      return GRPC_STATUS_INTERNAL;
+    }
+    ciphertext += bytes_written;
+    ciphertext_length -= bytes_written;
+    total_ciphertext_length -= bytes_written;
+    plaintext += bytes_written;
+    plaintext_length -= bytes_written;
+  }
+  if (total_ciphertext_length > kAesGcmTagLength) {
+    aes_gcm_format_errors(
+        "Not enough plaintext buffer to hold encrypted ciphertext.",
+        error_details);
+    memset(plaintext_vec.iov_base, 0x00, plaintext_vec.iov_len);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  uint8_t tag[kAesGcmTagLength];
+  uint8_t* tag_tmp = tag;
+  if (ciphertext_length > 0) {
+    memcpy(tag_tmp, ciphertext, ciphertext_length);
+    tag_tmp += ciphertext_length;
+    total_ciphertext_length -= ciphertext_length;
+  }
+  for (; i < ciphertext_vec_length; i++) {
+    ciphertext = static_cast<uint8_t*>(ciphertext_vec[i].iov_base);
+    ciphertext_length = ciphertext_vec[i].iov_len;
+    if (ciphertext == nullptr) {
+      if (ciphertext_length == 0) {
+        continue;
+      }
+      aes_gcm_format_errors("ciphertext is nullptr.", error_details);
+      memset(plaintext_vec.iov_base, 0x00, plaintext_vec.iov_len);
+      return GRPC_STATUS_INVALID_ARGUMENT;
+    }
+    memcpy(tag_tmp, ciphertext, ciphertext_length);
+    tag_tmp += ciphertext_length;
+    total_ciphertext_length -= ciphertext_length;
+  }
+  if (!EVP_CIPHER_CTX_ctrl(aes_gcm_crypter->ctx, EVP_CTRL_GCM_SET_TAG,
+                           kAesGcmTagLength, reinterpret_cast<void*>(tag))) {
+    aes_gcm_format_errors("Setting tag failed.", error_details);
+    memset(plaintext_vec.iov_base, 0x00, plaintext_vec.iov_len);
+    return GRPC_STATUS_INTERNAL;
+  }
+  int bytes_written_temp = 0;
+  if (!EVP_DecryptFinal_ex(aes_gcm_crypter->ctx, nullptr,
+                           &bytes_written_temp)) {
+    aes_gcm_format_errors("Checking tag failed.", error_details);
+    memset(plaintext_vec.iov_base, 0x00, plaintext_vec.iov_len);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  if (bytes_written_temp != 0) {
+    aes_gcm_format_errors("Openssl wrote some unexpected bytes.",
+                          error_details);
+    memset(plaintext_vec.iov_base, 0x00, plaintext_vec.iov_len);
+    return GRPC_STATUS_INTERNAL;
+  }
+  *plaintext_bytes_written = plaintext_vec.iov_len - plaintext_length;
+  return GRPC_STATUS_OK;
+}
+
+static void gsec_aes_gcm_aead_crypter_destroy(gsec_aead_crypter* crypter) {
+  gsec_aes_gcm_aead_crypter* aes_gcm_crypter =
+      reinterpret_cast<gsec_aes_gcm_aead_crypter*>(
+          const_cast<gsec_aead_crypter*>(crypter));
+  gpr_free(aes_gcm_crypter->key);
+  gpr_free(aes_gcm_crypter->rekey_data);
+  EVP_CIPHER_CTX_free(aes_gcm_crypter->ctx);
+}
+
+static const gsec_aead_crypter_vtable vtable = {
+    gsec_aes_gcm_aead_crypter_encrypt_iovec,
+    gsec_aes_gcm_aead_crypter_decrypt_iovec,
+    gsec_aes_gcm_aead_crypter_max_ciphertext_and_tag_length,
+    gsec_aes_gcm_aead_crypter_max_plaintext_length,
+    gsec_aes_gcm_aead_crypter_nonce_length,
+    gsec_aes_gcm_aead_crypter_key_length,
+    gsec_aes_gcm_aead_crypter_tag_length,
+    gsec_aes_gcm_aead_crypter_destroy};
+
+static grpc_status_code aes_gcm_new_evp_cipher_ctx(
+    gsec_aes_gcm_aead_crypter* aes_gcm_crypter, char** error_details) {
+  const EVP_CIPHER* cipher = nullptr;
+  bool is_rekey = aes_gcm_crypter->rekey_data != nullptr;
+  switch (is_rekey ? kRekeyAeadKeyLen : aes_gcm_crypter->key_length) {
+    case kAes128GcmKeyLength:
+      cipher = EVP_aes_128_gcm();
+      break;
+    case kAes256GcmKeyLength:
+      cipher = EVP_aes_256_gcm();
+      break;
+  }
+  const uint8_t* aead_key = aes_gcm_crypter->key;
+  uint8_t aead_key_rekey[kRekeyAeadKeyLen];
+  if (is_rekey) {
+    if (aes_gcm_derive_aead_key(aead_key_rekey, aes_gcm_crypter->key,
+                                aes_gcm_crypter->rekey_data->kdf_counter) !=
+        GRPC_STATUS_OK) {
+      aes_gcm_format_errors("Deriving key failed.", error_details);
+      return GRPC_STATUS_INTERNAL;
+    }
+    aead_key = aead_key_rekey;
+  }
+  if (!EVP_DecryptInit_ex(aes_gcm_crypter->ctx, cipher, nullptr, aead_key,
+                          nullptr)) {
+    aes_gcm_format_errors("Setting key failed.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  if (!EVP_CIPHER_CTX_ctrl(aes_gcm_crypter->ctx, EVP_CTRL_GCM_SET_IVLEN,
+                           static_cast<int>(aes_gcm_crypter->nonce_length),
+                           nullptr)) {
+    aes_gcm_format_errors("Setting nonce length failed.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  return GRPC_STATUS_OK;
+}
+
+grpc_status_code gsec_aes_gcm_aead_crypter_create(const uint8_t* key,
+                                                  size_t key_length,
+                                                  size_t nonce_length,
+                                                  size_t tag_length, bool rekey,
+                                                  gsec_aead_crypter** crypter,
+                                                  char** error_details) {
+  if (key == nullptr) {
+    aes_gcm_format_errors("key is nullptr.", error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  if (crypter == nullptr) {
+    aes_gcm_format_errors("crypter is nullptr.", error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  *crypter = nullptr;
+  if ((rekey && key_length != kAes128GcmRekeyKeyLength) ||
+      (!rekey && key_length != kAes128GcmKeyLength &&
+       key_length != kAes256GcmKeyLength) ||
+      (tag_length != kAesGcmTagLength) ||
+      (nonce_length != kAesGcmNonceLength)) {
+    aes_gcm_format_errors(
+        "Invalid key and/or nonce and/or tag length are provided at AEAD "
+        "crypter instance construction time.",
+        error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  gsec_aes_gcm_aead_crypter* aes_gcm_crypter =
+      static_cast<gsec_aes_gcm_aead_crypter*>(
+          gpr_malloc(sizeof(gsec_aes_gcm_aead_crypter)));
+  aes_gcm_crypter->crypter.vtable = &vtable;
+  aes_gcm_crypter->nonce_length = nonce_length;
+  aes_gcm_crypter->tag_length = tag_length;
+  if (rekey) {
+    aes_gcm_crypter->key_length = kKdfKeyLen;
+    aes_gcm_crypter->rekey_data = static_cast<gsec_aes_gcm_aead_rekey_data*>(
+        gpr_malloc(sizeof(gsec_aes_gcm_aead_rekey_data)));
+    memcpy(aes_gcm_crypter->rekey_data->nonce_mask, key + kKdfKeyLen,
+           kAesGcmNonceLength);
+    // Set kdf_counter to all-zero for initial key derivation.
+    memset(aes_gcm_crypter->rekey_data->kdf_counter, 0, kKdfCounterLen);
+  } else {
+    aes_gcm_crypter->key_length = key_length;
+    aes_gcm_crypter->rekey_data = nullptr;
+  }
+  aes_gcm_crypter->key =
+      static_cast<uint8_t*>(gpr_malloc(aes_gcm_crypter->key_length));
+  memcpy(aes_gcm_crypter->key, key, aes_gcm_crypter->key_length);
+  aes_gcm_crypter->ctx = EVP_CIPHER_CTX_new();
+  grpc_status_code status =
+      aes_gcm_new_evp_cipher_ctx(aes_gcm_crypter, error_details);
+  if (status != GRPC_STATUS_OK) {
+    gsec_aes_gcm_aead_crypter_destroy(&aes_gcm_crypter->crypter);
+    gpr_free(aes_gcm_crypter);
+    return status;
+  }
+  *crypter = &aes_gcm_crypter->crypter;
+  return GRPC_STATUS_OK;
+}
diff --git a/src/core/tsi/alts/crypt/gsec.cc b/src/core/tsi/alts/crypt/gsec.cc
new file mode 100644
index 0000000..6236591
--- /dev/null
+++ b/src/core/tsi/alts/crypt/gsec.cc
@@ -0,0 +1,189 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/crypt/gsec.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+
+static const char vtable_error_msg[] =
+    "crypter or crypter->vtable has not been initialized properly";
+
+static void maybe_copy_error_msg(const char* src, char** dst) {
+  if (dst != nullptr && src != nullptr) {
+    *dst = static_cast<char*>(gpr_malloc(strlen(src) + 1));
+    memcpy(*dst, src, strlen(src) + 1);
+  }
+}
+
+grpc_status_code gsec_aead_crypter_encrypt(
+    gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+    const uint8_t* aad, size_t aad_length, const uint8_t* plaintext,
+    size_t plaintext_length, uint8_t* ciphertext_and_tag,
+    size_t ciphertext_and_tag_length, size_t* bytes_written,
+    char** error_details) {
+  if (crypter != nullptr && crypter->vtable != nullptr &&
+      crypter->vtable->encrypt_iovec != nullptr) {
+    struct iovec aad_vec = {(void*)aad, aad_length};
+    struct iovec plaintext_vec = {(void*)plaintext, plaintext_length};
+    struct iovec ciphertext_vec = {ciphertext_and_tag,
+                                   ciphertext_and_tag_length};
+    return crypter->vtable->encrypt_iovec(
+        crypter, nonce, nonce_length, &aad_vec, 1, &plaintext_vec, 1,
+        ciphertext_vec, bytes_written, error_details);
+  }
+  /* An error occurred. */
+  maybe_copy_error_msg(vtable_error_msg, error_details);
+  return GRPC_STATUS_INVALID_ARGUMENT;
+}
+
+grpc_status_code gsec_aead_crypter_encrypt_iovec(
+    gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+    const struct iovec* aad_vec, size_t aad_vec_length,
+    const struct iovec* plaintext_vec, size_t plaintext_vec_length,
+    struct iovec ciphertext_vec, size_t* ciphertext_bytes_written,
+    char** error_details) {
+  if (crypter != nullptr && crypter->vtable != nullptr &&
+      crypter->vtable->encrypt_iovec != nullptr) {
+    return crypter->vtable->encrypt_iovec(
+        crypter, nonce, nonce_length, aad_vec, aad_vec_length, plaintext_vec,
+        plaintext_vec_length, ciphertext_vec, ciphertext_bytes_written,
+        error_details);
+  }
+  /* An error occurred. */
+  maybe_copy_error_msg(vtable_error_msg, error_details);
+  return GRPC_STATUS_INVALID_ARGUMENT;
+}
+
+grpc_status_code gsec_aead_crypter_decrypt(
+    gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+    const uint8_t* aad, size_t aad_length, const uint8_t* ciphertext_and_tag,
+    size_t ciphertext_and_tag_length, uint8_t* plaintext,
+    size_t plaintext_length, size_t* bytes_written, char** error_details) {
+  if (crypter != nullptr && crypter->vtable != nullptr &&
+      crypter->vtable->decrypt_iovec != nullptr) {
+    struct iovec aad_vec = {(void*)aad, aad_length};
+    struct iovec ciphertext_vec = {(void*)ciphertext_and_tag,
+                                   ciphertext_and_tag_length};
+    struct iovec plaintext_vec = {plaintext, plaintext_length};
+    return crypter->vtable->decrypt_iovec(
+        crypter, nonce, nonce_length, &aad_vec, 1, &ciphertext_vec, 1,
+        plaintext_vec, bytes_written, error_details);
+  }
+  /* An error occurred. */
+  maybe_copy_error_msg(vtable_error_msg, error_details);
+  return GRPC_STATUS_INVALID_ARGUMENT;
+}
+
+grpc_status_code gsec_aead_crypter_decrypt_iovec(
+    gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+    const struct iovec* aad_vec, size_t aad_vec_length,
+    const struct iovec* ciphertext_vec, size_t ciphertext_vec_length,
+    struct iovec plaintext_vec, size_t* plaintext_bytes_written,
+    char** error_details) {
+  if (crypter != nullptr && crypter->vtable != nullptr &&
+      crypter->vtable->encrypt_iovec != nullptr) {
+    return crypter->vtable->decrypt_iovec(
+        crypter, nonce, nonce_length, aad_vec, aad_vec_length, ciphertext_vec,
+        ciphertext_vec_length, plaintext_vec, plaintext_bytes_written,
+        error_details);
+  }
+  /* An error occurred. */
+  maybe_copy_error_msg(vtable_error_msg, error_details);
+  return GRPC_STATUS_INVALID_ARGUMENT;
+}
+
+grpc_status_code gsec_aead_crypter_max_ciphertext_and_tag_length(
+    const gsec_aead_crypter* crypter, size_t plaintext_length,
+    size_t* max_ciphertext_and_tag_length_to_return, char** error_details) {
+  if (crypter != nullptr && crypter->vtable != nullptr &&
+      crypter->vtable->max_ciphertext_and_tag_length != nullptr) {
+    return crypter->vtable->max_ciphertext_and_tag_length(
+        crypter, plaintext_length, max_ciphertext_and_tag_length_to_return,
+        error_details);
+  }
+  /* An error occurred. */
+  maybe_copy_error_msg(vtable_error_msg, error_details);
+  return GRPC_STATUS_INVALID_ARGUMENT;
+}
+
+grpc_status_code gsec_aead_crypter_max_plaintext_length(
+    const gsec_aead_crypter* crypter, size_t ciphertext_and_tag_length,
+    size_t* max_plaintext_length_to_return, char** error_details) {
+  if (crypter != nullptr && crypter->vtable != nullptr &&
+      crypter->vtable->max_plaintext_length != nullptr) {
+    return crypter->vtable->max_plaintext_length(
+        crypter, ciphertext_and_tag_length, max_plaintext_length_to_return,
+        error_details);
+  }
+  /* An error occurred. */
+  maybe_copy_error_msg(vtable_error_msg, error_details);
+  return GRPC_STATUS_INVALID_ARGUMENT;
+}
+
+grpc_status_code gsec_aead_crypter_nonce_length(
+    const gsec_aead_crypter* crypter, size_t* nonce_length_to_return,
+    char** error_details) {
+  if (crypter != nullptr && crypter->vtable != nullptr &&
+      crypter->vtable->nonce_length != nullptr) {
+    return crypter->vtable->nonce_length(crypter, nonce_length_to_return,
+                                         error_details);
+  }
+  /* An error occurred. */
+  maybe_copy_error_msg(vtable_error_msg, error_details);
+  return GRPC_STATUS_INVALID_ARGUMENT;
+}
+
+grpc_status_code gsec_aead_crypter_key_length(const gsec_aead_crypter* crypter,
+                                              size_t* key_length_to_return,
+                                              char** error_details) {
+  if (crypter != nullptr && crypter->vtable != nullptr &&
+      crypter->vtable->key_length != nullptr) {
+    return crypter->vtable->key_length(crypter, key_length_to_return,
+                                       error_details);
+  }
+  /* An error occurred */
+  maybe_copy_error_msg(vtable_error_msg, error_details);
+  return GRPC_STATUS_INVALID_ARGUMENT;
+}
+
+grpc_status_code gsec_aead_crypter_tag_length(const gsec_aead_crypter* crypter,
+                                              size_t* tag_length_to_return,
+                                              char** error_details) {
+  if (crypter != nullptr && crypter->vtable != nullptr &&
+      crypter->vtable->tag_length != nullptr) {
+    return crypter->vtable->tag_length(crypter, tag_length_to_return,
+                                       error_details);
+  }
+  /* An error occurred. */
+  maybe_copy_error_msg(vtable_error_msg, error_details);
+  return GRPC_STATUS_INVALID_ARGUMENT;
+}
+
+void gsec_aead_crypter_destroy(gsec_aead_crypter* crypter) {
+  if (crypter != nullptr) {
+    if (crypter->vtable != nullptr && crypter->vtable->destruct != nullptr) {
+      crypter->vtable->destruct(crypter);
+    }
+    gpr_free(crypter);
+  }
+}
diff --git a/src/core/tsi/alts/crypt/gsec.h b/src/core/tsi/alts/crypt/gsec.h
new file mode 100644
index 0000000..4d65caa
--- /dev/null
+++ b/src/core/tsi/alts/crypt/gsec.h
@@ -0,0 +1,454 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_CRYPT_GSEC_H
+#define GRPC_CORE_TSI_ALTS_CRYPT_GSEC_H
+
+#include <grpc/support/port_platform.h>
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <grpc/grpc.h>
+
+struct iovec {
+  void* iov_base;
+  size_t iov_len;
+};
+
+/**
+ * A gsec interface for AEAD encryption schemes. The API is thread-compatible.
+ * Each implementation of this interface should specify supported values for
+ * key, nonce, and tag lengths.
+ */
+
+/* Key, nonce, and tag length in bytes */
+const size_t kAesGcmNonceLength = 12;
+const size_t kAesGcmTagLength = 16;
+const size_t kAes128GcmKeyLength = 16;
+const size_t kAes256GcmKeyLength = 32;
+
+// The first 32 bytes are used as a KDF key and the remaining 12 bytes are used
+// to mask the nonce.
+const size_t kAes128GcmRekeyKeyLength = 44;
+
+typedef struct gsec_aead_crypter gsec_aead_crypter;
+
+/**
+ * The gsec_aead_crypter is an API for different AEAD implementations such as
+ * AES_GCM. It encapsulates all AEAD-related operations in the format of
+ * V-table that stores pointers to functions implementing those operations.
+ * It also provides helper functions to wrap each of those function pointers.
+ *
+ * A typical usage of this object would be:
+ *
+ *------------------------------------------------------------------------------
+ * // Declare a gsec_aead_crypter object, and create and assign an instance
+ * // of specific AEAD implementation e.g., AES_GCM to it. We assume both
+ * // key and nonce contain cryptographically secure random bytes, and the key
+ * // can be derived from an upper-layer application.
+ * gsec_aead_crypter* crypter;
+ * char* error_in_creation;
+ * // User can populate the message with any 100 bytes data.
+ * uint8_t* message = gpr_malloc(100);
+ * grpc_status_code creation_status = gsec_aes_gcm_aead_crypter_create(key,
+ *                                                      kAes128GcmKeyLength,
+ *                                                      kAesGcmNonceLength,
+ *                                                      kAesGcmTagLength,
+ *                                                      &crypter,
+ *                                                      false,
+ *                                                      0
+ *                                                      &error_in_creation);
+ *
+ * if (creation_status == GRPC_STATUS_OK) {
+ *    // Allocate a correct amount of memory to hold a ciphertext.
+ *    size_t clength = 0;
+ *    gsec_aead_crypter_max_ciphertext_and_tag_length(crypter, 100, &clength,
+ *                                                    nullptr);
+ *    uint8_t* ciphertext = gpr_malloc(clength);
+ *
+ *    // Perform encryption
+ *    size_t num_encrypted_bytes = 0;
+ *    char* error_in_encryption = nullptr;
+ *    grpc_status_code status = gsec_aead_crypter_encrypt(crypter, nonce,
+ *                                                        kAesGcmNonceLength,
+ *                                                        nullptr, 0, message,
+ *                                                        100, ciphertext,
+ *                                                        clength,
+ *                                                        &num_encrypted_bytes,
+ *                                                        &error_in_encryption);
+ * if (status == GRPC_STATUS_OK) {
+ *       // Allocate a correct amount of memory to hold a plaintext.
+ *       size_t plength = 0;
+ *       gsec_aead_crypter_max_plaintext_length(crypter, num_encrypted_bytes,
+ *                                              &plength, nullptr);
+ *       uint8_t* plaintext = gpr_malloc(plength);
+ *
+ *       // Perform decryption.
+ *       size_t num_decrypted_bytes = 0;
+ *       char* error_in_decryption = nullptr;
+ *       status = gsec_aead_crypter_decrypt(crypter, nonce,
+ *                                          kAesGcmNonceLength, nullptr, 0,
+ *                                          ciphertext, num_encrypted_bytes,
+ *                                          plaintext, plength,
+ *                                          &num_decrypted_bytes,
+ *                                          &error_in_decryption);
+ *       if (status != GRPC_STATUS_OK) {
+ *         fprintf(stderr, "AEAD decrypt operation failed with error code:"
+ *                         "%d, message: %s\n", status, error_in_decryption);
+ *       }
+ *       ...
+ *       gpr_free(plaintext);
+ *       gpr_free(error_in_decryption);
+ *    } else {
+ *        fprintf(stderr, "AEAD encrypt operation failed with error code:"
+ *                        "%d, message: %s\n", status, error_in_encryption);
+ *    }
+ *    ...
+ *    gpr_free(ciphertext);
+ *    gpr_free(error_in_encryption);
+ * } else {
+ *   fprintf(stderr, "Creation of AEAD crypter instance failed with error code:"
+ *                   "%d, message: %s\n", creation_status, error_in_creation);
+ * }
+ *
+ * // Destruct AEAD crypter instance.
+ * if (creation_status == GRPC_STATUS_OK) {
+ *   gsec_aead_crypter_destroy(crypter);
+ * }
+ * gpr_free(error_in_creation);
+ * gpr_free(message);
+ * -----------------------------------------------------------------------------
+ */
+
+/* V-table for gsec AEAD operations */
+typedef struct gsec_aead_crypter_vtable {
+  grpc_status_code (*encrypt_iovec)(
+      gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+      const struct iovec* aad_vec, size_t aad_vec_length,
+      const struct iovec* plaintext_vec, size_t plaintext_vec_length,
+      struct iovec ciphertext_vec, size_t* ciphertext_bytes_written,
+      char** error_details);
+  grpc_status_code (*decrypt_iovec)(
+      gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+      const struct iovec* aad_vec, size_t aad_vec_length,
+      const struct iovec* ciphertext_vec, size_t ciphertext_vec_length,
+      struct iovec plaintext_vec, size_t* plaintext_bytes_written,
+      char** error_details);
+  grpc_status_code (*max_ciphertext_and_tag_length)(
+      const gsec_aead_crypter* crypter, size_t plaintext_length,
+      size_t* max_ciphertext_and_tag_length_to_return, char** error_details);
+  grpc_status_code (*max_plaintext_length)(
+      const gsec_aead_crypter* crypter, size_t ciphertext_and_tag_length,
+      size_t* max_plaintext_length_to_return, char** error_details);
+  grpc_status_code (*nonce_length)(const gsec_aead_crypter* crypter,
+                                   size_t* nonce_length_to_return,
+                                   char** error_details);
+  grpc_status_code (*key_length)(const gsec_aead_crypter* crypter,
+                                 size_t* key_length_to_return,
+                                 char** error_details);
+  grpc_status_code (*tag_length)(const gsec_aead_crypter* crypter,
+                                 size_t* tag_length_to_return,
+                                 char** error_details);
+  void (*destruct)(gsec_aead_crypter* crypter);
+} gsec_aead_crypter_vtable;
+
+/* Main struct for gsec interface */
+struct gsec_aead_crypter {
+  const struct gsec_aead_crypter_vtable* vtable;
+};
+
+/**
+ * This method performs an AEAD encrypt operation.
+ *
+ * - crypter: AEAD crypter instance.
+ * - nonce: buffer containing a nonce with its size equal to nonce_length.
+ * - nonce_length: size of nonce buffer, and must be equal to the value returned
+ *   from method gsec_aead_crypter_nonce_length.
+ * - aad: buffer containing data that needs to be authenticated but not
+ *   encrypted with its size equal to aad_length.
+ * - aad_length: size of aad buffer, which should be zero if the buffer is
+ *   nullptr.
+ * - plaintext: buffer containing data that needs to be both encrypted and
+ *   authenticated with its size equal to plaintext_length.
+ * - plaintext_length: size of plaintext buffer, which should be zero if
+ *   plaintext is nullptr.
+ * - ciphertext_and_tag: buffer that will contain ciphertext and tags the method
+ *   produced. The buffer should not overlap the plaintext buffer, and pointers
+ *   to those buffers should not be equal. Also if the ciphertext+tag buffer is
+ *   nullptr, the plaintext_length should be zero.
+ * - ciphertext_and_tag_length: size of ciphertext+tag buffer, which should be
+ *   at least as long as the one returned from method
+ *   gsec_aead_crypter_max_ciphertext_and_tag_length.
+ * - bytes_written: the actual number of bytes written to the ciphertext+tag
+ *   buffer. If bytes_written is nullptr, the plaintext_length should be zero.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On the success of encryption, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ *
+ */
+grpc_status_code gsec_aead_crypter_encrypt(
+    gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+    const uint8_t* aad, size_t aad_length, const uint8_t* plaintext,
+    size_t plaintext_length, uint8_t* ciphertext_and_tag,
+    size_t ciphertext_and_tag_length, size_t* bytes_written,
+    char** error_details);
+
+/**
+ * This method performs an AEAD encrypt operation.
+ *
+ * - crypter: AEAD crypter instance.
+ * - nonce: buffer containing a nonce with its size equal to nonce_length.
+ * - nonce_length: size of nonce buffer, and must be equal to the value returned
+ *   from method gsec_aead_crypter_nonce_length.
+ * - aad_vec: an iovec array containing data that needs to be authenticated but
+ *   not encrypted.
+ * - aad_vec_length: the array length of aad_vec.
+ * - plaintext_vec: an iovec array containing data that needs to be both
+ *   encrypted and authenticated.
+ * - plaintext_vec_length: the array length of plaintext_vec.
+ * - ciphertext_vec: an iovec containing a ciphertext buffer. The buffer should
+ *   not overlap the plaintext buffer.
+ * - ciphertext_bytes_written: the actual number of bytes written to
+ *   ciphertext_vec.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On the success of encryption, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ *
+ */
+grpc_status_code gsec_aead_crypter_encrypt_iovec(
+    gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+    const struct iovec* aad_vec, size_t aad_vec_length,
+    const struct iovec* plaintext_vec, size_t plaintext_vec_length,
+    struct iovec ciphertext_vec, size_t* ciphertext_bytes_written,
+    char** error_details);
+
+/**
+ * This method performs an AEAD decrypt operation.
+ *
+ * - crypter: AEAD crypter instance.
+ * - nonce: buffer containing a nonce with its size equal to nonce_length.
+ * - nonce_length: size of nonce buffer, and must be equal to the value returned
+ *   from method gsec_aead_crypter_nonce_length.
+ * - aad: buffer containing data that needs to be authenticated only.
+ * - aad_length: size of aad buffer, which should be zero if the buffer is
+ *   nullptr.
+ * - ciphertext_and_tag: buffer containing ciphertext and tag.
+ * - ciphertext_and_tag_length: length of ciphertext and tag. It should be zero
+ *   if any of plaintext, ciphertext_and_tag, or bytes_written is nullptr. Also,
+ *   ciphertext_and_tag_length should be at least as large as the tag length set
+ *   at AEAD crypter instance construction time.
+ * - plaintext: buffer containing decrypted and authenticated data the method
+ *   produced. The buffer should not overlap with the ciphertext+tag buffer, and
+ *   pointers to those buffers should not be equal.
+ * - plaintext_length: size of plaintext buffer, which should be at least as
+ *   long as the one returned from gsec_aead_crypter_max_plaintext_length
+ *   method.
+ * - bytes_written: the actual number of bytes written to the plaintext
+ *   buffer.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On the success of decryption, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code gsec_aead_crypter_decrypt(
+    gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+    const uint8_t* aad, size_t aad_length, const uint8_t* ciphertext_and_tag,
+    size_t ciphertext_and_tag_length, uint8_t* plaintext,
+    size_t plaintext_length, size_t* bytes_written, char** error_details);
+
+/**
+ * This method performs an AEAD decrypt operation.
+ *
+ * - crypter: AEAD crypter instance.
+ * - nonce: buffer containing a nonce with its size equal to nonce_length.
+ * - nonce_length: size of nonce buffer, and must be equal to the value returned
+ *   from method gsec_aead_crypter_nonce_length.
+ * - aad_vec: an iovec array containing data that needs to be authenticated but
+ *   not encrypted.
+ * - aad_vec_length: the array length of aad_vec.
+ * - ciphertext_vec: an iovec array containing the ciphertext and tag.
+ * - ciphertext_vec_length: the array length of ciphertext_vec.
+ * - plaintext_vec: an iovec containing a plaintext buffer. The buffer should
+ *   not overlap the ciphertext buffer.
+ * - plaintext_bytes_written: the actual number of bytes written to
+ *   plaintext_vec.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On the success of decryption, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code gsec_aead_crypter_decrypt_iovec(
+    gsec_aead_crypter* crypter, const uint8_t* nonce, size_t nonce_length,
+    const struct iovec* aad_vec, size_t aad_vec_length,
+    const struct iovec* ciphertext_vec, size_t ciphertext_vec_length,
+    struct iovec plaintext_vec, size_t* plaintext_bytes_written,
+    char** error_details);
+
+/**
+ * This method computes the size of ciphertext+tag buffer that must be passed to
+ * gsec_aead_crypter_encrypt function to ensure correct encryption of a
+ * plaintext. The actual size of ciphertext+tag written to the buffer could be
+ * smaller.
+ *
+ * - crypter: AEAD crypter instance.
+ * - plaintext_length: length of plaintext.
+ * - max_ciphertext_and_tag_length_to_return: the size of ciphertext+tag buffer
+ *   the method returns.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On the success of execution, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code gsec_aead_crypter_max_ciphertext_and_tag_length(
+    const gsec_aead_crypter* crypter, size_t plaintext_length,
+    size_t* max_ciphertext_and_tag_length_to_return, char** error_details);
+
+/**
+ * This method computes the size of plaintext buffer that must be passed to
+ * gsec_aead_crypter_decrypt function to ensure correct decryption of a
+ * ciphertext. The actual size of plaintext written to the buffer could be
+ * smaller.
+ *
+ * - crypter: AEAD crypter instance.
+ * - ciphertext_and_tag_length: length of ciphertext and tag.
+ * - max_plaintext_length_to_return: the size of plaintext buffer the method
+ *   returns.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On the success of execution, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code gsec_aead_crypter_max_plaintext_length(
+    const gsec_aead_crypter* crypter, size_t ciphertext_and_tag_length,
+    size_t* max_plaintext_length_to_return, char** error_details);
+
+/**
+ * This method returns a valid size of nonce array used at the construction of
+ * AEAD crypter instance. It is also the size that should be passed to encrypt
+ * and decrypt methods executed on the instance.
+ *
+ * - crypter: AEAD crypter instance.
+ * - nonce_length_to_return: the length of nonce array the method returns.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On the success of execution, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code gsec_aead_crypter_nonce_length(
+    const gsec_aead_crypter* crypter, size_t* nonce_length_to_return,
+    char** error_details);
+
+/**
+ * This method returns a valid size of key array used at the construction of
+ * AEAD crypter instance. It is also the size that should be passed to encrypt
+ * and decrypt methods executed on the instance.
+ *
+ * - crypter: AEAD crypter instance.
+ * - key_length_to_return: the length of key array the method returns.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On the success of execution, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code gsec_aead_crypter_key_length(const gsec_aead_crypter* crypter,
+                                              size_t* key_length_to_return,
+                                              char** error_details);
+/**
+ * This method returns a valid size of tag array used at the construction of
+ * AEAD crypter instance. It is also the size that should be passed to encrypt
+ * and decrypt methods executed on the instance.
+ *
+ * - crypter: AEAD crypter instance.
+ * - tag_length_to_return: the length of tag array the method returns.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On the success of execution, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code gsec_aead_crypter_tag_length(const gsec_aead_crypter* crypter,
+                                              size_t* tag_length_to_return,
+                                              char** error_details);
+
+/**
+ * This method destroys an AEAD crypter instance by de-allocating all of its
+ * occupied memory.
+ *
+ * - crypter: AEAD crypter instance that needs to be destroyed.
+ */
+void gsec_aead_crypter_destroy(gsec_aead_crypter* crypter);
+
+/**
+ * This method creates an AEAD crypter instance of AES-GCM encryption scheme
+ * which supports 16 and 32 bytes long keys, 12 and 16 bytes long nonces, and
+ * 16 bytes long tags. It should be noted that once the lengths of key, nonce,
+ * and tag are determined at construction time, they cannot be modified later.
+ *
+ * - key: buffer containing a key which is binded with AEAD crypter instance.
+ * - key_length: length of a key in bytes, which should be 44 if rekeying is
+ *   enabled and 16 or 32 otherwise.
+ * - nonce_length: length of a nonce in bytes, which should be either 12 or 16.
+ * - tag_length: length of a tag in bytes, which should be always 16.
+ * - rekey: enable nonce-based rekeying and nonce-masking.
+ * - crypter: address of AES_GCM crypter instance returned from the method.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On success of instance creation, it stores the address of instance at
+ * crypter. Otherwise, it returns an error status code together with its details
+ * specified in error_details.
+ */
+grpc_status_code gsec_aes_gcm_aead_crypter_create(const uint8_t* key,
+                                                  size_t key_length,
+                                                  size_t nonce_length,
+                                                  size_t tag_length, bool rekey,
+                                                  gsec_aead_crypter** crypter,
+                                                  char** error_details);
+
+#endif /* GRPC_CORE_TSI_ALTS_CRYPT_GSEC_H */
diff --git a/src/core/tsi/alts/frame_protector/alts_counter.cc b/src/core/tsi/alts/frame_protector/alts_counter.cc
new file mode 100644
index 0000000..de163e3
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/alts_counter.cc
@@ -0,0 +1,118 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/frame_protector/alts_counter.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+
+static void maybe_copy_error_msg(const char* src, char** dst) {
+  if (dst != nullptr && src != nullptr) {
+    *dst = static_cast<char*>(gpr_malloc(strlen(src) + 1));
+    memcpy(*dst, src, strlen(src) + 1);
+  }
+}
+
+grpc_status_code alts_counter_create(bool is_client, size_t counter_size,
+                                     size_t overflow_size,
+                                     alts_counter** crypter_counter,
+                                     char** error_details) {
+  /* Perform input sanity check. */
+  if (counter_size == 0) {
+    const char error_msg[] = "counter_size is invalid.";
+    maybe_copy_error_msg(error_msg, error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (overflow_size == 0 || overflow_size >= counter_size) {
+    const char error_msg[] = "overflow_size is invalid.";
+    maybe_copy_error_msg(error_msg, error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (crypter_counter == nullptr) {
+    const char error_msg[] = "crypter_counter is nullptr.";
+    maybe_copy_error_msg(error_msg, error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  *crypter_counter =
+      static_cast<alts_counter*>(gpr_malloc(sizeof(**crypter_counter)));
+  (*crypter_counter)->size = counter_size;
+  (*crypter_counter)->overflow_size = overflow_size;
+  (*crypter_counter)->counter =
+      static_cast<unsigned char*>(gpr_zalloc(counter_size));
+  if (is_client) {
+    ((*crypter_counter)->counter)[counter_size - 1] = 0x80;
+  }
+  return GRPC_STATUS_OK;
+}
+
+grpc_status_code alts_counter_increment(alts_counter* crypter_counter,
+                                        bool* is_overflow,
+                                        char** error_details) {
+  /* Perform input sanity check. */
+  if (crypter_counter == nullptr) {
+    const char error_msg[] = "crypter_counter is nullptr.";
+    maybe_copy_error_msg(error_msg, error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (is_overflow == nullptr) {
+    const char error_msg[] = "is_overflow is nullptr.";
+    maybe_copy_error_msg(error_msg, error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  /* Increment the internal counter. */
+  size_t i = 0;
+  for (; i < crypter_counter->overflow_size; i++) {
+    (crypter_counter->counter)[i]++;
+    if ((crypter_counter->counter)[i] != 0x00) {
+      break;
+    }
+  }
+  /**
+   * If the lower overflow_size bytes are all zero, the counter has overflowed.
+   */
+  if (i == crypter_counter->overflow_size) {
+    *is_overflow = true;
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  *is_overflow = false;
+  return GRPC_STATUS_OK;
+}
+
+size_t alts_counter_get_size(alts_counter* crypter_counter) {
+  if (crypter_counter == nullptr) {
+    return 0;
+  }
+  return crypter_counter->size;
+}
+
+unsigned char* alts_counter_get_counter(alts_counter* crypter_counter) {
+  if (crypter_counter == nullptr) {
+    return nullptr;
+  }
+  return crypter_counter->counter;
+}
+
+void alts_counter_destroy(alts_counter* crypter_counter) {
+  if (crypter_counter != nullptr) {
+    gpr_free(crypter_counter->counter);
+    gpr_free(crypter_counter);
+  }
+}
diff --git a/src/core/tsi/alts/frame_protector/alts_counter.h b/src/core/tsi/alts/frame_protector/alts_counter.h
new file mode 100644
index 0000000..d705638
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/alts_counter.h
@@ -0,0 +1,98 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_COUNTER_H
+#define GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_COUNTER_H
+
+#include <grpc/support/port_platform.h>
+
+#include <stdbool.h>
+#include <stdlib.h>
+
+#include <grpc/grpc.h>
+
+/* Main struct for a crypter counter managed within seal/unseal operations. */
+typedef struct alts_counter {
+  size_t size;
+  size_t overflow_size;
+  unsigned char* counter;
+} alts_counter;
+
+/**
+ * This method creates and initializes an alts_counter instance.
+ *
+ * - is_client: a flag indicating if the alts_counter instance will be used
+ *   at client (is_client = true) or server (is_client = false) side.
+ * - counter_size: size of buffer holding the counter value.
+ * - overflow_size: overflow size in bytes. The counter instance can be used
+ *   to produce at most 2^(overflow_size*8) frames.
+ * - crypter_counter: an alts_counter instance to be returned from the method.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code alts_counter_create(bool is_client, size_t counter_size,
+                                     size_t overflow_size,
+                                     alts_counter** crypter_counter,
+                                     char** error_details);
+
+/**
+ * This method increments the internal counter.
+ *
+ * - crypter_counter: an alts_counter instance.
+ * - is_overflow: after incrementing the internal counter, if an overflow
+ *   occurs, is_overflow is set to true, and no further calls to
+ *   alts_counter_increment() should be made. Otherwise, is_overflow is set to
+ *   false.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code alts_counter_increment(alts_counter* crypter_counter,
+                                        bool* is_overflow,
+                                        char** error_details);
+
+/**
+ * This method returns the size of counter buffer.
+ *
+ * - crypter_counter: an alts_counter instance.
+ */
+size_t alts_counter_get_size(alts_counter* crypter_counter);
+
+/**
+ * This method returns the counter buffer.
+ *
+ * - crypter_counter: an alts_counter instance.
+ */
+unsigned char* alts_counter_get_counter(alts_counter* crypter_counter);
+
+/**
+ * This method de-allocates all memory allocated to an alts_coutner instance.
+ * - crypter_counter: an alts_counter instance.
+ */
+void alts_counter_destroy(alts_counter* crypter_counter);
+
+#endif /* GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_COUNTER_H */
diff --git a/src/core/tsi/alts/frame_protector/alts_crypter.cc b/src/core/tsi/alts/frame_protector/alts_crypter.cc
new file mode 100644
index 0000000..56f0512
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/alts_crypter.cc
@@ -0,0 +1,66 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/frame_protector/alts_crypter.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+
+static void maybe_copy_error_msg(const char* src, char** dst) {
+  if (dst != nullptr && src != nullptr) {
+    *dst = static_cast<char*>(gpr_malloc(strlen(src) + 1));
+    memcpy(*dst, src, strlen(src) + 1);
+  }
+}
+
+grpc_status_code alts_crypter_process_in_place(
+    alts_crypter* crypter, unsigned char* data, size_t data_allocated_size,
+    size_t data_size, size_t* output_size, char** error_details) {
+  if (crypter != nullptr && crypter->vtable != nullptr &&
+      crypter->vtable->process_in_place != nullptr) {
+    return crypter->vtable->process_in_place(crypter, data, data_allocated_size,
+                                             data_size, output_size,
+                                             error_details);
+  }
+  /* An error occurred. */
+  const char error_msg[] =
+      "crypter or crypter->vtable has not been initialized properly.";
+  maybe_copy_error_msg(error_msg, error_details);
+  return GRPC_STATUS_INVALID_ARGUMENT;
+}
+
+size_t alts_crypter_num_overhead_bytes(const alts_crypter* crypter) {
+  if (crypter != nullptr && crypter->vtable != nullptr &&
+      crypter->vtable->num_overhead_bytes != nullptr) {
+    return crypter->vtable->num_overhead_bytes(crypter);
+  }
+  /* An error occurred. */
+  return 0;
+}
+
+void alts_crypter_destroy(alts_crypter* crypter) {
+  if (crypter != nullptr) {
+    if (crypter->vtable != nullptr && crypter->vtable->destruct != nullptr) {
+      crypter->vtable->destruct(crypter);
+    }
+    gpr_free(crypter);
+  }
+}
diff --git a/src/core/tsi/alts/frame_protector/alts_crypter.h b/src/core/tsi/alts/frame_protector/alts_crypter.h
new file mode 100644
index 0000000..3140778
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/alts_crypter.h
@@ -0,0 +1,255 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_CRYPTER_H
+#define GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_CRYPTER_H
+
+#include <grpc/support/port_platform.h>
+
+#include <stdbool.h>
+#include <string.h>
+
+#include <grpc/grpc.h>
+
+#include "src/core/tsi/alts/crypt/gsec.h"
+
+/**
+ * An alts_crypter interface for an ALTS record protocol providing
+ * seal/unseal functionality. The interface is thread-compatible.
+ */
+
+typedef struct alts_crypter alts_crypter;
+
+/**
+ * A typical usage of the interface would be
+ *------------------------------------------------------------------------------
+ * // Perform a seal operation. We assume the gsec_aead_crypter instance -
+ * // client_aead_crypter is created beforehand with a 16-byte key and 12-byte
+ * // nonce length.
+ *
+ * alts_crypter* client = nullptr;
+ * char* client_error_in_creation = nullptr;
+ * unsigned char* data = nullptr;
+ * grpc_status_code client_status =
+ *                 alts_seal_crypter_create(client_aead_crypter, 1, 5, &client,
+ *                                          &client_error_in_creation);
+ * if (client_status == GRPC_STATUS_OK) {
+ *   size_t data_size = 100;
+ *   size_t num_overhead_bytes = alts_crypter_num_overhead_bytes(client);
+ *   size_t data_allocated_size = data_size + num_overhead_bytes;
+ *   data = gpr_malloc(data_allocated_size);
+ *   char* client_error_in_seal = nullptr;
+ *   // Client performs a seal operation.
+ *   client_status = alts_crypter_process_in_place(client, data,
+ *                                                 data_allocated_size,
+ *                                                 &data_size,
+ *                                                 &client_error_in_seal);
+ *   if (client_status != GRPC_STATUS_OK) {
+ *     fprintf(stderr, "seal operation failed with error code:"
+ *                     "%d, message: %s\n", client_status,
+ *                      client_error_in_seal);
+ *    }
+ *    gpr_free(client_error_in_seal);
+ * } else {
+ *     fprintf(stderr, "alts_crypter instance creation failed with error"
+ *                     "code: %d, message: %s\n", client_status,
+ *                      client_error_in_creation);
+ * }
+ *
+ * ...
+ *
+ * gpr_free(client_error_in_creation);
+ * alts_crypter_destroy(client);
+ *
+ * ...
+ *
+ * // Perform an unseal operation. We assume the gsec_aead_crypter instance -
+ * // server_aead_crypter is created beforehand with a 16-byte key and 12-byte
+ * // nonce length. The key used in the creation of gsec_aead_crypter instances
+ * // at server and client sides should be identical.
+ *
+ * alts_crypter* server = nullptr;
+ * char* server_error_in_creation = nullptr;
+ * grpc_status_code server_status =
+ *               alts_unseal_crypter_create(server_aead_crypter, 0, 5, &server,
+ *                                          &server_error_in_creation);
+ * if (server_status == GRPC_STATUS_OK) {
+ *   size_t num_overhead_bytes = alts_crypter_num_overhead_bytes(server);
+ *   size_t data_size = 100 + num_overhead_bytes;
+ *   size_t data_allocated_size = data_size;
+ *   char* server_error_in_unseal = nullptr;
+ *   // Server performs an unseal operation.
+ *   server_status = alts_crypter_process_in_place(server, data,
+ *                                                 data_allocated_size,
+ *                                                 &data_size,
+ *                                                 &server_error_in_unseal);
+ *   if (server_status != GRPC_STATUS_OK) {
+ *     fprintf(stderr, "unseal operation failed with error code:"
+ *                     "%d, message: %s\n", server_status,
+ *                      server_error_in_unseal);
+ *   }
+ *   gpr_free(server_error_in_unseal);
+ * } else {
+ *     fprintf(stderr, "alts_crypter instance creation failed with error"
+ *                     "code: %d, message: %s\n", server_status,
+ *                      server_error_in_creation);
+ * }
+ *
+ * ...
+ *
+ * gpr_free(data);
+ * gpr_free(server_error_in_creation);
+ * alts_crypter_destroy(server);
+ *
+ * ...
+ *------------------------------------------------------------------------------
+ */
+
+/* V-table for alts_crypter operations */
+typedef struct alts_crypter_vtable {
+  size_t (*num_overhead_bytes)(const alts_crypter* crypter);
+  grpc_status_code (*process_in_place)(alts_crypter* crypter,
+                                       unsigned char* data,
+                                       size_t data_allocated_size,
+                                       size_t data_size, size_t* output_size,
+                                       char** error_details);
+  void (*destruct)(alts_crypter* crypter);
+} alts_crypter_vtable;
+
+/* Main struct for alts_crypter interface */
+struct alts_crypter {
+  const alts_crypter_vtable* vtable;
+};
+
+/**
+ * This method gets the number of overhead bytes needed for sealing data that
+ * is the difference in size between the protected and raw data. The counter
+ * value used in a seal or unseal operation is locally maintained (not sent or
+ * received from the other peer) and therefore, will not be counted as part of
+ * overhead bytes.
+ *
+ * - crypter: an alts_crypter instance.
+ *
+ * On success, the method returns the number of overhead bytes. Otherwise, it
+ * returns zero.
+ *
+ */
+size_t alts_crypter_num_overhead_bytes(const alts_crypter* crypter);
+
+/**
+ * This method performs either a seal or an unseal operation depending on the
+ * alts_crypter instance - crypter passed to the method. If the crypter is
+ * an instance implementing a seal operation, the method will perform a seal
+ * operation. That is, it seals raw data and stores the result in-place, and the
+ * memory allocated for data must be at least data_length +
+ * alts_crypter_num_overhead_bytes(). If the crypter is an instance
+ * implementing an unseal operation, the method will perform an unseal
+ * operation. That is, it unseals protected data and stores the result in-place.
+ * The size of unsealed data will be data_length -
+ * alts_crypter_num_overhead_bytes(). Integrity tag will be verified during
+ * the unseal operation, and if verification fails, the data will be wiped.
+ * The counters used in both seal and unseal operations are managed internally.
+ *
+ * - crypter: an alts_crypter instance.
+ * - data: if the method performs a seal operation, the data represents raw data
+ *   that needs to be sealed. It also plays the role of buffer to hold the
+ *   protected data as a result of seal. If the method performs an unseal
+ *   operation, the data represents protected data that needs to be unsealed. It
+ *   also plays the role of buffer to hold raw data as a result of unseal.
+ * - data_allocated_size: the size of data buffer. The parameter is used to
+ *   check whether the result of either seal or unseal can be safely written to
+ *   the data buffer.
+ * - data_size: if the method performs a seal operation, data_size
+ *   represents the size of raw data that needs to be sealed, and if the method
+ *   performs an unseal operation, data_size represents the size of protected
+ *   data that needs to be unsealed.
+ * - output_size: size of data written to the data buffer after a seal or an
+ *   unseal operation.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is legal to pass nullptr into error_details and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code alts_crypter_process_in_place(
+    alts_crypter* crypter, unsigned char* data, size_t data_allocated_size,
+    size_t data_size, size_t* output_size, char** error_details);
+
+/**
+ * This method creates an alts_crypter instance to be used to perform a seal
+ * operation, given a gsec_aead_crypter instance and a flag indicating if the
+ * created instance will be used at the client or server side. It takes
+ * ownership of gsec_aead_crypter instance.
+ *
+ * - gc: a gsec_aead_crypter instance used to perform AEAD encryption.
+ * - is_client: a flag indicating if the alts_crypter instance will be
+ *   used at the client (is_client = true) or server (is_client =
+ *   false) side.
+ * - overflow_size: overflow size of counter in bytes.
+ * - crypter: an alts_crypter instance to be returned from the method.
+ * - error_details: a buffer containing an error message if the method does
+ *   not function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On success of creation, the method returns GRPC_STATUS_OK.
+ * Otherwise, it returns an error status code along with its details specified
+ * in error_details (if error_details is not nullptr).
+ */
+grpc_status_code alts_seal_crypter_create(gsec_aead_crypter* gc, bool is_client,
+                                          size_t overflow_size,
+                                          alts_crypter** crypter,
+                                          char** error_details);
+
+/**
+ * This method creates an alts_crypter instance used to perform an unseal
+ * operation, given a gsec_aead_crypter instance and a flag indicating if the
+ * created instance will be used at the client or server side. It takes
+ * ownership of gsec_aead_crypter instance.
+ *
+ * - gc: a gsec_aead_crypter instance used to perform AEAD decryption.
+ * - is_client: a flag indicating if the alts_crypter instance will be
+ *   used at the client (is_client = true) or server (is_client =
+ *   false) side.
+ * - overflow_size: overflow size of counter in bytes.
+ * - crypter: an alts_crypter instance to be returned from the method.
+ * - error_details: a buffer containing an error message if the method does
+ *   not function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On success of creation, the method returns GRPC_STATUS_OK.
+ * Otherwise, it returns an error status code along with its details specified
+ * in error_details (if error_details is not nullptr).
+ */
+grpc_status_code alts_unseal_crypter_create(gsec_aead_crypter* gc,
+                                            bool is_client,
+                                            size_t overflow_size,
+                                            alts_crypter** crypter,
+                                            char** error_details);
+
+/**
+ * This method destroys an alts_crypter instance by de-allocating all of its
+ * occupied memory. A gsec_aead_crypter instance passed in at alts_crypter
+ * instance creation time will be destroyed in this method.
+ *
+ * - crypter: an alts_crypter instance.
+ */
+void alts_crypter_destroy(alts_crypter* crypter);
+
+#endif /* GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_CRYPTER_H */
diff --git a/src/core/tsi/alts/frame_protector/alts_frame_protector.cc b/src/core/tsi/alts/frame_protector/alts_frame_protector.cc
new file mode 100644
index 0000000..bfa0b7a
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/alts_frame_protector.cc
@@ -0,0 +1,407 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/frame_protector/alts_frame_protector.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/gpr/useful.h"
+#include "src/core/tsi/alts/crypt/gsec.h"
+#include "src/core/tsi/alts/frame_protector/alts_crypter.h"
+#include "src/core/tsi/alts/frame_protector/frame_handler.h"
+#include "src/core/tsi/transport_security.h"
+
+constexpr size_t kMinFrameLength = 1024;
+constexpr size_t kDefaultFrameLength = 16 * 1024;
+constexpr size_t kMaxFrameLength = 1024 * 1024;
+
+// Limit k on number of frames such that at most 2^(8 * k) frames can be sent.
+constexpr size_t kAltsRecordProtocolRekeyFrameLimit = 8;
+constexpr size_t kAltsRecordProtocolFrameLimit = 5;
+
+/* Main struct for alts_frame_protector. */
+struct alts_frame_protector {
+  tsi_frame_protector base;
+  alts_crypter* seal_crypter;
+  alts_crypter* unseal_crypter;
+  alts_frame_writer* writer;
+  alts_frame_reader* reader;
+  unsigned char* in_place_protect_buffer;
+  unsigned char* in_place_unprotect_buffer;
+  size_t in_place_protect_bytes_buffered;
+  size_t in_place_unprotect_bytes_processed;
+  size_t max_protected_frame_size;
+  size_t max_unprotected_frame_size;
+  size_t overhead_length;
+  size_t counter_overflow;
+};
+
+static tsi_result seal(alts_frame_protector* impl) {
+  char* error_details = nullptr;
+  size_t output_size = 0;
+  grpc_status_code status = alts_crypter_process_in_place(
+      impl->seal_crypter, impl->in_place_protect_buffer,
+      impl->max_protected_frame_size, impl->in_place_protect_bytes_buffered,
+      &output_size, &error_details);
+  impl->in_place_protect_bytes_buffered = output_size;
+  if (status != GRPC_STATUS_OK) {
+    gpr_log(GPR_ERROR, "%s", error_details);
+    gpr_free(error_details);
+    return TSI_INTERNAL_ERROR;
+  }
+  return TSI_OK;
+}
+
+static size_t max_encrypted_payload_bytes(alts_frame_protector* impl) {
+  return impl->max_protected_frame_size - kFrameHeaderSize;
+}
+
+static tsi_result alts_protect_flush(tsi_frame_protector* self,
+                                     unsigned char* protected_output_frames,
+                                     size_t* protected_output_frames_size,
+                                     size_t* still_pending_size) {
+  if (self == nullptr || protected_output_frames == nullptr ||
+      protected_output_frames_size == nullptr ||
+      still_pending_size == nullptr) {
+    gpr_log(GPR_ERROR, "Invalid nullptr arguments to alts_protect_flush().");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_frame_protector* impl = reinterpret_cast<alts_frame_protector*>(self);
+  /**
+   * If there's nothing to flush (i.e., in_place_protect_buffer is empty),
+   * we're done.
+   */
+  if (impl->in_place_protect_bytes_buffered == 0) {
+    *protected_output_frames_size = 0;
+    *still_pending_size = 0;
+    return TSI_OK;
+  }
+  /**
+   * If a new frame can start being processed, we encrypt the payload and reset
+   * the frame writer to point to in_place_protect_buffer that holds the newly
+   * sealed frame.
+   */
+  if (alts_is_frame_writer_done(impl->writer)) {
+    tsi_result result = seal(impl);
+    if (result != TSI_OK) {
+      return result;
+    }
+    if (!alts_reset_frame_writer(impl->writer, impl->in_place_protect_buffer,
+                                 impl->in_place_protect_bytes_buffered)) {
+      gpr_log(GPR_ERROR, "Couldn't reset frame writer.");
+      return TSI_INTERNAL_ERROR;
+    }
+  }
+  /**
+   * Write the sealed frame as much as possible to protected_output_frames. It's
+   * possible a frame will not be written out completely by a single flush
+   * (i.e., still_pending_size != 0), in which case the flush should be called
+   * iteratively until a complete frame has been written out.
+   */
+  size_t written_frame_bytes = *protected_output_frames_size;
+  if (!alts_write_frame_bytes(impl->writer, protected_output_frames,
+                              &written_frame_bytes)) {
+    gpr_log(GPR_ERROR, "Couldn't write frame bytes.");
+    return TSI_INTERNAL_ERROR;
+  }
+  *protected_output_frames_size = written_frame_bytes;
+  *still_pending_size = alts_get_num_writer_bytes_remaining(impl->writer);
+  /**
+   * If the current frame has been finished processing (i.e., sealed and written
+   * out completely), we empty in_place_protect_buffer.
+   */
+  if (alts_is_frame_writer_done(impl->writer)) {
+    impl->in_place_protect_bytes_buffered = 0;
+  }
+  return TSI_OK;
+}
+
+static tsi_result alts_protect(tsi_frame_protector* self,
+                               const unsigned char* unprotected_bytes,
+                               size_t* unprotected_bytes_size,
+                               unsigned char* protected_output_frames,
+                               size_t* protected_output_frames_size) {
+  if (self == nullptr || unprotected_bytes == nullptr ||
+      unprotected_bytes_size == nullptr || protected_output_frames == nullptr ||
+      protected_output_frames_size == nullptr) {
+    gpr_log(GPR_ERROR, "Invalid nullptr arguments to alts_protect().");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_frame_protector* impl = reinterpret_cast<alts_frame_protector*>(self);
+
+  /**
+   * If more payload can be buffered, we buffer it as much as possible to
+   * in_place_protect_buffer.
+   */
+  if (impl->in_place_protect_bytes_buffered + impl->overhead_length <
+      max_encrypted_payload_bytes(impl)) {
+    size_t bytes_to_buffer = GPR_MIN(*unprotected_bytes_size,
+                                     max_encrypted_payload_bytes(impl) -
+                                         impl->in_place_protect_bytes_buffered -
+                                         impl->overhead_length);
+    *unprotected_bytes_size = bytes_to_buffer;
+    if (bytes_to_buffer > 0) {
+      memcpy(
+          impl->in_place_protect_buffer + impl->in_place_protect_bytes_buffered,
+          unprotected_bytes, bytes_to_buffer);
+      impl->in_place_protect_bytes_buffered += bytes_to_buffer;
+    }
+  } else {
+    *unprotected_bytes_size = 0;
+  }
+  /**
+   * If a full frame has been buffered, we output it. If the first condition
+   * holds, then there exists an unencrypted full frame. If the second
+   * condition holds, then there exists a full frame that has already been
+   * encrypted.
+   */
+  if (max_encrypted_payload_bytes(impl) ==
+          impl->in_place_protect_bytes_buffered + impl->overhead_length ||
+      max_encrypted_payload_bytes(impl) ==
+          impl->in_place_protect_bytes_buffered) {
+    size_t still_pending_size = 0;
+    return alts_protect_flush(self, protected_output_frames,
+                              protected_output_frames_size,
+                              &still_pending_size);
+  } else {
+    *protected_output_frames_size = 0;
+    return TSI_OK;
+  }
+}
+
+static tsi_result unseal(alts_frame_protector* impl) {
+  char* error_details = nullptr;
+  size_t output_size = 0;
+  grpc_status_code status = alts_crypter_process_in_place(
+      impl->unseal_crypter, impl->in_place_unprotect_buffer,
+      impl->max_unprotected_frame_size,
+      alts_get_output_bytes_read(impl->reader), &output_size, &error_details);
+  if (status != GRPC_STATUS_OK) {
+    gpr_log(GPR_ERROR, "%s", error_details);
+    gpr_free(error_details);
+    return TSI_DATA_CORRUPTED;
+  }
+  return TSI_OK;
+}
+
+static void ensure_buffer_size(alts_frame_protector* impl) {
+  if (!alts_has_read_frame_length(impl->reader)) {
+    return;
+  }
+  size_t buffer_space_remaining = impl->max_unprotected_frame_size -
+                                  alts_get_output_bytes_read(impl->reader);
+  /**
+   * Check if we need to resize in_place_unprotect_buffer in order to hold
+   * remaining bytes of a full frame.
+   */
+  if (buffer_space_remaining < alts_get_reader_bytes_remaining(impl->reader)) {
+    size_t buffer_len = alts_get_output_bytes_read(impl->reader) +
+                        alts_get_reader_bytes_remaining(impl->reader);
+    unsigned char* buffer = static_cast<unsigned char*>(gpr_malloc(buffer_len));
+    memcpy(buffer, impl->in_place_unprotect_buffer,
+           alts_get_output_bytes_read(impl->reader));
+    impl->max_unprotected_frame_size = buffer_len;
+    gpr_free(impl->in_place_unprotect_buffer);
+    impl->in_place_unprotect_buffer = buffer;
+    alts_reset_reader_output_buffer(
+        impl->reader, buffer + alts_get_output_bytes_read(impl->reader));
+  }
+}
+
+static tsi_result alts_unprotect(tsi_frame_protector* self,
+                                 const unsigned char* protected_frames_bytes,
+                                 size_t* protected_frames_bytes_size,
+                                 unsigned char* unprotected_bytes,
+                                 size_t* unprotected_bytes_size) {
+  if (self == nullptr || protected_frames_bytes == nullptr ||
+      protected_frames_bytes_size == nullptr || unprotected_bytes == nullptr ||
+      unprotected_bytes_size == nullptr) {
+    gpr_log(GPR_ERROR, "Invalid nullptr arguments to alts_unprotect().");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_frame_protector* impl = reinterpret_cast<alts_frame_protector*>(self);
+  /**
+   * If a new frame can start being processed, we reset the frame reader to
+   * point to in_place_unprotect_buffer that will be used to hold deframed
+   * result.
+   */
+  if (alts_is_frame_reader_done(impl->reader) &&
+      ((alts_get_output_buffer(impl->reader) == nullptr) ||
+       (alts_get_output_bytes_read(impl->reader) ==
+        impl->in_place_unprotect_bytes_processed + impl->overhead_length))) {
+    if (!alts_reset_frame_reader(impl->reader,
+                                 impl->in_place_unprotect_buffer)) {
+      gpr_log(GPR_ERROR, "Couldn't reset frame reader.");
+      return TSI_INTERNAL_ERROR;
+    }
+    impl->in_place_unprotect_bytes_processed = 0;
+  }
+  /**
+   * If a full frame has not yet been read, we read more bytes from
+   * protected_frames_bytes until a full frame has been read. We also need to
+   * make sure in_place_unprotect_buffer is large enough to hold a complete
+   * frame.
+   */
+  if (!alts_is_frame_reader_done(impl->reader)) {
+    ensure_buffer_size(impl);
+    *protected_frames_bytes_size =
+        GPR_MIN(impl->max_unprotected_frame_size -
+                    alts_get_output_bytes_read(impl->reader),
+                *protected_frames_bytes_size);
+    size_t read_frames_bytes_size = *protected_frames_bytes_size;
+    if (!alts_read_frame_bytes(impl->reader, protected_frames_bytes,
+                               &read_frames_bytes_size)) {
+      gpr_log(GPR_ERROR, "Failed to process frame.");
+      return TSI_INTERNAL_ERROR;
+    }
+    *protected_frames_bytes_size = read_frames_bytes_size;
+  } else {
+    *protected_frames_bytes_size = 0;
+  }
+  /**
+   * If a full frame has been read, we unseal it, and write out the
+   * deframed result to unprotected_bytes.
+   */
+  if (alts_is_frame_reader_done(impl->reader)) {
+    if (impl->in_place_unprotect_bytes_processed == 0) {
+      tsi_result result = unseal(impl);
+      if (result != TSI_OK) {
+        return result;
+      }
+    }
+    size_t bytes_to_write = GPR_MIN(
+        *unprotected_bytes_size, alts_get_output_bytes_read(impl->reader) -
+                                     impl->in_place_unprotect_bytes_processed -
+                                     impl->overhead_length);
+    if (bytes_to_write > 0) {
+      memcpy(unprotected_bytes,
+             impl->in_place_unprotect_buffer +
+                 impl->in_place_unprotect_bytes_processed,
+             bytes_to_write);
+    }
+    *unprotected_bytes_size = bytes_to_write;
+    impl->in_place_unprotect_bytes_processed += bytes_to_write;
+    return TSI_OK;
+  } else {
+    *unprotected_bytes_size = 0;
+    return TSI_OK;
+  }
+}
+
+static void alts_destroy(tsi_frame_protector* self) {
+  alts_frame_protector* impl = reinterpret_cast<alts_frame_protector*>(self);
+  if (impl != nullptr) {
+    alts_crypter_destroy(impl->seal_crypter);
+    alts_crypter_destroy(impl->unseal_crypter);
+    gpr_free(impl->in_place_protect_buffer);
+    gpr_free(impl->in_place_unprotect_buffer);
+    alts_destroy_frame_writer(impl->writer);
+    alts_destroy_frame_reader(impl->reader);
+    gpr_free(impl);
+  }
+}
+
+static const tsi_frame_protector_vtable alts_frame_protector_vtable = {
+    alts_protect, alts_protect_flush, alts_unprotect, alts_destroy};
+
+static grpc_status_code create_alts_crypters(const uint8_t* key,
+                                             size_t key_size, bool is_client,
+                                             bool is_rekey,
+                                             alts_frame_protector* impl,
+                                             char** error_details) {
+  grpc_status_code status;
+  gsec_aead_crypter* aead_crypter_seal = nullptr;
+  gsec_aead_crypter* aead_crypter_unseal = nullptr;
+  status = gsec_aes_gcm_aead_crypter_create(key, key_size, kAesGcmNonceLength,
+                                            kAesGcmTagLength, is_rekey,
+                                            &aead_crypter_seal, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  status = gsec_aes_gcm_aead_crypter_create(
+      key, key_size, kAesGcmNonceLength, kAesGcmTagLength, is_rekey,
+      &aead_crypter_unseal, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  size_t overflow_size = is_rekey ? kAltsRecordProtocolRekeyFrameLimit
+                                  : kAltsRecordProtocolFrameLimit;
+  status = alts_seal_crypter_create(aead_crypter_seal, is_client, overflow_size,
+                                    &impl->seal_crypter, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  status =
+      alts_unseal_crypter_create(aead_crypter_unseal, is_client, overflow_size,
+                                 &impl->unseal_crypter, error_details);
+  return status;
+}
+
+tsi_result alts_create_frame_protector(const uint8_t* key, size_t key_size,
+                                       bool is_client, bool is_rekey,
+                                       size_t* max_protected_frame_size,
+                                       tsi_frame_protector** self) {
+  if (key == nullptr || self == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to alts_create_frame_protector().");
+    return TSI_INTERNAL_ERROR;
+  }
+  char* error_details = nullptr;
+  alts_frame_protector* impl =
+      static_cast<alts_frame_protector*>(gpr_zalloc(sizeof(*impl)));
+  grpc_status_code status = create_alts_crypters(
+      key, key_size, is_client, is_rekey, impl, &error_details);
+  if (status != GRPC_STATUS_OK) {
+    gpr_log(GPR_ERROR, "Failed to create ALTS crypters, %s.", error_details);
+    gpr_free(error_details);
+    return TSI_INTERNAL_ERROR;
+  }
+  /**
+   * Set maximum frame size to be used by a frame protector. If it is nullptr, a
+   * default frame size will be used. Otherwise, the provided frame size will be
+   * adjusted (if not falling into a valid frame range) and used.
+   */
+  size_t max_protected_frame_size_to_set = kDefaultFrameLength;
+  if (max_protected_frame_size != nullptr) {
+    *max_protected_frame_size =
+        GPR_MIN(*max_protected_frame_size, kMaxFrameLength);
+    *max_protected_frame_size =
+        GPR_MAX(*max_protected_frame_size, kMinFrameLength);
+    max_protected_frame_size_to_set = *max_protected_frame_size;
+  }
+  impl->max_protected_frame_size = max_protected_frame_size_to_set;
+  impl->max_unprotected_frame_size = max_protected_frame_size_to_set;
+  impl->in_place_protect_bytes_buffered = 0;
+  impl->in_place_unprotect_bytes_processed = 0;
+  impl->in_place_protect_buffer = static_cast<unsigned char*>(
+      gpr_malloc(sizeof(unsigned char) * max_protected_frame_size_to_set));
+  impl->in_place_unprotect_buffer = static_cast<unsigned char*>(
+      gpr_malloc(sizeof(unsigned char) * max_protected_frame_size_to_set));
+  impl->overhead_length = alts_crypter_num_overhead_bytes(impl->seal_crypter);
+  impl->writer = alts_create_frame_writer();
+  impl->reader = alts_create_frame_reader();
+  impl->base.vtable = &alts_frame_protector_vtable;
+  *self = &impl->base;
+  return TSI_OK;
+}
diff --git a/src/core/tsi/alts/frame_protector/alts_frame_protector.h b/src/core/tsi/alts/frame_protector/alts_frame_protector.h
new file mode 100644
index 0000000..321bffa
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/alts_frame_protector.h
@@ -0,0 +1,55 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_FRAME_PROTECTOR_H
+#define GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_FRAME_PROTECTOR_H
+
+#include <grpc/support/port_platform.h>
+
+#include <stdbool.h>
+
+#include "src/core/tsi/transport_security_interface.h"
+
+typedef struct alts_frame_protector alts_frame_protector;
+
+/**
+ * TODO: Add a parameter to the interface to support the use of
+ * different record protocols within a frame protector.
+ *
+ * This method creates a frame protector.
+ *
+ * - key: a symmetric key used to seal/unseal frames.
+ * - key_size: the size of symmetric key.
+ * - is_client: a flag indicating if the frame protector will be used at client
+ *   (is_client = true) or server (is_client = false) side.
+ * - is_rekey: a flag indicating if the frame protector will use an AEAD with
+ *   rekeying.
+ * - max_protected_frame_size: an in/out parameter indicating max frame size
+ *   to be used by the frame protector. If it is nullptr, the default frame
+ *   size will be used. Otherwise, the provided frame size will be adjusted (if
+ *   not falling into a valid frame range) and used.
+ * - self: a pointer to the frame protector returned from the method.
+ *
+ * This method returns TSI_OK on success and TSI_INTERNAL_ERROR otherwise.
+ */
+tsi_result alts_create_frame_protector(const uint8_t* key, size_t key_size,
+                                       bool is_client, bool is_rekey,
+                                       size_t* max_protected_frame_size,
+                                       tsi_frame_protector** self);
+
+#endif /* GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_FRAME_PROTECTOR_H */
diff --git a/src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc b/src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc
new file mode 100644
index 0000000..0574ed5
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc
@@ -0,0 +1,114 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h"
+
+#include <grpc/support/alloc.h>
+
+static void maybe_copy_error_msg(const char* src, char** dst) {
+  if (dst != nullptr && src != nullptr) {
+    *dst = static_cast<char*>(gpr_malloc(strlen(src) + 1));
+    memcpy(*dst, src, strlen(src) + 1);
+  }
+}
+
+grpc_status_code input_sanity_check(
+    const alts_record_protocol_crypter* rp_crypter, const unsigned char* data,
+    size_t* output_size, char** error_details) {
+  if (rp_crypter == nullptr) {
+    maybe_copy_error_msg("alts_crypter instance is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  } else if (data == nullptr) {
+    maybe_copy_error_msg("data is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  } else if (output_size == nullptr) {
+    maybe_copy_error_msg("output_size is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  return GRPC_STATUS_OK;
+}
+
+grpc_status_code increment_counter(alts_record_protocol_crypter* rp_crypter,
+                                   char** error_details) {
+  bool is_overflow = false;
+  grpc_status_code status =
+      alts_counter_increment(rp_crypter->ctr, &is_overflow, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  if (is_overflow) {
+    const char error_msg[] =
+        "crypter counter is wrapped. The connection"
+        "should be closed and the key should be deleted.";
+    maybe_copy_error_msg(error_msg, error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  return GRPC_STATUS_OK;
+}
+
+size_t alts_record_protocol_crypter_num_overhead_bytes(const alts_crypter* c) {
+  if (c != nullptr) {
+    size_t num_overhead_bytes = 0;
+    char* error_details = nullptr;
+    const alts_record_protocol_crypter* rp_crypter =
+        reinterpret_cast<const alts_record_protocol_crypter*>(c);
+    grpc_status_code status = gsec_aead_crypter_tag_length(
+        rp_crypter->crypter, &num_overhead_bytes, &error_details);
+    if (status == GRPC_STATUS_OK) {
+      return num_overhead_bytes;
+    }
+  }
+  return 0;
+}
+
+void alts_record_protocol_crypter_destruct(alts_crypter* c) {
+  if (c != nullptr) {
+    alts_record_protocol_crypter* rp_crypter =
+        reinterpret_cast<alts_record_protocol_crypter*>(c);
+    alts_counter_destroy(rp_crypter->ctr);
+    gsec_aead_crypter_destroy(rp_crypter->crypter);
+  }
+}
+
+alts_record_protocol_crypter* alts_crypter_create_common(
+    gsec_aead_crypter* crypter, bool is_client, size_t overflow_size,
+    char** error_details) {
+  if (crypter != nullptr) {
+    auto* rp_crypter = static_cast<alts_record_protocol_crypter*>(
+        gpr_malloc(sizeof(alts_record_protocol_crypter)));
+    size_t counter_size = 0;
+    grpc_status_code status =
+        gsec_aead_crypter_nonce_length(crypter, &counter_size, error_details);
+    if (status != GRPC_STATUS_OK) {
+      return nullptr;
+    }
+    /* Create a counter. */
+    status = alts_counter_create(is_client, counter_size, overflow_size,
+                                 &rp_crypter->ctr, error_details);
+    if (status != GRPC_STATUS_OK) {
+      return nullptr;
+    }
+    rp_crypter->crypter = crypter;
+    return rp_crypter;
+  }
+  const char error_msg[] = "crypter is nullptr.";
+  maybe_copy_error_msg(error_msg, error_details);
+  return nullptr;
+}
diff --git a/src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h b/src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h
new file mode 100644
index 0000000..682a8f7
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h
@@ -0,0 +1,114 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_RECORD_PROTOCOL_CRYPTER_COMMON_H
+#define GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_RECORD_PROTOCOL_CRYPTER_COMMON_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/grpc.h>
+
+#include "src/core/tsi/alts/frame_protector/alts_counter.h"
+#include "src/core/tsi/alts/frame_protector/alts_crypter.h"
+
+/**
+ * This file contains common implementation that will be used in both seal and
+ * unseal operations.
+ */
+
+/**
+ * Main struct for alts_record_protocol_crypter that will be used in both
+ * seal and unseal operations.
+ */
+typedef struct alts_record_protocol_crypter {
+  alts_crypter base;
+  gsec_aead_crypter* crypter;
+  alts_counter* ctr;
+} alts_record_protocol_crypter;
+
+/**
+ * This method performs input sanity checks on a subset of inputs to
+ * alts_crypter_process_in_place() for both seal and unseal operations.
+ *
+ * - rp_crypter: an alts_record_protocol_crypter instance.
+ * - data: it represents raw data that needs to be sealed in a seal operation or
+ *   protected data that needs to be unsealed in an unseal operation.
+ * - output_size: size of data written to the data buffer after a seal or
+ *   unseal operation.
+ * - error_details: a buffer containing an error message if any of checked
+ *   inputs is nullptr. It is legal to pass nullptr into error_details and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code input_sanity_check(
+    const alts_record_protocol_crypter* rp_crypter, const unsigned char* data,
+    size_t* output_size, char** error_details);
+
+/**
+ * This method increments the counter within an alts_record_protocol_crypter
+ * instance.
+ *
+ * - rp_crypter: an alts_record_protocol_crypter instance.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly or the counter is wrapped. It is legal to pass nullptr
+ *   into error_details and otherwise, the parameter should be freed with
+ *   gpr_free.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise,
+ * it returns an error status code along with its details specified in
+ * error_details (if error_details is not nullptr).
+ */
+grpc_status_code increment_counter(alts_record_protocol_crypter* rp_crypter,
+                                   char** error_details);
+
+/**
+ * This method creates an alts_crypter instance, and populates the fields
+ * that are common to both seal and unseal operations.
+ *
+ * - crypter: a gsec_aead_crypter instance used to perform AEAD decryption. The
+ *   function does not take ownership of crypter.
+ * - is_client: a flag indicating if the alts_crypter instance will be
+ *   used at the client (is_client = true) or server (is_client =
+ *   false) side.
+ * - overflow_size: overflow size of counter in bytes.
+ * - error_details: a buffer containing an error message if the method does
+ *   not function correctly. It is legal to pass nullptr into error_details, and
+ *   otherwise, the parameter should be freed with gpr_free.
+ *
+ * On success of creation, the method returns alts_record_protocol_crypter
+ * instance. Otherwise, it returns nullptr with its details specified in
+ * error_details (if error_details is not nullptr).
+ *
+ */
+alts_record_protocol_crypter* alts_crypter_create_common(
+    gsec_aead_crypter* crypter, bool is_client, size_t overflow_size,
+    char** error_details);
+
+/**
+ * For the following two methods, please refer to the corresponding API in
+ * alts_crypter.h for detailed specifications.
+ */
+size_t alts_record_protocol_crypter_num_overhead_bytes(const alts_crypter* c);
+
+void alts_record_protocol_crypter_destruct(alts_crypter* c);
+
+#endif /* GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_ALTS_RECORD_PROTOCOL_CRYPTER_COMMON_H \
+        */
diff --git a/src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc b/src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc
new file mode 100644
index 0000000..f407831
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc
@@ -0,0 +1,105 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/support/alloc.h>
+
+#include "src/core/tsi/alts/frame_protector/alts_counter.h"
+#include "src/core/tsi/alts/frame_protector/alts_crypter.h"
+#include "src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h"
+
+static void maybe_copy_error_msg(const char* src, char** dst) {
+  if (dst != nullptr && src != nullptr) {
+    *dst = static_cast<char*>(gpr_malloc(strlen(src) + 1));
+    memcpy(*dst, src, strlen(src) + 1);
+  }
+}
+
+/* Perform input santity check for a seal operation. */
+static grpc_status_code seal_check(alts_crypter* c, const unsigned char* data,
+                                   size_t data_allocated_size, size_t data_size,
+                                   size_t* output_size, char** error_details) {
+  /* Do common input sanity check. */
+  grpc_status_code status = input_sanity_check(
+      reinterpret_cast<const alts_record_protocol_crypter*>(c), data,
+      output_size, error_details);
+  if (status != GRPC_STATUS_OK) return status;
+  /* Do seal-specific check. */
+  size_t num_overhead_bytes =
+      alts_crypter_num_overhead_bytes(reinterpret_cast<const alts_crypter*>(c));
+  if (data_size == 0) {
+    const char error_msg[] = "data_size is zero.";
+    maybe_copy_error_msg(error_msg, error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (data_size + num_overhead_bytes > data_allocated_size) {
+    const char error_msg[] =
+        "data_allocated_size is smaller than sum of data_size and "
+        "num_overhead_bytes.";
+    maybe_copy_error_msg(error_msg, error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  return GRPC_STATUS_OK;
+}
+
+static grpc_status_code alts_seal_crypter_process_in_place(
+    alts_crypter* c, unsigned char* data, size_t data_allocated_size,
+    size_t data_size, size_t* output_size, char** error_details) {
+  grpc_status_code status = seal_check(c, data, data_allocated_size, data_size,
+                                       output_size, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  /* Do AEAD encryption. */
+  alts_record_protocol_crypter* rp_crypter =
+      reinterpret_cast<alts_record_protocol_crypter*>(c);
+  status = gsec_aead_crypter_encrypt(
+      rp_crypter->crypter, alts_counter_get_counter(rp_crypter->ctr),
+      alts_counter_get_size(rp_crypter->ctr), nullptr /* aad */,
+      0 /* aad_length */, data, data_size, data, data_allocated_size,
+      output_size, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  /* Increment the crypter counter. */
+  return increment_counter(rp_crypter, error_details);
+}
+
+static const alts_crypter_vtable vtable = {
+    alts_record_protocol_crypter_num_overhead_bytes,
+    alts_seal_crypter_process_in_place, alts_record_protocol_crypter_destruct};
+
+grpc_status_code alts_seal_crypter_create(gsec_aead_crypter* gc, bool is_client,
+                                          size_t overflow_size,
+                                          alts_crypter** crypter,
+                                          char** error_details) {
+  if (crypter == nullptr) {
+    const char error_msg[] = "crypter is nullptr.";
+    maybe_copy_error_msg(error_msg, error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  alts_record_protocol_crypter* rp_crypter =
+      alts_crypter_create_common(gc, !is_client, overflow_size, error_details);
+  if (rp_crypter == nullptr) {
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  rp_crypter->base.vtable = &vtable;
+  *crypter = &rp_crypter->base;
+  return GRPC_STATUS_OK;
+}
diff --git a/src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc b/src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc
new file mode 100644
index 0000000..51bea24
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc
@@ -0,0 +1,103 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/support/alloc.h>
+
+#include "src/core/tsi/alts/frame_protector/alts_counter.h"
+#include "src/core/tsi/alts/frame_protector/alts_crypter.h"
+#include "src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h"
+
+static void maybe_copy_error_msg(const char* src, char** dst) {
+  if (dst != nullptr && src != nullptr) {
+    *dst = static_cast<char*>(gpr_malloc(strlen(src) + 1));
+    memcpy(*dst, src, strlen(src) + 1);
+  }
+}
+
+/* Perform input santity check. */
+static grpc_status_code unseal_check(alts_crypter* c, const unsigned char* data,
+                                     size_t data_allocated_size,
+                                     size_t data_size, size_t* output_size,
+                                     char** error_details) {
+  /* Do common input sanity check. */
+  grpc_status_code status = input_sanity_check(
+      reinterpret_cast<const alts_record_protocol_crypter*>(c), data,
+      output_size, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  /* Do unseal-specific input check. */
+  size_t num_overhead_bytes =
+      alts_crypter_num_overhead_bytes(reinterpret_cast<const alts_crypter*>(c));
+  if (num_overhead_bytes > data_size) {
+    const char error_msg[] = "data_size is smaller than num_overhead_bytes.";
+    maybe_copy_error_msg(error_msg, error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  return GRPC_STATUS_OK;
+}
+
+static grpc_status_code alts_unseal_crypter_process_in_place(
+    alts_crypter* c, unsigned char* data, size_t data_allocated_size,
+    size_t data_size, size_t* output_size, char** error_details) {
+  grpc_status_code status = unseal_check(c, data, data_allocated_size,
+                                         data_size, output_size, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  /* Do AEAD decryption. */
+  alts_record_protocol_crypter* rp_crypter =
+      reinterpret_cast<alts_record_protocol_crypter*>(c);
+  status = gsec_aead_crypter_decrypt(
+      rp_crypter->crypter, alts_counter_get_counter(rp_crypter->ctr),
+      alts_counter_get_size(rp_crypter->ctr), nullptr /* aad */,
+      0 /* aad_length */, data, data_size, data, data_allocated_size,
+      output_size, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  /* Increment the crypter counter. */
+  return increment_counter(rp_crypter, error_details);
+}
+
+static const alts_crypter_vtable vtable = {
+    alts_record_protocol_crypter_num_overhead_bytes,
+    alts_unseal_crypter_process_in_place,
+    alts_record_protocol_crypter_destruct};
+
+grpc_status_code alts_unseal_crypter_create(gsec_aead_crypter* gc,
+                                            bool is_client,
+                                            size_t overflow_size,
+                                            alts_crypter** crypter,
+                                            char** error_details) {
+  if (crypter == nullptr) {
+    const char error_msg[] = "crypter is nullptr.";
+    maybe_copy_error_msg(error_msg, error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  alts_record_protocol_crypter* rp_crypter =
+      alts_crypter_create_common(gc, is_client, overflow_size, error_details);
+  if (rp_crypter == nullptr) {
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  rp_crypter->base.vtable = &vtable;
+  *crypter = &rp_crypter->base;
+  return GRPC_STATUS_OK;
+}
diff --git a/src/core/tsi/alts/frame_protector/frame_handler.cc b/src/core/tsi/alts/frame_protector/frame_handler.cc
new file mode 100644
index 0000000..d3fda63
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/frame_handler.cc
@@ -0,0 +1,218 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/frame_protector/frame_handler.h"
+
+#include <limits.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/gpr/useful.h"
+
+/* Use little endian to interpret a string of bytes as uint32_t. */
+static uint32_t load_32_le(const unsigned char* buffer) {
+  return (((uint32_t)buffer[3]) << 24) | (((uint32_t)buffer[2]) << 16) |
+         (((uint32_t)buffer[1]) << 8) | ((uint32_t)buffer[0]);
+}
+
+/* Store uint32_t as a string of little endian bytes. */
+static void store_32_le(uint32_t value, unsigned char* buffer) {
+  buffer[3] = (unsigned char)(value >> 24) & 0xFF;
+  buffer[2] = (unsigned char)(value >> 16) & 0xFF;
+  buffer[1] = (unsigned char)(value >> 8) & 0xFF;
+  buffer[0] = (unsigned char)(value)&0xFF;
+}
+
+/* Frame writer implementation. */
+alts_frame_writer* alts_create_frame_writer() {
+  alts_frame_writer* writer =
+      static_cast<alts_frame_writer*>(gpr_zalloc(sizeof(*writer)));
+  return writer;
+}
+
+bool alts_reset_frame_writer(alts_frame_writer* writer,
+                             const unsigned char* buffer, size_t length) {
+  if (buffer == nullptr) return false;
+  size_t max_input_size = SIZE_MAX - kFrameLengthFieldSize;
+  if (length > max_input_size) {
+    gpr_log(GPR_ERROR, "length must be at most %zu", max_input_size);
+    return false;
+  }
+  writer->input_buffer = buffer;
+  writer->input_size = length;
+  writer->input_bytes_written = 0;
+  writer->header_bytes_written = 0;
+  store_32_le(
+      static_cast<uint32_t>(writer->input_size + kFrameMessageTypeFieldSize),
+      writer->header_buffer);
+  store_32_le(kFrameMessageType, writer->header_buffer + kFrameLengthFieldSize);
+  return true;
+}
+
+bool alts_write_frame_bytes(alts_frame_writer* writer, unsigned char* output,
+                            size_t* bytes_size) {
+  if (bytes_size == nullptr || output == nullptr) return false;
+  if (alts_is_frame_writer_done(writer)) {
+    *bytes_size = 0;
+    return true;
+  }
+  size_t bytes_written = 0;
+  /* Write some header bytes, if needed. */
+  if (writer->header_bytes_written != sizeof(writer->header_buffer)) {
+    size_t bytes_to_write =
+        GPR_MIN(*bytes_size,
+                sizeof(writer->header_buffer) - writer->header_bytes_written);
+    memcpy(output, writer->header_buffer + writer->header_bytes_written,
+           bytes_to_write);
+    bytes_written += bytes_to_write;
+    *bytes_size -= bytes_to_write;
+    writer->header_bytes_written += bytes_to_write;
+    output += bytes_to_write;
+    if (writer->header_bytes_written != sizeof(writer->header_buffer)) {
+      *bytes_size = bytes_written;
+      return true;
+    }
+  }
+  /* Write some non-header bytes. */
+  size_t bytes_to_write =
+      GPR_MIN(writer->input_size - writer->input_bytes_written, *bytes_size);
+  memcpy(output, writer->input_buffer, bytes_to_write);
+  writer->input_buffer += bytes_to_write;
+  bytes_written += bytes_to_write;
+  writer->input_bytes_written += bytes_to_write;
+  *bytes_size = bytes_written;
+  return true;
+}
+
+bool alts_is_frame_writer_done(alts_frame_writer* writer) {
+  return writer->input_buffer == nullptr ||
+         writer->input_size == writer->input_bytes_written;
+}
+
+size_t alts_get_num_writer_bytes_remaining(alts_frame_writer* writer) {
+  return (sizeof(writer->header_buffer) - writer->header_bytes_written) +
+         (writer->input_size - writer->input_bytes_written);
+}
+
+void alts_destroy_frame_writer(alts_frame_writer* writer) { gpr_free(writer); }
+
+/* Frame reader implementation. */
+alts_frame_reader* alts_create_frame_reader() {
+  alts_frame_reader* reader =
+      static_cast<alts_frame_reader*>(gpr_zalloc(sizeof(*reader)));
+  return reader;
+}
+
+bool alts_is_frame_reader_done(alts_frame_reader* reader) {
+  return reader->output_buffer == nullptr ||
+         (reader->header_bytes_read == sizeof(reader->header_buffer) &&
+          reader->bytes_remaining == 0);
+}
+
+bool alts_has_read_frame_length(alts_frame_reader* reader) {
+  return sizeof(reader->header_buffer) == reader->header_bytes_read;
+}
+
+size_t alts_get_reader_bytes_remaining(alts_frame_reader* reader) {
+  return alts_has_read_frame_length(reader) ? reader->bytes_remaining : 0;
+}
+
+void alts_reset_reader_output_buffer(alts_frame_reader* reader,
+                                     unsigned char* buffer) {
+  reader->output_buffer = buffer;
+}
+
+bool alts_reset_frame_reader(alts_frame_reader* reader, unsigned char* buffer) {
+  if (buffer == nullptr) return false;
+  reader->output_buffer = buffer;
+  reader->bytes_remaining = 0;
+  reader->header_bytes_read = 0;
+  reader->output_bytes_read = 0;
+  return true;
+}
+
+bool alts_read_frame_bytes(alts_frame_reader* reader,
+                           const unsigned char* bytes, size_t* bytes_size) {
+  if (bytes_size == nullptr) return false;
+  if (bytes == nullptr) {
+    *bytes_size = 0;
+    return false;
+  }
+  if (alts_is_frame_reader_done(reader)) {
+    *bytes_size = 0;
+    return true;
+  }
+  size_t bytes_processed = 0;
+  /* Process the header, if needed. */
+  if (reader->header_bytes_read != sizeof(reader->header_buffer)) {
+    size_t bytes_to_write = GPR_MIN(
+        *bytes_size, sizeof(reader->header_buffer) - reader->header_bytes_read);
+    memcpy(reader->header_buffer + reader->header_bytes_read, bytes,
+           bytes_to_write);
+    reader->header_bytes_read += bytes_to_write;
+    bytes_processed += bytes_to_write;
+    bytes += bytes_to_write;
+    *bytes_size -= bytes_to_write;
+    if (reader->header_bytes_read != sizeof(reader->header_buffer)) {
+      *bytes_size = bytes_processed;
+      return true;
+    }
+    size_t frame_length = load_32_le(reader->header_buffer);
+    if (frame_length < kFrameMessageTypeFieldSize ||
+        frame_length > kFrameMaxSize) {
+      gpr_log(GPR_ERROR,
+              "Bad frame length (should be at least %zu, and at most %zu)",
+              kFrameMessageTypeFieldSize, kFrameMaxSize);
+      *bytes_size = 0;
+      return false;
+    }
+    size_t message_type =
+        load_32_le(reader->header_buffer + kFrameLengthFieldSize);
+    if (message_type != kFrameMessageType) {
+      gpr_log(GPR_ERROR, "Unsupported message type %zu (should be %zu)",
+              message_type, kFrameMessageType);
+      *bytes_size = 0;
+      return false;
+    }
+    reader->bytes_remaining = frame_length - kFrameMessageTypeFieldSize;
+  }
+  /* Process the non-header bytes. */
+  size_t bytes_to_write = GPR_MIN(*bytes_size, reader->bytes_remaining);
+  memcpy(reader->output_buffer, bytes, bytes_to_write);
+  reader->output_buffer += bytes_to_write;
+  bytes_processed += bytes_to_write;
+  reader->bytes_remaining -= bytes_to_write;
+  reader->output_bytes_read += bytes_to_write;
+  *bytes_size = bytes_processed;
+  return true;
+}
+
+size_t alts_get_output_bytes_read(alts_frame_reader* reader) {
+  return reader->output_bytes_read;
+}
+
+unsigned char* alts_get_output_buffer(alts_frame_reader* reader) {
+  return reader->output_buffer;
+}
+
+void alts_destroy_frame_reader(alts_frame_reader* reader) { gpr_free(reader); }
diff --git a/src/core/tsi/alts/frame_protector/frame_handler.h b/src/core/tsi/alts/frame_protector/frame_handler.h
new file mode 100644
index 0000000..a703ff4
--- /dev/null
+++ b/src/core/tsi/alts/frame_protector/frame_handler.h
@@ -0,0 +1,236 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_FRAME_HANDLER_H
+#define GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_FRAME_HANDLER_H
+
+#include <grpc/support/port_platform.h>
+
+#include <stdbool.h>
+#include <stdlib.h>
+
+const size_t kFrameMessageType = 0x06;
+const size_t kFrameLengthFieldSize = 4;
+const size_t kFrameMessageTypeFieldSize = 4;
+const size_t kFrameMaxSize = 1024 * 1024;
+const size_t kFrameHeaderSize =
+    kFrameLengthFieldSize + kFrameMessageTypeFieldSize;
+
+/**
+ * Implementation of frame reader and frame writer. All APIs in the
+ * header are thread-compatible.
+ */
+
+/**
+ * Main struct for a frame writer. It reads frames from an input buffer, and
+ * writes the contents as raw bytes. It does not own the input buffer.
+ */
+typedef struct alts_frame_writer {
+  const unsigned char* input_buffer;
+  unsigned char header_buffer[kFrameHeaderSize];
+  size_t input_bytes_written;
+  size_t header_bytes_written;
+  size_t input_size;
+} alts_frame_writer;
+
+/**
+ * Main struct for a frame reader. It reads raw bytes and puts the framed
+ * result into an output buffer. It does not own the output buffer.
+ */
+typedef struct alts_frame_reader {
+  unsigned char* output_buffer;
+  unsigned char header_buffer[kFrameHeaderSize];
+  size_t header_bytes_read;
+  size_t output_bytes_read;
+  size_t bytes_remaining;
+} alts_frame_reader;
+
+/**
+ * This method creates a frame writer instance and initializes its internal
+ * states.
+ */
+alts_frame_writer* alts_create_frame_writer();
+
+/**
+ * This method resets internal states of a frame writer and prepares to write
+ * a single frame. It does not take ownership of payload_buffer.
+ * The payload_buffer must outlive the writer.
+ *
+ * - writer: a frame writer instance.
+ * - buffer: a buffer storing full payload data to be framed.
+ * - length: size of payload data.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool alts_reset_frame_writer(alts_frame_writer* writer,
+                             const unsigned char* buffer, size_t length);
+
+/**
+ * This method writes up to bytes_size bytes of a frame to output.
+ *
+ * - writer: a frame writer instance.
+ * - output: an output buffer used to store the frame.
+ * - bytes_size: an in/out parameter that stores the size of output buffer
+ *   before the call, and gets written the number of frame bytes written to the
+ *   buffer.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool alts_write_frame_bytes(alts_frame_writer* writer, unsigned char* output,
+                            size_t* bytes_size);
+
+/**
+ * This method checks if a reset can be called to write a new frame. It returns
+ * true if it's the first time to frame a payload, or the current frame has
+ * been finished processing. It returns false if it's not ready yet to start a
+ * new frame (e.g., more payload data needs to be accumulated to process the
+ * current frame).
+ *
+ * if (alts_is_frame_writer_done(writer)) {
+ *   // a new frame can be written, call reset.
+ *   alts_reset_frame_writer(writer, payload_buffer, payload_size);
+ * } else {
+ *   // accumulate more payload data until a full frame can be written.
+ * }
+ *
+ * - writer: a frame writer instance.
+ */
+bool alts_is_frame_writer_done(alts_frame_writer* writer);
+
+/**
+ * This method returns the number of bytes left to write before a complete frame
+ * is formed.
+ *
+ * - writer: a frame writer instance.
+ */
+size_t alts_get_num_writer_bytes_remaining(alts_frame_writer* writer);
+
+/**
+ * This method destroys a frame writer instance.
+ *
+ * - writer: a frame writer instance.
+ */
+void alts_destroy_frame_writer(alts_frame_writer* writer);
+
+/**
+ * This method creates a frame reader instance and initializes its internal
+ * states.
+ */
+alts_frame_reader* alts_create_frame_reader();
+
+/**
+ * This method resets internal states of a frame reader (including setting its
+ * output_buffer with buffer), and prepares to write processed bytes to
+ * an output_buffer. It does not take ownership of buffer. The buffer must
+ * outlive reader.
+ *
+ * - reader: a frame reader instance.
+ * - buffer: an output buffer used to store deframed results.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool alts_reset_frame_reader(alts_frame_reader* reader, unsigned char* buffer);
+
+/**
+ * This method processes up to the number of bytes given in bytes_size. It may
+ * choose not to process all the bytes, if, for instance, more bytes are
+ * given to the method than required to complete the current frame.
+ *
+ * - reader: a frame reader instance.
+ * - bytes: a buffer that stores data to be processed.
+ * - bytes_size: an in/out parameter that stores the size of bytes before the
+ *   call and gets written the number of bytes processed.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool alts_read_frame_bytes(alts_frame_reader* reader,
+                           const unsigned char* bytes, size_t* bytes_size);
+
+/**
+ * This method checks if a frame length has been read.
+ *
+ * - reader: a frame reader instance.
+ *
+ * The method returns true if a frame length has been read and false otherwise.
+ */
+bool alts_has_read_frame_length(alts_frame_reader* reader);
+
+/**
+ * This method returns the number of bytes the frame reader intends to write.
+ * It may only be called if alts_has_read_frame_length() returns true.
+ *
+ * - reader: a frame reader instance.
+ */
+size_t alts_get_reader_bytes_remaining(alts_frame_reader* reader);
+
+/**
+ * This method resets output_buffer but does not otherwise modify other internal
+ * states of a frame reader instance. After being set, the new output_buffer
+ * will hold the deframed payload held by the original output_buffer. It does
+ * not take ownership of buffer. The buffer must outlive the reader.
+ * To distinguish between two reset methods on a frame reader,
+ *
+ * if (alts_fh_is_frame_reader_done(reader)) {
+ *   // if buffer contains a full payload to be deframed, call reset.
+ *   alts_reset_frame_reader(reader, buffer);
+ * }
+ *
+ * // if remaining buffer space is not enough to hold a full payload
+ * if (buffer_space_remaining < alts_get_reader_bytes_remaining(reader)) {
+ *   // allocate enough space for a new buffer, copy back data processed so far,
+ *   // and call reset.
+ *   alts_reset_reader_output_buffer(reader, new_buffer).
+ * }
+ *
+ * - reader: a frame reader instance.
+ * - buffer: a buffer used to set reader's output_buffer.
+ */
+void alts_reset_reader_output_buffer(alts_frame_reader* reader,
+                                     unsigned char* buffer);
+
+/**
+ * This method checks if reset can be called to start processing a new frame.
+ * If true and reset was previously called, a full frame has been processed and
+ * the content of the frame is available in output_buffer.
+
+ * - reader: a frame reader instance.
+ */
+bool alts_is_frame_reader_done(alts_frame_reader* reader);
+
+/**
+ * This method returns output_bytes_read of a frame reader instance.
+ *
+ * - reader: a frame reader instance.
+ */
+size_t alts_get_output_bytes_read(alts_frame_reader* reader);
+
+/**
+ * This method returns output_buffer of a frame reader instance.
+ *
+ * - reader: a frame reader instance.
+ */
+unsigned char* alts_get_output_buffer(alts_frame_reader* reader);
+
+/**
+ * This method destroys a frame reader instance.
+ *
+ * - reader: a frame reader instance.
+ */
+void alts_destroy_frame_reader(alts_frame_reader* reader);
+
+#endif /* GRPC_CORE_TSI_ALTS_FRAME_PROTECTOR_FRAME_HANDLER_H */
diff --git a/src/core/tsi/alts/handshaker/alts_handshaker_client.cc b/src/core/tsi/alts/handshaker/alts_handshaker_client.cc
new file mode 100644
index 0000000..40f30e4
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_handshaker_client.cc
@@ -0,0 +1,316 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/handshaker/alts_handshaker_client.h"
+
+#include <grpc/byte_buffer.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/tsi/alts/handshaker/alts_handshaker_service_api.h"
+
+const int kHandshakerClientOpNum = 4;
+
+typedef struct alts_grpc_handshaker_client {
+  alts_handshaker_client base;
+  grpc_call* call;
+  alts_grpc_caller grpc_caller;
+} alts_grpc_handshaker_client;
+
+static grpc_call_error grpc_start_batch(grpc_call* call, const grpc_op* ops,
+                                        size_t nops, void* tag) {
+  return grpc_call_start_batch(call, ops, nops, tag, nullptr);
+}
+
+/**
+ * Populate grpc operation data with the fields of ALTS TSI event and make a
+ * grpc call.
+ */
+static tsi_result make_grpc_call(alts_handshaker_client* client,
+                                 alts_tsi_event* event, bool is_start) {
+  GPR_ASSERT(client != nullptr && event != nullptr);
+  alts_grpc_handshaker_client* grpc_client =
+      reinterpret_cast<alts_grpc_handshaker_client*>(client);
+  grpc_op ops[kHandshakerClientOpNum];
+  memset(ops, 0, sizeof(ops));
+  grpc_op* op = ops;
+  if (is_start) {
+    op->op = GRPC_OP_SEND_INITIAL_METADATA;
+    op->data.send_initial_metadata.count = 0;
+    op++;
+    GPR_ASSERT(op - ops <= kHandshakerClientOpNum);
+    op->op = GRPC_OP_RECV_INITIAL_METADATA;
+    op->data.recv_initial_metadata.recv_initial_metadata =
+        &event->initial_metadata;
+    op++;
+    GPR_ASSERT(op - ops <= kHandshakerClientOpNum);
+  }
+  op->op = GRPC_OP_SEND_MESSAGE;
+  op->data.send_message.send_message = event->send_buffer;
+  op++;
+  GPR_ASSERT(op - ops <= kHandshakerClientOpNum);
+  op->op = GRPC_OP_RECV_MESSAGE;
+  op->data.recv_message.recv_message = &event->recv_buffer;
+  op++;
+  GPR_ASSERT(op - ops <= kHandshakerClientOpNum);
+  GPR_ASSERT(grpc_client->grpc_caller != nullptr);
+  if (grpc_client->grpc_caller(grpc_client->call, ops,
+                               static_cast<size_t>(op - ops),
+                               (void*)event) != GRPC_CALL_OK) {
+    gpr_log(GPR_ERROR, "Start batch operation failed");
+    return TSI_INTERNAL_ERROR;
+  }
+  return TSI_OK;
+}
+
+/* Create and populate a client_start handshaker request, then serialize it. */
+static grpc_byte_buffer* get_serialized_start_client(alts_tsi_event* event) {
+  bool ok = true;
+  grpc_gcp_handshaker_req* req =
+      grpc_gcp_handshaker_req_create(CLIENT_START_REQ);
+  ok &= grpc_gcp_handshaker_req_set_handshake_protocol(
+      req, grpc_gcp_HandshakeProtocol_ALTS);
+  ok &= grpc_gcp_handshaker_req_add_application_protocol(
+      req, ALTS_APPLICATION_PROTOCOL);
+  ok &= grpc_gcp_handshaker_req_add_record_protocol(req, ALTS_RECORD_PROTOCOL);
+  grpc_gcp_rpc_protocol_versions* versions = &event->options->rpc_versions;
+  ok &= grpc_gcp_handshaker_req_set_rpc_versions(
+      req, versions->max_rpc_version.major, versions->max_rpc_version.minor,
+      versions->min_rpc_version.major, versions->min_rpc_version.minor);
+  char* target_name = grpc_slice_to_c_string(event->target_name);
+  ok &= grpc_gcp_handshaker_req_set_target_name(req, target_name);
+  target_service_account* ptr =
+      (reinterpret_cast<grpc_alts_credentials_client_options*>(event->options))
+          ->target_account_list_head;
+  while (ptr != nullptr) {
+    grpc_gcp_handshaker_req_add_target_identity_service_account(req, ptr->data);
+    ptr = ptr->next;
+  }
+  grpc_slice slice;
+  ok &= grpc_gcp_handshaker_req_encode(req, &slice);
+  grpc_byte_buffer* buffer = nullptr;
+  if (ok) {
+    buffer = grpc_raw_byte_buffer_create(&slice, 1 /* number of slices */);
+  }
+  grpc_slice_unref(slice);
+  gpr_free(target_name);
+  grpc_gcp_handshaker_req_destroy(req);
+  return buffer;
+}
+
+static tsi_result handshaker_client_start_client(alts_handshaker_client* client,
+                                                 alts_tsi_event* event) {
+  if (client == nullptr || event == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to alts_grpc_handshaker_client_start_client()");
+    return TSI_INVALID_ARGUMENT;
+  }
+  grpc_byte_buffer* buffer = get_serialized_start_client(event);
+  if (buffer == nullptr) {
+    gpr_log(GPR_ERROR, "get_serialized_start_client() failed");
+    return TSI_INTERNAL_ERROR;
+  }
+  event->send_buffer = buffer;
+  tsi_result result = make_grpc_call(client, event, true /* is_start */);
+  if (result != TSI_OK) {
+    gpr_log(GPR_ERROR, "make_grpc_call() failed");
+  }
+  return result;
+}
+
+/* Create and populate a start_server handshaker request, then serialize it. */
+static grpc_byte_buffer* get_serialized_start_server(
+    alts_tsi_event* event, grpc_slice* bytes_received) {
+  GPR_ASSERT(bytes_received != nullptr);
+  grpc_gcp_handshaker_req* req =
+      grpc_gcp_handshaker_req_create(SERVER_START_REQ);
+  bool ok = grpc_gcp_handshaker_req_add_application_protocol(
+      req, ALTS_APPLICATION_PROTOCOL);
+  ok &= grpc_gcp_handshaker_req_param_add_record_protocol(
+      req, grpc_gcp_HandshakeProtocol_ALTS, ALTS_RECORD_PROTOCOL);
+  ok &= grpc_gcp_handshaker_req_set_in_bytes(
+      req, reinterpret_cast<const char*> GRPC_SLICE_START_PTR(*bytes_received),
+      GRPC_SLICE_LENGTH(*bytes_received));
+  grpc_gcp_rpc_protocol_versions* versions = &event->options->rpc_versions;
+  ok &= grpc_gcp_handshaker_req_set_rpc_versions(
+      req, versions->max_rpc_version.major, versions->max_rpc_version.minor,
+      versions->min_rpc_version.major, versions->min_rpc_version.minor);
+  grpc_slice req_slice;
+  ok &= grpc_gcp_handshaker_req_encode(req, &req_slice);
+  grpc_byte_buffer* buffer = nullptr;
+  if (ok) {
+    buffer = grpc_raw_byte_buffer_create(&req_slice, 1 /* number of slices */);
+  }
+  grpc_slice_unref(req_slice);
+  grpc_gcp_handshaker_req_destroy(req);
+  return buffer;
+}
+
+static tsi_result handshaker_client_start_server(alts_handshaker_client* client,
+                                                 alts_tsi_event* event,
+                                                 grpc_slice* bytes_received) {
+  if (client == nullptr || event == nullptr || bytes_received == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to alts_grpc_handshaker_client_start_server()");
+    return TSI_INVALID_ARGUMENT;
+  }
+  grpc_byte_buffer* buffer = get_serialized_start_server(event, bytes_received);
+  if (buffer == nullptr) {
+    gpr_log(GPR_ERROR, "get_serialized_start_server() failed");
+    return TSI_INTERNAL_ERROR;
+  }
+  event->send_buffer = buffer;
+  tsi_result result = make_grpc_call(client, event, true /* is_start */);
+  if (result != TSI_OK) {
+    gpr_log(GPR_ERROR, "make_grpc_call() failed");
+  }
+  return result;
+}
+
+/* Create and populate a next handshaker request, then serialize it. */
+static grpc_byte_buffer* get_serialized_next(grpc_slice* bytes_received) {
+  GPR_ASSERT(bytes_received != nullptr);
+  grpc_gcp_handshaker_req* req = grpc_gcp_handshaker_req_create(NEXT_REQ);
+  bool ok = grpc_gcp_handshaker_req_set_in_bytes(
+      req, reinterpret_cast<const char*> GRPC_SLICE_START_PTR(*bytes_received),
+      GRPC_SLICE_LENGTH(*bytes_received));
+  grpc_slice req_slice;
+  ok &= grpc_gcp_handshaker_req_encode(req, &req_slice);
+  grpc_byte_buffer* buffer = nullptr;
+  if (ok) {
+    buffer = grpc_raw_byte_buffer_create(&req_slice, 1 /* number of slices */);
+  }
+  grpc_slice_unref(req_slice);
+  grpc_gcp_handshaker_req_destroy(req);
+  return buffer;
+}
+
+static tsi_result handshaker_client_next(alts_handshaker_client* client,
+                                         alts_tsi_event* event,
+                                         grpc_slice* bytes_received) {
+  if (client == nullptr || event == nullptr || bytes_received == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to alts_grpc_handshaker_client_next()");
+    return TSI_INVALID_ARGUMENT;
+  }
+  grpc_byte_buffer* buffer = get_serialized_next(bytes_received);
+  if (buffer == nullptr) {
+    gpr_log(GPR_ERROR, "get_serialized_next() failed");
+    return TSI_INTERNAL_ERROR;
+  }
+  event->send_buffer = buffer;
+  tsi_result result = make_grpc_call(client, event, false /* is_start */);
+  if (result != TSI_OK) {
+    gpr_log(GPR_ERROR, "make_grpc_call() failed");
+  }
+  return result;
+}
+
+static void handshaker_client_destruct(alts_handshaker_client* client) {
+  if (client == nullptr) {
+    return;
+  }
+  alts_grpc_handshaker_client* grpc_client =
+      reinterpret_cast<alts_grpc_handshaker_client*>(client);
+  grpc_call_unref(grpc_client->call);
+}
+
+static const alts_handshaker_client_vtable vtable = {
+    handshaker_client_start_client, handshaker_client_start_server,
+    handshaker_client_next, handshaker_client_destruct};
+
+alts_handshaker_client* alts_grpc_handshaker_client_create(
+    grpc_channel* channel, grpc_completion_queue* queue,
+    const char* handshaker_service_url) {
+  if (channel == nullptr || queue == nullptr ||
+      handshaker_service_url == nullptr) {
+    gpr_log(GPR_ERROR, "Invalid arguments to alts_handshaker_client_create()");
+    return nullptr;
+  }
+  alts_grpc_handshaker_client* client =
+      static_cast<alts_grpc_handshaker_client*>(gpr_zalloc(sizeof(*client)));
+  client->grpc_caller = grpc_start_batch;
+  grpc_slice slice = grpc_slice_from_copied_string(handshaker_service_url);
+  client->call = grpc_channel_create_call(
+      channel, nullptr, GRPC_PROPAGATE_DEFAULTS, queue,
+      grpc_slice_from_static_string(ALTS_SERVICE_METHOD), &slice,
+      gpr_inf_future(GPR_CLOCK_REALTIME), nullptr);
+  client->base.vtable = &vtable;
+  grpc_slice_unref(slice);
+  return &client->base;
+}
+
+namespace grpc_core {
+namespace internal {
+
+void alts_handshaker_client_set_grpc_caller_for_testing(
+    alts_handshaker_client* client, alts_grpc_caller caller) {
+  GPR_ASSERT(client != nullptr && caller != nullptr);
+  alts_grpc_handshaker_client* grpc_client =
+      reinterpret_cast<alts_grpc_handshaker_client*>(client);
+  grpc_client->grpc_caller = caller;
+}
+
+}  // namespace internal
+}  // namespace grpc_core
+
+tsi_result alts_handshaker_client_start_client(alts_handshaker_client* client,
+                                               alts_tsi_event* event) {
+  if (client != nullptr && client->vtable != nullptr &&
+      client->vtable->client_start != nullptr) {
+    return client->vtable->client_start(client, event);
+  }
+  gpr_log(GPR_ERROR,
+          "client or client->vtable has not been initialized properly");
+  return TSI_INVALID_ARGUMENT;
+}
+
+tsi_result alts_handshaker_client_start_server(alts_handshaker_client* client,
+                                               alts_tsi_event* event,
+                                               grpc_slice* bytes_received) {
+  if (client != nullptr && client->vtable != nullptr &&
+      client->vtable->server_start != nullptr) {
+    return client->vtable->server_start(client, event, bytes_received);
+  }
+  gpr_log(GPR_ERROR,
+          "client or client->vtable has not been initialized properly");
+  return TSI_INVALID_ARGUMENT;
+}
+
+tsi_result alts_handshaker_client_next(alts_handshaker_client* client,
+                                       alts_tsi_event* event,
+                                       grpc_slice* bytes_received) {
+  if (client != nullptr && client->vtable != nullptr &&
+      client->vtable->next != nullptr) {
+    return client->vtable->next(client, event, bytes_received);
+  }
+  gpr_log(GPR_ERROR,
+          "client or client->vtable has not been initialized properly");
+  return TSI_INVALID_ARGUMENT;
+}
+
+void alts_handshaker_client_destroy(alts_handshaker_client* client) {
+  if (client != nullptr) {
+    if (client->vtable != nullptr && client->vtable->destruct != nullptr) {
+      client->vtable->destruct(client);
+    }
+    gpr_free(client);
+  }
+}
diff --git a/src/core/tsi/alts/handshaker/alts_handshaker_client.h b/src/core/tsi/alts/handshaker/alts_handshaker_client.h
new file mode 100644
index 0000000..fb2d2cf
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_handshaker_client.h
@@ -0,0 +1,137 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_CLIENT_H
+#define GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_CLIENT_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/grpc.h>
+
+#include "src/core/tsi/alts/handshaker/alts_tsi_event.h"
+
+#define ALTS_SERVICE_METHOD "/grpc.gcp.HandshakerService/DoHandshake"
+#define ALTS_APPLICATION_PROTOCOL "grpc"
+#define ALTS_RECORD_PROTOCOL "ALTSRP_GCM_AES128_REKEY"
+
+const size_t kAltsAes128GcmRekeyKeyLength = 44;
+
+/**
+ * A ALTS handshaker client interface. It is used to communicate with
+ * ALTS handshaker service by scheduling a handshaker request that could be one
+ * of client_start, server_start, and next handshaker requests. All APIs in the
+ * header are thread-compatible.
+ */
+typedef struct alts_handshaker_client alts_handshaker_client;
+
+/* A function that makes the grpc call to the handshaker service. */
+typedef grpc_call_error (*alts_grpc_caller)(grpc_call* call, const grpc_op* ops,
+                                            size_t nops, void* tag);
+
+/* V-table for ALTS handshaker client operations. */
+typedef struct alts_handshaker_client_vtable {
+  tsi_result (*client_start)(alts_handshaker_client* client,
+                             alts_tsi_event* event);
+  tsi_result (*server_start)(alts_handshaker_client* client,
+                             alts_tsi_event* event, grpc_slice* bytes_received);
+  tsi_result (*next)(alts_handshaker_client* client, alts_tsi_event* event,
+                     grpc_slice* bytes_received);
+  void (*destruct)(alts_handshaker_client* client);
+} alts_handshaker_client_vtable;
+
+struct alts_handshaker_client {
+  const alts_handshaker_client_vtable* vtable;
+};
+
+/**
+ * This method schedules a client_start handshaker request to ALTS handshaker
+ * service.
+ *
+ * - client: ALTS handshaker client instance.
+ * - event: ALTS TSI event instance.
+ *
+ * It returns TSI_OK on success and an error status code on failure.
+ */
+tsi_result alts_handshaker_client_start_client(alts_handshaker_client* client,
+                                               alts_tsi_event* event);
+
+/**
+ * This method schedules a server_start handshaker request to ALTS handshaker
+ * service.
+ *
+ * - client: ALTS handshaker client instance.
+ * - event: ALTS TSI event instance.
+ * - bytes_received: bytes in out_frames returned from the peer's handshaker
+ *   response.
+ *
+ * It returns TSI_OK on success and an error status code on failure.
+ */
+tsi_result alts_handshaker_client_start_server(alts_handshaker_client* client,
+                                               alts_tsi_event* event,
+                                               grpc_slice* bytes_received);
+
+/**
+ * This method schedules a next handshaker request to ALTS handshaker service.
+ *
+ * - client: ALTS handshaker client instance.
+ * - event: ALTS TSI event instance.
+ * - bytes_received: bytes in out_frames returned from the peer's handshaker
+ *   response.
+ *
+ * It returns TSI_OK on success and an error status code on failure.
+ */
+tsi_result alts_handshaker_client_next(alts_handshaker_client* client,
+                                       alts_tsi_event* event,
+                                       grpc_slice* bytes_received);
+
+/**
+ * This method destroys a ALTS handshaker client.
+ *
+ * - client: a ALTS handshaker client instance.
+ */
+void alts_handshaker_client_destroy(alts_handshaker_client* client);
+
+/**
+ * This method creates a ALTS handshaker client.
+ *
+ * - channel: grpc channel to ALTS handshaker service.
+ * - queue: grpc completion queue.
+ * - handshaker_service_url: address of ALTS handshaker service in the format of
+ *   "host:port".
+ *
+ * It returns the created ALTS handshaker client on success, and NULL on
+ * failure.
+ */
+alts_handshaker_client* alts_grpc_handshaker_client_create(
+    grpc_channel* channel, grpc_completion_queue* queue,
+    const char* handshaker_service_url);
+
+namespace grpc_core {
+namespace internal {
+
+/**
+ * Unsafe, use for testing only. It allows the caller to change the way that
+ * GRPC calls are made to the handshaker service.
+ */
+void alts_handshaker_client_set_grpc_caller_for_testing(
+    alts_handshaker_client* client, alts_grpc_caller caller);
+
+}  // namespace internal
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_CLIENT_H */
diff --git a/src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc b/src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc
new file mode 100644
index 0000000..256e414
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc
@@ -0,0 +1,520 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/handshaker/alts_handshaker_service_api.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "src/core/tsi/alts/handshaker/transport_security_common_api.h"
+
+/* HandshakerReq */
+grpc_gcp_handshaker_req* grpc_gcp_handshaker_req_create(
+    grpc_gcp_handshaker_req_type type) {
+  grpc_gcp_handshaker_req* req =
+      static_cast<grpc_gcp_handshaker_req*>(gpr_zalloc(sizeof(*req)));
+  switch (type) {
+    case CLIENT_START_REQ:
+      req->has_client_start = true;
+      break;
+    case SERVER_START_REQ:
+      req->has_server_start = true;
+      break;
+    case NEXT_REQ:
+      req->has_next = true;
+      break;
+  }
+  return req;
+}
+
+void grpc_gcp_handshaker_req_destroy(grpc_gcp_handshaker_req* req) {
+  if (req == nullptr) {
+    return;
+  }
+  if (req->has_client_start) {
+    /* Destroy client_start request. */
+    destroy_repeated_field_list_identity(
+        static_cast<repeated_field*>(req->client_start.target_identities.arg));
+    destroy_repeated_field_list_string(static_cast<repeated_field*>(
+        req->client_start.application_protocols.arg));
+    destroy_repeated_field_list_string(
+        static_cast<repeated_field*>(req->client_start.record_protocols.arg));
+    if (req->client_start.has_local_identity) {
+      destroy_slice(static_cast<grpc_slice*>(
+          req->client_start.local_identity.hostname.arg));
+      destroy_slice(static_cast<grpc_slice*>(
+          req->client_start.local_identity.service_account.arg));
+    }
+    if (req->client_start.has_local_endpoint) {
+      destroy_slice(static_cast<grpc_slice*>(
+          req->client_start.local_endpoint.ip_address.arg));
+    }
+    if (req->client_start.has_remote_endpoint) {
+      destroy_slice(static_cast<grpc_slice*>(
+          req->client_start.remote_endpoint.ip_address.arg));
+    }
+    destroy_slice(static_cast<grpc_slice*>(req->client_start.target_name.arg));
+  } else if (req->has_server_start) {
+    /* Destroy server_start request. */
+    size_t i = 0;
+    for (i = 0; i < req->server_start.handshake_parameters_count; i++) {
+      destroy_repeated_field_list_identity(
+          static_cast<repeated_field*>(req->server_start.handshake_parameters[i]
+                                           .value.local_identities.arg));
+      destroy_repeated_field_list_string(
+          static_cast<repeated_field*>(req->server_start.handshake_parameters[i]
+                                           .value.record_protocols.arg));
+    }
+    destroy_repeated_field_list_string(static_cast<repeated_field*>(
+        req->server_start.application_protocols.arg));
+    if (req->server_start.has_local_endpoint) {
+      destroy_slice(static_cast<grpc_slice*>(
+          req->server_start.local_endpoint.ip_address.arg));
+    }
+    if (req->server_start.has_remote_endpoint) {
+      destroy_slice(static_cast<grpc_slice*>(
+          req->server_start.remote_endpoint.ip_address.arg));
+    }
+    destroy_slice(static_cast<grpc_slice*>(req->server_start.in_bytes.arg));
+  } else {
+    /* Destroy next request. */
+    destroy_slice(static_cast<grpc_slice*>(req->next.in_bytes.arg));
+  }
+  gpr_free(req);
+}
+
+bool grpc_gcp_handshaker_req_set_handshake_protocol(
+    grpc_gcp_handshaker_req* req,
+    grpc_gcp_handshake_protocol handshake_protocol) {
+  if (req == nullptr || !req->has_client_start) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_handshaker_req_set_handshake_protocol().");
+    return false;
+  }
+  req->client_start.has_handshake_security_protocol = true;
+  req->client_start.handshake_security_protocol = handshake_protocol;
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_set_target_name(grpc_gcp_handshaker_req* req,
+                                             const char* target_name) {
+  if (req == nullptr || target_name == nullptr || !req->has_client_start) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_handshaker_req_set_target_name().");
+    return false;
+  }
+  grpc_slice* slice = create_slice(target_name, strlen(target_name));
+  req->client_start.target_name.arg = slice;
+  req->client_start.target_name.funcs.encode = encode_string_or_bytes_cb;
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_add_application_protocol(
+    grpc_gcp_handshaker_req* req, const char* application_protocol) {
+  if (req == nullptr || application_protocol == nullptr || req->has_next) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_handshaker_req_add_application_protocol().");
+    return false;
+  }
+  grpc_slice* slice =
+      create_slice(application_protocol, strlen(application_protocol));
+  if (req->has_client_start) {
+    add_repeated_field(reinterpret_cast<repeated_field**>(
+                           &req->client_start.application_protocols.arg),
+                       slice);
+    req->client_start.application_protocols.funcs.encode =
+        encode_repeated_string_cb;
+  } else {
+    add_repeated_field(reinterpret_cast<repeated_field**>(
+                           &req->server_start.application_protocols.arg),
+                       slice);
+    req->server_start.application_protocols.funcs.encode =
+        encode_repeated_string_cb;
+  }
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_add_record_protocol(grpc_gcp_handshaker_req* req,
+                                                 const char* record_protocol) {
+  if (req == nullptr || record_protocol == nullptr || !req->has_client_start) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_handshaker_req_add_record_protocol().");
+    return false;
+  }
+  grpc_slice* slice = create_slice(record_protocol, strlen(record_protocol));
+  add_repeated_field(reinterpret_cast<repeated_field**>(
+                         &req->client_start.record_protocols.arg),
+                     slice);
+  req->client_start.record_protocols.funcs.encode = encode_repeated_string_cb;
+  return true;
+}
+
+static void set_identity_hostname(grpc_gcp_identity* identity,
+                                  const char* hostname) {
+  grpc_slice* slice = create_slice(hostname, strlen(hostname));
+  identity->hostname.arg = slice;
+  identity->hostname.funcs.encode = encode_string_or_bytes_cb;
+}
+
+static void set_identity_service_account(grpc_gcp_identity* identity,
+                                         const char* service_account) {
+  grpc_slice* slice = create_slice(service_account, strlen(service_account));
+  identity->service_account.arg = slice;
+  identity->service_account.funcs.encode = encode_string_or_bytes_cb;
+}
+
+bool grpc_gcp_handshaker_req_add_target_identity_hostname(
+    grpc_gcp_handshaker_req* req, const char* hostname) {
+  if (req == nullptr || hostname == nullptr || !req->has_client_start) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_handshaker_req_add_target_identity_hostname().");
+    return false;
+  }
+  grpc_gcp_identity* target_identity =
+      static_cast<grpc_gcp_identity*>(gpr_zalloc(sizeof(*target_identity)));
+  set_identity_hostname(target_identity, hostname);
+  req->client_start.target_identities.funcs.encode =
+      encode_repeated_identity_cb;
+  add_repeated_field(reinterpret_cast<repeated_field**>(
+                         &req->client_start.target_identities.arg),
+                     target_identity);
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_add_target_identity_service_account(
+    grpc_gcp_handshaker_req* req, const char* service_account) {
+  if (req == nullptr || service_account == nullptr || !req->has_client_start) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_handshaker_req_add_target_identity_service_account().");
+    return false;
+  }
+  grpc_gcp_identity* target_identity =
+      static_cast<grpc_gcp_identity*>(gpr_zalloc(sizeof(*target_identity)));
+  set_identity_service_account(target_identity, service_account);
+  req->client_start.target_identities.funcs.encode =
+      encode_repeated_identity_cb;
+  add_repeated_field(reinterpret_cast<repeated_field**>(
+                         &req->client_start.target_identities.arg),
+                     target_identity);
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_set_local_identity_hostname(
+    grpc_gcp_handshaker_req* req, const char* hostname) {
+  if (req == nullptr || hostname == nullptr || !req->has_client_start) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_handshaker_req_set_local_identity_hostname().");
+    return false;
+  }
+  req->client_start.has_local_identity = true;
+  set_identity_hostname(&req->client_start.local_identity, hostname);
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_set_local_identity_service_account(
+    grpc_gcp_handshaker_req* req, const char* service_account) {
+  if (req == nullptr || service_account == nullptr || !req->has_client_start) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_handshaker_req_set_local_identity_service_account().");
+    return false;
+  }
+  req->client_start.has_local_identity = true;
+  set_identity_service_account(&req->client_start.local_identity,
+                               service_account);
+  return true;
+}
+
+static void set_endpoint(grpc_gcp_endpoint* endpoint, const char* ip_address,
+                         size_t port, grpc_gcp_network_protocol protocol) {
+  grpc_slice* slice = create_slice(ip_address, strlen(ip_address));
+  endpoint->ip_address.arg = slice;
+  endpoint->ip_address.funcs.encode = encode_string_or_bytes_cb;
+  endpoint->has_port = true;
+  endpoint->port = static_cast<int32_t>(port);
+  endpoint->has_protocol = true;
+  endpoint->protocol = protocol;
+}
+
+bool grpc_gcp_handshaker_req_set_rpc_versions(grpc_gcp_handshaker_req* req,
+                                              uint32_t max_major,
+                                              uint32_t max_minor,
+                                              uint32_t min_major,
+                                              uint32_t min_minor) {
+  if (req == nullptr || req->has_next) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_handshaker_req_set_rpc_versions().");
+    return false;
+  }
+  if (req->has_client_start) {
+    req->client_start.has_rpc_versions = true;
+    grpc_gcp_rpc_protocol_versions_set_max(&req->client_start.rpc_versions,
+                                           max_major, max_minor);
+    grpc_gcp_rpc_protocol_versions_set_min(&req->client_start.rpc_versions,
+                                           min_major, min_minor);
+  } else {
+    req->server_start.has_rpc_versions = true;
+    grpc_gcp_rpc_protocol_versions_set_max(&req->server_start.rpc_versions,
+                                           max_major, max_minor);
+    grpc_gcp_rpc_protocol_versions_set_min(&req->server_start.rpc_versions,
+                                           min_major, min_minor);
+  }
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_set_local_endpoint(
+    grpc_gcp_handshaker_req* req, const char* ip_address, size_t port,
+    grpc_gcp_network_protocol protocol) {
+  if (req == nullptr || ip_address == nullptr || port > 65535 ||
+      req->has_next) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_handshaker_req_set_local_endpoint().");
+    return false;
+  }
+  if (req->has_client_start) {
+    req->client_start.has_local_endpoint = true;
+    set_endpoint(&req->client_start.local_endpoint, ip_address, port, protocol);
+  } else {
+    req->server_start.has_local_endpoint = true;
+    set_endpoint(&req->server_start.local_endpoint, ip_address, port, protocol);
+  }
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_set_remote_endpoint(
+    grpc_gcp_handshaker_req* req, const char* ip_address, size_t port,
+    grpc_gcp_network_protocol protocol) {
+  if (req == nullptr || ip_address == nullptr || port > 65535 ||
+      req->has_next) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_handshaker_req_set_remote_endpoint().");
+    return false;
+  }
+  if (req->has_client_start) {
+    req->client_start.has_remote_endpoint = true;
+    set_endpoint(&req->client_start.remote_endpoint, ip_address, port,
+                 protocol);
+  } else {
+    req->server_start.has_remote_endpoint = true;
+    set_endpoint(&req->server_start.remote_endpoint, ip_address, port,
+                 protocol);
+  }
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_set_in_bytes(grpc_gcp_handshaker_req* req,
+                                          const char* in_bytes, size_t size) {
+  if (req == nullptr || in_bytes == nullptr || req->has_client_start) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_handshaker_req_set_in_bytes().");
+    return false;
+  }
+  grpc_slice* slice = create_slice(in_bytes, size);
+  if (req->has_next) {
+    req->next.in_bytes.arg = slice;
+    req->next.in_bytes.funcs.encode = &encode_string_or_bytes_cb;
+  } else {
+    req->server_start.in_bytes.arg = slice;
+    req->server_start.in_bytes.funcs.encode = &encode_string_or_bytes_cb;
+  }
+  return true;
+}
+
+static grpc_gcp_server_handshake_parameters* server_start_find_param(
+    grpc_gcp_handshaker_req* req, int32_t key) {
+  size_t i = 0;
+  for (i = 0; i < req->server_start.handshake_parameters_count; i++) {
+    if (req->server_start.handshake_parameters[i].key == key) {
+      return &req->server_start.handshake_parameters[i].value;
+    }
+  }
+  req->server_start
+      .handshake_parameters[req->server_start.handshake_parameters_count]
+      .has_key = true;
+  req->server_start
+      .handshake_parameters[req->server_start.handshake_parameters_count]
+      .has_value = true;
+  req->server_start
+      .handshake_parameters[req->server_start.handshake_parameters_count++]
+      .key = key;
+  return &req->server_start
+              .handshake_parameters
+                  [req->server_start.handshake_parameters_count - 1]
+              .value;
+}
+
+bool grpc_gcp_handshaker_req_param_add_record_protocol(
+    grpc_gcp_handshaker_req* req, grpc_gcp_handshake_protocol key,
+    const char* record_protocol) {
+  if (req == nullptr || record_protocol == nullptr || !req->has_server_start) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_handshaker_req_param_add_record_protocol().");
+    return false;
+  }
+  grpc_gcp_server_handshake_parameters* param =
+      server_start_find_param(req, key);
+  grpc_slice* slice = create_slice(record_protocol, strlen(record_protocol));
+  add_repeated_field(
+      reinterpret_cast<repeated_field**>(&param->record_protocols.arg), slice);
+  param->record_protocols.funcs.encode = &encode_repeated_string_cb;
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_param_add_local_identity_hostname(
+    grpc_gcp_handshaker_req* req, grpc_gcp_handshake_protocol key,
+    const char* hostname) {
+  if (req == nullptr || hostname == nullptr || !req->has_server_start) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_handshaker_req_param_add_local_identity_hostname().");
+    return false;
+  }
+  grpc_gcp_server_handshake_parameters* param =
+      server_start_find_param(req, key);
+  grpc_gcp_identity* local_identity =
+      static_cast<grpc_gcp_identity*>(gpr_zalloc(sizeof(*local_identity)));
+  set_identity_hostname(local_identity, hostname);
+  add_repeated_field(
+      reinterpret_cast<repeated_field**>(&param->local_identities.arg),
+      local_identity);
+  param->local_identities.funcs.encode = &encode_repeated_identity_cb;
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_param_add_local_identity_service_account(
+    grpc_gcp_handshaker_req* req, grpc_gcp_handshake_protocol key,
+    const char* service_account) {
+  if (req == nullptr || service_account == nullptr || !req->has_server_start) {
+    gpr_log(
+        GPR_ERROR,
+        "Invalid arguments to "
+        "grpc_gcp_handshaker_req_param_add_local_identity_service_account().");
+    return false;
+  }
+  grpc_gcp_server_handshake_parameters* param =
+      server_start_find_param(req, key);
+  grpc_gcp_identity* local_identity =
+      static_cast<grpc_gcp_identity*>(gpr_zalloc(sizeof(*local_identity)));
+  set_identity_service_account(local_identity, service_account);
+  add_repeated_field(
+      reinterpret_cast<repeated_field**>(&param->local_identities.arg),
+      local_identity);
+  param->local_identities.funcs.encode = &encode_repeated_identity_cb;
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_encode(grpc_gcp_handshaker_req* req,
+                                    grpc_slice* slice) {
+  if (req == nullptr || slice == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to grpc_gcp_handshaker_req_encode().");
+    return false;
+  }
+  pb_ostream_t size_stream;
+  memset(&size_stream, 0, sizeof(pb_ostream_t));
+  if (!pb_encode(&size_stream, grpc_gcp_HandshakerReq_fields, req)) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&size_stream));
+    return false;
+  }
+  size_t encoded_length = size_stream.bytes_written;
+  *slice = grpc_slice_malloc(encoded_length);
+  pb_ostream_t output_stream =
+      pb_ostream_from_buffer(GRPC_SLICE_START_PTR(*slice), encoded_length);
+  if (!pb_encode(&output_stream, grpc_gcp_HandshakerReq_fields, req) != 0) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&output_stream));
+    return false;
+  }
+  return true;
+}
+
+/* HandshakerResp. */
+grpc_gcp_handshaker_resp* grpc_gcp_handshaker_resp_create(void) {
+  grpc_gcp_handshaker_resp* resp =
+      static_cast<grpc_gcp_handshaker_resp*>(gpr_zalloc(sizeof(*resp)));
+  return resp;
+}
+
+void grpc_gcp_handshaker_resp_destroy(grpc_gcp_handshaker_resp* resp) {
+  if (resp != nullptr) {
+    destroy_slice(static_cast<grpc_slice*>(resp->out_frames.arg));
+    if (resp->has_status) {
+      destroy_slice(static_cast<grpc_slice*>(resp->status.details.arg));
+    }
+    if (resp->has_result) {
+      destroy_slice(
+          static_cast<grpc_slice*>(resp->result.application_protocol.arg));
+      destroy_slice(static_cast<grpc_slice*>(resp->result.record_protocol.arg));
+      destroy_slice(static_cast<grpc_slice*>(resp->result.key_data.arg));
+      if (resp->result.has_local_identity) {
+        destroy_slice(
+            static_cast<grpc_slice*>(resp->result.local_identity.hostname.arg));
+        destroy_slice(static_cast<grpc_slice*>(
+            resp->result.local_identity.service_account.arg));
+      }
+      if (resp->result.has_peer_identity) {
+        destroy_slice(
+            static_cast<grpc_slice*>(resp->result.peer_identity.hostname.arg));
+        destroy_slice(static_cast<grpc_slice*>(
+            resp->result.peer_identity.service_account.arg));
+      }
+    }
+    gpr_free(resp);
+  }
+}
+
+bool grpc_gcp_handshaker_resp_decode(grpc_slice encoded_handshaker_resp,
+                                     grpc_gcp_handshaker_resp* resp) {
+  if (resp == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr argument to grpc_gcp_handshaker_resp_decode().");
+    return false;
+  }
+  pb_istream_t stream =
+      pb_istream_from_buffer(GRPC_SLICE_START_PTR(encoded_handshaker_resp),
+                             GRPC_SLICE_LENGTH(encoded_handshaker_resp));
+  resp->out_frames.funcs.decode = decode_string_or_bytes_cb;
+  resp->status.details.funcs.decode = decode_string_or_bytes_cb;
+  resp->result.application_protocol.funcs.decode = decode_string_or_bytes_cb;
+  resp->result.record_protocol.funcs.decode = decode_string_or_bytes_cb;
+  resp->result.key_data.funcs.decode = decode_string_or_bytes_cb;
+  resp->result.peer_identity.hostname.funcs.decode = decode_string_or_bytes_cb;
+  resp->result.peer_identity.service_account.funcs.decode =
+      decode_string_or_bytes_cb;
+  resp->result.local_identity.hostname.funcs.decode = decode_string_or_bytes_cb;
+  resp->result.local_identity.service_account.funcs.decode =
+      decode_string_or_bytes_cb;
+  if (!pb_decode(&stream, grpc_gcp_HandshakerResp_fields, resp)) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&stream));
+    return false;
+  }
+  return true;
+}
diff --git a/src/core/tsi/alts/handshaker/alts_handshaker_service_api.h b/src/core/tsi/alts/handshaker/alts_handshaker_service_api.h
new file mode 100644
index 0000000..5df56a8
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_handshaker_service_api.h
@@ -0,0 +1,323 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_SERVICE_API_H
+#define GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_SERVICE_API_H
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h"
+
+/**
+ * An implementation of nanopb thin wrapper used to set/get and
+ * serialize/de-serialize of ALTS handshake requests and responses.
+ *
+ * All APIs in the header are thread-compatible. A typical usage of this API at
+ * the client side is as follows:
+ *
+ * -----------------------------------------------------------------------------
+ * // Create, populate, and serialize an ALTS client_start handshake request to
+ * // send to the server.
+ * grpc_gcp_handshaker_req* req =
+ *     grpc_gcp_handshaker_req_create(CLIENT_START_REQ);
+ * grpc_gcp_handshaker_req_set_handshake_protocol(
+       req, grpc_gcp_HandshakeProtocol_ALTS);
+ * grpc_gcp_handshaker_req_add_application_protocol(req, "grpc");
+ * grpc_gcp_handshaker_req_add_record_protocol(req, "ALTSRP_GCM_AES128");
+ * grpc_slice client_slice;
+ * if (!grpc_gcp_handshaker_req_encode(req, &client_slice)) {
+ *   fprintf(stderr, "ALTS handshake request encoding failed.";
+ * }
+ *
+ * // De-serialize a data stream received from the server, and store the result
+ * // at ALTS handshake response.
+ * grpc_gcp_handshaker_resp* resp = grpc_gcp_handshaker_resp_create();
+ * if (!grpc_gcp_handshaker_resp_decode(server_slice, resp)) {
+ *    fprintf(stderr, "ALTS handshake response decoding failed.");
+ * }
+ * // To access a variable-length datatype field (i.e., pb_callback_t),
+ * // access its "arg" subfield (if it has been set).
+ * if (resp->out_frames.arg != nullptr) {
+ *   grpc_slice* slice = resp->out_frames.arg;
+ * }
+ * // To access a fixed-length datatype field (i.e., not pb_calback_t),
+ * // access the field directly (if it has been set).
+ * if (resp->has_status && resp->status->has_code) {
+ *   uint32_t code = resp->status->code;
+ * }
+ *------------------------------------------------------------------------------
+ */
+
+/**
+ * This method creates an ALTS handshake request.
+ *
+ * - type: an enum type value that can be either CLIENT_START_REQ,
+ *   SERVER_START_REQ, or NEXT_REQ to indicate the created instance will be
+ *   client_start, server_start, and next handshake request message
+ * respectively.
+ *
+ * The method returns a pointer to the created instance.
+ */
+grpc_gcp_handshaker_req* grpc_gcp_handshaker_req_create(
+    grpc_gcp_handshaker_req_type type);
+
+/**
+ * This method sets the value for handshake_security_protocol field of ALTS
+ * client_start handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - handshake_protocol: a enum type value representing the handshake security
+ *   protocol.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_set_handshake_protocol(
+    grpc_gcp_handshaker_req* req,
+    grpc_gcp_handshake_protocol handshake_protocol);
+
+/**
+ * This method sets the value for target_name field of ALTS client_start
+ * handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - target_name: a target name to be set.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_set_target_name(grpc_gcp_handshaker_req* req,
+                                             const char* target_name);
+
+/**
+ * This method adds an application protocol supported by the server (or
+ * client) to ALTS server_start (or client_start) handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - application_protocol: an application protocol (e.g., grpc) to be added.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_add_application_protocol(
+    grpc_gcp_handshaker_req* req, const char* application_protocol);
+
+/**
+ * This method adds a record protocol supported by the client to ALTS
+ * client_start handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - record_protocol: a record protocol (e.g., ALTSRP_GCM_AES128) to be
+ *   added.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_add_record_protocol(grpc_gcp_handshaker_req* req,
+                                                 const char* record_protocol);
+
+/**
+ * This method adds a target server identity represented as hostname and
+ * acceptable by a client to ALTS client_start handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - hostname: a string representation of hostname at the connection
+ *   endpoint to be added.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_add_target_identity_hostname(
+    grpc_gcp_handshaker_req* req, const char* hostname);
+
+/**
+ * This method adds a target server identity represented as service account and
+ * acceptable by a client to ALTS client_start handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - service_account: a string representation of service account at the
+ *   connection endpoint to be added.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_add_target_identity_service_account(
+    grpc_gcp_handshaker_req* req, const char* service_account);
+
+/**
+ * This method sets the hostname for local_identity field of ALTS client_start
+ * handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - hostname: a string representation of hostname.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_set_local_identity_hostname(
+    grpc_gcp_handshaker_req* req, const char* hostname);
+
+/**
+ * This method sets the service account for local_identity field of ALTS
+ * client_start handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - service_account: a string representation of service account.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_set_local_identity_service_account(
+    grpc_gcp_handshaker_req* req, const char* service_account);
+
+/**
+ * This method sets the value for local_endpoint field of either ALTS
+ * client_start or server_start handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - ip_address: a string representation of ip address associated with the
+ *   local endpoint, that could be either IPv4 or IPv6.
+ * - port: a port number associated with the local endpoint.
+ * - protocol: a network protocol (e.g., TCP or UDP) associated with the
+ *   local endpoint.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_set_local_endpoint(
+    grpc_gcp_handshaker_req* req, const char* ip_address, size_t port,
+    grpc_gcp_network_protocol protocol);
+
+/**
+ * This method sets the value for remote_endpoint field of either ALTS
+ * client_start or server_start handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - ip_address: a string representation of ip address associated with the
+ *   remote endpoint, that could be either IPv4 or IPv6.
+ * - port: a port number associated with the remote endpoint.
+ * - protocol: a network protocol (e.g., TCP or UDP) associated with the
+ *   remote endpoint.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_set_remote_endpoint(
+    grpc_gcp_handshaker_req* req, const char* ip_address, size_t port,
+    grpc_gcp_network_protocol protocol);
+
+/**
+ * This method sets the value for in_bytes field of either ALTS server_start or
+ * next handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - in_bytes: a buffer containing bytes taken from out_frames of the peer's
+ *   ALTS handshake response. It is possible that the peer's out_frames are
+ * split into multiple handshake request messages.
+ * - size: size of in_bytes buffer.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_set_in_bytes(grpc_gcp_handshaker_req* req,
+                                          const char* in_bytes, size_t size);
+
+/**
+ * This method adds a record protocol to handshake parameters mapped by the
+ * handshake protocol for ALTS server_start handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - key: an enum type value representing a handshake security protocol.
+ * - record_protocol: a record protocol to be added.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_param_add_record_protocol(
+    grpc_gcp_handshaker_req* req, grpc_gcp_handshake_protocol key,
+    const char* record_protocol);
+
+/**
+ * This method adds a local identity represented as hostname to handshake
+ * parameters mapped by the handshake protocol for ALTS server_start handshake
+ * request.
+ *
+ * - req: an ALTS handshake request.
+ * - key: an enum type value representing a handshake security protocol.
+ * - hostname: a string representation of hostname to be added.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_param_add_local_identity_hostname(
+    grpc_gcp_handshaker_req* req, grpc_gcp_handshake_protocol key,
+    const char* hostname);
+
+/**
+ * This method adds a local identity represented as service account to handshake
+ * parameters mapped by the handshake protocol for ALTS server_start handshake
+ * request.
+ *
+ * - req: an ALTS handshake request.
+ * - key: an enum type value representing a handshake security protocol.
+ * - service_account: a string representation of service account to be added.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_param_add_local_identity_service_account(
+    grpc_gcp_handshaker_req* req, grpc_gcp_handshake_protocol key,
+    const char* service_account);
+
+/**
+ * This method sets the value for rpc_versions field of either ALTS
+ * client_start or server_start handshake request.
+ *
+ * - req: an ALTS handshake request.
+ * - max_major: a major version of maximum supported RPC version.
+ * - max_minor: a minor version of maximum supported RPC version.
+ * - min_major: a major version of minimum supported RPC version.
+ * - min_minor: a minor version of minimum supported RPC version.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_set_rpc_versions(grpc_gcp_handshaker_req* req,
+                                              uint32_t max_major,
+                                              uint32_t max_minor,
+                                              uint32_t min_major,
+                                              uint32_t min_minor);
+
+/**
+ * This method serializes an ALTS handshake request and returns a data stream.
+ *
+ * - req: an ALTS handshake request.
+ * - slice: a data stream where the serialized result will be written.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_req_encode(grpc_gcp_handshaker_req* req,
+                                    grpc_slice* slice);
+
+/* This method destroys an ALTS handshake request. */
+void grpc_gcp_handshaker_req_destroy(grpc_gcp_handshaker_req* req);
+
+/* This method creates an ALTS handshake response. */
+grpc_gcp_handshaker_resp* grpc_gcp_handshaker_resp_create(void);
+
+/**
+ * This method de-serializes a data stream and stores the result
+ * in an ALTS handshake response.
+ *
+ * - slice: a data stream containing a serialized ALTS handshake response.
+ * - resp: an ALTS handshake response used to hold de-serialized result.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_handshaker_resp_decode(grpc_slice slice,
+                                     grpc_gcp_handshaker_resp* resp);
+
+/* This method destroys an ALTS handshake response. */
+void grpc_gcp_handshaker_resp_destroy(grpc_gcp_handshaker_resp* resp);
+
+#endif /* GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_SERVICE_API_H */
diff --git a/src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc b/src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc
new file mode 100644
index 0000000..e0e4184
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc
@@ -0,0 +1,143 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h"
+
+void add_repeated_field(repeated_field** head, const void* data) {
+  repeated_field* field =
+      static_cast<repeated_field*>(gpr_zalloc(sizeof(*field)));
+  field->data = data;
+  if (*head == nullptr) {
+    *head = field;
+    (*head)->next = nullptr;
+  } else {
+    field->next = *head;
+    *head = field;
+  }
+}
+
+void destroy_repeated_field_list_identity(repeated_field* head) {
+  repeated_field* field = head;
+  while (field != nullptr) {
+    repeated_field* next_field = field->next;
+    const grpc_gcp_identity* identity =
+        static_cast<const grpc_gcp_identity*>(field->data);
+    destroy_slice(static_cast<grpc_slice*>(identity->hostname.arg));
+    destroy_slice(static_cast<grpc_slice*>(identity->service_account.arg));
+    gpr_free((void*)identity);
+    gpr_free(field);
+    field = next_field;
+  }
+}
+
+void destroy_repeated_field_list_string(repeated_field* head) {
+  repeated_field* field = head;
+  while (field != nullptr) {
+    repeated_field* next_field = field->next;
+    destroy_slice((grpc_slice*)field->data);
+    gpr_free(field);
+    field = next_field;
+  }
+}
+
+grpc_slice* create_slice(const char* data, size_t size) {
+  grpc_slice slice = grpc_slice_from_copied_buffer(data, size);
+  grpc_slice* cb_slice =
+      static_cast<grpc_slice*>(gpr_zalloc(sizeof(*cb_slice)));
+  memcpy(cb_slice, &slice, sizeof(*cb_slice));
+  return cb_slice;
+}
+
+void destroy_slice(grpc_slice* slice) {
+  if (slice != nullptr) {
+    grpc_slice_unref(*slice);
+    gpr_free(slice);
+  }
+}
+
+bool encode_string_or_bytes_cb(pb_ostream_t* stream, const pb_field_t* field,
+                               void* const* arg) {
+  grpc_slice* slice = static_cast<grpc_slice*>(*arg);
+  if (!pb_encode_tag_for_field(stream, field)) return false;
+  return pb_encode_string(stream, GRPC_SLICE_START_PTR(*slice),
+                          GRPC_SLICE_LENGTH(*slice));
+}
+
+bool encode_repeated_identity_cb(pb_ostream_t* stream, const pb_field_t* field,
+                                 void* const* arg) {
+  repeated_field* var = static_cast<repeated_field*>(*arg);
+  while (var != nullptr) {
+    if (!pb_encode_tag_for_field(stream, field)) return false;
+    if (!pb_encode_submessage(stream, grpc_gcp_Identity_fields,
+                              (grpc_gcp_identity*)var->data))
+      return false;
+    var = var->next;
+  }
+  return true;
+}
+
+bool encode_repeated_string_cb(pb_ostream_t* stream, const pb_field_t* field,
+                               void* const* arg) {
+  repeated_field* var = static_cast<repeated_field*>(*arg);
+  while (var != nullptr) {
+    if (!pb_encode_tag_for_field(stream, field)) return false;
+    const grpc_slice* slice = static_cast<const grpc_slice*>(var->data);
+    if (!pb_encode_string(stream, GRPC_SLICE_START_PTR(*slice),
+                          GRPC_SLICE_LENGTH(*slice)))
+      return false;
+    var = var->next;
+  }
+  return true;
+}
+
+bool decode_string_or_bytes_cb(pb_istream_t* stream, const pb_field_t* field,
+                               void** arg) {
+  grpc_slice slice = grpc_slice_malloc(stream->bytes_left);
+  grpc_slice* cb_slice =
+      static_cast<grpc_slice*>(gpr_zalloc(sizeof(*cb_slice)));
+  memcpy(cb_slice, &slice, sizeof(*cb_slice));
+  if (!pb_read(stream, GRPC_SLICE_START_PTR(*cb_slice), stream->bytes_left))
+    return false;
+  *arg = cb_slice;
+  return true;
+}
+
+bool decode_repeated_identity_cb(pb_istream_t* stream, const pb_field_t* field,
+                                 void** arg) {
+  grpc_gcp_identity* identity =
+      static_cast<grpc_gcp_identity*>(gpr_zalloc(sizeof(*identity)));
+  identity->hostname.funcs.decode = decode_string_or_bytes_cb;
+  identity->service_account.funcs.decode = decode_string_or_bytes_cb;
+  add_repeated_field(reinterpret_cast<repeated_field**>(arg), identity);
+  if (!pb_decode(stream, grpc_gcp_Identity_fields, identity)) return false;
+  return true;
+}
+
+bool decode_repeated_string_cb(pb_istream_t* stream, const pb_field_t* field,
+                               void** arg) {
+  grpc_slice slice = grpc_slice_malloc(stream->bytes_left);
+  grpc_slice* cb_slice =
+      static_cast<grpc_slice*>(gpr_zalloc(sizeof(*cb_slice)));
+  memcpy(cb_slice, &slice, sizeof(grpc_slice));
+  if (!pb_read(stream, GRPC_SLICE_START_PTR(*cb_slice), stream->bytes_left))
+    return false;
+  add_repeated_field(reinterpret_cast<repeated_field**>(arg), cb_slice);
+  return true;
+}
diff --git a/src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h b/src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h
new file mode 100644
index 0000000..8fe8f73
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h
@@ -0,0 +1,149 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_SERVICE_API_UTIL_H
+#define GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_SERVICE_API_UTIL_H
+
+#include <grpc/support/port_platform.h>
+
+#include "third_party/nanopb/pb_decode.h"
+#include "third_party/nanopb/pb_encode.h"
+
+#include <grpc/slice.h>
+#include <grpc/slice_buffer.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/tsi/alts/handshaker/handshaker.pb.h"
+
+/**
+ * An implementation of utility functions used to serialize/
+ * de-serialize ALTS handshake requests/responses. All APIs in the header
+ * are thread-compatible.
+ */
+
+/* Renaming of message/field structs generated by nanopb compiler. */
+typedef grpc_gcp_HandshakeProtocol grpc_gcp_handshake_protocol;
+typedef grpc_gcp_NetworkProtocol grpc_gcp_network_protocol;
+typedef grpc_gcp_Identity grpc_gcp_identity;
+typedef grpc_gcp_NextHandshakeMessageReq grpc_gcp_next_handshake_message_req;
+typedef grpc_gcp_ServerHandshakeParameters grpc_gcp_server_handshake_parameters;
+typedef grpc_gcp_Endpoint grpc_gcp_endpoint;
+typedef grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry
+    grpc_gcp_handshake_parameters_entry;
+typedef grpc_gcp_StartClientHandshakeReq grpc_gcp_start_client_handshake_req;
+typedef grpc_gcp_StartServerHandshakeReq grpc_gcp_start_server_handshake_req;
+typedef grpc_gcp_HandshakerReq grpc_gcp_handshaker_req;
+typedef grpc_gcp_HandshakerResult grpc_gcp_handshaker_result;
+typedef grpc_gcp_HandshakerStatus grpc_gcp_handshaker_status;
+typedef grpc_gcp_HandshakerResp grpc_gcp_handshaker_resp;
+
+typedef enum {
+  CLIENT_START_REQ = 0, /* StartClientHandshakeReq. */
+  SERVER_START_REQ = 1, /* StartServerHandshakeReq. */
+  NEXT_REQ = 2,         /* NextHandshakeMessageReq. */
+} grpc_gcp_handshaker_req_type;
+
+/**
+ *  A struct representing a repeated field. The struct is used to organize all
+ *  instances of a specific repeated field into a linked list, which then will
+ *  be used at encode/decode phase. For instance at the encode phase, the encode
+ *  function will iterate through the list, encode each field, and then output
+ *  the result to the stream.
+ */
+typedef struct repeated_field_ {
+  struct repeated_field_* next;
+  const void* data;
+} repeated_field;
+
+/**
+ * This method adds a repeated field to the head of repeated field list.
+ *
+ * - head: a head of repeated field list.
+ * - field: a repeated field to be added to the list.
+ */
+void add_repeated_field(repeated_field** head, const void* field);
+
+/**
+ * This method destroys a repeated field list that consists of string type
+ * fields.
+ *
+ * - head: a head of repeated field list.
+ */
+void destroy_repeated_field_list_string(repeated_field* head);
+
+/**
+ * This method destroys a repeated field list that consists of
+ * grpc_gcp_identity type fields.
+ *
+ * - head: a head of repeated field list.
+ */
+void destroy_repeated_field_list_identity(repeated_field* head);
+
+/**
+ * This method creates a grpc_slice instance by copying a data buffer. It is
+ * similar to grpc_slice_from_copied_buffer() except that it returns an instance
+ * allocated from the heap.
+ *
+ * - data: a data buffer to be copied to grpc_slice instance.
+ * - size: size of data buffer.
+ */
+grpc_slice* create_slice(const char* data, size_t size);
+
+/* This method destroys a grpc_slice instance. */
+void destroy_slice(grpc_slice* slice);
+
+/**
+ * The following encode/decode functions will be assigned to encode/decode
+ * function pointers of pb_callback_t struct (defined in
+ * //third_party/nanopb/pb.h), that represent a repeated field with a dynamic
+ * length (e.g., a string type or repeated field).
+ */
+
+/* This method is an encode callback function for a string or byte array. */
+bool encode_string_or_bytes_cb(pb_ostream_t* stream, const pb_field_t* field,
+                               void* const* arg);
+
+/**
+ * This method is an encode callback function for a repeated grpc_gcp_identity
+ * field.
+ */
+bool encode_repeated_identity_cb(pb_ostream_t* stream, const pb_field_t* field,
+                                 void* const* arg);
+
+/* This method is an encode callback function for a repeated string field. */
+bool encode_repeated_string_cb(pb_ostream_t* stream, const pb_field_t* field,
+                               void* const* arg);
+
+/**
+ * This method is a decode callback function for a string or byte array field.
+ */
+bool decode_string_or_bytes_cb(pb_istream_t* stream, const pb_field_t* field,
+                               void** arg);
+/**
+ * This method is a decode callback function for a repeated grpc_gcp_identity
+ * field.
+ */
+bool decode_repeated_identity_cb(pb_istream_t* stream, const pb_field_t* field,
+                                 void** arg);
+
+/* This method is a decode callback function for a repeated string field. */
+bool decode_repeated_string_cb(pb_istream_t* stream, const pb_field_t* field,
+                               void** arg);
+
+#endif /* GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_SERVICE_API_UTIL_H */
diff --git a/src/core/tsi/alts/handshaker/alts_tsi_event.cc b/src/core/tsi/alts/handshaker/alts_tsi_event.cc
new file mode 100644
index 0000000..ec0bf12
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_tsi_event.cc
@@ -0,0 +1,73 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/handshaker/alts_tsi_event.h"
+
+#include <grpc/grpc.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+tsi_result alts_tsi_event_create(alts_tsi_handshaker* handshaker,
+                                 tsi_handshaker_on_next_done_cb cb,
+                                 void* user_data,
+                                 grpc_alts_credentials_options* options,
+                                 grpc_slice target_name,
+                                 alts_tsi_event** event) {
+  if (event == nullptr || handshaker == nullptr || cb == nullptr) {
+    gpr_log(GPR_ERROR, "Invalid arguments to alts_tsi_event_create()");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_tsi_event* e = static_cast<alts_tsi_event*>(gpr_zalloc(sizeof(*e)));
+  e->handshaker = handshaker;
+  e->cb = cb;
+  e->user_data = user_data;
+  e->options = grpc_alts_credentials_options_copy(options);
+  e->target_name = grpc_slice_copy(target_name);
+  grpc_metadata_array_init(&e->initial_metadata);
+  grpc_metadata_array_init(&e->trailing_metadata);
+  *event = e;
+  return TSI_OK;
+}
+
+void alts_tsi_event_dispatch_to_handshaker(alts_tsi_event* event, bool is_ok) {
+  if (event == nullptr) {
+    gpr_log(
+        GPR_ERROR,
+        "ALTS TSI event is nullptr in alts_tsi_event_dispatch_to_handshaker()");
+    return;
+  }
+  alts_tsi_handshaker_handle_response(event->handshaker, event->recv_buffer,
+                                      event->status, &event->details, event->cb,
+                                      event->user_data, is_ok);
+}
+
+void alts_tsi_event_destroy(alts_tsi_event* event) {
+  if (event == nullptr) {
+    return;
+  }
+  grpc_byte_buffer_destroy(event->send_buffer);
+  grpc_byte_buffer_destroy(event->recv_buffer);
+  grpc_metadata_array_destroy(&event->initial_metadata);
+  grpc_metadata_array_destroy(&event->trailing_metadata);
+  grpc_slice_unref(event->details);
+  grpc_slice_unref(event->target_name);
+  grpc_alts_credentials_options_destroy(event->options);
+  gpr_free(event);
+}
diff --git a/src/core/tsi/alts/handshaker/alts_tsi_event.h b/src/core/tsi/alts/handshaker/alts_tsi_event.h
new file mode 100644
index 0000000..043e75d
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_tsi_event.h
@@ -0,0 +1,93 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_EVENT_H
+#define GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_EVENT_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/byte_buffer.h>
+#include <grpc/byte_buffer_reader.h>
+
+#include "src/core/tsi/alts/handshaker/alts_tsi_handshaker.h"
+#include "src/core/tsi/transport_security_interface.h"
+
+/**
+ * A ALTS TSI event interface. In asynchronous implementation of
+ * tsi_handshaker_next(), the function will exit after scheduling a handshaker
+ * request to ALTS handshaker service without waiting for response to return.
+ * The event is used to link the scheduled handshaker request with the
+ * corresponding response so that enough context information can be inferred
+ * from it to handle the response. All APIs in the header are thread-compatible.
+ */
+
+/**
+ * Main struct for ALTS TSI event. It retains ownership on send_buffer and
+ * recv_buffer, but not on handshaker.
+ */
+typedef struct alts_tsi_event {
+  alts_tsi_handshaker* handshaker;
+  grpc_byte_buffer* send_buffer;
+  grpc_byte_buffer* recv_buffer;
+  grpc_status_code status;
+  grpc_slice details;
+  grpc_metadata_array initial_metadata;
+  grpc_metadata_array trailing_metadata;
+  tsi_handshaker_on_next_done_cb cb;
+  void* user_data;
+  grpc_alts_credentials_options* options;
+  grpc_slice target_name;
+} alts_tsi_event;
+
+/**
+ * This method creates a ALTS TSI event.
+ *
+ * - handshaker: ALTS TSI handshaker instance associated with the event to be
+ *   created. The created event does not own the handshaker instance.
+ * - cb: callback function to be called when handling data received from ALTS
+ *   handshaker service.
+ * - user_data: argument to callback function.
+ * - options: ALTS credentials options.
+ * - target_name: name of endpoint used for secure naming check.
+ * - event: address of ALTS TSI event instance to be returned from the method.
+ *
+ * It returns TSI_OK on success and an error status code on failure.
+ */
+tsi_result alts_tsi_event_create(alts_tsi_handshaker* handshaker,
+                                 tsi_handshaker_on_next_done_cb cb,
+                                 void* user_data,
+                                 grpc_alts_credentials_options* options,
+                                 grpc_slice target_name,
+                                 alts_tsi_event** event);
+
+/**
+ * This method dispatches a ALTS TSI event received from the handshaker service,
+ * and a boolean flag indicating if the event is valid to read to ALTS TSI
+ * handshaker to process. It is called by TSI thread.
+ *
+ * - event: ALTS TSI event instance.
+ * - is_ok: a boolean value indicating if the event is valid to read.
+ */
+void alts_tsi_event_dispatch_to_handshaker(alts_tsi_event* event, bool is_ok);
+
+/**
+ * This method destroys the ALTS TSI event.
+ */
+void alts_tsi_event_destroy(alts_tsi_event* event);
+
+#endif /* GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_EVENT_H */
diff --git a/src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc b/src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc
new file mode 100644
index 0000000..529f210
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc
@@ -0,0 +1,483 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/handshaker/alts_tsi_handshaker.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/thd_id.h>
+
+#include "src/core/lib/gpr/host_port.h"
+#include "src/core/lib/gprpp/thd.h"
+#include "src/core/tsi/alts/frame_protector/alts_frame_protector.h"
+#include "src/core/tsi/alts/handshaker/alts_handshaker_client.h"
+#include "src/core/tsi/alts/handshaker/alts_tsi_utils.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h"
+#include "src/core/tsi/alts_transport_security.h"
+
+#define TSI_ALTS_INITIAL_BUFFER_SIZE 256
+
+static alts_shared_resource* kSharedResource = alts_get_shared_resource();
+
+/* Main struct for ALTS TSI handshaker. */
+typedef struct alts_tsi_handshaker {
+  tsi_handshaker base;
+  alts_handshaker_client* client;
+  grpc_slice recv_bytes;
+  grpc_slice target_name;
+  unsigned char* buffer;
+  size_t buffer_size;
+  bool is_client;
+  bool has_sent_start_message;
+  grpc_alts_credentials_options* options;
+} alts_tsi_handshaker;
+
+/* Main struct for ALTS TSI handshaker result. */
+typedef struct alts_tsi_handshaker_result {
+  tsi_handshaker_result base;
+  char* peer_identity;
+  char* key_data;
+  unsigned char* unused_bytes;
+  size_t unused_bytes_size;
+  grpc_slice rpc_versions;
+  bool is_client;
+} alts_tsi_handshaker_result;
+
+static tsi_result handshaker_result_extract_peer(
+    const tsi_handshaker_result* self, tsi_peer* peer) {
+  if (self == nullptr || peer == nullptr) {
+    gpr_log(GPR_ERROR, "Invalid argument to handshaker_result_extract_peer()");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_tsi_handshaker_result* result =
+      reinterpret_cast<alts_tsi_handshaker_result*>(
+          const_cast<tsi_handshaker_result*>(self));
+  GPR_ASSERT(kTsiAltsNumOfPeerProperties == 3);
+  tsi_result ok = tsi_construct_peer(kTsiAltsNumOfPeerProperties, peer);
+  int index = 0;
+  if (ok != TSI_OK) {
+    gpr_log(GPR_ERROR, "Failed to construct tsi peer");
+    return ok;
+  }
+  GPR_ASSERT(&peer->properties[index] != nullptr);
+  ok = tsi_construct_string_peer_property_from_cstring(
+      TSI_CERTIFICATE_TYPE_PEER_PROPERTY, TSI_ALTS_CERTIFICATE_TYPE,
+      &peer->properties[index]);
+  if (ok != TSI_OK) {
+    tsi_peer_destruct(peer);
+    gpr_log(GPR_ERROR, "Failed to set tsi peer property");
+    return ok;
+  }
+  index++;
+  GPR_ASSERT(&peer->properties[index] != nullptr);
+  ok = tsi_construct_string_peer_property_from_cstring(
+      TSI_ALTS_SERVICE_ACCOUNT_PEER_PROPERTY, result->peer_identity,
+      &peer->properties[index]);
+  if (ok != TSI_OK) {
+    tsi_peer_destruct(peer);
+    gpr_log(GPR_ERROR, "Failed to set tsi peer property");
+  }
+  index++;
+  GPR_ASSERT(&peer->properties[index] != nullptr);
+  ok = tsi_construct_string_peer_property(
+      TSI_ALTS_RPC_VERSIONS,
+      reinterpret_cast<char*>(GRPC_SLICE_START_PTR(result->rpc_versions)),
+      GRPC_SLICE_LENGTH(result->rpc_versions), &peer->properties[2]);
+  if (ok != TSI_OK) {
+    tsi_peer_destruct(peer);
+    gpr_log(GPR_ERROR, "Failed to set tsi peer property");
+  }
+  GPR_ASSERT(++index == kTsiAltsNumOfPeerProperties);
+  return ok;
+}
+
+static tsi_result handshaker_result_create_zero_copy_grpc_protector(
+    const tsi_handshaker_result* self, size_t* max_output_protected_frame_size,
+    tsi_zero_copy_grpc_protector** protector) {
+  if (self == nullptr || protector == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to create_zero_copy_grpc_protector()");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_tsi_handshaker_result* result =
+      reinterpret_cast<alts_tsi_handshaker_result*>(
+          const_cast<tsi_handshaker_result*>(self));
+  tsi_result ok = alts_zero_copy_grpc_protector_create(
+      reinterpret_cast<const uint8_t*>(result->key_data),
+      kAltsAes128GcmRekeyKeyLength, /*is_rekey=*/true, result->is_client,
+      /*is_integrity_only=*/false, max_output_protected_frame_size, protector);
+  if (ok != TSI_OK) {
+    gpr_log(GPR_ERROR, "Failed to create zero-copy grpc protector");
+  }
+  return ok;
+}
+
+static tsi_result handshaker_result_create_frame_protector(
+    const tsi_handshaker_result* self, size_t* max_output_protected_frame_size,
+    tsi_frame_protector** protector) {
+  if (self == nullptr || protector == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to handshaker_result_create_frame_protector()");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_tsi_handshaker_result* result =
+      reinterpret_cast<alts_tsi_handshaker_result*>(
+          const_cast<tsi_handshaker_result*>(self));
+  tsi_result ok = alts_create_frame_protector(
+      reinterpret_cast<const uint8_t*>(result->key_data),
+      kAltsAes128GcmRekeyKeyLength, result->is_client, /*is_rekey=*/true,
+      max_output_protected_frame_size, protector);
+  if (ok != TSI_OK) {
+    gpr_log(GPR_ERROR, "Failed to create frame protector");
+  }
+  return ok;
+}
+
+static tsi_result handshaker_result_get_unused_bytes(
+    const tsi_handshaker_result* self, const unsigned char** bytes,
+    size_t* bytes_size) {
+  if (self == nullptr || bytes == nullptr || bytes_size == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to handshaker_result_get_unused_bytes()");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_tsi_handshaker_result* result =
+      reinterpret_cast<alts_tsi_handshaker_result*>(
+          const_cast<tsi_handshaker_result*>(self));
+  *bytes = result->unused_bytes;
+  *bytes_size = result->unused_bytes_size;
+  return TSI_OK;
+}
+
+static void handshaker_result_destroy(tsi_handshaker_result* self) {
+  if (self == nullptr) {
+    return;
+  }
+  alts_tsi_handshaker_result* result =
+      reinterpret_cast<alts_tsi_handshaker_result*>(
+          const_cast<tsi_handshaker_result*>(self));
+  gpr_free(result->peer_identity);
+  gpr_free(result->key_data);
+  gpr_free(result->unused_bytes);
+  grpc_slice_unref(result->rpc_versions);
+  gpr_free(result);
+}
+
+static const tsi_handshaker_result_vtable result_vtable = {
+    handshaker_result_extract_peer,
+    handshaker_result_create_zero_copy_grpc_protector,
+    handshaker_result_create_frame_protector,
+    handshaker_result_get_unused_bytes, handshaker_result_destroy};
+
+static tsi_result create_handshaker_result(grpc_gcp_handshaker_resp* resp,
+                                           bool is_client,
+                                           tsi_handshaker_result** self) {
+  if (self == nullptr || resp == nullptr) {
+    gpr_log(GPR_ERROR, "Invalid arguments to create_handshaker_result()");
+    return TSI_INVALID_ARGUMENT;
+  }
+  grpc_slice* key = static_cast<grpc_slice*>(resp->result.key_data.arg);
+  GPR_ASSERT(key != nullptr);
+  grpc_slice* identity =
+      static_cast<grpc_slice*>(resp->result.peer_identity.service_account.arg);
+  if (identity == nullptr) {
+    gpr_log(GPR_ERROR, "Invalid service account");
+    return TSI_FAILED_PRECONDITION;
+  }
+  if (GRPC_SLICE_LENGTH(*key) < kAltsAes128GcmRekeyKeyLength) {
+    gpr_log(GPR_ERROR, "Bad key length");
+    return TSI_FAILED_PRECONDITION;
+  }
+  alts_tsi_handshaker_result* result =
+      static_cast<alts_tsi_handshaker_result*>(gpr_zalloc(sizeof(*result)));
+  result->key_data =
+      static_cast<char*>(gpr_zalloc(kAltsAes128GcmRekeyKeyLength));
+  memcpy(result->key_data, GRPC_SLICE_START_PTR(*key),
+         kAltsAes128GcmRekeyKeyLength);
+  result->peer_identity = grpc_slice_to_c_string(*identity);
+  if (!resp->result.has_peer_rpc_versions) {
+    gpr_log(GPR_ERROR, "Peer does not set RPC protocol versions.");
+    return TSI_FAILED_PRECONDITION;
+  }
+  if (!grpc_gcp_rpc_protocol_versions_encode(&resp->result.peer_rpc_versions,
+                                             &result->rpc_versions)) {
+    gpr_log(GPR_ERROR, "Failed to serialize peer's RPC protocol versions.");
+    return TSI_FAILED_PRECONDITION;
+  }
+  result->is_client = is_client;
+  result->base.vtable = &result_vtable;
+  *self = &result->base;
+  return TSI_OK;
+}
+
+static tsi_result handshaker_next(
+    tsi_handshaker* self, const unsigned char* received_bytes,
+    size_t received_bytes_size, const unsigned char** bytes_to_send,
+    size_t* bytes_to_send_size, tsi_handshaker_result** result,
+    tsi_handshaker_on_next_done_cb cb, void* user_data) {
+  if (self == nullptr || cb == nullptr) {
+    gpr_log(GPR_ERROR, "Invalid arguments to handshaker_next()");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_tsi_handshaker* handshaker =
+      reinterpret_cast<alts_tsi_handshaker*>(self);
+  tsi_result ok = TSI_OK;
+  alts_tsi_event* event = nullptr;
+  ok = alts_tsi_event_create(handshaker, cb, user_data, handshaker->options,
+                             handshaker->target_name, &event);
+  if (ok != TSI_OK) {
+    gpr_log(GPR_ERROR, "Failed to create ALTS TSI event");
+    return ok;
+  }
+  grpc_slice slice = (received_bytes == nullptr || received_bytes_size == 0)
+                         ? grpc_empty_slice()
+                         : grpc_slice_from_copied_buffer(
+                               reinterpret_cast<const char*>(received_bytes),
+                               received_bytes_size);
+  if (!handshaker->has_sent_start_message) {
+    ok = handshaker->is_client
+             ? alts_handshaker_client_start_client(handshaker->client, event)
+             : alts_handshaker_client_start_server(handshaker->client, event,
+                                                   &slice);
+    handshaker->has_sent_start_message = true;
+  } else {
+    if (!GRPC_SLICE_IS_EMPTY(handshaker->recv_bytes)) {
+      grpc_slice_unref(handshaker->recv_bytes);
+    }
+    handshaker->recv_bytes = grpc_slice_ref(slice);
+    ok = alts_handshaker_client_next(handshaker->client, event, &slice);
+  }
+  grpc_slice_unref(slice);
+  if (ok != TSI_OK) {
+    gpr_log(GPR_ERROR, "Failed to schedule ALTS handshaker requests");
+    return ok;
+  }
+  return TSI_ASYNC;
+}
+
+static void handshaker_destroy(tsi_handshaker* self) {
+  if (self == nullptr) {
+    return;
+  }
+  alts_tsi_handshaker* handshaker =
+      reinterpret_cast<alts_tsi_handshaker*>(self);
+  alts_handshaker_client_destroy(handshaker->client);
+  grpc_slice_unref(handshaker->recv_bytes);
+  grpc_slice_unref(handshaker->target_name);
+  grpc_alts_credentials_options_destroy(handshaker->options);
+  gpr_free(handshaker->buffer);
+  gpr_free(handshaker);
+}
+
+static const tsi_handshaker_vtable handshaker_vtable = {
+    nullptr,        nullptr, nullptr, nullptr, nullptr, handshaker_destroy,
+    handshaker_next};
+
+static void thread_worker(void* arg) {
+  while (true) {
+    grpc_event event = grpc_completion_queue_next(
+        kSharedResource->cq, gpr_inf_future(GPR_CLOCK_REALTIME), nullptr);
+    GPR_ASSERT(event.type != GRPC_QUEUE_TIMEOUT);
+    if (event.type == GRPC_QUEUE_SHUTDOWN) {
+      /* signal alts_tsi_shutdown() to destroy completion queue. */
+      grpc_tsi_alts_signal_for_cq_destroy();
+      break;
+    }
+    /* event.type == GRPC_OP_COMPLETE. */
+    alts_tsi_event* alts_event = static_cast<alts_tsi_event*>(event.tag);
+    alts_tsi_event_dispatch_to_handshaker(alts_event, event.success);
+    alts_tsi_event_destroy(alts_event);
+  }
+}
+
+static void init_shared_resources(const char* handshaker_service_url) {
+  GPR_ASSERT(handshaker_service_url != nullptr);
+  gpr_mu_lock(&kSharedResource->mu);
+  if (kSharedResource->channel == nullptr) {
+    gpr_cv_init(&kSharedResource->cv);
+    kSharedResource->channel =
+        grpc_insecure_channel_create(handshaker_service_url, nullptr, nullptr);
+    kSharedResource->cq = grpc_completion_queue_create_for_next(nullptr);
+    kSharedResource->thread =
+        grpc_core::Thread("alts_tsi_handshaker", &thread_worker, nullptr);
+    kSharedResource->thread.Start();
+  }
+  gpr_mu_unlock(&kSharedResource->mu);
+}
+
+tsi_result alts_tsi_handshaker_create(
+    const grpc_alts_credentials_options* options, const char* target_name,
+    const char* handshaker_service_url, bool is_client, tsi_handshaker** self) {
+  if (handshaker_service_url == nullptr || self == nullptr ||
+      options == nullptr || (is_client && target_name == nullptr)) {
+    gpr_log(GPR_ERROR, "Invalid arguments to alts_tsi_handshaker_create()");
+    return TSI_INVALID_ARGUMENT;
+  }
+  init_shared_resources(handshaker_service_url);
+  alts_handshaker_client* client = alts_grpc_handshaker_client_create(
+      kSharedResource->channel, kSharedResource->cq, handshaker_service_url);
+  if (client == nullptr) {
+    gpr_log(GPR_ERROR, "Failed to create ALTS handshaker client");
+    return TSI_FAILED_PRECONDITION;
+  }
+  alts_tsi_handshaker* handshaker =
+      static_cast<alts_tsi_handshaker*>(gpr_zalloc(sizeof(*handshaker)));
+  handshaker->client = client;
+  handshaker->buffer_size = TSI_ALTS_INITIAL_BUFFER_SIZE;
+  handshaker->buffer =
+      static_cast<unsigned char*>(gpr_zalloc(handshaker->buffer_size));
+  handshaker->is_client = is_client;
+  handshaker->has_sent_start_message = false;
+  handshaker->target_name = target_name == nullptr
+                                ? grpc_empty_slice()
+                                : grpc_slice_from_static_string(target_name);
+  handshaker->options = grpc_alts_credentials_options_copy(options);
+  handshaker->base.vtable = &handshaker_vtable;
+  *self = &handshaker->base;
+  return TSI_OK;
+}
+
+static bool is_handshake_finished_properly(grpc_gcp_handshaker_resp* resp) {
+  GPR_ASSERT(resp != nullptr);
+  if (resp->has_result) {
+    return true;
+  }
+  return false;
+}
+
+static void set_unused_bytes(tsi_handshaker_result* self,
+                             grpc_slice* recv_bytes, size_t bytes_consumed) {
+  GPR_ASSERT(recv_bytes != nullptr && self != nullptr);
+  if (GRPC_SLICE_LENGTH(*recv_bytes) == bytes_consumed) {
+    return;
+  }
+  alts_tsi_handshaker_result* result =
+      reinterpret_cast<alts_tsi_handshaker_result*>(self);
+  result->unused_bytes_size = GRPC_SLICE_LENGTH(*recv_bytes) - bytes_consumed;
+  result->unused_bytes =
+      static_cast<unsigned char*>(gpr_zalloc(result->unused_bytes_size));
+  memcpy(result->unused_bytes,
+         GRPC_SLICE_START_PTR(*recv_bytes) + bytes_consumed,
+         result->unused_bytes_size);
+}
+
+void alts_tsi_handshaker_handle_response(alts_tsi_handshaker* handshaker,
+                                         grpc_byte_buffer* recv_buffer,
+                                         grpc_status_code status,
+                                         grpc_slice* details,
+                                         tsi_handshaker_on_next_done_cb cb,
+                                         void* user_data, bool is_ok) {
+  /* Invalid input check. */
+  if (cb == nullptr) {
+    gpr_log(GPR_ERROR,
+            "cb is nullptr in alts_tsi_handshaker_handle_response()");
+    return;
+  }
+  if (handshaker == nullptr || recv_buffer == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to alts_tsi_handshaker_handle_response()");
+    cb(TSI_INTERNAL_ERROR, user_data, nullptr, 0, nullptr);
+    return;
+  }
+  /* Failed grpc call check. */
+  if (!is_ok || status != GRPC_STATUS_OK) {
+    gpr_log(GPR_ERROR, "grpc call made to handshaker service failed");
+    if (details != nullptr) {
+      char* error_details = grpc_slice_to_c_string(*details);
+      gpr_log(GPR_ERROR, "error details:%s", error_details);
+      gpr_free(error_details);
+    }
+    cb(TSI_INTERNAL_ERROR, user_data, nullptr, 0, nullptr);
+    return;
+  }
+  grpc_gcp_handshaker_resp* resp =
+      alts_tsi_utils_deserialize_response(recv_buffer);
+  /* Invalid handshaker response check. */
+  if (resp == nullptr) {
+    gpr_log(GPR_ERROR, "alts_tsi_utils_deserialize_response() failed");
+    cb(TSI_DATA_CORRUPTED, user_data, nullptr, 0, nullptr);
+    return;
+  }
+  grpc_slice* slice = static_cast<grpc_slice*>(resp->out_frames.arg);
+  unsigned char* bytes_to_send = nullptr;
+  size_t bytes_to_send_size = 0;
+  if (slice != nullptr) {
+    bytes_to_send_size = GRPC_SLICE_LENGTH(*slice);
+    while (bytes_to_send_size > handshaker->buffer_size) {
+      handshaker->buffer_size *= 2;
+      handshaker->buffer = static_cast<unsigned char*>(
+          gpr_realloc(handshaker->buffer, handshaker->buffer_size));
+    }
+    memcpy(handshaker->buffer, GRPC_SLICE_START_PTR(*slice),
+           bytes_to_send_size);
+    bytes_to_send = handshaker->buffer;
+  }
+  tsi_handshaker_result* result = nullptr;
+  if (is_handshake_finished_properly(resp)) {
+    create_handshaker_result(resp, handshaker->is_client, &result);
+    set_unused_bytes(result, &handshaker->recv_bytes, resp->bytes_consumed);
+  }
+  grpc_status_code code = static_cast<grpc_status_code>(resp->status.code);
+  grpc_gcp_handshaker_resp_destroy(resp);
+  cb(alts_tsi_utils_convert_to_tsi_result(code), user_data, bytes_to_send,
+     bytes_to_send_size, result);
+}
+
+namespace grpc_core {
+namespace internal {
+
+bool alts_tsi_handshaker_get_has_sent_start_message_for_testing(
+    alts_tsi_handshaker* handshaker) {
+  GPR_ASSERT(handshaker != nullptr);
+  return handshaker->has_sent_start_message;
+}
+
+bool alts_tsi_handshaker_get_is_client_for_testing(
+    alts_tsi_handshaker* handshaker) {
+  GPR_ASSERT(handshaker != nullptr);
+  return handshaker->is_client;
+}
+
+void alts_tsi_handshaker_set_recv_bytes_for_testing(
+    alts_tsi_handshaker* handshaker, grpc_slice* slice) {
+  GPR_ASSERT(handshaker != nullptr && slice != nullptr);
+  handshaker->recv_bytes = grpc_slice_ref(*slice);
+}
+
+grpc_slice alts_tsi_handshaker_get_recv_bytes_for_testing(
+    alts_tsi_handshaker* handshaker) {
+  GPR_ASSERT(handshaker != nullptr);
+  return handshaker->recv_bytes;
+}
+
+void alts_tsi_handshaker_set_client_for_testing(
+    alts_tsi_handshaker* handshaker, alts_handshaker_client* client) {
+  GPR_ASSERT(handshaker != nullptr && client != nullptr);
+  alts_handshaker_client_destroy(handshaker->client);
+  handshaker->client = client;
+}
+
+}  // namespace internal
+}  // namespace grpc_core
diff --git a/src/core/tsi/alts/handshaker/alts_tsi_handshaker.h b/src/core/tsi/alts/handshaker/alts_tsi_handshaker.h
new file mode 100644
index 0000000..227b30c
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_tsi_handshaker.h
@@ -0,0 +1,83 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_HANDSHAKER_H
+#define GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_HANDSHAKER_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/grpc.h>
+
+#include "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h"
+#include "src/core/tsi/alts_transport_security.h"
+#include "src/core/tsi/transport_security.h"
+#include "src/core/tsi/transport_security_interface.h"
+
+#define TSI_ALTS_SERVICE_ACCOUNT_PEER_PROPERTY "service_accont"
+#define TSI_ALTS_CERTIFICATE_TYPE "ALTS"
+#define TSI_ALTS_RPC_VERSIONS "rpc_versions"
+
+const size_t kTsiAltsNumOfPeerProperties = 3;
+
+/**
+ * Main struct for ALTS TSI handshaker. All APIs in the header are
+ * thread-comptabile.
+ */
+typedef struct alts_tsi_handshaker alts_tsi_handshaker;
+
+/**
+ * This method creates a ALTS TSI handshaker instance.
+ *
+ * - options: ALTS credentials options containing information passed from TSI
+ *   caller (e.g., rpc protocol versions).
+ * - target_name: the name of the endpoint that the channel is connecting to,
+ *   and will be used for secure naming check.
+ * - handshaker_service_url: address of ALTS handshaker service in the format of
+ *   "host:port".
+ * - is_client: boolean value indicating if the handshaker is used at the client
+ *   (is_client = true) or server (is_client = false) side.
+ * - self: address of ALTS TSI handshaker instance to be returned from the
+ *   method.
+ *
+ * It returns TSI_OK on success and an error status code on failure.
+ */
+tsi_result alts_tsi_handshaker_create(
+    const grpc_alts_credentials_options* options, const char* target_name,
+    const char* handshaker_service_url, bool is_client, tsi_handshaker** self);
+
+/**
+ * This method handles handshaker response returned from ALTS handshaker
+ * service.
+ *
+ * - handshaker: ALTS TSI handshaker instance.
+ * - recv_buffer: buffer holding data received from the handshaker service.
+ * - status: status of the grpc call made to the handshaker service.
+ * - details: error details of the grpc call made to the handshaker service.
+ * - cb: callback function of ALTS TSI event.
+ * - user_data: argument of callback function.
+ * - is_ok: a boolean value indicating if the handshaker response is ok to read.
+ *
+ */
+void alts_tsi_handshaker_handle_response(alts_tsi_handshaker* handshaker,
+                                         grpc_byte_buffer* recv_buffer,
+                                         grpc_status_code status,
+                                         grpc_slice* details,
+                                         tsi_handshaker_on_next_done_cb cb,
+                                         void* user_data, bool is_ok);
+
+#endif /* GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_HANDSHAKER_H */
diff --git a/src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h b/src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h
new file mode 100644
index 0000000..9b7b9bb
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h
@@ -0,0 +1,52 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_HANDSHAKER_PRIVATE_H
+#define GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_HANDSHAKER_PRIVATE_H
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/handshaker/alts_handshaker_client.h"
+
+namespace grpc_core {
+namespace internal {
+
+/**
+ * Unsafe, use for testing only. It allows the caller to change the way the
+ * ALTS TSI handshaker schedules handshaker requests.
+ */
+void alts_tsi_handshaker_set_client_for_testing(alts_tsi_handshaker* handshaker,
+                                                alts_handshaker_client* client);
+
+/* For testing only. */
+bool alts_tsi_handshaker_get_has_sent_start_message_for_testing(
+    alts_tsi_handshaker* handshaker);
+
+bool alts_tsi_handshaker_get_is_client_for_testing(
+    alts_tsi_handshaker* handshaker);
+
+void alts_tsi_handshaker_set_recv_bytes_for_testing(
+    alts_tsi_handshaker* handshaker, grpc_slice* slice);
+
+grpc_slice alts_tsi_handshaker_get_recv_bytes_for_testing(
+    alts_tsi_handshaker* handshaker);
+
+}  // namespace internal
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_HANDSHAKER_PRIVATE_H */
diff --git a/src/core/tsi/alts/handshaker/alts_tsi_utils.cc b/src/core/tsi/alts/handshaker/alts_tsi_utils.cc
new file mode 100644
index 0000000..d9b5e6c
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_tsi_utils.cc
@@ -0,0 +1,58 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/handshaker/alts_tsi_utils.h"
+
+#include <grpc/byte_buffer_reader.h>
+
+tsi_result alts_tsi_utils_convert_to_tsi_result(grpc_status_code code) {
+  switch (code) {
+    case GRPC_STATUS_OK:
+      return TSI_OK;
+    case GRPC_STATUS_UNKNOWN:
+      return TSI_UNKNOWN_ERROR;
+    case GRPC_STATUS_INVALID_ARGUMENT:
+      return TSI_INVALID_ARGUMENT;
+    case GRPC_STATUS_NOT_FOUND:
+      return TSI_NOT_FOUND;
+    case GRPC_STATUS_INTERNAL:
+      return TSI_INTERNAL_ERROR;
+    default:
+      return TSI_UNKNOWN_ERROR;
+  }
+}
+
+grpc_gcp_handshaker_resp* alts_tsi_utils_deserialize_response(
+    grpc_byte_buffer* resp_buffer) {
+  GPR_ASSERT(resp_buffer != nullptr);
+  grpc_byte_buffer_reader bbr;
+  grpc_byte_buffer_reader_init(&bbr, resp_buffer);
+  grpc_slice slice = grpc_byte_buffer_reader_readall(&bbr);
+  grpc_gcp_handshaker_resp* resp = grpc_gcp_handshaker_resp_create();
+  bool ok = grpc_gcp_handshaker_resp_decode(slice, resp);
+  grpc_slice_unref(slice);
+  grpc_byte_buffer_reader_destroy(&bbr);
+  if (!ok) {
+    grpc_gcp_handshaker_resp_destroy(resp);
+    gpr_log(GPR_ERROR, "grpc_gcp_handshaker_resp_decode() failed");
+    return nullptr;
+  }
+  return resp;
+}
diff --git a/src/core/tsi/alts/handshaker/alts_tsi_utils.h b/src/core/tsi/alts/handshaker/alts_tsi_utils.h
new file mode 100644
index 0000000..9ef649d
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/alts_tsi_utils.h
@@ -0,0 +1,52 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_UTILS_H
+#define GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_UTILS_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/byte_buffer.h>
+#include <grpc/grpc.h>
+
+#include "src/core/tsi/alts/handshaker/alts_handshaker_service_api.h"
+#include "src/core/tsi/transport_security_interface.h"
+
+/**
+ * This method converts grpc_status_code code to the corresponding tsi_result
+ * code.
+ *
+ * - code: grpc_status_code code.
+ *
+ * It returns the converted tsi_result code.
+ */
+tsi_result alts_tsi_utils_convert_to_tsi_result(grpc_status_code code);
+
+/**
+ * This method deserializes a handshaker response returned from ALTS handshaker
+ * service.
+ *
+ * - bytes_received: data returned from ALTS handshaker service.
+ *
+ * It returns a deserialized handshaker response on success and nullptr on
+ * failure.
+ */
+grpc_gcp_handshaker_resp* alts_tsi_utils_deserialize_response(
+    grpc_byte_buffer* resp_buffer);
+
+#endif /* GRPC_CORE_TSI_ALTS_HANDSHAKER_ALTS_TSI_UTILS_H */
diff --git a/src/core/tsi/alts/handshaker/altscontext.pb.c b/src/core/tsi/alts/handshaker/altscontext.pb.c
new file mode 100644
index 0000000..81a82f5
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/altscontext.pb.c
@@ -0,0 +1,48 @@
+/* Automatically generated nanopb constant definitions */
+/* Generated by nanopb-0.3.7-dev */
+
+#include "src/core/tsi/alts/handshaker/altscontext.pb.h"
+
+/* @@protoc_insertion_point(includes) */
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+
+
+const pb_field_t grpc_gcp_AltsContext_fields[7] = {
+    PB_FIELD(  1, STRING  , OPTIONAL, CALLBACK, FIRST, grpc_gcp_AltsContext, application_protocol, application_protocol, 0),
+    PB_FIELD(  2, STRING  , OPTIONAL, CALLBACK, OTHER, grpc_gcp_AltsContext, record_protocol, application_protocol, 0),
+    PB_FIELD(  3, UENUM   , OPTIONAL, STATIC  , OTHER, grpc_gcp_AltsContext, security_level, record_protocol, 0),
+    PB_FIELD(  4, STRING  , OPTIONAL, CALLBACK, OTHER, grpc_gcp_AltsContext, peer_service_account, security_level, 0),
+    PB_FIELD(  5, STRING  , OPTIONAL, CALLBACK, OTHER, grpc_gcp_AltsContext, local_service_account, peer_service_account, 0),
+    PB_FIELD(  6, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_AltsContext, peer_rpc_versions, local_service_account, &grpc_gcp_RpcProtocolVersions_fields),
+    PB_LAST_FIELD
+};
+
+
+/* Check that field information fits in pb_field_t */
+#if !defined(PB_FIELD_32BIT)
+/* If you get an error here, it means that you need to define PB_FIELD_32BIT
+ * compile-time option. You can do that in pb.h or on compiler command line.
+ * 
+ * The reason you need to do this is that some of your messages contain tag
+ * numbers or field sizes that are larger than what can fit in 8 or 16 bit
+ * field descriptors.
+ */
+PB_STATIC_ASSERT((pb_membersize(grpc_gcp_AltsContext, peer_rpc_versions) < 65536), YOU_MUST_DEFINE_PB_FIELD_32BIT_FOR_MESSAGES_grpc_gcp_AltsContext)
+#endif
+
+#if !defined(PB_FIELD_16BIT) && !defined(PB_FIELD_32BIT)
+/* If you get an error here, it means that you need to define PB_FIELD_16BIT
+ * compile-time option. You can do that in pb.h or on compiler command line.
+ * 
+ * The reason you need to do this is that some of your messages contain tag
+ * numbers or field sizes that are larger than what can fit in the default
+ * 8 bit descriptors.
+ */
+PB_STATIC_ASSERT((pb_membersize(grpc_gcp_AltsContext, peer_rpc_versions) < 256), YOU_MUST_DEFINE_PB_FIELD_16BIT_FOR_MESSAGES_grpc_gcp_AltsContext)
+#endif
+
+
+/* @@protoc_insertion_point(eof) */
diff --git a/src/core/tsi/alts/handshaker/altscontext.pb.h b/src/core/tsi/alts/handshaker/altscontext.pb.h
new file mode 100644
index 0000000..3e72d7f
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/altscontext.pb.h
@@ -0,0 +1,64 @@
+/* Automatically generated nanopb header */
+/* Generated by nanopb-0.3.7-dev */
+
+#ifndef PB_GRPC_GCP_ALTSCONTEXT_PB_H_INCLUDED
+#define PB_GRPC_GCP_ALTSCONTEXT_PB_H_INCLUDED
+#include "third_party/nanopb/pb.h"
+#include "src/core/tsi/alts/handshaker/transport_security_common.pb.h"
+
+/* @@protoc_insertion_point(includes) */
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Struct definitions */
+typedef struct _grpc_gcp_AltsContext {
+    pb_callback_t application_protocol;
+    pb_callback_t record_protocol;
+    bool has_security_level;
+    grpc_gcp_SecurityLevel security_level;
+    pb_callback_t peer_service_account;
+    pb_callback_t local_service_account;
+    bool has_peer_rpc_versions;
+    grpc_gcp_RpcProtocolVersions peer_rpc_versions;
+/* @@protoc_insertion_point(struct:grpc_gcp_AltsContext) */
+} grpc_gcp_AltsContext;
+
+/* Default values for struct fields */
+
+/* Initializer values for message structs */
+#define grpc_gcp_AltsContext_init_default        {{{NULL}, NULL}, {{NULL}, NULL}, false, (grpc_gcp_SecurityLevel)0, {{NULL}, NULL}, {{NULL}, NULL}, false, grpc_gcp_RpcProtocolVersions_init_default}
+#define grpc_gcp_AltsContext_init_zero           {{{NULL}, NULL}, {{NULL}, NULL}, false, (grpc_gcp_SecurityLevel)0, {{NULL}, NULL}, {{NULL}, NULL}, false, grpc_gcp_RpcProtocolVersions_init_zero}
+
+/* Field tags (for use in manual encoding/decoding) */
+#define grpc_gcp_AltsContext_application_protocol_tag 1
+#define grpc_gcp_AltsContext_record_protocol_tag 2
+#define grpc_gcp_AltsContext_security_level_tag  3
+#define grpc_gcp_AltsContext_peer_service_account_tag 4
+#define grpc_gcp_AltsContext_local_service_account_tag 5
+#define grpc_gcp_AltsContext_peer_rpc_versions_tag 6
+
+/* Struct field encoding specification for nanopb */
+extern const pb_field_t grpc_gcp_AltsContext_fields[7];
+
+/* Maximum encoded size of messages (where known) */
+/* grpc_gcp_AltsContext_size depends on runtime parameters */
+
+/* Message IDs (where set with "msgid" option) */
+#ifdef PB_MSGID
+
+#define ALTSCONTEXT_MESSAGES \
+
+
+#endif
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+/* @@protoc_insertion_point(eof) */
+
+#endif
diff --git a/src/core/tsi/alts/handshaker/handshaker.pb.c b/src/core/tsi/alts/handshaker/handshaker.pb.c
new file mode 100644
index 0000000..bd992df
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/handshaker.pb.c
@@ -0,0 +1,123 @@
+/* Automatically generated nanopb constant definitions */
+/* Generated by nanopb-0.3.7-dev */
+
+#include "src/core/tsi/alts/handshaker/handshaker.pb.h"
+
+/* @@protoc_insertion_point(includes) */
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+
+
+const pb_field_t grpc_gcp_Endpoint_fields[4] = {
+    PB_FIELD(  1, STRING  , OPTIONAL, CALLBACK, FIRST, grpc_gcp_Endpoint, ip_address, ip_address, 0),
+    PB_FIELD(  2, INT32   , OPTIONAL, STATIC  , OTHER, grpc_gcp_Endpoint, port, ip_address, 0),
+    PB_FIELD(  3, UENUM   , OPTIONAL, STATIC  , OTHER, grpc_gcp_Endpoint, protocol, port, 0),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_gcp_Identity_fields[3] = {
+    PB_FIELD(  1, STRING  , OPTIONAL, CALLBACK, FIRST, grpc_gcp_Identity, service_account, service_account, 0),
+    PB_FIELD(  2, STRING  , OPTIONAL, CALLBACK, OTHER, grpc_gcp_Identity, hostname, service_account, 0),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_gcp_StartClientHandshakeReq_fields[10] = {
+    PB_FIELD(  1, UENUM   , OPTIONAL, STATIC  , FIRST, grpc_gcp_StartClientHandshakeReq, handshake_security_protocol, handshake_security_protocol, 0),
+    PB_FIELD(  2, STRING  , REPEATED, CALLBACK, OTHER, grpc_gcp_StartClientHandshakeReq, application_protocols, handshake_security_protocol, 0),
+    PB_FIELD(  3, STRING  , REPEATED, CALLBACK, OTHER, grpc_gcp_StartClientHandshakeReq, record_protocols, application_protocols, 0),
+    PB_FIELD(  4, MESSAGE , REPEATED, CALLBACK, OTHER, grpc_gcp_StartClientHandshakeReq, target_identities, record_protocols, &grpc_gcp_Identity_fields),
+    PB_FIELD(  5, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_StartClientHandshakeReq, local_identity, target_identities, &grpc_gcp_Identity_fields),
+    PB_FIELD(  6, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_StartClientHandshakeReq, local_endpoint, local_identity, &grpc_gcp_Endpoint_fields),
+    PB_FIELD(  7, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_StartClientHandshakeReq, remote_endpoint, local_endpoint, &grpc_gcp_Endpoint_fields),
+    PB_FIELD(  8, STRING  , OPTIONAL, CALLBACK, OTHER, grpc_gcp_StartClientHandshakeReq, target_name, remote_endpoint, 0),
+    PB_FIELD(  9, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_StartClientHandshakeReq, rpc_versions, target_name, &grpc_gcp_RpcProtocolVersions_fields),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_gcp_ServerHandshakeParameters_fields[3] = {
+    PB_FIELD(  1, STRING  , REPEATED, CALLBACK, FIRST, grpc_gcp_ServerHandshakeParameters, record_protocols, record_protocols, 0),
+    PB_FIELD(  2, MESSAGE , REPEATED, CALLBACK, OTHER, grpc_gcp_ServerHandshakeParameters, local_identities, record_protocols, &grpc_gcp_Identity_fields),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_gcp_StartServerHandshakeReq_fields[7] = {
+    PB_FIELD(  1, STRING  , REPEATED, CALLBACK, FIRST, grpc_gcp_StartServerHandshakeReq, application_protocols, application_protocols, 0),
+    PB_FIELD(  2, MESSAGE , REPEATED, STATIC  , OTHER, grpc_gcp_StartServerHandshakeReq, handshake_parameters, application_protocols, &grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_fields),
+    PB_FIELD(  3, BYTES   , OPTIONAL, CALLBACK, OTHER, grpc_gcp_StartServerHandshakeReq, in_bytes, handshake_parameters, 0),
+    PB_FIELD(  4, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_StartServerHandshakeReq, local_endpoint, in_bytes, &grpc_gcp_Endpoint_fields),
+    PB_FIELD(  5, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_StartServerHandshakeReq, remote_endpoint, local_endpoint, &grpc_gcp_Endpoint_fields),
+    PB_FIELD(  6, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_StartServerHandshakeReq, rpc_versions, remote_endpoint, &grpc_gcp_RpcProtocolVersions_fields),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_fields[3] = {
+    PB_FIELD(  1, INT32   , OPTIONAL, STATIC  , FIRST, grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry, key, key, 0),
+    PB_FIELD(  2, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry, value, key, &grpc_gcp_ServerHandshakeParameters_fields),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_gcp_NextHandshakeMessageReq_fields[2] = {
+    PB_FIELD(  1, BYTES   , OPTIONAL, CALLBACK, FIRST, grpc_gcp_NextHandshakeMessageReq, in_bytes, in_bytes, 0),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_gcp_HandshakerReq_fields[4] = {
+    PB_FIELD(  1, MESSAGE , OPTIONAL, STATIC  , FIRST, grpc_gcp_HandshakerReq, client_start, client_start, &grpc_gcp_StartClientHandshakeReq_fields),
+    PB_FIELD(  2, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_HandshakerReq, server_start, client_start, &grpc_gcp_StartServerHandshakeReq_fields),
+    PB_FIELD(  3, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_HandshakerReq, next, server_start, &grpc_gcp_NextHandshakeMessageReq_fields),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_gcp_HandshakerResult_fields[8] = {
+    PB_FIELD(  1, STRING  , OPTIONAL, CALLBACK, FIRST, grpc_gcp_HandshakerResult, application_protocol, application_protocol, 0),
+    PB_FIELD(  2, STRING  , OPTIONAL, CALLBACK, OTHER, grpc_gcp_HandshakerResult, record_protocol, application_protocol, 0),
+    PB_FIELD(  3, BYTES   , OPTIONAL, CALLBACK, OTHER, grpc_gcp_HandshakerResult, key_data, record_protocol, 0),
+    PB_FIELD(  4, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_HandshakerResult, peer_identity, key_data, &grpc_gcp_Identity_fields),
+    PB_FIELD(  5, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_HandshakerResult, local_identity, peer_identity, &grpc_gcp_Identity_fields),
+    PB_FIELD(  6, BOOL    , OPTIONAL, STATIC  , OTHER, grpc_gcp_HandshakerResult, keep_channel_open, local_identity, 0),
+    PB_FIELD(  7, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_HandshakerResult, peer_rpc_versions, keep_channel_open, &grpc_gcp_RpcProtocolVersions_fields),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_gcp_HandshakerStatus_fields[3] = {
+    PB_FIELD(  1, UINT32  , OPTIONAL, STATIC  , FIRST, grpc_gcp_HandshakerStatus, code, code, 0),
+    PB_FIELD(  2, STRING  , OPTIONAL, CALLBACK, OTHER, grpc_gcp_HandshakerStatus, details, code, 0),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_gcp_HandshakerResp_fields[5] = {
+    PB_FIELD(  1, BYTES   , OPTIONAL, CALLBACK, FIRST, grpc_gcp_HandshakerResp, out_frames, out_frames, 0),
+    PB_FIELD(  2, UINT32  , OPTIONAL, STATIC  , OTHER, grpc_gcp_HandshakerResp, bytes_consumed, out_frames, 0),
+    PB_FIELD(  3, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_HandshakerResp, result, bytes_consumed, &grpc_gcp_HandshakerResult_fields),
+    PB_FIELD(  4, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_HandshakerResp, status, result, &grpc_gcp_HandshakerStatus_fields),
+    PB_LAST_FIELD
+};
+
+
+/* Check that field information fits in pb_field_t */
+#if !defined(PB_FIELD_32BIT)
+/* If you get an error here, it means that you need to define PB_FIELD_32BIT
+ * compile-time option. You can do that in pb.h or on compiler command line.
+ * 
+ * The reason you need to do this is that some of your messages contain tag
+ * numbers or field sizes that are larger than what can fit in 8 or 16 bit
+ * field descriptors.
+ */
+PB_STATIC_ASSERT((pb_membersize(grpc_gcp_StartClientHandshakeReq, target_identities) < 65536 && pb_membersize(grpc_gcp_StartClientHandshakeReq, local_identity) < 65536 && pb_membersize(grpc_gcp_StartClientHandshakeReq, local_endpoint) < 65536 && pb_membersize(grpc_gcp_StartClientHandshakeReq, remote_endpoint) < 65536 && pb_membersize(grpc_gcp_StartClientHandshakeReq, rpc_versions) < 65536 && pb_membersize(grpc_gcp_ServerHandshakeParameters, local_identities) < 65536 && pb_membersize(grpc_gcp_StartServerHandshakeReq, handshake_parameters[0]) < 65536 && pb_membersize(grpc_gcp_StartServerHandshakeReq, local_endpoint) < 65536 && pb_membersize(grpc_gcp_StartServerHandshakeReq, remote_endpoint) < 65536 && pb_membersize(grpc_gcp_StartServerHandshakeReq, rpc_versions) < 65536 && pb_membersize(grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry, value) < 65536 && pb_membersize(grpc_gcp_HandshakerReq, client_start) < 65536 && pb_membersize(grpc_gcp_HandshakerReq, server_start) < 65536 && pb_membersize(grpc_gcp_HandshakerReq, next) < 65536 && pb_membersize(grpc_gcp_HandshakerResult, peer_identity) < 65536 && pb_membersize(grpc_gcp_HandshakerResult, local_identity) < 65536 && pb_membersize(grpc_gcp_HandshakerResult, peer_rpc_versions) < 65536 && pb_membersize(grpc_gcp_HandshakerResp, result) < 65536 && pb_membersize(grpc_gcp_HandshakerResp, status) < 65536), YOU_MUST_DEFINE_PB_FIELD_32BIT_FOR_MESSAGES_grpc_gcp_Endpoint_grpc_gcp_Identity_grpc_gcp_StartClientHandshakeReq_grpc_gcp_ServerHandshakeParameters_grpc_gcp_StartServerHandshakeReq_grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_grpc_gcp_NextHandshakeMessageReq_grpc_gcp_HandshakerReq_grpc_gcp_HandshakerResult_grpc_gcp_HandshakerStatus_grpc_gcp_HandshakerResp)
+#endif
+
+#if !defined(PB_FIELD_16BIT) && !defined(PB_FIELD_32BIT)
+/* If you get an error here, it means that you need to define PB_FIELD_16BIT
+ * compile-time option. You can do that in pb.h or on compiler command line.
+ * 
+ * The reason you need to do this is that some of your messages contain tag
+ * numbers or field sizes that are larger than what can fit in the default
+ * 8 bit descriptors.
+ */
+PB_STATIC_ASSERT((pb_membersize(grpc_gcp_StartClientHandshakeReq, target_identities) < 256 && pb_membersize(grpc_gcp_StartClientHandshakeReq, local_identity) < 256 && pb_membersize(grpc_gcp_StartClientHandshakeReq, local_endpoint) < 256 && pb_membersize(grpc_gcp_StartClientHandshakeReq, remote_endpoint) < 256 && pb_membersize(grpc_gcp_StartClientHandshakeReq, rpc_versions) < 256 && pb_membersize(grpc_gcp_ServerHandshakeParameters, local_identities) < 256 && pb_membersize(grpc_gcp_StartServerHandshakeReq, handshake_parameters[0]) < 256 && pb_membersize(grpc_gcp_StartServerHandshakeReq, local_endpoint) < 256 && pb_membersize(grpc_gcp_StartServerHandshakeReq, remote_endpoint) < 256 && pb_membersize(grpc_gcp_StartServerHandshakeReq, rpc_versions) < 256 && pb_membersize(grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry, value) < 256 && pb_membersize(grpc_gcp_HandshakerReq, client_start) < 256 && pb_membersize(grpc_gcp_HandshakerReq, server_start) < 256 && pb_membersize(grpc_gcp_HandshakerReq, next) < 256 && pb_membersize(grpc_gcp_HandshakerResult, peer_identity) < 256 && pb_membersize(grpc_gcp_HandshakerResult, local_identity) < 256 && pb_membersize(grpc_gcp_HandshakerResult, peer_rpc_versions) < 256 && pb_membersize(grpc_gcp_HandshakerResp, result) < 256 && pb_membersize(grpc_gcp_HandshakerResp, status) < 256), YOU_MUST_DEFINE_PB_FIELD_16BIT_FOR_MESSAGES_grpc_gcp_Endpoint_grpc_gcp_Identity_grpc_gcp_StartClientHandshakeReq_grpc_gcp_ServerHandshakeParameters_grpc_gcp_StartServerHandshakeReq_grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_grpc_gcp_NextHandshakeMessageReq_grpc_gcp_HandshakerReq_grpc_gcp_HandshakerResult_grpc_gcp_HandshakerStatus_grpc_gcp_HandshakerResp)
+#endif
+
+
+/* @@protoc_insertion_point(eof) */
diff --git a/src/core/tsi/alts/handshaker/handshaker.pb.h b/src/core/tsi/alts/handshaker/handshaker.pb.h
new file mode 100644
index 0000000..0805a14
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/handshaker.pb.h
@@ -0,0 +1,255 @@
+/* Automatically generated nanopb header */
+/* Generated by nanopb-0.3.7-dev */
+
+#ifndef PB_GRPC_GCP_HANDSHAKER_PB_H_INCLUDED
+#define PB_GRPC_GCP_HANDSHAKER_PB_H_INCLUDED
+#include "third_party/nanopb/pb.h"
+#include "src/core/tsi/alts/handshaker/transport_security_common.pb.h"
+
+/* @@protoc_insertion_point(includes) */
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Enum definitions */
+typedef enum _grpc_gcp_HandshakeProtocol {
+    grpc_gcp_HandshakeProtocol_HANDSHAKE_PROTOCOL_UNSPECIFIED = 0,
+    grpc_gcp_HandshakeProtocol_TLS = 1,
+    grpc_gcp_HandshakeProtocol_ALTS = 2
+} grpc_gcp_HandshakeProtocol;
+#define _grpc_gcp_HandshakeProtocol_MIN grpc_gcp_HandshakeProtocol_HANDSHAKE_PROTOCOL_UNSPECIFIED
+#define _grpc_gcp_HandshakeProtocol_MAX grpc_gcp_HandshakeProtocol_ALTS
+#define _grpc_gcp_HandshakeProtocol_ARRAYSIZE ((grpc_gcp_HandshakeProtocol)(grpc_gcp_HandshakeProtocol_ALTS+1))
+
+typedef enum _grpc_gcp_NetworkProtocol {
+    grpc_gcp_NetworkProtocol_NETWORK_PROTOCOL_UNSPECIFIED = 0,
+    grpc_gcp_NetworkProtocol_TCP = 1,
+    grpc_gcp_NetworkProtocol_UDP = 2
+} grpc_gcp_NetworkProtocol;
+#define _grpc_gcp_NetworkProtocol_MIN grpc_gcp_NetworkProtocol_NETWORK_PROTOCOL_UNSPECIFIED
+#define _grpc_gcp_NetworkProtocol_MAX grpc_gcp_NetworkProtocol_UDP
+#define _grpc_gcp_NetworkProtocol_ARRAYSIZE ((grpc_gcp_NetworkProtocol)(grpc_gcp_NetworkProtocol_UDP+1))
+
+/* Struct definitions */
+typedef struct _grpc_gcp_Identity {
+    pb_callback_t service_account;
+    pb_callback_t hostname;
+/* @@protoc_insertion_point(struct:grpc_gcp_Identity) */
+} grpc_gcp_Identity;
+
+typedef struct _grpc_gcp_NextHandshakeMessageReq {
+    pb_callback_t in_bytes;
+/* @@protoc_insertion_point(struct:grpc_gcp_NextHandshakeMessageReq) */
+} grpc_gcp_NextHandshakeMessageReq;
+
+typedef struct _grpc_gcp_ServerHandshakeParameters {
+    pb_callback_t record_protocols;
+    pb_callback_t local_identities;
+/* @@protoc_insertion_point(struct:grpc_gcp_ServerHandshakeParameters) */
+} grpc_gcp_ServerHandshakeParameters;
+
+typedef struct _grpc_gcp_Endpoint {
+    pb_callback_t ip_address;
+    bool has_port;
+    int32_t port;
+    bool has_protocol;
+    grpc_gcp_NetworkProtocol protocol;
+/* @@protoc_insertion_point(struct:grpc_gcp_Endpoint) */
+} grpc_gcp_Endpoint;
+
+typedef struct _grpc_gcp_HandshakerResult {
+    pb_callback_t application_protocol;
+    pb_callback_t record_protocol;
+    pb_callback_t key_data;
+    bool has_peer_identity;
+    grpc_gcp_Identity peer_identity;
+    bool has_local_identity;
+    grpc_gcp_Identity local_identity;
+    bool has_keep_channel_open;
+    bool keep_channel_open;
+    bool has_peer_rpc_versions;
+    grpc_gcp_RpcProtocolVersions peer_rpc_versions;
+/* @@protoc_insertion_point(struct:grpc_gcp_HandshakerResult) */
+} grpc_gcp_HandshakerResult;
+
+typedef struct _grpc_gcp_HandshakerStatus {
+    bool has_code;
+    uint32_t code;
+    pb_callback_t details;
+/* @@protoc_insertion_point(struct:grpc_gcp_HandshakerStatus) */
+} grpc_gcp_HandshakerStatus;
+
+typedef struct _grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry {
+    bool has_key;
+    int32_t key;
+    bool has_value;
+    grpc_gcp_ServerHandshakeParameters value;
+/* @@protoc_insertion_point(struct:grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry) */
+} grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry;
+
+typedef struct _grpc_gcp_HandshakerResp {
+    pb_callback_t out_frames;
+    bool has_bytes_consumed;
+    uint32_t bytes_consumed;
+    bool has_result;
+    grpc_gcp_HandshakerResult result;
+    bool has_status;
+    grpc_gcp_HandshakerStatus status;
+/* @@protoc_insertion_point(struct:grpc_gcp_HandshakerResp) */
+} grpc_gcp_HandshakerResp;
+
+typedef struct _grpc_gcp_StartClientHandshakeReq {
+    bool has_handshake_security_protocol;
+    grpc_gcp_HandshakeProtocol handshake_security_protocol;
+    pb_callback_t application_protocols;
+    pb_callback_t record_protocols;
+    pb_callback_t target_identities;
+    bool has_local_identity;
+    grpc_gcp_Identity local_identity;
+    bool has_local_endpoint;
+    grpc_gcp_Endpoint local_endpoint;
+    bool has_remote_endpoint;
+    grpc_gcp_Endpoint remote_endpoint;
+    pb_callback_t target_name;
+    bool has_rpc_versions;
+    grpc_gcp_RpcProtocolVersions rpc_versions;
+/* @@protoc_insertion_point(struct:grpc_gcp_StartClientHandshakeReq) */
+} grpc_gcp_StartClientHandshakeReq;
+
+typedef struct _grpc_gcp_StartServerHandshakeReq {
+    pb_callback_t application_protocols;
+    pb_size_t handshake_parameters_count;
+    grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry handshake_parameters[3];
+    pb_callback_t in_bytes;
+    bool has_local_endpoint;
+    grpc_gcp_Endpoint local_endpoint;
+    bool has_remote_endpoint;
+    grpc_gcp_Endpoint remote_endpoint;
+    bool has_rpc_versions;
+    grpc_gcp_RpcProtocolVersions rpc_versions;
+/* @@protoc_insertion_point(struct:grpc_gcp_StartServerHandshakeReq) */
+} grpc_gcp_StartServerHandshakeReq;
+
+typedef struct _grpc_gcp_HandshakerReq {
+    bool has_client_start;
+    grpc_gcp_StartClientHandshakeReq client_start;
+    bool has_server_start;
+    grpc_gcp_StartServerHandshakeReq server_start;
+    bool has_next;
+    grpc_gcp_NextHandshakeMessageReq next;
+/* @@protoc_insertion_point(struct:grpc_gcp_HandshakerReq) */
+} grpc_gcp_HandshakerReq;
+
+/* Default values for struct fields */
+
+/* Initializer values for message structs */
+#define grpc_gcp_Endpoint_init_default           {{{NULL}, NULL}, false, 0, false, (grpc_gcp_NetworkProtocol)0}
+#define grpc_gcp_Identity_init_default           {{{NULL}, NULL}, {{NULL}, NULL}}
+#define grpc_gcp_StartClientHandshakeReq_init_default {false, (grpc_gcp_HandshakeProtocol)0, {{NULL}, NULL}, {{NULL}, NULL}, {{NULL}, NULL}, false, grpc_gcp_Identity_init_default, false, grpc_gcp_Endpoint_init_default, false, grpc_gcp_Endpoint_init_default, {{NULL}, NULL}, false, grpc_gcp_RpcProtocolVersions_init_default}
+#define grpc_gcp_ServerHandshakeParameters_init_default {{{NULL}, NULL}, {{NULL}, NULL}}
+#define grpc_gcp_StartServerHandshakeReq_init_default {{{NULL}, NULL}, 0, {grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_init_default, grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_init_default, grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_init_default}, {{NULL}, NULL}, false, grpc_gcp_Endpoint_init_default, false, grpc_gcp_Endpoint_init_default, false, grpc_gcp_RpcProtocolVersions_init_default}
+#define grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_init_default {false, 0, false, grpc_gcp_ServerHandshakeParameters_init_default}
+#define grpc_gcp_NextHandshakeMessageReq_init_default {{{NULL}, NULL}}
+#define grpc_gcp_HandshakerReq_init_default      {false, grpc_gcp_StartClientHandshakeReq_init_default, false, grpc_gcp_StartServerHandshakeReq_init_default, false, grpc_gcp_NextHandshakeMessageReq_init_default}
+#define grpc_gcp_HandshakerResult_init_default   {{{NULL}, NULL}, {{NULL}, NULL}, {{NULL}, NULL}, false, grpc_gcp_Identity_init_default, false, grpc_gcp_Identity_init_default, false, 0, false, grpc_gcp_RpcProtocolVersions_init_default}
+#define grpc_gcp_HandshakerStatus_init_default   {false, 0, {{NULL}, NULL}}
+#define grpc_gcp_HandshakerResp_init_default     {{{NULL}, NULL}, false, 0, false, grpc_gcp_HandshakerResult_init_default, false, grpc_gcp_HandshakerStatus_init_default}
+#define grpc_gcp_Endpoint_init_zero              {{{NULL}, NULL}, false, 0, false, (grpc_gcp_NetworkProtocol)0}
+#define grpc_gcp_Identity_init_zero              {{{NULL}, NULL}, {{NULL}, NULL}}
+#define grpc_gcp_StartClientHandshakeReq_init_zero {false, (grpc_gcp_HandshakeProtocol)0, {{NULL}, NULL}, {{NULL}, NULL}, {{NULL}, NULL}, false, grpc_gcp_Identity_init_zero, false, grpc_gcp_Endpoint_init_zero, false, grpc_gcp_Endpoint_init_zero, {{NULL}, NULL}, false, grpc_gcp_RpcProtocolVersions_init_zero}
+#define grpc_gcp_ServerHandshakeParameters_init_zero {{{NULL}, NULL}, {{NULL}, NULL}}
+#define grpc_gcp_StartServerHandshakeReq_init_zero {{{NULL}, NULL}, 0, {grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_init_zero, grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_init_zero, grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_init_zero}, {{NULL}, NULL}, false, grpc_gcp_Endpoint_init_zero, false, grpc_gcp_Endpoint_init_zero, false, grpc_gcp_RpcProtocolVersions_init_zero}
+#define grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_init_zero {false, 0, false, grpc_gcp_ServerHandshakeParameters_init_zero}
+#define grpc_gcp_NextHandshakeMessageReq_init_zero {{{NULL}, NULL}}
+#define grpc_gcp_HandshakerReq_init_zero         {false, grpc_gcp_StartClientHandshakeReq_init_zero, false, grpc_gcp_StartServerHandshakeReq_init_zero, false, grpc_gcp_NextHandshakeMessageReq_init_zero}
+#define grpc_gcp_HandshakerResult_init_zero      {{{NULL}, NULL}, {{NULL}, NULL}, {{NULL}, NULL}, false, grpc_gcp_Identity_init_zero, false, grpc_gcp_Identity_init_zero, false, 0, false, grpc_gcp_RpcProtocolVersions_init_zero}
+#define grpc_gcp_HandshakerStatus_init_zero      {false, 0, {{NULL}, NULL}}
+#define grpc_gcp_HandshakerResp_init_zero        {{{NULL}, NULL}, false, 0, false, grpc_gcp_HandshakerResult_init_zero, false, grpc_gcp_HandshakerStatus_init_zero}
+
+/* Field tags (for use in manual encoding/decoding) */
+#define grpc_gcp_Identity_service_account_tag    1
+#define grpc_gcp_Identity_hostname_tag           2
+#define grpc_gcp_NextHandshakeMessageReq_in_bytes_tag 1
+#define grpc_gcp_ServerHandshakeParameters_record_protocols_tag 1
+#define grpc_gcp_ServerHandshakeParameters_local_identities_tag 2
+#define grpc_gcp_Endpoint_ip_address_tag         1
+#define grpc_gcp_Endpoint_port_tag               2
+#define grpc_gcp_Endpoint_protocol_tag           3
+#define grpc_gcp_HandshakerResult_application_protocol_tag 1
+#define grpc_gcp_HandshakerResult_record_protocol_tag 2
+#define grpc_gcp_HandshakerResult_key_data_tag   3
+#define grpc_gcp_HandshakerResult_peer_identity_tag 4
+#define grpc_gcp_HandshakerResult_local_identity_tag 5
+#define grpc_gcp_HandshakerResult_keep_channel_open_tag 6
+#define grpc_gcp_HandshakerResult_peer_rpc_versions_tag 7
+#define grpc_gcp_HandshakerStatus_code_tag       1
+#define grpc_gcp_HandshakerStatus_details_tag    2
+#define grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_key_tag 1
+#define grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_value_tag 2
+#define grpc_gcp_HandshakerResp_out_frames_tag   1
+#define grpc_gcp_HandshakerResp_bytes_consumed_tag 2
+#define grpc_gcp_HandshakerResp_result_tag       3
+#define grpc_gcp_HandshakerResp_status_tag       4
+#define grpc_gcp_StartClientHandshakeReq_handshake_security_protocol_tag 1
+#define grpc_gcp_StartClientHandshakeReq_application_protocols_tag 2
+#define grpc_gcp_StartClientHandshakeReq_record_protocols_tag 3
+#define grpc_gcp_StartClientHandshakeReq_target_identities_tag 4
+#define grpc_gcp_StartClientHandshakeReq_local_identity_tag 5
+#define grpc_gcp_StartClientHandshakeReq_local_endpoint_tag 6
+#define grpc_gcp_StartClientHandshakeReq_remote_endpoint_tag 7
+#define grpc_gcp_StartClientHandshakeReq_target_name_tag 8
+#define grpc_gcp_StartClientHandshakeReq_rpc_versions_tag 9
+#define grpc_gcp_StartServerHandshakeReq_application_protocols_tag 1
+#define grpc_gcp_StartServerHandshakeReq_handshake_parameters_tag 2
+#define grpc_gcp_StartServerHandshakeReq_in_bytes_tag 3
+#define grpc_gcp_StartServerHandshakeReq_local_endpoint_tag 4
+#define grpc_gcp_StartServerHandshakeReq_remote_endpoint_tag 5
+#define grpc_gcp_StartServerHandshakeReq_rpc_versions_tag 6
+#define grpc_gcp_HandshakerReq_client_start_tag  1
+#define grpc_gcp_HandshakerReq_server_start_tag  2
+#define grpc_gcp_HandshakerReq_next_tag          3
+
+/* Struct field encoding specification for nanopb */
+extern const pb_field_t grpc_gcp_Endpoint_fields[4];
+extern const pb_field_t grpc_gcp_Identity_fields[3];
+extern const pb_field_t grpc_gcp_StartClientHandshakeReq_fields[10];
+extern const pb_field_t grpc_gcp_ServerHandshakeParameters_fields[3];
+extern const pb_field_t grpc_gcp_StartServerHandshakeReq_fields[7];
+extern const pb_field_t grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_fields[3];
+extern const pb_field_t grpc_gcp_NextHandshakeMessageReq_fields[2];
+extern const pb_field_t grpc_gcp_HandshakerReq_fields[4];
+extern const pb_field_t grpc_gcp_HandshakerResult_fields[8];
+extern const pb_field_t grpc_gcp_HandshakerStatus_fields[3];
+extern const pb_field_t grpc_gcp_HandshakerResp_fields[5];
+
+/* Maximum encoded size of messages (where known) */
+/* grpc_gcp_Endpoint_size depends on runtime parameters */
+/* grpc_gcp_Identity_size depends on runtime parameters */
+/* grpc_gcp_StartClientHandshakeReq_size depends on runtime parameters */
+/* grpc_gcp_ServerHandshakeParameters_size depends on runtime parameters */
+/* grpc_gcp_StartServerHandshakeReq_size depends on runtime parameters */
+#define grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_size (17 + grpc_gcp_ServerHandshakeParameters_size)
+/* grpc_gcp_NextHandshakeMessageReq_size depends on runtime parameters */
+#define grpc_gcp_HandshakerReq_size              (18 + grpc_gcp_StartClientHandshakeReq_size + grpc_gcp_StartServerHandshakeReq_size + grpc_gcp_NextHandshakeMessageReq_size)
+/* grpc_gcp_HandshakerResult_size depends on runtime parameters */
+/* grpc_gcp_HandshakerStatus_size depends on runtime parameters */
+/* grpc_gcp_HandshakerResp_size depends on runtime parameters */
+
+/* Message IDs (where set with "msgid" option) */
+#ifdef PB_MSGID
+
+#define HANDSHAKER_MESSAGES \
+
+
+#endif
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+/* @@protoc_insertion_point(eof) */
+
+#endif
diff --git a/src/core/tsi/alts/handshaker/proto/altscontext.proto b/src/core/tsi/alts/handshaker/proto/altscontext.proto
new file mode 100644
index 0000000..d195b37
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/proto/altscontext.proto
@@ -0,0 +1,41 @@
+// Copyright 2018 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+import "transport_security_common.proto";
+
+package grpc.gcp;
+
+option java_package = "io.grpc.alts";
+
+message AltsContext {
+  // The application protocol negotiated for this connection.
+  string application_protocol = 1;
+
+  // The record protocol negotiated for this connection.
+  string record_protocol = 2;
+
+  // The security level of the created secure channel.
+  SecurityLevel security_level = 3;
+
+  // The peer service account.
+  string peer_service_account = 4;
+
+  // The local service account.
+  string local_service_account = 5;
+
+  // The RPC protocol versions supported by the peer.
+  RpcProtocolVersions peer_rpc_versions = 6;
+}
diff --git a/src/core/tsi/alts/handshaker/proto/handshaker.options b/src/core/tsi/alts/handshaker/proto/handshaker.options
new file mode 100644
index 0000000..702ba38
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/proto/handshaker.options
@@ -0,0 +1,2 @@
+handshaker.proto no_unions:true
+grpc.gcp.StartServerHandshakeReq.handshake_parameters max_count:3
diff --git a/src/core/tsi/alts/handshaker/proto/handshaker.proto b/src/core/tsi/alts/handshaker/proto/handshaker.proto
new file mode 100644
index 0000000..46b8b09
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/proto/handshaker.proto
@@ -0,0 +1,220 @@
+// Copyright 2018 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+import "transport_security_common.proto";
+
+package grpc.gcp;
+
+option java_package = "io.grpc.alts";
+
+enum HandshakeProtocol {
+  // Default value.
+  HANDSHAKE_PROTOCOL_UNSPECIFIED = 0;
+
+  // TLS handshake protocol.
+  TLS = 1;
+
+  // Application Layer Transport Security handshake protocol.
+  ALTS = 2;
+}
+
+enum NetworkProtocol {
+  NETWORK_PROTOCOL_UNSPECIFIED = 0;
+  TCP = 1;
+  UDP = 2;
+}
+
+message Endpoint {
+  // IP address. It should contain an IPv4 or IPv6 string literal, e.g.
+  // "192.168.0.1" or "2001:db8::1".
+  string ip_address = 1;
+
+  // Port number.
+  int32 port = 2;
+
+  // Network protocol (e.g., TCP, UDP) associated with this endpoint.
+  NetworkProtocol protocol = 3;
+}
+
+message Identity {
+  oneof identity_oneof {
+    // Service account of a connection endpoint.
+    string service_account = 1;
+
+    // Hostname of a connection endpoint.
+    string hostname = 2;
+  }
+}
+
+message StartClientHandshakeReq {
+  // Handshake security protocol requested by the client.
+  HandshakeProtocol handshake_security_protocol = 1;
+
+  // The application protocols supported by the client, e.g., "h2" (for http2),
+  // "grpc".
+  repeated string application_protocols = 2;
+
+  // The record protocols supported by the client, e.g.,
+  // "ALTSRP_GCM_AES128".
+  repeated string record_protocols = 3;
+
+  // (Optional) Describes which server identities are acceptable by the client.
+  // If target identities are provided and none of them matches the peer
+  // identity of the server, handshake will fail.
+  repeated Identity target_identities = 4;
+
+  // (Optional) Application may specify a local identity. Otherwise, the
+  // handshaker chooses a default local identity.
+  Identity local_identity = 5;
+
+  // (Optional) Local endpoint information of the connection to the server,
+  // such as local IP address, port number, and network protocol.
+  Endpoint local_endpoint = 6;
+
+  // (Optional) Endpoint information of the remote server, such as IP address,
+  // port number, and network protocool.
+  Endpoint remote_endpoint = 7;
+
+  // (Optional) If target name is provided, a secure naming check is performed
+  // to verify that the peer authenticated identity is indeed authorized to run
+  // the target name.
+  string target_name = 8;
+
+  // (Optional) RPC protocol versions supported by the client.
+  RpcProtocolVersions rpc_versions = 9;
+}
+
+message ServerHandshakeParameters {
+  // The record protocols supported by the server, e.g.,
+  // "ALTSRP_GCM_AES128".
+  repeated string record_protocols = 1;
+
+  // (Optional) A list of local identities supported by the server, if
+  // specified. Otherwise, the handshaker chooses a default local identity.
+  repeated Identity local_identities = 2;
+}
+
+message StartServerHandshakeReq {
+  // The application protocols supported by the server, e.g., "h2" (for http2),
+  // "grpc".
+  repeated string application_protocols = 1;
+
+  // Handshake parameters (record protocols and local identities supported by
+  // the server) mapped by the handshake protocol. Each handshake security
+  // protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+  // identities. Since protobuf does not support enum as key to the map, the key
+  // to handshake_parameters is the integer value of HandshakeProtocol enum.
+  map<int32, ServerHandshakeParameters> handshake_parameters = 2;
+
+  // Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+  // that the peer's out_frames are split into multiple HandshakReq messages.
+  bytes in_bytes = 3;
+
+  // (Optional) Local endpoint information of the connection to the client,
+  // such as local IP address, port number, and network protocol.
+  Endpoint local_endpoint = 4;
+
+  // (Optional) Endpoint information of the remote client, such as IP address,
+  // port number, and network protocool.
+  Endpoint remote_endpoint = 5;
+
+  // (Optional) RPC protocol versions supported by the server.
+  RpcProtocolVersions rpc_versions = 6;
+}
+
+message NextHandshakeMessageReq {
+  // Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+  // that the peer's out_frames are split into multiple NextHandshakerMessageReq
+  // messages.
+  bytes in_bytes = 1;
+}
+
+message HandshakerReq {
+  oneof req_oneof {
+    // The start client handshake request message.
+    StartClientHandshakeReq client_start = 1;
+
+    // The start server handshake request message.
+    StartServerHandshakeReq server_start = 2;
+
+    // The next handshake request message.
+    NextHandshakeMessageReq next = 3;
+  }
+}
+
+message HandshakerResult {
+  // The application protocol negotiated for this connection.
+  string application_protocol = 1;
+
+  // The record protocol negotiated for this connection.
+  string record_protocol = 2;
+
+  // Cryptographic key data. The key data may be more than the key length
+  // required for the record protocol, thus the client of the handshaker
+  // service needs to truncate the key data into the right key length.
+  bytes key_data = 3;
+
+  // The authenticated identity of the peer.
+  Identity peer_identity = 4;
+
+  // The local identity used in the handshake.
+  Identity local_identity = 5;
+
+  // Indicate whether the handshaker service client should keep the channel
+  // between the handshaker service open, e.g., in order to handle
+  // post-handshake messages in the future.
+  bool keep_channel_open = 6;
+
+  // The RPC protocol versions supported by the peer.
+  RpcProtocolVersions peer_rpc_versions = 7;
+}
+
+message HandshakerStatus {
+  // The status code. This could be the gRPC status code.
+  uint32 code = 1;
+
+  // The status details.
+  string details = 2;
+}
+
+message HandshakerResp {
+  // Frames to be given to the peer for the NextHandshakeMessageReq. May be
+  // empty if no out_frames have to be sent to the peer or if in_bytes in the
+  // HandshakerReq are incomplete. All the non-empty out frames must be sent to
+  // the peer even if the handshaker status is not OK as these frames may
+  // contain the alert frames.
+  bytes out_frames = 1;
+
+  // Number of bytes in the in_bytes consumed by the handshaker. It is possible
+  // that part of in_bytes in HandshakerReq was unrelated to the handshake
+  // process.
+  uint32 bytes_consumed = 2;
+
+  // This is set iff the handshake was successful. out_frames may still be set
+  // to frames that needs to be forwarded to the peer.
+  HandshakerResult result = 3;
+
+  // Status of the handshaker.
+  HandshakerStatus status = 4;
+}
+
+service HandshakerService {
+  // Accepts a stream of handshaker request, returning a stream of handshaker
+  // response.
+  rpc DoHandshake(stream HandshakerReq)
+      returns (stream HandshakerResp) {
+  }
+}
diff --git a/src/core/tsi/alts/handshaker/proto/transport_security_common.proto b/src/core/tsi/alts/handshaker/proto/transport_security_common.proto
new file mode 100644
index 0000000..41983ab
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/proto/transport_security_common.proto
@@ -0,0 +1,40 @@
+// Copyright 2018 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package grpc.gcp;
+
+option java_package = "io.grpc.alts";
+
+// The security level of the created channel. The list is sorted in increasing
+// level of security. This order must always be maintained.
+enum SecurityLevel {
+  SECURITY_NONE = 0;
+  INTEGRITY_ONLY = 1;
+  INTEGRITY_AND_PRIVACY = 2;
+}
+
+// Max and min supported RPC protocol versions.
+message RpcProtocolVersions {
+  // RPC version contains a major version and a minor version.
+  message Version {
+    uint32 major = 1;
+    uint32 minor = 2;
+  }
+  // Maximum supported RPC version.
+  Version max_rpc_version = 1;
+  // Minimum supported RPC version.
+  Version min_rpc_version = 2;
+}
diff --git a/src/core/tsi/alts/handshaker/transport_security_common.pb.c b/src/core/tsi/alts/handshaker/transport_security_common.pb.c
new file mode 100644
index 0000000..6063c76
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/transport_security_common.pb.c
@@ -0,0 +1,50 @@
+/* Automatically generated nanopb constant definitions */
+/* Generated by nanopb-0.3.7-dev */
+
+#include "src/core/tsi/alts/handshaker/transport_security_common.pb.h"
+
+/* @@protoc_insertion_point(includes) */
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+
+
+const pb_field_t grpc_gcp_RpcProtocolVersions_fields[3] = {
+    PB_FIELD(  1, MESSAGE , OPTIONAL, STATIC  , FIRST, grpc_gcp_RpcProtocolVersions, max_rpc_version, max_rpc_version, &grpc_gcp_RpcProtocolVersions_Version_fields),
+    PB_FIELD(  2, MESSAGE , OPTIONAL, STATIC  , OTHER, grpc_gcp_RpcProtocolVersions, min_rpc_version, max_rpc_version, &grpc_gcp_RpcProtocolVersions_Version_fields),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_gcp_RpcProtocolVersions_Version_fields[3] = {
+    PB_FIELD(  1, UINT32  , OPTIONAL, STATIC  , FIRST, grpc_gcp_RpcProtocolVersions_Version, major, major, 0),
+    PB_FIELD(  2, UINT32  , OPTIONAL, STATIC  , OTHER, grpc_gcp_RpcProtocolVersions_Version, minor, major, 0),
+    PB_LAST_FIELD
+};
+
+
+/* Check that field information fits in pb_field_t */
+#if !defined(PB_FIELD_32BIT)
+/* If you get an error here, it means that you need to define PB_FIELD_32BIT
+ * compile-time option. You can do that in pb.h or on compiler command line.
+ * 
+ * The reason you need to do this is that some of your messages contain tag
+ * numbers or field sizes that are larger than what can fit in 8 or 16 bit
+ * field descriptors.
+ */
+PB_STATIC_ASSERT((pb_membersize(grpc_gcp_RpcProtocolVersions, max_rpc_version) < 65536 && pb_membersize(grpc_gcp_RpcProtocolVersions, min_rpc_version) < 65536), YOU_MUST_DEFINE_PB_FIELD_32BIT_FOR_MESSAGES_grpc_gcp_RpcProtocolVersions_grpc_gcp_RpcProtocolVersions_Version)
+#endif
+
+#if !defined(PB_FIELD_16BIT) && !defined(PB_FIELD_32BIT)
+/* If you get an error here, it means that you need to define PB_FIELD_16BIT
+ * compile-time option. You can do that in pb.h or on compiler command line.
+ * 
+ * The reason you need to do this is that some of your messages contain tag
+ * numbers or field sizes that are larger than what can fit in the default
+ * 8 bit descriptors.
+ */
+PB_STATIC_ASSERT((pb_membersize(grpc_gcp_RpcProtocolVersions, max_rpc_version) < 256 && pb_membersize(grpc_gcp_RpcProtocolVersions, min_rpc_version) < 256), YOU_MUST_DEFINE_PB_FIELD_16BIT_FOR_MESSAGES_grpc_gcp_RpcProtocolVersions_grpc_gcp_RpcProtocolVersions_Version)
+#endif
+
+
+/* @@protoc_insertion_point(eof) */
diff --git a/src/core/tsi/alts/handshaker/transport_security_common.pb.h b/src/core/tsi/alts/handshaker/transport_security_common.pb.h
new file mode 100644
index 0000000..49096df
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/transport_security_common.pb.h
@@ -0,0 +1,78 @@
+/* Automatically generated nanopb header */
+/* Generated by nanopb-0.3.7-dev */
+
+#ifndef PB_GRPC_GCP_TRANSPORT_SECURITY_COMMON_PB_H_INCLUDED
+#define PB_GRPC_GCP_TRANSPORT_SECURITY_COMMON_PB_H_INCLUDED
+#include "third_party/nanopb/pb.h"
+/* @@protoc_insertion_point(includes) */
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Enum definitions */
+typedef enum _grpc_gcp_SecurityLevel {
+    grpc_gcp_SecurityLevel_SECURITY_NONE = 0,
+    grpc_gcp_SecurityLevel_INTEGRITY_ONLY = 1,
+    grpc_gcp_SecurityLevel_INTEGRITY_AND_PRIVACY = 2
+} grpc_gcp_SecurityLevel;
+#define _grpc_gcp_SecurityLevel_MIN grpc_gcp_SecurityLevel_SECURITY_NONE
+#define _grpc_gcp_SecurityLevel_MAX grpc_gcp_SecurityLevel_INTEGRITY_AND_PRIVACY
+#define _grpc_gcp_SecurityLevel_ARRAYSIZE ((grpc_gcp_SecurityLevel)(grpc_gcp_SecurityLevel_INTEGRITY_AND_PRIVACY+1))
+
+/* Struct definitions */
+typedef struct _grpc_gcp_RpcProtocolVersions_Version {
+    bool has_major;
+    uint32_t major;
+    bool has_minor;
+    uint32_t minor;
+/* @@protoc_insertion_point(struct:grpc_gcp_RpcProtocolVersions_Version) */
+} grpc_gcp_RpcProtocolVersions_Version;
+
+typedef struct _grpc_gcp_RpcProtocolVersions {
+    bool has_max_rpc_version;
+    grpc_gcp_RpcProtocolVersions_Version max_rpc_version;
+    bool has_min_rpc_version;
+    grpc_gcp_RpcProtocolVersions_Version min_rpc_version;
+/* @@protoc_insertion_point(struct:grpc_gcp_RpcProtocolVersions) */
+} grpc_gcp_RpcProtocolVersions;
+
+/* Default values for struct fields */
+
+/* Initializer values for message structs */
+#define grpc_gcp_RpcProtocolVersions_init_default {false, grpc_gcp_RpcProtocolVersions_Version_init_default, false, grpc_gcp_RpcProtocolVersions_Version_init_default}
+#define grpc_gcp_RpcProtocolVersions_Version_init_default {false, 0, false, 0}
+#define grpc_gcp_RpcProtocolVersions_init_zero   {false, grpc_gcp_RpcProtocolVersions_Version_init_zero, false, grpc_gcp_RpcProtocolVersions_Version_init_zero}
+#define grpc_gcp_RpcProtocolVersions_Version_init_zero {false, 0, false, 0}
+
+/* Field tags (for use in manual encoding/decoding) */
+#define grpc_gcp_RpcProtocolVersions_Version_major_tag 1
+#define grpc_gcp_RpcProtocolVersions_Version_minor_tag 2
+#define grpc_gcp_RpcProtocolVersions_max_rpc_version_tag 1
+#define grpc_gcp_RpcProtocolVersions_min_rpc_version_tag 2
+
+/* Struct field encoding specification for nanopb */
+extern const pb_field_t grpc_gcp_RpcProtocolVersions_fields[3];
+extern const pb_field_t grpc_gcp_RpcProtocolVersions_Version_fields[3];
+
+/* Maximum encoded size of messages (where known) */
+#define grpc_gcp_RpcProtocolVersions_size        28
+#define grpc_gcp_RpcProtocolVersions_Version_size 12
+
+/* Message IDs (where set with "msgid" option) */
+#ifdef PB_MSGID
+
+#define TRANSPORT_SECURITY_COMMON_MESSAGES \
+
+
+#endif
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+/* @@protoc_insertion_point(eof) */
+
+#endif
diff --git a/src/core/tsi/alts/handshaker/transport_security_common_api.cc b/src/core/tsi/alts/handshaker/transport_security_common_api.cc
new file mode 100644
index 0000000..8a7edb5
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/transport_security_common_api.cc
@@ -0,0 +1,196 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/handshaker/transport_security_common_api.h"
+
+bool grpc_gcp_rpc_protocol_versions_set_max(
+    grpc_gcp_rpc_protocol_versions* versions, uint32_t max_major,
+    uint32_t max_minor) {
+  if (versions == nullptr) {
+    gpr_log(GPR_ERROR,
+            "versions is nullptr in "
+            "grpc_gcp_rpc_protocol_versions_set_max().");
+    return false;
+  }
+  versions->has_max_rpc_version = true;
+  versions->max_rpc_version.has_major = true;
+  versions->max_rpc_version.has_minor = true;
+  versions->max_rpc_version.major = max_major;
+  versions->max_rpc_version.minor = max_minor;
+  return true;
+}
+
+bool grpc_gcp_rpc_protocol_versions_set_min(
+    grpc_gcp_rpc_protocol_versions* versions, uint32_t min_major,
+    uint32_t min_minor) {
+  if (versions == nullptr) {
+    gpr_log(GPR_ERROR,
+            "versions is nullptr in "
+            "grpc_gcp_rpc_protocol_versions_set_min().");
+    return false;
+  }
+  versions->has_min_rpc_version = true;
+  versions->min_rpc_version.has_major = true;
+  versions->min_rpc_version.has_minor = true;
+  versions->min_rpc_version.major = min_major;
+  versions->min_rpc_version.minor = min_minor;
+  return true;
+}
+
+size_t grpc_gcp_rpc_protocol_versions_encode_length(
+    const grpc_gcp_rpc_protocol_versions* versions) {
+  if (versions == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_rpc_protocol_versions_encode_length().");
+    return 0;
+  }
+  pb_ostream_t size_stream;
+  memset(&size_stream, 0, sizeof(pb_ostream_t));
+  if (!pb_encode(&size_stream, grpc_gcp_RpcProtocolVersions_fields, versions)) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&size_stream));
+    return 0;
+  }
+  return size_stream.bytes_written;
+}
+
+bool grpc_gcp_rpc_protocol_versions_encode_to_raw_bytes(
+    const grpc_gcp_rpc_protocol_versions* versions, uint8_t* bytes,
+    size_t bytes_length) {
+  if (versions == nullptr || bytes == nullptr || bytes_length == 0) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_rpc_protocol_versions_encode_to_raw_bytes().");
+    return false;
+  }
+  pb_ostream_t output_stream = pb_ostream_from_buffer(bytes, bytes_length);
+  if (!pb_encode(&output_stream, grpc_gcp_RpcProtocolVersions_fields,
+                 versions)) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&output_stream));
+    return false;
+  }
+  return true;
+}
+
+bool grpc_gcp_rpc_protocol_versions_encode(
+    const grpc_gcp_rpc_protocol_versions* versions, grpc_slice* slice) {
+  if (versions == nullptr || slice == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_rpc_protocol_versions_encode().");
+    return false;
+  }
+  size_t encoded_length =
+      grpc_gcp_rpc_protocol_versions_encode_length(versions);
+  if (encoded_length == 0) return false;
+  *slice = grpc_slice_malloc(encoded_length);
+  return grpc_gcp_rpc_protocol_versions_encode_to_raw_bytes(
+      versions, GRPC_SLICE_START_PTR(*slice), encoded_length);
+}
+
+bool grpc_gcp_rpc_protocol_versions_decode(
+    grpc_slice slice, grpc_gcp_rpc_protocol_versions* versions) {
+  if (versions == nullptr) {
+    gpr_log(GPR_ERROR,
+            "version is nullptr in "
+            "grpc_gcp_rpc_protocol_versions_decode().");
+    return false;
+  }
+  pb_istream_t stream = pb_istream_from_buffer(GRPC_SLICE_START_PTR(slice),
+                                               GRPC_SLICE_LENGTH(slice));
+  if (!pb_decode(&stream, grpc_gcp_RpcProtocolVersions_fields, versions)) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&stream));
+    return false;
+  }
+  return true;
+}
+
+bool grpc_gcp_rpc_protocol_versions_copy(
+    const grpc_gcp_rpc_protocol_versions* src,
+    grpc_gcp_rpc_protocol_versions* dst) {
+  if ((src == nullptr && dst != nullptr) ||
+      (src != nullptr && dst == nullptr)) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_rpc_protocol_versions_copy().");
+    return false;
+  }
+  if (src == nullptr) {
+    return true;
+  }
+  grpc_gcp_rpc_protocol_versions_set_max(dst, src->max_rpc_version.major,
+                                         src->max_rpc_version.minor);
+  grpc_gcp_rpc_protocol_versions_set_min(dst, src->min_rpc_version.major,
+                                         src->min_rpc_version.minor);
+  return true;
+}
+
+namespace grpc_core {
+namespace internal {
+
+int grpc_gcp_rpc_protocol_version_compare(
+    const grpc_gcp_rpc_protocol_versions_version* v1,
+    const grpc_gcp_rpc_protocol_versions_version* v2) {
+  if ((v1->major > v2->major) ||
+      (v1->major == v2->major && v1->minor > v2->minor)) {
+    return 1;
+  }
+  if ((v1->major < v2->major) ||
+      (v1->major == v2->major && v1->minor < v2->minor)) {
+    return -1;
+  }
+  return 0;
+}
+
+}  // namespace internal
+}  // namespace grpc_core
+
+bool grpc_gcp_rpc_protocol_versions_check(
+    const grpc_gcp_rpc_protocol_versions* local_versions,
+    const grpc_gcp_rpc_protocol_versions* peer_versions,
+    grpc_gcp_rpc_protocol_versions_version* highest_common_version) {
+  if (local_versions == nullptr || peer_versions == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid arguments to "
+            "grpc_gcp_rpc_protocol_versions_check().");
+    return false;
+  }
+  /* max_common_version is MIN(local.max, peer.max) */
+  const grpc_gcp_rpc_protocol_versions_version* max_common_version =
+      grpc_core::internal::grpc_gcp_rpc_protocol_version_compare(
+          &local_versions->max_rpc_version, &peer_versions->max_rpc_version) > 0
+          ? &peer_versions->max_rpc_version
+          : &local_versions->max_rpc_version;
+  /* min_common_version is MAX(local.min, peer.min) */
+  const grpc_gcp_rpc_protocol_versions_version* min_common_version =
+      grpc_core::internal::grpc_gcp_rpc_protocol_version_compare(
+          &local_versions->min_rpc_version, &peer_versions->min_rpc_version) > 0
+          ? &local_versions->min_rpc_version
+          : &peer_versions->min_rpc_version;
+  bool result = grpc_core::internal::grpc_gcp_rpc_protocol_version_compare(
+                    max_common_version, min_common_version) >= 0
+                    ? true
+                    : false;
+  if (result && highest_common_version != nullptr) {
+    memcpy(highest_common_version, max_common_version,
+           sizeof(grpc_gcp_rpc_protocol_versions_version));
+  }
+  return result;
+}
diff --git a/src/core/tsi/alts/handshaker/transport_security_common_api.h b/src/core/tsi/alts/handshaker/transport_security_common_api.h
new file mode 100644
index 0000000..68228cb
--- /dev/null
+++ b/src/core/tsi/alts/handshaker/transport_security_common_api.h
@@ -0,0 +1,163 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_HANDSHAKER_TRANSPORT_SECURITY_COMMON_API_H
+#define GRPC_CORE_TSI_ALTS_HANDSHAKER_TRANSPORT_SECURITY_COMMON_API_H
+
+#include <grpc/support/port_platform.h>
+
+#include "third_party/nanopb/pb_decode.h"
+#include "third_party/nanopb/pb_encode.h"
+
+#include <grpc/slice.h>
+#include <grpc/slice_buffer.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/tsi/alts/handshaker/transport_security_common.pb.h"
+
+typedef grpc_gcp_RpcProtocolVersions grpc_gcp_rpc_protocol_versions;
+
+typedef grpc_gcp_RpcProtocolVersions_Version
+    grpc_gcp_rpc_protocol_versions_version;
+
+/**
+ * This method sets the value for max_rpc_versions field of rpc protocol
+ * versions.
+ *
+ * - versions: an rpc protocol version instance.
+ * - max_major: a major version of maximum supported RPC version.
+ * - max_minor: a minor version of maximum supported RPC version.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_rpc_protocol_versions_set_max(
+    grpc_gcp_rpc_protocol_versions* versions, uint32_t max_major,
+    uint32_t max_minor);
+
+/**
+ * This method sets the value for min_rpc_versions field of rpc protocol
+ * versions.
+ *
+ * - versions: an rpc protocol version instance.
+ * - min_major: a major version of minimum supported RPC version.
+ * - min_minor: a minor version of minimum supported RPC version.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_rpc_protocol_versions_set_min(
+    grpc_gcp_rpc_protocol_versions* versions, uint32_t min_major,
+    uint32_t min_minor);
+
+/**
+ * This method computes serialized byte length of rpc protocol versions.
+ *
+ * - versions: an rpc protocol versions instance.
+ *
+ * The method returns serialized byte length. It returns 0 on failure.
+ */
+size_t grpc_gcp_rpc_protocol_versions_encode_length(
+    const grpc_gcp_rpc_protocol_versions* versions);
+
+/**
+ * This method serializes rpc protocol versions and writes the result to
+ * the memory buffer provided by the caller. Caller is responsible for
+ * allocating sufficient memory to store the serialized data.
+ *
+ * - versions: an rpc protocol versions instance.
+ * - bytes: bytes buffer where the result will be written to.
+ * - bytes_length: length of the bytes buffer.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_rpc_protocol_versions_encode_to_raw_bytes(
+    const grpc_gcp_rpc_protocol_versions* versions, uint8_t* bytes,
+    size_t bytes_length);
+
+/**
+ * This method serializes an rpc protocol version and returns serialized rpc
+ * versions in grpc slice.
+ *
+ * - versions: an rpc protocol versions instance.
+ * - slice: grpc slice where the serialized result will be written.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_rpc_protocol_versions_encode(
+    const grpc_gcp_rpc_protocol_versions* versions, grpc_slice* slice);
+
+/**
+ * This method de-serializes input in grpc slice form and stores the result
+ * in rpc protocol versions.
+ *
+ * - slice: a data stream containing a serialized rpc protocol version.
+ * - versions: an rpc protocol version instance used to hold de-serialized
+ *   result.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_rpc_protocol_versions_decode(
+    grpc_slice slice, grpc_gcp_rpc_protocol_versions* versions);
+
+/**
+ * This method performs a deep copy operation on rpc protocol versions
+ * instance.
+ *
+ * - src: rpc protocol versions instance that needs to be copied.
+ * - dst: rpc protocol versions instance that stores the copied result.
+ *
+ * The method returns true on success and false otherwise.
+ */
+bool grpc_gcp_rpc_protocol_versions_copy(
+    const grpc_gcp_rpc_protocol_versions* src,
+    grpc_gcp_rpc_protocol_versions* dst);
+
+/**
+ * This method performs a version check between local and peer rpc protocol
+ * versions.
+ *
+ * - local_versions: local rpc protocol versions instance.
+ * - peer_versions: peer rpc protocol versions instance.
+ * - highest_common_version: an output parameter that will store the highest
+ *   common rpc protocol version both parties agreed on.
+ *
+ * The method returns true if the check passes which means both parties agreed
+ * on a common rpc protocol to use, and false otherwise.
+ */
+bool grpc_gcp_rpc_protocol_versions_check(
+    const grpc_gcp_rpc_protocol_versions* local_versions,
+    const grpc_gcp_rpc_protocol_versions* peer_versions,
+    grpc_gcp_rpc_protocol_versions_version* highest_common_version);
+
+namespace grpc_core {
+namespace internal {
+
+/**
+ * Exposed for testing only.
+ * The method returns 0 if v1 = v2,
+ *            returns 1 if v1 > v2,
+ *            returns -1 if v1 < v2.
+ */
+int grpc_gcp_rpc_protocol_version_compare(
+    const grpc_gcp_rpc_protocol_versions_version* v1,
+    const grpc_gcp_rpc_protocol_versions_version* v2);
+
+}  // namespace internal
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_TSI_ALTS_HANDSHAKER_TRANSPORT_SECURITY_COMMON_API_H */
diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc
new file mode 100644
index 0000000..7ba03eb
--- /dev/null
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc
@@ -0,0 +1,180 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h"
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/slice/slice_internal.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h"
+
+/* Main struct for alts_grpc_integrity_only_record_protocol.  */
+typedef struct alts_grpc_integrity_only_record_protocol {
+  alts_grpc_record_protocol base;
+  grpc_slice_buffer data_sb;
+  unsigned char* tag_buf;
+} alts_grpc_integrity_only_record_protocol;
+
+/* --- alts_grpc_record_protocol methods implementation. --- */
+
+static tsi_result alts_grpc_integrity_only_protect(
+    alts_grpc_record_protocol* rp, grpc_slice_buffer* unprotected_slices,
+    grpc_slice_buffer* protected_slices) {
+  /* Input sanity check.  */
+  if (rp == nullptr || unprotected_slices == nullptr ||
+      protected_slices == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to alts_grpc_record_protocol protect.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  /* Allocates memory for header and tag slices.  */
+  grpc_slice header_slice = GRPC_SLICE_MALLOC(rp->header_length);
+  grpc_slice tag_slice = GRPC_SLICE_MALLOC(rp->tag_length);
+  /* Calls alts_iovec_record_protocol protect.  */
+  char* error_details = nullptr;
+  iovec_t header_iovec = {GRPC_SLICE_START_PTR(header_slice),
+                          GRPC_SLICE_LENGTH(header_slice)};
+  iovec_t tag_iovec = {GRPC_SLICE_START_PTR(tag_slice),
+                       GRPC_SLICE_LENGTH(tag_slice)};
+  alts_grpc_record_protocol_convert_slice_buffer_to_iovec(rp,
+                                                          unprotected_slices);
+  grpc_status_code status = alts_iovec_record_protocol_integrity_only_protect(
+      rp->iovec_rp, rp->iovec_buf, unprotected_slices->count, header_iovec,
+      tag_iovec, &error_details);
+  if (status != GRPC_STATUS_OK) {
+    gpr_log(GPR_ERROR, "Failed to protect, %s", error_details);
+    gpr_free(error_details);
+    return TSI_INTERNAL_ERROR;
+  }
+  /* Appends result to protected_slices.  */
+  grpc_slice_buffer_add(protected_slices, header_slice);
+  grpc_slice_buffer_move_into(unprotected_slices, protected_slices);
+  grpc_slice_buffer_add(protected_slices, tag_slice);
+  return TSI_OK;
+}
+
+static tsi_result alts_grpc_integrity_only_unprotect(
+    alts_grpc_record_protocol* rp, grpc_slice_buffer* protected_slices,
+    grpc_slice_buffer* unprotected_slices) {
+  /* Input sanity check.  */
+  if (rp == nullptr || protected_slices == nullptr ||
+      unprotected_slices == nullptr) {
+    gpr_log(
+        GPR_ERROR,
+        "Invalid nullptr arguments to alts_grpc_record_protocol unprotect.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  if (protected_slices->length < rp->header_length + rp->tag_length) {
+    gpr_log(GPR_ERROR, "Protected slices do not have sufficient data.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  /* In this method, rp points to alts_grpc_record_protocol struct
+   * and integrity_only_record_protocol points to
+   * alts_grpc_integrity_only_record_protocol struct.  */
+  alts_grpc_integrity_only_record_protocol* integrity_only_record_protocol =
+      reinterpret_cast<alts_grpc_integrity_only_record_protocol*>(rp);
+  /* Strips frame header from protected slices.  */
+  grpc_slice_buffer_reset_and_unref_internal(&rp->header_sb);
+  grpc_slice_buffer_move_first(protected_slices, rp->header_length,
+                               &rp->header_sb);
+  GPR_ASSERT(rp->header_sb.length == rp->header_length);
+  iovec_t header_iovec = alts_grpc_record_protocol_get_header_iovec(rp);
+  /* Moves protected slices data to data_sb and leaves the remaining tag.  */
+  grpc_slice_buffer_reset_and_unref_internal(
+      &integrity_only_record_protocol->data_sb);
+  grpc_slice_buffer_move_first(protected_slices,
+                               protected_slices->length - rp->tag_length,
+                               &integrity_only_record_protocol->data_sb);
+  GPR_ASSERT(protected_slices->length == rp->tag_length);
+  iovec_t tag_iovec = {nullptr, rp->tag_length};
+  if (protected_slices->count == 1) {
+    tag_iovec.iov_base = GRPC_SLICE_START_PTR(protected_slices->slices[0]);
+  } else {
+    /* Frame tag is in multiple slices, copies the tag bytes from slice
+     * buffer to a single flat buffer.  */
+    alts_grpc_record_protocol_copy_slice_buffer(
+        protected_slices, integrity_only_record_protocol->tag_buf);
+    tag_iovec.iov_base = integrity_only_record_protocol->tag_buf;
+  }
+  /* Calls alts_iovec_record_protocol unprotect.  */
+  char* error_details = nullptr;
+  alts_grpc_record_protocol_convert_slice_buffer_to_iovec(
+      rp, &integrity_only_record_protocol->data_sb);
+  grpc_status_code status = alts_iovec_record_protocol_integrity_only_unprotect(
+      rp->iovec_rp, rp->iovec_buf,
+      integrity_only_record_protocol->data_sb.count, header_iovec, tag_iovec,
+      &error_details);
+  if (status != GRPC_STATUS_OK) {
+    gpr_log(GPR_ERROR, "Failed to unprotect, %s", error_details);
+    gpr_free(error_details);
+    return TSI_INTERNAL_ERROR;
+  }
+  grpc_slice_buffer_reset_and_unref_internal(&rp->header_sb);
+  grpc_slice_buffer_reset_and_unref_internal(protected_slices);
+  grpc_slice_buffer_move_into(&integrity_only_record_protocol->data_sb,
+                              unprotected_slices);
+  return TSI_OK;
+}
+
+static void alts_grpc_integrity_only_destruct(alts_grpc_record_protocol* rp) {
+  if (rp == nullptr) {
+    return;
+  }
+  alts_grpc_integrity_only_record_protocol* integrity_only_rp =
+      reinterpret_cast<alts_grpc_integrity_only_record_protocol*>(rp);
+  grpc_slice_buffer_destroy_internal(&integrity_only_rp->data_sb);
+  gpr_free(integrity_only_rp->tag_buf);
+}
+
+static const alts_grpc_record_protocol_vtable
+    alts_grpc_integrity_only_record_protocol_vtable = {
+        alts_grpc_integrity_only_protect, alts_grpc_integrity_only_unprotect,
+        alts_grpc_integrity_only_destruct};
+
+tsi_result alts_grpc_integrity_only_record_protocol_create(
+    gsec_aead_crypter* crypter, size_t overflow_size, bool is_client,
+    bool is_protect, alts_grpc_record_protocol** rp) {
+  if (crypter == nullptr || rp == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to alts_grpc_record_protocol create.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_grpc_integrity_only_record_protocol* impl =
+      static_cast<alts_grpc_integrity_only_record_protocol*>(
+          gpr_zalloc(sizeof(alts_grpc_integrity_only_record_protocol)));
+  /* Calls alts_grpc_record_protocol init.  */
+  tsi_result result = alts_grpc_record_protocol_init(
+      &impl->base, crypter, overflow_size, is_client,
+      /*is_integrity_only=*/true, is_protect);
+  if (result != TSI_OK) {
+    gpr_free(impl);
+    return result;
+  }
+  /* Initializes slice buffer for data_sb.  */
+  grpc_slice_buffer_init(&impl->data_sb);
+  /* Allocates tag buffer.  */
+  impl->tag_buf =
+      static_cast<unsigned char*>(gpr_malloc(impl->base.tag_length));
+  impl->base.vtable = &alts_grpc_integrity_only_record_protocol_vtable;
+  *rp = &impl->base;
+  return TSI_OK;
+}
diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h
new file mode 100644
index 0000000..8d68b27
--- /dev/null
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h
@@ -0,0 +1,52 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_INTEGRITY_ONLY_RECORD_PROTOCOL_H
+#define GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_INTEGRITY_ONLY_RECORD_PROTOCOL_H
+
+#include <grpc/support/port_platform.h>
+
+#include <stdbool.h>
+
+#include "src/core/tsi/alts/crypt/gsec.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h"
+
+/**
+ * This method creates an integrity-only alts_grpc_record_protocol instance,
+ * given a gsec_aead_crypter instance and a flag indicating if the created
+ * instance will be used at the client or server side. The ownership of
+ * gsec_aead_crypter instance is transferred to this new object.
+ *
+ * - crypter: a gsec_aead_crypter instance used to perform AEAD decryption.
+ * - overflow_size: overflow size of counter in bytes.
+ * - is_client: a flag indicating if the alts_grpc_record_protocol instance will
+ *   be used at the client or server side.
+ * - is_protect: a flag indicating if the alts_grpc_record_protocol instance
+ *   will be used for protect or unprotect.
+ * - rp: an alts_grpc_record_protocol instance to be returned from
+ *   the method.
+ *
+ * This method returns TSI_OK in case of success or a specific error code in
+ * case of failure.
+ */
+tsi_result alts_grpc_integrity_only_record_protocol_create(
+    gsec_aead_crypter* crypter, size_t overflow_size, bool is_client,
+    bool is_protect, alts_grpc_record_protocol** rp);
+
+#endif /* GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_INTEGRITY_ONLY_RECORD_PROTOCOL_H \
+        */
diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc
new file mode 100644
index 0000000..d4fd88d
--- /dev/null
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc
@@ -0,0 +1,144 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h"
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/slice/slice_internal.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h"
+
+/* Privacy-integrity alts_grpc_record_protocol object uses the same struct
+ * defined in alts_grpc_record_protocol_common.h.  */
+
+/* --- alts_grpc_record_protocol methods implementation. --- */
+
+static tsi_result alts_grpc_privacy_integrity_protect(
+    alts_grpc_record_protocol* rp, grpc_slice_buffer* unprotected_slices,
+    grpc_slice_buffer* protected_slices) {
+  /* Input sanity check.  */
+  if (rp == nullptr || unprotected_slices == nullptr ||
+      protected_slices == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to alts_grpc_record_protocol protect.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  /* Allocates memory for output frame. In privacy-integrity protect, the
+   * protected frame is stored in a newly allocated buffer.  */
+  size_t protected_frame_size =
+      unprotected_slices->length + rp->header_length +
+      alts_iovec_record_protocol_get_tag_length(rp->iovec_rp);
+  grpc_slice protected_slice = GRPC_SLICE_MALLOC(protected_frame_size);
+  iovec_t protected_iovec = {GRPC_SLICE_START_PTR(protected_slice),
+                             GRPC_SLICE_LENGTH(protected_slice)};
+  /* Calls alts_iovec_record_protocol protect.  */
+  char* error_details = nullptr;
+  alts_grpc_record_protocol_convert_slice_buffer_to_iovec(rp,
+                                                          unprotected_slices);
+  grpc_status_code status =
+      alts_iovec_record_protocol_privacy_integrity_protect(
+          rp->iovec_rp, rp->iovec_buf, unprotected_slices->count,
+          protected_iovec, &error_details);
+  if (status != GRPC_STATUS_OK) {
+    gpr_log(GPR_ERROR, "Failed to protect, %s", error_details);
+    gpr_free(error_details);
+    grpc_slice_unref(protected_slice);
+    return TSI_INTERNAL_ERROR;
+  }
+  grpc_slice_buffer_add(protected_slices, protected_slice);
+  grpc_slice_buffer_reset_and_unref_internal(unprotected_slices);
+  return TSI_OK;
+}
+
+static tsi_result alts_grpc_privacy_integrity_unprotect(
+    alts_grpc_record_protocol* rp, grpc_slice_buffer* protected_slices,
+    grpc_slice_buffer* unprotected_slices) {
+  /* Input sanity check.  */
+  if (rp == nullptr || protected_slices == nullptr ||
+      unprotected_slices == nullptr) {
+    gpr_log(
+        GPR_ERROR,
+        "Invalid nullptr arguments to alts_grpc_record_protocol unprotect.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  /* Allocates memory for output frame. In privacy-integrity unprotect, the
+   * unprotected data are stored in a newly allocated buffer.  */
+  if (protected_slices->length < rp->header_length + rp->tag_length) {
+    gpr_log(GPR_ERROR, "Protected slices do not have sufficient data.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  size_t unprotected_frame_size =
+      protected_slices->length - rp->header_length - rp->tag_length;
+  grpc_slice unprotected_slice = GRPC_SLICE_MALLOC(unprotected_frame_size);
+  iovec_t unprotected_iovec = {GRPC_SLICE_START_PTR(unprotected_slice),
+                               GRPC_SLICE_LENGTH(unprotected_slice)};
+  /* Strips frame header from protected slices.  */
+  grpc_slice_buffer_reset_and_unref_internal(&rp->header_sb);
+  grpc_slice_buffer_move_first(protected_slices, rp->header_length,
+                               &rp->header_sb);
+  iovec_t header_iovec = alts_grpc_record_protocol_get_header_iovec(rp);
+  /* Calls alts_iovec_record_protocol unprotect.  */
+  char* error_details = nullptr;
+  alts_grpc_record_protocol_convert_slice_buffer_to_iovec(rp, protected_slices);
+  grpc_status_code status =
+      alts_iovec_record_protocol_privacy_integrity_unprotect(
+          rp->iovec_rp, header_iovec, rp->iovec_buf, protected_slices->count,
+          unprotected_iovec, &error_details);
+  if (status != GRPC_STATUS_OK) {
+    gpr_log(GPR_ERROR, "Failed to unprotect, %s", error_details);
+    gpr_free(error_details);
+    grpc_slice_unref(unprotected_slice);
+    return TSI_INTERNAL_ERROR;
+  }
+  grpc_slice_buffer_reset_and_unref_internal(&rp->header_sb);
+  grpc_slice_buffer_reset_and_unref_internal(protected_slices);
+  grpc_slice_buffer_add(unprotected_slices, unprotected_slice);
+  return TSI_OK;
+}
+
+static const alts_grpc_record_protocol_vtable
+    alts_grpc_privacy_integrity_record_protocol_vtable = {
+        alts_grpc_privacy_integrity_protect,
+        alts_grpc_privacy_integrity_unprotect, nullptr};
+
+tsi_result alts_grpc_privacy_integrity_record_protocol_create(
+    gsec_aead_crypter* crypter, size_t overflow_size, bool is_client,
+    bool is_protect, alts_grpc_record_protocol** rp) {
+  if (crypter == nullptr || rp == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to alts_grpc_record_protocol create.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  auto* impl = static_cast<alts_grpc_record_protocol*>(
+      gpr_zalloc(sizeof(alts_grpc_record_protocol)));
+  /* Calls alts_grpc_record_protocol init.  */
+  tsi_result result =
+      alts_grpc_record_protocol_init(impl, crypter, overflow_size, is_client,
+                                     /*is_integrity_only=*/false, is_protect);
+  if (result != TSI_OK) {
+    gpr_free(impl);
+    return result;
+  }
+  impl->vtable = &alts_grpc_privacy_integrity_record_protocol_vtable;
+  *rp = impl;
+  return TSI_OK;
+}
diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h
new file mode 100644
index 0000000..1e34aef
--- /dev/null
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h
@@ -0,0 +1,49 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_PRIVACY_INTEGRITY_RECORD_PROTOCOL_H
+#define GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_PRIVACY_INTEGRITY_RECORD_PROTOCOL_H
+
+#include <grpc/support/port_platform.h>
+
+#include <stdbool.h>
+
+#include "src/core/tsi/alts/crypt/gsec.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h"
+
+/**
+ * This method creates a privacy-integrity alts_grpc_record_protocol instance,
+ * given a gsec_aead_crypter instance and a flag indicating if the created
+ * instance will be used at the client or server side. The ownership of
+ * gsec_aead_crypter instance is transferred to this new object.
+ *
+ * - crypter: a gsec_aead_crypter instance used to perform AEAD decryption.
+ * - is_client: a flag indicating if the alts_grpc_record_protocol instance will
+ *   be used at the client or server side.
+ * - rp: an alts_grpc_record_protocol instance to be returned from
+ *   the method.
+ *
+ * This method returns TSI_OK in case of success or a specific error code in
+ * case of failure.
+ */
+tsi_result alts_grpc_privacy_integrity_record_protocol_create(
+    gsec_aead_crypter* crypter, size_t overflow_size, bool is_client,
+    bool is_protect, alts_grpc_record_protocol** rp);
+
+#endif /* GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_PRIVACY_INTEGRITY_RECORD_PROTOCOL_H \
+        */
diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h
new file mode 100644
index 0000000..d1e433d
--- /dev/null
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h
@@ -0,0 +1,91 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_RECORD_PROTOCOL_H
+#define GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_RECORD_PROTOCOL_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/slice_buffer.h>
+
+#include "src/core/tsi/transport_security_interface.h"
+
+/**
+ * This alts_grpc_record_protocol object protects and unprotects a single frame
+ * stored in grpc slice buffer with zero or minimized memory copy.
+ * Implementations of this object must be thread compatible.
+ */
+typedef struct alts_grpc_record_protocol alts_grpc_record_protocol;
+
+/**
+ * This methods performs protect operation on unprotected data and appends the
+ * protected frame to protected_slices. The caller needs to ensure the length
+ * of unprotected data plus the frame overhead is less than or equal to the
+ * maximum frame length. The input unprotected data slice buffer will be
+ * cleared, although the actual unprotected data bytes are not modified.
+ *
+ * - self: an alts_grpc_record_protocol instance.
+ * - unprotected_slices: the unprotected data to be protected.
+ * - protected_slices: slice buffer where the protected frame is appended.
+ *
+ * This method returns TSI_OK in case of success or a specific error code in
+ * case of failure.
+ */
+tsi_result alts_grpc_record_protocol_protect(
+    alts_grpc_record_protocol* self, grpc_slice_buffer* unprotected_slices,
+    grpc_slice_buffer* protected_slices);
+
+/**
+ * This methods performs unprotect operation on a full frame of protected data
+ * and appends unprotected data to unprotected_slices. It is the caller's
+ * responsibility to prepare a full frame of data before calling this method.
+ * The input protected frame slice buffer will be cleared, although the actual
+ * protected data bytes are not modified.
+ *
+ * - self: an alts_grpc_record_protocol instance.
+ * - protected_slices: a full frame of protected data in grpc slices.
+ * - unprotected_slices: slice buffer where unprotected data is appended.
+ *
+ * This method returns TSI_OK in case of success or a specific error code in
+ * case of failure.
+ */
+tsi_result alts_grpc_record_protocol_unprotect(
+    alts_grpc_record_protocol* self, grpc_slice_buffer* protected_slices,
+    grpc_slice_buffer* unprotected_slices);
+
+/**
+ * This method returns maximum allowed unprotected data size, given maximum
+ * protected frame size.
+ *
+ * - self: an alts_grpc_record_protocol instance.
+ * - max_protected_frame_size: maximum protected frame size.
+ *
+ * On success, the method returns the maximum allowed unprotected data size.
+ * Otherwise, it returns zero.
+ */
+size_t alts_grpc_record_protocol_max_unprotected_data_size(
+    const alts_grpc_record_protocol* self, size_t max_protected_frame_size);
+
+/**
+ * This method destroys an alts_grpc_record_protocol instance by de-allocating
+ * all of its occupied memory.
+ */
+void alts_grpc_record_protocol_destroy(alts_grpc_record_protocol* self);
+
+#endif /* GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_RECORD_PROTOCOL_H \
+        */
diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc
new file mode 100644
index 0000000..ff91aea
--- /dev/null
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc
@@ -0,0 +1,173 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/gpr/useful.h"
+#include "src/core/lib/slice/slice_internal.h"
+
+const size_t kInitialIovecBufferSize = 8;
+
+/* Makes sure iovec_buf in alts_grpc_record_protocol is large enough.  */
+static void ensure_iovec_buf_size(alts_grpc_record_protocol* rp,
+                                  const grpc_slice_buffer* sb) {
+  GPR_ASSERT(rp != nullptr && sb != nullptr);
+  if (sb->count <= rp->iovec_buf_length) {
+    return;
+  }
+  /* At least double the iovec buffer size.  */
+  rp->iovec_buf_length = GPR_MAX(sb->count, 2 * rp->iovec_buf_length);
+  rp->iovec_buf = static_cast<iovec_t*>(
+      gpr_realloc(rp->iovec_buf, rp->iovec_buf_length * sizeof(iovec_t)));
+}
+
+/* --- Implementation of methods defined in tsi_grpc_record_protocol_common.h.
+ * --- */
+
+void alts_grpc_record_protocol_convert_slice_buffer_to_iovec(
+    alts_grpc_record_protocol* rp, const grpc_slice_buffer* sb) {
+  GPR_ASSERT(rp != nullptr && sb != nullptr);
+  ensure_iovec_buf_size(rp, sb);
+  for (size_t i = 0; i < sb->count; i++) {
+    rp->iovec_buf[i].iov_base = GRPC_SLICE_START_PTR(sb->slices[i]);
+    rp->iovec_buf[i].iov_len = GRPC_SLICE_LENGTH(sb->slices[i]);
+  }
+}
+
+void alts_grpc_record_protocol_copy_slice_buffer(const grpc_slice_buffer* src,
+                                                 unsigned char* dst) {
+  GPR_ASSERT(src != nullptr && dst != nullptr);
+  for (size_t i = 0; i < src->count; i++) {
+    size_t slice_length = GRPC_SLICE_LENGTH(src->slices[i]);
+    memcpy(dst, GRPC_SLICE_START_PTR(src->slices[i]), slice_length);
+    dst += slice_length;
+  }
+}
+
+iovec_t alts_grpc_record_protocol_get_header_iovec(
+    alts_grpc_record_protocol* rp) {
+  iovec_t header_iovec = {nullptr, 0};
+  if (rp == nullptr) {
+    return header_iovec;
+  }
+  header_iovec.iov_len = rp->header_length;
+  if (rp->header_sb.count == 1) {
+    header_iovec.iov_base = GRPC_SLICE_START_PTR(rp->header_sb.slices[0]);
+  } else {
+    /* Frame header is in multiple slices, copies the header bytes from slice
+     * buffer to a single flat buffer.  */
+    alts_grpc_record_protocol_copy_slice_buffer(&rp->header_sb, rp->header_buf);
+    header_iovec.iov_base = rp->header_buf;
+  }
+  return header_iovec;
+}
+
+tsi_result alts_grpc_record_protocol_init(alts_grpc_record_protocol* rp,
+                                          gsec_aead_crypter* crypter,
+                                          size_t overflow_size, bool is_client,
+                                          bool is_integrity_only,
+                                          bool is_protect) {
+  if (rp == nullptr || crypter == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to alts_grpc_record_protocol init.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  /* Creates alts_iovec_record_protocol.  */
+  char* error_details = nullptr;
+  grpc_status_code status = alts_iovec_record_protocol_create(
+      crypter, overflow_size, is_client, is_integrity_only, is_protect,
+      &rp->iovec_rp, &error_details);
+  if (status != GRPC_STATUS_OK) {
+    gpr_log(GPR_ERROR, "Failed to create alts_iovec_record_protocol, %s.",
+            error_details);
+    gpr_free(error_details);
+    return TSI_INTERNAL_ERROR;
+  }
+  /* Allocates header slice buffer.  */
+  grpc_slice_buffer_init(&rp->header_sb);
+  /* Allocates header buffer.  */
+  rp->header_length = alts_iovec_record_protocol_get_header_length();
+  rp->header_buf = static_cast<unsigned char*>(gpr_malloc(rp->header_length));
+  rp->tag_length = alts_iovec_record_protocol_get_tag_length(rp->iovec_rp);
+  /* Allocates iovec buffer.  */
+  rp->iovec_buf_length = kInitialIovecBufferSize;
+  rp->iovec_buf =
+      static_cast<iovec_t*>(gpr_malloc(rp->iovec_buf_length * sizeof(iovec_t)));
+  return TSI_OK;
+}
+
+/* --- Implementation of methods defined in tsi_grpc_record_protocol.h. --- */
+tsi_result alts_grpc_record_protocol_protect(
+    alts_grpc_record_protocol* self, grpc_slice_buffer* unprotected_slices,
+    grpc_slice_buffer* protected_slices) {
+  if (grpc_core::ExecCtx::Get() == nullptr || self == nullptr ||
+      self->vtable == nullptr || unprotected_slices == nullptr ||
+      protected_slices == nullptr) {
+    return TSI_INVALID_ARGUMENT;
+  }
+  if (self->vtable->protect == nullptr) {
+    return TSI_UNIMPLEMENTED;
+  }
+  return self->vtable->protect(self, unprotected_slices, protected_slices);
+}
+
+tsi_result alts_grpc_record_protocol_unprotect(
+    alts_grpc_record_protocol* self, grpc_slice_buffer* protected_slices,
+    grpc_slice_buffer* unprotected_slices) {
+  if (grpc_core::ExecCtx::Get() == nullptr || self == nullptr ||
+      self->vtable == nullptr || protected_slices == nullptr ||
+      unprotected_slices == nullptr) {
+    return TSI_INVALID_ARGUMENT;
+  }
+  if (self->vtable->unprotect == nullptr) {
+    return TSI_UNIMPLEMENTED;
+  }
+  return self->vtable->unprotect(self, protected_slices, unprotected_slices);
+}
+
+void alts_grpc_record_protocol_destroy(alts_grpc_record_protocol* self) {
+  if (self == nullptr) {
+    return;
+  }
+  if (self->vtable->destruct != nullptr) {
+    self->vtable->destruct(self);
+  }
+  alts_iovec_record_protocol_destroy(self->iovec_rp);
+  grpc_slice_buffer_destroy_internal(&self->header_sb);
+  gpr_free(self->header_buf);
+  gpr_free(self->iovec_buf);
+  gpr_free(self);
+}
+
+/* Integrity-only and privacy-integrity share the same implementation. No need
+ * to call vtable.  */
+size_t alts_grpc_record_protocol_max_unprotected_data_size(
+    const alts_grpc_record_protocol* self, size_t max_protected_frame_size) {
+  if (self == nullptr) {
+    return 0;
+  }
+  return alts_iovec_record_protocol_max_unprotected_data_size(
+      self->iovec_rp, max_protected_frame_size);
+}
diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h
new file mode 100644
index 0000000..43b8a4a
--- /dev/null
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h
@@ -0,0 +1,100 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_RECORD_PROTOCOL_COMMON_H
+#define GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_RECORD_PROTOCOL_COMMON_H
+
+/**
+ * this file contains alts_grpc_record_protocol internals and internal-only
+ * helper functions. The public functions of alts_grpc_record_protocol are
+ * defined in the alts_grpc_record_protocol.h.
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h"
+
+/* V-table for alts_grpc_record_protocol implementations.  */
+typedef struct {
+  tsi_result (*protect)(alts_grpc_record_protocol* self,
+                        grpc_slice_buffer* unprotected_slices,
+                        grpc_slice_buffer* protected_slices);
+  tsi_result (*unprotect)(alts_grpc_record_protocol* self,
+                          grpc_slice_buffer* protected_slices,
+                          grpc_slice_buffer* unprotected_slices);
+  void (*destruct)(alts_grpc_record_protocol* self);
+} alts_grpc_record_protocol_vtable;
+
+/* Main struct for alts_grpc_record_protocol implementation, shared by both
+ * integrity-only record protocol and privacy-integrity record protocol.
+ * Integrity-only record protocol has additional data elements.
+ * Privacy-integrity record protocol uses this struct directly.  */
+struct alts_grpc_record_protocol {
+  const alts_grpc_record_protocol_vtable* vtable;
+  alts_iovec_record_protocol* iovec_rp;
+  grpc_slice_buffer header_sb;
+  unsigned char* header_buf;
+  size_t header_length;
+  size_t tag_length;
+  iovec_t* iovec_buf;
+  size_t iovec_buf_length;
+};
+
+/**
+ * Converts the slices of input sb into iovec_t's and puts the result into
+ * rp->iovec_buf. Note that the actual data are not copied, only
+ * pointers and lengths are copied.
+ */
+void alts_grpc_record_protocol_convert_slice_buffer_to_iovec(
+    alts_grpc_record_protocol* rp, const grpc_slice_buffer* sb);
+
+/**
+ * Copies bytes from slice buffer to destination buffer. Caller is responsible
+ * for allocating enough memory of destination buffer. This method is used for
+ * copying frame header and tag in case they are stored in multiple slices.
+ */
+void alts_grpc_record_protocol_copy_slice_buffer(const grpc_slice_buffer* src,
+                                                 unsigned char* dst);
+
+/**
+ * This method returns an iovec object pointing to the frame header stored in
+ * rp->header_sb. If the frame header is stored in multiple slices,
+ * this method will copy the bytes in rp->header_sb to
+ * rp->header_buf, and return an iovec object pointing to
+ * rp->header_buf.
+ */
+iovec_t alts_grpc_record_protocol_get_header_iovec(
+    alts_grpc_record_protocol* rp);
+
+/**
+ * Initializes an alts_grpc_record_protocol object, given a gsec_aead_crypter
+ * instance, the overflow size of the counter in bytes, a flag indicating if the
+ * object is used for client or server side, a flag indicating if it is used for
+ * integrity-only or privacy-integrity mode, and a flag indicating if it is for
+ * protect or unprotect. The ownership of gsec_aead_crypter object is
+ * transferred to the alts_grpc_record_protocol object.
+ */
+tsi_result alts_grpc_record_protocol_init(alts_grpc_record_protocol* rp,
+                                          gsec_aead_crypter* crypter,
+                                          size_t overflow_size, bool is_client,
+                                          bool is_integrity_only,
+                                          bool is_protect);
+
+#endif /* GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_GRPC_RECORD_PROTOCOL_COMMON_H \
+        */
diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc b/src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc
new file mode 100644
index 0000000..6a548e5
--- /dev/null
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc
@@ -0,0 +1,476 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/tsi/alts/frame_protector/alts_counter.h"
+
+struct alts_iovec_record_protocol {
+  alts_counter* ctr;
+  gsec_aead_crypter* crypter;
+  size_t tag_length;
+  bool is_integrity_only;
+  bool is_protect;
+};
+
+/* Copies error message to destination.  */
+static void maybe_copy_error_msg(const char* src, char** dst) {
+  if (dst != nullptr && src != nullptr) {
+    *dst = static_cast<char*>(gpr_malloc(strlen(src) + 1));
+    memcpy(*dst, src, strlen(src) + 1);
+  }
+}
+
+/* Appends error message to destination.  */
+static void maybe_append_error_msg(const char* appendix, char** dst) {
+  if (dst != nullptr && appendix != nullptr) {
+    int dst_len = static_cast<int>(strlen(*dst));
+    *dst = static_cast<char*>(realloc(*dst, dst_len + strlen(appendix) + 1));
+    assert(*dst != nullptr);
+    memcpy(*dst + dst_len, appendix, strlen(appendix) + 1);
+  }
+}
+
+/* Use little endian to interpret a string of bytes as uint32_t.  */
+static uint32_t load_32_le(const unsigned char* buffer) {
+  return (((uint32_t)buffer[3]) << 24) | (((uint32_t)buffer[2]) << 16) |
+         (((uint32_t)buffer[1]) << 8) | ((uint32_t)buffer[0]);
+}
+
+/* Store uint32_t as a string of little endian bytes.  */
+static void store_32_le(uint32_t value, unsigned char* buffer) {
+  buffer[3] = (unsigned char)(value >> 24) & 0xFF;
+  buffer[2] = (unsigned char)(value >> 16) & 0xFF;
+  buffer[1] = (unsigned char)(value >> 8) & 0xFF;
+  buffer[0] = (unsigned char)(value)&0xFF;
+}
+
+/* Ensures header and tag iovec have sufficient length.  */
+static grpc_status_code ensure_header_and_tag_length(
+    const alts_iovec_record_protocol* rp, iovec_t header, iovec_t tag,
+    char** error_details) {
+  if (rp == nullptr) {
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  if (header.iov_base == nullptr) {
+    maybe_copy_error_msg("Header is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (header.iov_len != alts_iovec_record_protocol_get_header_length()) {
+    maybe_copy_error_msg("Header length is incorrect.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (tag.iov_base == nullptr) {
+    maybe_copy_error_msg("Tag is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (tag.iov_len != rp->tag_length) {
+    maybe_copy_error_msg("Tag length is incorrect.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  return GRPC_STATUS_OK;
+}
+
+/* Increments crypter counter and checks overflow.  */
+static grpc_status_code increment_counter(alts_counter* counter,
+                                          char** error_details) {
+  if (counter == nullptr) {
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  bool is_overflow = false;
+  grpc_status_code status =
+      alts_counter_increment(counter, &is_overflow, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  if (is_overflow) {
+    maybe_copy_error_msg("Crypter counter is overflowed.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  return GRPC_STATUS_OK;
+}
+
+/* Given an array of iovec, computes the total length of buffer.  */
+static size_t get_total_length(const iovec_t* vec, size_t vec_length) {
+  size_t total_length = 0;
+  for (size_t i = 0; i < vec_length; ++i) {
+    total_length += vec[i].iov_len;
+  }
+  return total_length;
+}
+
+/* Writes frame header given data and tag length.  */
+static grpc_status_code write_frame_header(size_t data_length,
+                                           unsigned char* header,
+                                           char** error_details) {
+  if (header == nullptr) {
+    maybe_copy_error_msg("Header is nullptr.", error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  size_t frame_length = kZeroCopyFrameMessageTypeFieldSize + data_length;
+  store_32_le(static_cast<uint32_t>(frame_length), header);
+  store_32_le(kZeroCopyFrameMessageType,
+              header + kZeroCopyFrameLengthFieldSize);
+  return GRPC_STATUS_OK;
+}
+
+/* Verifies frame header given protected data length.  */
+static grpc_status_code verify_frame_header(size_t data_length,
+                                            unsigned char* header,
+                                            char** error_details) {
+  if (header == nullptr) {
+    maybe_copy_error_msg("Header is nullptr.", error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  size_t frame_length = load_32_le(header);
+  if (frame_length != kZeroCopyFrameMessageTypeFieldSize + data_length) {
+    maybe_copy_error_msg("Bad frame length.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  size_t message_type = load_32_le(header + kZeroCopyFrameLengthFieldSize);
+  if (message_type != kZeroCopyFrameMessageType) {
+    maybe_copy_error_msg("Unsupported message type.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  return GRPC_STATUS_OK;
+}
+
+/* --- alts_iovec_record_protocol methods implementation. --- */
+
+size_t alts_iovec_record_protocol_get_header_length() {
+  return kZeroCopyFrameHeaderSize;
+}
+
+size_t alts_iovec_record_protocol_get_tag_length(
+    const alts_iovec_record_protocol* rp) {
+  if (rp != nullptr) {
+    return rp->tag_length;
+  }
+  return 0;
+}
+
+size_t alts_iovec_record_protocol_max_unprotected_data_size(
+    const alts_iovec_record_protocol* rp, size_t max_protected_frame_size) {
+  if (rp == nullptr) {
+    return 0;
+  }
+  size_t overhead_bytes_size =
+      kZeroCopyFrameMessageTypeFieldSize + rp->tag_length;
+  if (max_protected_frame_size <= overhead_bytes_size) return 0;
+  return max_protected_frame_size - overhead_bytes_size;
+}
+
+grpc_status_code alts_iovec_record_protocol_integrity_only_protect(
+    alts_iovec_record_protocol* rp, const iovec_t* unprotected_vec,
+    size_t unprotected_vec_length, iovec_t header, iovec_t tag,
+    char** error_details) {
+  /* Input sanity checks.  */
+  if (rp == nullptr) {
+    maybe_copy_error_msg("Input iovec_record_protocol is nullptr.",
+                         error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (!rp->is_integrity_only) {
+    maybe_copy_error_msg(
+        "Integrity-only operations are not allowed for this object.",
+        error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  if (!rp->is_protect) {
+    maybe_copy_error_msg("Protect operations are not allowed for this object.",
+                         error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  grpc_status_code status =
+      ensure_header_and_tag_length(rp, header, tag, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  /* Unprotected data should not be zero length.  */
+  size_t data_length =
+      get_total_length(unprotected_vec, unprotected_vec_length);
+  /* Sets frame header.  */
+  status = write_frame_header(data_length + rp->tag_length,
+                              static_cast<unsigned char*>(header.iov_base),
+                              error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  /* Computes frame tag by calling AEAD crypter.  */
+  size_t bytes_written = 0;
+  status = gsec_aead_crypter_encrypt_iovec(
+      rp->crypter, alts_counter_get_counter(rp->ctr),
+      alts_counter_get_size(rp->ctr), unprotected_vec, unprotected_vec_length,
+      /* plaintext_vec = */ nullptr, /* plaintext_vec_length = */ 0, tag,
+      &bytes_written, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  if (bytes_written != rp->tag_length) {
+    maybe_copy_error_msg("Bytes written expects to be the same as tag length.",
+                         error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  /* Increments the crypter counter.  */
+  return increment_counter(rp->ctr, error_details);
+}
+
+grpc_status_code alts_iovec_record_protocol_integrity_only_unprotect(
+    alts_iovec_record_protocol* rp, const iovec_t* protected_vec,
+    size_t protected_vec_length, iovec_t header, iovec_t tag,
+    char** error_details) {
+  /* Input sanity checks.  */
+  if (rp == nullptr) {
+    maybe_copy_error_msg("Input iovec_record_protocol is nullptr.",
+                         error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (!rp->is_integrity_only) {
+    maybe_copy_error_msg(
+        "Integrity-only operations are not allowed for this object.",
+        error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  if (rp->is_protect) {
+    maybe_copy_error_msg(
+        "Unprotect operations are not allowed for this object.", error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  grpc_status_code status =
+      ensure_header_and_tag_length(rp, header, tag, error_details);
+  if (status != GRPC_STATUS_OK) return status;
+  /* Protected data should not be zero length.  */
+  size_t data_length = get_total_length(protected_vec, protected_vec_length);
+  /* Verifies frame header.  */
+  status = verify_frame_header(data_length + rp->tag_length,
+                               static_cast<unsigned char*>(header.iov_base),
+                               error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  /* Verifies frame tag by calling AEAD crypter.  */
+  iovec_t plaintext = {nullptr, 0};
+  size_t bytes_written = 0;
+  status = gsec_aead_crypter_decrypt_iovec(
+      rp->crypter, alts_counter_get_counter(rp->ctr),
+      alts_counter_get_size(rp->ctr), protected_vec, protected_vec_length, &tag,
+      1, plaintext, &bytes_written, error_details);
+  if (status != GRPC_STATUS_OK || bytes_written != 0) {
+    maybe_append_error_msg(" Frame tag verification failed.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  /* Increments the crypter counter.  */
+  return increment_counter(rp->ctr, error_details);
+}
+
+grpc_status_code alts_iovec_record_protocol_privacy_integrity_protect(
+    alts_iovec_record_protocol* rp, const iovec_t* unprotected_vec,
+    size_t unprotected_vec_length, iovec_t protected_frame,
+    char** error_details) {
+  /* Input sanity checks.  */
+  if (rp == nullptr) {
+    maybe_copy_error_msg("Input iovec_record_protocol is nullptr.",
+                         error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (rp->is_integrity_only) {
+    maybe_copy_error_msg(
+        "Privacy-integrity operations are not allowed for this object.",
+        error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  if (!rp->is_protect) {
+    maybe_copy_error_msg("Protect operations are not allowed for this object.",
+                         error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  /* Unprotected data should not be zero length.  */
+  size_t data_length =
+      get_total_length(unprotected_vec, unprotected_vec_length);
+  /* Ensures protected frame iovec has sufficient size.  */
+  if (protected_frame.iov_base == nullptr) {
+    maybe_copy_error_msg("Protected frame is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (protected_frame.iov_len !=
+      alts_iovec_record_protocol_get_header_length() + data_length +
+          rp->tag_length) {
+    maybe_copy_error_msg("Protected frame size is incorrect.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  /* Writer frame header.  */
+  grpc_status_code status = write_frame_header(
+      data_length + rp->tag_length,
+      static_cast<unsigned char*>(protected_frame.iov_base), error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  /* Encrypt unprotected data by calling AEAD crypter.  */
+  unsigned char* ciphertext_buffer =
+      static_cast<unsigned char*>(protected_frame.iov_base) +
+      alts_iovec_record_protocol_get_header_length();
+  iovec_t ciphertext = {ciphertext_buffer, data_length + rp->tag_length};
+  size_t bytes_written = 0;
+  status = gsec_aead_crypter_encrypt_iovec(
+      rp->crypter, alts_counter_get_counter(rp->ctr),
+      alts_counter_get_size(rp->ctr), /* aad_vec = */ nullptr,
+      /* aad_vec_length = */ 0, unprotected_vec, unprotected_vec_length,
+      ciphertext, &bytes_written, error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  if (bytes_written != data_length + rp->tag_length) {
+    maybe_copy_error_msg(
+        "Bytes written expects to be data length plus tag length.",
+        error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  /* Increments the crypter counter. */
+  return increment_counter(rp->ctr, error_details);
+}
+
+grpc_status_code alts_iovec_record_protocol_privacy_integrity_unprotect(
+    alts_iovec_record_protocol* rp, iovec_t header,
+    const iovec_t* protected_vec, size_t protected_vec_length,
+    iovec_t unprotected_data, char** error_details) {
+  /* Input sanity checks.  */
+  if (rp == nullptr) {
+    maybe_copy_error_msg("Input iovec_record_protocol is nullptr.",
+                         error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (rp->is_integrity_only) {
+    maybe_copy_error_msg(
+        "Privacy-integrity operations are not allowed for this object.",
+        error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  if (rp->is_protect) {
+    maybe_copy_error_msg(
+        "Unprotect operations are not allowed for this object.", error_details);
+    return GRPC_STATUS_FAILED_PRECONDITION;
+  }
+  /* Protected data size should be no less than tag size.  */
+  size_t protected_data_length =
+      get_total_length(protected_vec, protected_vec_length);
+  if (protected_data_length < rp->tag_length) {
+    maybe_copy_error_msg(
+        "Protected data length should be more than the tag length.",
+        error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  /* Ensures header has sufficient size.  */
+  if (header.iov_base == nullptr) {
+    maybe_copy_error_msg("Header is nullptr.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  if (header.iov_len != alts_iovec_record_protocol_get_header_length()) {
+    maybe_copy_error_msg("Header length is incorrect.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  /* Ensures unprotected data iovec has sufficient size.  */
+  if (unprotected_data.iov_len != protected_data_length - rp->tag_length) {
+    maybe_copy_error_msg("Unprotected data size is incorrect.", error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  /* Verify frame header.  */
+  grpc_status_code status = verify_frame_header(
+      protected_data_length, static_cast<unsigned char*>(header.iov_base),
+      error_details);
+  if (status != GRPC_STATUS_OK) {
+    return status;
+  }
+  /* Decrypt protected data by calling AEAD crypter.  */
+  size_t bytes_written = 0;
+  status = gsec_aead_crypter_decrypt_iovec(
+      rp->crypter, alts_counter_get_counter(rp->ctr),
+      alts_counter_get_size(rp->ctr), /* aad_vec = */ nullptr,
+      /* aad_vec_length = */ 0, protected_vec, protected_vec_length,
+      unprotected_data, &bytes_written, error_details);
+  if (status != GRPC_STATUS_OK) {
+    maybe_append_error_msg(" Frame decryption failed.", error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  if (bytes_written != protected_data_length - rp->tag_length) {
+    maybe_copy_error_msg(
+        "Bytes written expects to be protected data length minus tag length.",
+        error_details);
+    return GRPC_STATUS_INTERNAL;
+  }
+  /* Increments the crypter counter. */
+  return increment_counter(rp->ctr, error_details);
+}
+
+grpc_status_code alts_iovec_record_protocol_create(
+    gsec_aead_crypter* crypter, size_t overflow_size, bool is_client,
+    bool is_integrity_only, bool is_protect, alts_iovec_record_protocol** rp,
+    char** error_details) {
+  if (crypter == nullptr || rp == nullptr) {
+    maybe_copy_error_msg(
+        "Invalid nullptr arguments to alts_iovec_record_protocol create.",
+        error_details);
+    return GRPC_STATUS_INVALID_ARGUMENT;
+  }
+  alts_iovec_record_protocol* impl = static_cast<alts_iovec_record_protocol*>(
+      gpr_zalloc(sizeof(alts_iovec_record_protocol)));
+  /* Gets counter length.  */
+  size_t counter_length = 0;
+  grpc_status_code status =
+      gsec_aead_crypter_nonce_length(crypter, &counter_length, error_details);
+  if (status != GRPC_STATUS_OK) {
+    goto cleanup;
+  }
+  /* Creates counters.  */
+  status =
+      alts_counter_create(is_protect ? !is_client : is_client, counter_length,
+                          overflow_size, &impl->ctr, error_details);
+  if (status != GRPC_STATUS_OK) {
+    goto cleanup;
+  }
+  /* Gets tag length.  */
+  status =
+      gsec_aead_crypter_tag_length(crypter, &impl->tag_length, error_details);
+  if (status != GRPC_STATUS_OK) {
+    goto cleanup;
+  }
+  impl->crypter = crypter;
+  impl->is_integrity_only = is_integrity_only;
+  impl->is_protect = is_protect;
+  *rp = impl;
+  return GRPC_STATUS_OK;
+cleanup:
+  alts_counter_destroy(impl->ctr);
+  gpr_free(impl);
+  return GRPC_STATUS_FAILED_PRECONDITION;
+}
+
+void alts_iovec_record_protocol_destroy(alts_iovec_record_protocol* rp) {
+  if (rp != nullptr) {
+    alts_counter_destroy(rp->ctr);
+    gsec_aead_crypter_destroy(rp->crypter);
+    gpr_free(rp);
+  }
+}
diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h b/src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h
new file mode 100644
index 0000000..0b7d1bf
--- /dev/null
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h
@@ -0,0 +1,199 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_IOVEC_RECORD_PROTOCOL_H
+#define GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_IOVEC_RECORD_PROTOCOL_H
+
+#include <grpc/support/port_platform.h>
+
+#include <stdbool.h>
+
+#include "src/core/tsi/alts/crypt/gsec.h"
+
+constexpr size_t kZeroCopyFrameMessageType = 0x06;
+constexpr size_t kZeroCopyFrameLengthFieldSize = 4;
+constexpr size_t kZeroCopyFrameMessageTypeFieldSize = 4;
+constexpr size_t kZeroCopyFrameHeaderSize =
+    kZeroCopyFrameLengthFieldSize + kZeroCopyFrameMessageTypeFieldSize;
+
+// Limit k on number of frames such that at most 2^(8 * k) frames can be sent.
+constexpr size_t kAltsRecordProtocolRekeyFrameLimit = 8;
+constexpr size_t kAltsRecordProtocolFrameLimit = 5;
+
+/* An implementation of alts record protocol. The API is thread-compatible. */
+
+typedef struct iovec iovec_t;
+
+typedef struct alts_iovec_record_protocol alts_iovec_record_protocol;
+
+/**
+ * This method gets the length of record protocol frame header.
+ */
+size_t alts_iovec_record_protocol_get_header_length();
+
+/**
+ * This method gets the length of record protocol frame tag.
+ *
+ * - rp: an alts_iovec_record_protocol instance.
+ *
+ * On success, the method returns the length of record protocol frame tag.
+ * Otherwise, it returns zero.
+ */
+size_t alts_iovec_record_protocol_get_tag_length(
+    const alts_iovec_record_protocol* rp);
+
+/**
+ * This method returns maximum allowed unprotected data size, given maximum
+ * protected frame size.
+ *
+ * - rp: an alts_iovec_record_protocol instance.
+ * - max_protected_frame_size: maximum protected frame size.
+ *
+ * On success, the method returns the maximum allowed unprotected data size.
+ * Otherwise, it returns zero.
+ */
+size_t alts_iovec_record_protocol_max_unprotected_data_size(
+    const alts_iovec_record_protocol* rp, size_t max_protected_frame_size);
+
+/**
+ * This method performs integrity-only protect operation on a
+ * alts_iovec_record_protocol instance, i.e., compute frame header and tag. The
+ * caller needs to allocate the memory for header and tag prior to calling this
+ * method.
+ *
+ * - rp: an alts_iovec_record_protocol instance.
+ * - unprotected_vec: an iovec array containing unprotected data.
+ * - unprotected_vec_length: the array length of unprotected_vec.
+ * - header: an iovec containing the output frame header.
+ * - tag: an iovec containing the output frame tag.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is OK to pass nullptr into error_details.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise, it returns an
+ * error status code along with its details specified in error_details (if
+ * error_details is not nullptr).
+ */
+grpc_status_code alts_iovec_record_protocol_integrity_only_protect(
+    alts_iovec_record_protocol* rp, const iovec_t* unprotected_vec,
+    size_t unprotected_vec_length, iovec_t header, iovec_t tag,
+    char** error_details);
+
+/**
+ * This method performs integrity-only unprotect operation on a
+ * alts_iovec_record_protocol instance, i.e., verify frame header and tag.
+ *
+ * - rp: an alts_iovec_record_protocol instance.
+ * - protected_vec: an iovec array containing protected data.
+ * - protected_vec_length: the array length of protected_vec.
+ * - header: an iovec containing the frame header.
+ * - tag: an iovec containing the frame tag.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is OK to pass nullptr into error_details.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise, it returns an
+ * error status code along with its details specified in error_details (if
+ * error_details is not nullptr).
+ */
+grpc_status_code alts_iovec_record_protocol_integrity_only_unprotect(
+    alts_iovec_record_protocol* rp, const iovec_t* protected_vec,
+    size_t protected_vec_length, iovec_t header, iovec_t tag,
+    char** error_details);
+
+/**
+ * This method performs privacy-integrity protect operation on a
+ * alts_iovec_record_protocol instance, i.e., compute a protected frame. The
+ * caller needs to allocate the memory for the protected frame prior to calling
+ * this method.
+ *
+ * - rp: an alts_iovec_record_protocol instance.
+ * - unprotected_vec: an iovec array containing unprotected data.
+ * - unprotected_vec_length: the array length of unprotected_vec.
+ * - protected_frame: an iovec containing the output protected frame.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is OK to pass nullptr into error_details.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise, it returns an
+ * error status code along with its details specified in error_details (if
+ * error_details is not nullptr).
+ */
+grpc_status_code alts_iovec_record_protocol_privacy_integrity_protect(
+    alts_iovec_record_protocol* rp, const iovec_t* unprotected_vec,
+    size_t unprotected_vec_length, iovec_t protected_frame,
+    char** error_details);
+
+/**
+ * This method performs privacy-integrity unprotect operation on a
+ * alts_iovec_record_protocol instance given a full protected frame, i.e.,
+ * compute the unprotected data. The caller needs to allocated the memory for
+ * the unprotected data prior to calling this method.
+ *
+ * - rp: an alts_iovec_record_protocol instance.
+ * - header: an iovec containing the frame header.
+ * - protected_vec: an iovec array containing protected data including the tag.
+ * - protected_vec_length: the array length of protected_vec.
+ * - unprotected_data: an iovec containing the output unprotected data.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is OK to pass nullptr into error_details.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise, it returns an
+ * error status code along with its details specified in error_details (if
+ * error_details is not nullptr).
+ */
+grpc_status_code alts_iovec_record_protocol_privacy_integrity_unprotect(
+    alts_iovec_record_protocol* rp, iovec_t header,
+    const iovec_t* protected_vec, size_t protected_vec_length,
+    iovec_t unprotected_data, char** error_details);
+
+/**
+ * This method creates an alts_iovec_record_protocol instance, given a
+ * gsec_aead_crypter instance, a flag indicating if the created instance will be
+ * used at the client or server side, and a flag indicating if the created
+ * instance will be used for integrity-only mode or privacy-integrity mode. The
+ * ownership of gsec_aead_crypter instance is transferred to this new object.
+ *
+ * - crypter: a gsec_aead_crypter instance used to perform AEAD decryption.
+ * - overflow_size: overflow size of counter in bytes.
+ * - is_client: a flag indicating if the alts_iovec_record_protocol instance
+ *   will be used at the client or server side.
+ * - is_integrity_only: a flag indicating if the alts_iovec_record_protocol
+ *   instance will be used for integrity-only or privacy-integrity mode.
+ * - is_protect: a flag indicating if the alts_grpc_record_protocol instance
+ *   will be used for protect or unprotect.
+ * - rp: an alts_iovec_record_protocol instance to be returned from
+ *   the method.
+ * - error_details: a buffer containing an error message if the method does not
+ *   function correctly. It is OK to pass nullptr into error_details.
+ *
+ * On success, the method returns GRPC_STATUS_OK. Otherwise, it returns an
+ * error status code along with its details specified in error_details (if
+ * error_details is not nullptr).
+ */
+grpc_status_code alts_iovec_record_protocol_create(
+    gsec_aead_crypter* crypter, size_t overflow_size, bool is_client,
+    bool is_integrity_only, bool is_protect, alts_iovec_record_protocol** rp,
+    char** error_details);
+
+/**
+ * This method destroys an alts_iovec_record_protocol instance by de-allocating
+ * all of its occupied memory. A gsec_aead_crypter instance passed in at
+ * gsec_alts_crypter instance creation time will be destroyed in this method.
+ */
+void alts_iovec_record_protocol_destroy(alts_iovec_record_protocol* rp);
+
+#endif /* GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_IOVEC_RECORD_PROTOCOL_H \
+        */
diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc b/src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc
new file mode 100644
index 0000000..8c76496
--- /dev/null
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc
@@ -0,0 +1,295 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/gpr/useful.h"
+#include "src/core/lib/slice/slice_internal.h"
+#include "src/core/tsi/alts/crypt/gsec.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h"
+#include "src/core/tsi/transport_security_grpc.h"
+
+constexpr size_t kMinFrameLength = 1024;
+constexpr size_t kDefaultFrameLength = 16 * 1024;
+constexpr size_t kMaxFrameLength = 1024 * 1024;
+
+/**
+ * Main struct for alts_zero_copy_grpc_protector.
+ * We choose to have two alts_grpc_record_protocol objects and two sets of slice
+ * buffers: one for protect and the other for unprotect, so that protect and
+ * unprotect can be executed in parallel. Implementations of this object must be
+ * thread compatible.
+ */
+typedef struct alts_zero_copy_grpc_protector {
+  tsi_zero_copy_grpc_protector base;
+  alts_grpc_record_protocol* record_protocol;
+  alts_grpc_record_protocol* unrecord_protocol;
+  size_t max_protected_frame_size;
+  size_t max_unprotected_data_size;
+  grpc_slice_buffer unprotected_staging_sb;
+  grpc_slice_buffer protected_sb;
+  grpc_slice_buffer protected_staging_sb;
+  uint32_t parsed_frame_size;
+} alts_zero_copy_grpc_protector;
+
+/**
+ * Given a slice buffer, parses the first 4 bytes little-endian unsigned frame
+ * size and returns the total frame size including the frame field. Caller
+ * needs to make sure the input slice buffer has at least 4 bytes. Returns true
+ * on success and false on failure.
+ */
+static bool read_frame_size(const grpc_slice_buffer* sb,
+                            uint32_t* total_frame_size) {
+  if (sb == nullptr || sb->length < kZeroCopyFrameLengthFieldSize) {
+    return false;
+  }
+  uint8_t frame_size_buffer[kZeroCopyFrameLengthFieldSize];
+  uint8_t* buf = frame_size_buffer;
+  /* Copies the first 4 bytes to a temporary buffer.  */
+  size_t remaining = kZeroCopyFrameLengthFieldSize;
+  for (size_t i = 0; i < sb->count; i++) {
+    size_t slice_length = GRPC_SLICE_LENGTH(sb->slices[i]);
+    if (remaining <= slice_length) {
+      memcpy(buf, GRPC_SLICE_START_PTR(sb->slices[i]), remaining);
+      remaining = 0;
+      break;
+    } else {
+      memcpy(buf, GRPC_SLICE_START_PTR(sb->slices[i]), slice_length);
+      buf += slice_length;
+      remaining -= slice_length;
+    }
+  }
+  GPR_ASSERT(remaining == 0);
+  /* Gets little-endian frame size.  */
+  uint32_t frame_size = (((uint32_t)frame_size_buffer[3]) << 24) |
+                        (((uint32_t)frame_size_buffer[2]) << 16) |
+                        (((uint32_t)frame_size_buffer[1]) << 8) |
+                        ((uint32_t)frame_size_buffer[0]);
+  if (frame_size > kMaxFrameLength) {
+    gpr_log(GPR_ERROR, "Frame size is larger than maximum frame size");
+    return false;
+  }
+  /* Returns frame size including frame length field.  */
+  *total_frame_size =
+      static_cast<uint32_t>(frame_size + kZeroCopyFrameLengthFieldSize);
+  return true;
+}
+
+/**
+ * Creates an alts_grpc_record_protocol object, given key, key size, and flags
+ * to indicate whether the record_protocol object uses the rekeying AEAD,
+ * whether the object is for client or server, whether the object is for
+ * integrity-only or privacy-integrity mode, and whether the object is is used
+ * for protect or unprotect.
+ */
+static tsi_result create_alts_grpc_record_protocol(
+    const uint8_t* key, size_t key_size, bool is_rekey, bool is_client,
+    bool is_integrity_only, bool is_protect,
+    alts_grpc_record_protocol** record_protocol) {
+  if (key == nullptr || record_protocol == nullptr) {
+    return TSI_INVALID_ARGUMENT;
+  }
+  grpc_status_code status;
+  gsec_aead_crypter* crypter = nullptr;
+  char* error_details = nullptr;
+  status = gsec_aes_gcm_aead_crypter_create(key, key_size, kAesGcmNonceLength,
+                                            kAesGcmTagLength, is_rekey,
+                                            &crypter, &error_details);
+  if (status != GRPC_STATUS_OK) {
+    gpr_log(GPR_ERROR, "Failed to create AEAD crypter, %s", error_details);
+    gpr_free(error_details);
+    return TSI_INTERNAL_ERROR;
+  }
+  size_t overflow_limit = is_rekey ? kAltsRecordProtocolRekeyFrameLimit
+                                   : kAltsRecordProtocolFrameLimit;
+  /* Creates alts_grpc_record_protocol with AEAD crypter ownership transferred.
+   */
+  tsi_result result =
+      is_integrity_only
+          ? alts_grpc_integrity_only_record_protocol_create(
+                crypter, overflow_limit, is_client, is_protect, record_protocol)
+          : alts_grpc_privacy_integrity_record_protocol_create(
+                crypter, overflow_limit, is_client, is_protect,
+                record_protocol);
+  if (result != TSI_OK) {
+    gsec_aead_crypter_destroy(crypter);
+    return result;
+  }
+  return TSI_OK;
+}
+
+/* --- tsi_zero_copy_grpc_protector methods implementation. --- */
+
+static tsi_result alts_zero_copy_grpc_protector_protect(
+    tsi_zero_copy_grpc_protector* self, grpc_slice_buffer* unprotected_slices,
+    grpc_slice_buffer* protected_slices) {
+  if (self == nullptr || unprotected_slices == nullptr ||
+      protected_slices == nullptr) {
+    gpr_log(GPR_ERROR, "Invalid nullptr arguments to zero-copy grpc protect.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_zero_copy_grpc_protector* protector =
+      reinterpret_cast<alts_zero_copy_grpc_protector*>(self);
+  /* Calls alts_grpc_record_protocol protect repeatly.  */
+  while (unprotected_slices->length > protector->max_unprotected_data_size) {
+    grpc_slice_buffer_move_first(unprotected_slices,
+                                 protector->max_unprotected_data_size,
+                                 &protector->unprotected_staging_sb);
+    tsi_result status = alts_grpc_record_protocol_protect(
+        protector->record_protocol, &protector->unprotected_staging_sb,
+        protected_slices);
+    if (status != TSI_OK) {
+      return status;
+    }
+  }
+  return alts_grpc_record_protocol_protect(
+      protector->record_protocol, unprotected_slices, protected_slices);
+}
+
+static tsi_result alts_zero_copy_grpc_protector_unprotect(
+    tsi_zero_copy_grpc_protector* self, grpc_slice_buffer* protected_slices,
+    grpc_slice_buffer* unprotected_slices) {
+  if (self == nullptr || unprotected_slices == nullptr ||
+      protected_slices == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to zero-copy grpc unprotect.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  alts_zero_copy_grpc_protector* protector =
+      reinterpret_cast<alts_zero_copy_grpc_protector*>(self);
+  grpc_slice_buffer_move_into(protected_slices, &protector->protected_sb);
+  /* Keep unprotecting each frame if possible.  */
+  while (protector->protected_sb.length >= kZeroCopyFrameLengthFieldSize) {
+    if (protector->parsed_frame_size == 0) {
+      /* We have not parsed frame size yet. Parses frame size.  */
+      if (!read_frame_size(&protector->protected_sb,
+                           &protector->parsed_frame_size)) {
+        grpc_slice_buffer_reset_and_unref_internal(&protector->protected_sb);
+        return TSI_DATA_CORRUPTED;
+      }
+    }
+    if (protector->protected_sb.length < protector->parsed_frame_size) break;
+    /* At this point, protected_sb contains at least one frame of data.  */
+    tsi_result status;
+    if (protector->protected_sb.length == protector->parsed_frame_size) {
+      status = alts_grpc_record_protocol_unprotect(protector->unrecord_protocol,
+                                                   &protector->protected_sb,
+                                                   unprotected_slices);
+    } else {
+      grpc_slice_buffer_move_first(&protector->protected_sb,
+                                   protector->parsed_frame_size,
+                                   &protector->protected_staging_sb);
+      status = alts_grpc_record_protocol_unprotect(
+          protector->unrecord_protocol, &protector->protected_staging_sb,
+          unprotected_slices);
+    }
+    protector->parsed_frame_size = 0;
+    if (status != TSI_OK) {
+      grpc_slice_buffer_reset_and_unref_internal(&protector->protected_sb);
+      return status;
+    }
+  }
+  return TSI_OK;
+}
+
+static void alts_zero_copy_grpc_protector_destroy(
+    tsi_zero_copy_grpc_protector* self) {
+  if (self == nullptr) {
+    return;
+  }
+  alts_zero_copy_grpc_protector* protector =
+      reinterpret_cast<alts_zero_copy_grpc_protector*>(self);
+  alts_grpc_record_protocol_destroy(protector->record_protocol);
+  alts_grpc_record_protocol_destroy(protector->unrecord_protocol);
+  grpc_slice_buffer_destroy_internal(&protector->unprotected_staging_sb);
+  grpc_slice_buffer_destroy_internal(&protector->protected_sb);
+  grpc_slice_buffer_destroy_internal(&protector->protected_staging_sb);
+  gpr_free(protector);
+}
+
+static const tsi_zero_copy_grpc_protector_vtable
+    alts_zero_copy_grpc_protector_vtable = {
+        alts_zero_copy_grpc_protector_protect,
+        alts_zero_copy_grpc_protector_unprotect,
+        alts_zero_copy_grpc_protector_destroy};
+
+tsi_result alts_zero_copy_grpc_protector_create(
+    const uint8_t* key, size_t key_size, bool is_rekey, bool is_client,
+    bool is_integrity_only, size_t* max_protected_frame_size,
+    tsi_zero_copy_grpc_protector** protector) {
+  if (grpc_core::ExecCtx::Get() == nullptr || key == nullptr ||
+      protector == nullptr) {
+    gpr_log(
+        GPR_ERROR,
+        "Invalid nullptr arguments to alts_zero_copy_grpc_protector create.");
+    return TSI_INVALID_ARGUMENT;
+  }
+  /* Creates alts_zero_copy_protector.  */
+  alts_zero_copy_grpc_protector* impl =
+      static_cast<alts_zero_copy_grpc_protector*>(
+          gpr_zalloc(sizeof(alts_zero_copy_grpc_protector)));
+  /* Creates alts_grpc_record_protocol objects.  */
+  tsi_result status = create_alts_grpc_record_protocol(
+      key, key_size, is_rekey, is_client, is_integrity_only,
+      /*is_protect=*/true, &impl->record_protocol);
+  if (status == TSI_OK) {
+    status = create_alts_grpc_record_protocol(
+        key, key_size, is_rekey, is_client, is_integrity_only,
+        /*is_protect=*/false, &impl->unrecord_protocol);
+    if (status == TSI_OK) {
+      /* Sets maximum frame size.  */
+      size_t max_protected_frame_size_to_set = kDefaultFrameLength;
+      if (max_protected_frame_size != nullptr) {
+        *max_protected_frame_size =
+            GPR_MIN(*max_protected_frame_size, kMaxFrameLength);
+        *max_protected_frame_size =
+            GPR_MAX(*max_protected_frame_size, kMinFrameLength);
+        max_protected_frame_size_to_set = *max_protected_frame_size;
+      }
+      impl->max_protected_frame_size = max_protected_frame_size_to_set;
+      impl->max_unprotected_data_size =
+          alts_grpc_record_protocol_max_unprotected_data_size(
+              impl->record_protocol, max_protected_frame_size_to_set);
+      GPR_ASSERT(impl->max_unprotected_data_size > 0);
+      /* Allocates internal slice buffers.  */
+      grpc_slice_buffer_init(&impl->unprotected_staging_sb);
+      grpc_slice_buffer_init(&impl->protected_sb);
+      grpc_slice_buffer_init(&impl->protected_staging_sb);
+      impl->parsed_frame_size = 0;
+      impl->base.vtable = &alts_zero_copy_grpc_protector_vtable;
+      *protector = &impl->base;
+      return TSI_OK;
+    }
+  }
+
+  /* Cleanup if create failed.  */
+  alts_grpc_record_protocol_destroy(impl->record_protocol);
+  alts_grpc_record_protocol_destroy(impl->unrecord_protocol);
+  gpr_free(impl);
+  return TSI_INTERNAL_ERROR;
+}
diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h b/src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h
new file mode 100644
index 0000000..71e953c
--- /dev/null
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h
@@ -0,0 +1,52 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_ZERO_COPY_GRPC_PROTECTOR_H
+#define GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_ZERO_COPY_GRPC_PROTECTOR_H
+
+#include <grpc/support/port_platform.h>
+
+#include <stdbool.h>
+
+#include "src/core/tsi/transport_security_grpc.h"
+
+/**
+ * This method creates an ALTS zero-copy grpc protector.
+ *
+ * - key: a symmetric key used to seal/unseal frames.
+ * - key_size: the size of symmetric key.
+ * - is_rekey: use rekeying AEAD crypter.
+ * - is_client: a flag indicating if the protector will be used at client or
+ *   server side.
+ * - is_integrity_only: a flag indicating if the protector instance will be
+ *   used for integrity-only or privacy-integrity mode.
+ * - max_protected_frame_size: an in/out parameter indicating max frame size
+ *   to be used by the protector. If it is nullptr, the default frame size will
+ *   be used. Otherwise, the provided frame size will be adjusted (if not
+ *   falling into a valid frame range) and used.
+ * - protector: a pointer to the zero-copy protector returned from the method.
+ *
+ * This method returns TSI_OK on success or a specific error code otherwise.
+ */
+tsi_result alts_zero_copy_grpc_protector_create(
+    const uint8_t* key, size_t key_size, bool is_rekey, bool is_client,
+    bool is_integrity_only, size_t* max_protected_frame_size,
+    tsi_zero_copy_grpc_protector** protector);
+
+#endif /* GRPC_CORE_TSI_ALTS_ZERO_COPY_FRAME_PROTECTOR_ALTS_ZERO_COPY_GRPC_PROTECTOR_H \
+        */
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index 7515679..dd3a8f9 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -220,6 +220,7 @@
     'src/core/ext/filters/http/server/http_server_filter.cc',
     'src/core/lib/http/httpcli_security_connector.cc',
     'src/core/lib/security/context/security_context.cc',
+    'src/core/lib/security/credentials/alts/alts_credentials.cc',
     'src/core/lib/security/credentials/composite/composite_credentials.cc',
     'src/core/lib/security/credentials/credentials.cc',
     'src/core/lib/security/credentials/credentials_metadata.cc',
@@ -233,6 +234,7 @@
     'src/core/lib/security/credentials/oauth2/oauth2_credentials.cc',
     'src/core/lib/security/credentials/plugin/plugin_credentials.cc',
     'src/core/lib/security/credentials/ssl/ssl_credentials.cc',
+    'src/core/lib/security/security_connector/alts_security_connector.cc',
     'src/core/lib/security/security_connector/security_connector.cc',
     'src/core/lib/security/transport/client_auth_filter.cc',
     'src/core/lib/security/transport/secure_endpoint.cc',
@@ -242,14 +244,45 @@
     'src/core/lib/security/transport/tsi_error.cc',
     'src/core/lib/security/util/json_util.cc',
     'src/core/lib/surface/init_secure.cc',
-    'src/core/tsi/alts_transport_security.cc',
-    'src/core/tsi/fake_transport_security.cc',
-    'src/core/tsi/ssl_transport_security.cc',
-    'src/core/tsi/transport_security_grpc.cc',
+    'src/core/tsi/alts/crypt/aes_gcm.cc',
+    'src/core/tsi/alts/crypt/gsec.cc',
+    'src/core/tsi/alts/frame_protector/alts_counter.cc',
+    'src/core/tsi/alts/frame_protector/alts_crypter.cc',
+    'src/core/tsi/alts/frame_protector/alts_frame_protector.cc',
+    'src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc',
+    'src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc',
+    'src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc',
+    'src/core/tsi/alts/frame_protector/frame_handler.cc',
+    'src/core/tsi/alts/handshaker/alts_handshaker_client.cc',
+    'src/core/tsi/alts/handshaker/alts_tsi_event.cc',
+    'src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc',
+    'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc',
+    'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc',
+    'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc',
+    'src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc',
+    'src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc',
+    'src/core/lib/security/credentials/alts/check_gcp_environment.cc',
+    'src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc',
+    'src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc',
+    'src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc',
+    'src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc',
+    'src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc',
+    'src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc',
+    'src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc',
+    'src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc',
+    'src/core/tsi/alts/handshaker/alts_tsi_utils.cc',
+    'src/core/tsi/alts/handshaker/transport_security_common_api.cc',
+    'src/core/tsi/alts/handshaker/altscontext.pb.c',
+    'src/core/tsi/alts/handshaker/handshaker.pb.c',
+    'src/core/tsi/alts/handshaker/transport_security_common.pb.c',
+    'third_party/nanopb/pb_common.c',
+    'third_party/nanopb/pb_decode.c',
+    'third_party/nanopb/pb_encode.c',
     'src/core/tsi/transport_security.cc',
     'src/core/tsi/transport_security_adapter.cc',
-    'src/core/ext/transport/chttp2/server/chttp2_server.cc',
-    'src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc',
+    'src/core/ext/transport/chttp2/client/insecure/channel_create.cc',
+    'src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc',
+    'src/core/ext/transport/chttp2/client/chttp2_connector.cc',
     'src/core/ext/filters/client_channel/backup_poller.cc',
     'src/core/ext/filters/client_channel/channel_connectivity.cc',
     'src/core/ext/filters/client_channel/client_channel.cc',
@@ -273,11 +306,14 @@
     'src/core/ext/filters/client_channel/subchannel_index.cc',
     'src/core/ext/filters/client_channel/uri_parser.cc',
     'src/core/ext/filters/deadline/deadline_filter.cc',
-    'src/core/ext/transport/chttp2/client/chttp2_connector.cc',
+    'src/core/tsi/alts_transport_security.cc',
+    'src/core/tsi/fake_transport_security.cc',
+    'src/core/tsi/ssl_transport_security.cc',
+    'src/core/tsi/transport_security_grpc.cc',
+    'src/core/ext/transport/chttp2/server/chttp2_server.cc',
+    'src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc',
     'src/core/ext/transport/chttp2/server/insecure/server_chttp2.cc',
     'src/core/ext/transport/chttp2/server/insecure/server_chttp2_posix.cc',
-    'src/core/ext/transport/chttp2/client/insecure/channel_create.cc',
-    'src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc',
     'src/core/ext/transport/inproc/inproc_plugin.cc',
     'src/core/ext/transport/inproc/inproc_transport.cc',
     'src/core/ext/filters/client_channel/lb_policy/grpclb/client_load_reporting_filter.cc',
@@ -286,9 +322,6 @@
     'src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.cc',
     'src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.cc',
     'src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c',
-    'third_party/nanopb/pb_common.c',
-    'third_party/nanopb/pb_decode.c',
-    'third_party/nanopb/pb_encode.c',
     'src/core/ext/filters/client_channel/resolver/fake/fake_resolver.cc',
     'src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc',
     'src/core/ext/filters/client_channel/lb_policy/subchannel_list.cc',
diff --git a/templates/CMakeLists.txt.template b/templates/CMakeLists.txt.template
index 0f08843..ef4d7d7 100644
--- a/templates/CMakeLists.txt.template
+++ b/templates/CMakeLists.txt.template
@@ -138,6 +138,8 @@
 
   ## Some libraries are shared even with BUILD_SHARED_LIBRARIES=OFF
   set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)
+  
+  add_definitions(-DPB_FIELD_16BIT)
 
   if (MSVC)
     include(cmake/msvc_static_runtime.cmake)
diff --git a/templates/Makefile.template b/templates/Makefile.template
index 390847b..196d12f 100644
--- a/templates/Makefile.template
+++ b/templates/Makefile.template
@@ -221,6 +221,8 @@
   %  endif
   % endfor
 
+  DEFINES += PB_FIELD_16BIT
+
   CPPFLAGS += $(CPPFLAGS_$(CONFIG))
   CFLAGS += $(CFLAGS_$(CONFIG))
   CXXFLAGS += $(CXXFLAGS_$(CONFIG))
diff --git a/templates/gRPC-Core.podspec.template b/templates/gRPC-Core.podspec.template
index c28b78d..3e80d60 100644
--- a/templates/gRPC-Core.podspec.template
+++ b/templates/gRPC-Core.podspec.template
@@ -144,7 +144,7 @@
     }
 
     s.default_subspecs = 'Interface', 'Implementation'
-    s.compiler_flags = '-DGRPC_ARES=0'
+    s.compiler_flags = '-DGRPC_ARES=0', '-DPB_FIELD_16BIT'
     s.libraries = 'c++'
 
     # Like many other C libraries, gRPC-Core has its public headers under `include/<libname>/` and its
diff --git a/templates/grpc.gyp.template b/templates/grpc.gyp.template
index 3363082..2ea0d06 100644
--- a/templates/grpc.gyp.template
+++ b/templates/grpc.gyp.template
@@ -60,11 +60,11 @@
       % endfor
       'cflags_c': [
         '-Werror',
-        '-std=c99'
+        '-std=c99',
       ],
       'cflags_cc': [
         '-Werror',
-        '-std=c++11'
+        '-std=c++11',
       ],
       'include_dirs': [
         '.',
@@ -127,7 +127,7 @@
               % endfor
               '-stdlib=libc++',
               '-std=c++11',
-              '-Wno-error=deprecated-declarations'
+              '-Wno-error=deprecated-declarations',
             ],
             % endif
           },
diff --git a/test/core/security/BUILD b/test/core/security/BUILD
index 9776e6d..68de2d1 100644
--- a/test/core/security/BUILD
+++ b/test/core/security/BUILD
@@ -161,3 +161,39 @@
         "//test/core/util:grpc_test_util",
     ],
 )
+
+grpc_cc_test(
+    name = "check_gcp_environment_linux_test",
+    srcs = ["check_gcp_environment_linux_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+    ],
+)
+
+grpc_cc_test(
+    name = "check_gcp_environment_windows_test",
+    srcs = ["check_gcp_environment_windows_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+    ],
+)
+
+grpc_cc_test(
+    name = "grpc_alts_credentials_options_test",
+    srcs = ["grpc_alts_credentials_options_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+    ],
+)
+
+grpc_cc_test(
+    name = "alts_security_connector_test",
+    srcs = ["alts_security_connector_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+    ],
+)
diff --git a/test/core/security/alts_security_connector_test.cc b/test/core/security/alts_security_connector_test.cc
new file mode 100644
index 0000000..103a493
--- /dev/null
+++ b/test/core/security/alts_security_connector_test.cc
@@ -0,0 +1,166 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <grpc/grpc.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/security/security_connector/alts_security_connector.h"
+#include "src/core/lib/transport/transport.h"
+#include "src/core/tsi/alts/handshaker/alts_tsi_handshaker.h"
+#include "src/core/tsi/transport_security.h"
+
+using grpc_core::internal::grpc_alts_auth_context_from_tsi_peer;
+
+/* This file contains unit tests of grpc_alts_auth_context_from_tsi_peer(). */
+static void test_invalid_input_failure() {
+  tsi_peer peer;
+  grpc_auth_context* ctx;
+  GPR_ASSERT(grpc_alts_auth_context_from_tsi_peer(nullptr, &ctx) ==
+             GRPC_SECURITY_ERROR);
+  GPR_ASSERT(grpc_alts_auth_context_from_tsi_peer(&peer, nullptr) ==
+             GRPC_SECURITY_ERROR);
+}
+
+static void test_empty_certificate_type_failure() {
+  tsi_peer peer;
+  grpc_auth_context* ctx = nullptr;
+  GPR_ASSERT(tsi_construct_peer(0, &peer) == TSI_OK);
+  GPR_ASSERT(grpc_alts_auth_context_from_tsi_peer(&peer, &ctx) ==
+             GRPC_SECURITY_ERROR);
+  GPR_ASSERT(ctx == nullptr);
+  tsi_peer_destruct(&peer);
+}
+
+static void test_empty_peer_property_failure() {
+  tsi_peer peer;
+  grpc_auth_context* ctx;
+  GPR_ASSERT(tsi_construct_peer(1, &peer) == TSI_OK);
+  GPR_ASSERT(tsi_construct_string_peer_property_from_cstring(
+                 TSI_CERTIFICATE_TYPE_PEER_PROPERTY, TSI_ALTS_CERTIFICATE_TYPE,
+                 &peer.properties[0]) == TSI_OK);
+  GPR_ASSERT(grpc_alts_auth_context_from_tsi_peer(&peer, &ctx) ==
+             GRPC_SECURITY_ERROR);
+  GPR_ASSERT(ctx == nullptr);
+  tsi_peer_destruct(&peer);
+}
+
+static void test_missing_rpc_protocol_versions_property_failure() {
+  tsi_peer peer;
+  grpc_auth_context* ctx;
+  GPR_ASSERT(tsi_construct_peer(kTsiAltsNumOfPeerProperties, &peer) == TSI_OK);
+  GPR_ASSERT(tsi_construct_string_peer_property_from_cstring(
+                 TSI_CERTIFICATE_TYPE_PEER_PROPERTY, TSI_ALTS_CERTIFICATE_TYPE,
+                 &peer.properties[0]) == TSI_OK);
+  GPR_ASSERT(tsi_construct_string_peer_property_from_cstring(
+                 TSI_ALTS_SERVICE_ACCOUNT_PEER_PROPERTY, "alice",
+                 &peer.properties[1]) == TSI_OK);
+  GPR_ASSERT(grpc_alts_auth_context_from_tsi_peer(&peer, &ctx) ==
+             GRPC_SECURITY_ERROR);
+  GPR_ASSERT(ctx == nullptr);
+  tsi_peer_destruct(&peer);
+}
+
+static void test_unknown_peer_property_failure() {
+  tsi_peer peer;
+  grpc_auth_context* ctx;
+  GPR_ASSERT(tsi_construct_peer(kTsiAltsNumOfPeerProperties, &peer) == TSI_OK);
+  GPR_ASSERT(tsi_construct_string_peer_property_from_cstring(
+                 TSI_CERTIFICATE_TYPE_PEER_PROPERTY, TSI_ALTS_CERTIFICATE_TYPE,
+                 &peer.properties[0]) == TSI_OK);
+  GPR_ASSERT(tsi_construct_string_peer_property_from_cstring(
+                 "unknown", "alice", &peer.properties[1]) == TSI_OK);
+  GPR_ASSERT(grpc_alts_auth_context_from_tsi_peer(&peer, &ctx) ==
+             GRPC_SECURITY_ERROR);
+  GPR_ASSERT(ctx == nullptr);
+  tsi_peer_destruct(&peer);
+}
+
+static bool test_identity(const grpc_auth_context* ctx,
+                          const char* expected_property_name,
+                          const char* expected_identity) {
+  grpc_auth_property_iterator it;
+  const grpc_auth_property* prop;
+  GPR_ASSERT(grpc_auth_context_peer_is_authenticated(ctx));
+  it = grpc_auth_context_peer_identity(ctx);
+  prop = grpc_auth_property_iterator_next(&it);
+  GPR_ASSERT(prop != nullptr);
+  if (strcmp(prop->name, expected_property_name) != 0) {
+    gpr_log(GPR_ERROR, "Expected peer identity property name %s and got %s.",
+            expected_property_name, prop->name);
+    return false;
+  }
+  if (strncmp(prop->value, expected_identity, prop->value_length) != 0) {
+    gpr_log(GPR_ERROR, "Expected peer identity %s and got got %s.",
+            expected_identity, prop->value);
+    return false;
+  }
+  return true;
+}
+
+static void test_alts_peer_to_auth_context_success() {
+  tsi_peer peer;
+  grpc_auth_context* ctx;
+  GPR_ASSERT(tsi_construct_peer(kTsiAltsNumOfPeerProperties, &peer) == TSI_OK);
+  GPR_ASSERT(tsi_construct_string_peer_property_from_cstring(
+                 TSI_CERTIFICATE_TYPE_PEER_PROPERTY, TSI_ALTS_CERTIFICATE_TYPE,
+                 &peer.properties[0]) == TSI_OK);
+  GPR_ASSERT(tsi_construct_string_peer_property_from_cstring(
+                 TSI_ALTS_SERVICE_ACCOUNT_PEER_PROPERTY, "alice",
+                 &peer.properties[1]) == TSI_OK);
+  grpc_gcp_rpc_protocol_versions peer_versions;
+  grpc_gcp_rpc_protocol_versions_set_max(&peer_versions,
+                                         GRPC_PROTOCOL_VERSION_MAX_MAJOR,
+                                         GRPC_PROTOCOL_VERSION_MAX_MINOR);
+  grpc_gcp_rpc_protocol_versions_set_min(&peer_versions,
+                                         GRPC_PROTOCOL_VERSION_MIN_MAJOR,
+                                         GRPC_PROTOCOL_VERSION_MIN_MINOR);
+  grpc_slice serialized_peer_versions;
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_encode(&peer_versions,
+                                                   &serialized_peer_versions));
+
+  GPR_ASSERT(tsi_construct_string_peer_property(
+                 TSI_ALTS_RPC_VERSIONS,
+                 reinterpret_cast<char*>(
+                     GRPC_SLICE_START_PTR(serialized_peer_versions)),
+                 GRPC_SLICE_LENGTH(serialized_peer_versions),
+                 &peer.properties[2]) == TSI_OK);
+  GPR_ASSERT(grpc_alts_auth_context_from_tsi_peer(&peer, &ctx) ==
+             GRPC_SECURITY_OK);
+  GPR_ASSERT(
+      test_identity(ctx, TSI_ALTS_SERVICE_ACCOUNT_PEER_PROPERTY, "alice"));
+  GRPC_AUTH_CONTEXT_UNREF(ctx, "test");
+  grpc_slice_unref(serialized_peer_versions);
+  tsi_peer_destruct(&peer);
+}
+
+int main(int argc, char** argv) {
+  /* Test. */
+  test_invalid_input_failure();
+  test_empty_certificate_type_failure();
+  test_empty_peer_property_failure();
+  test_unknown_peer_property_failure();
+  test_missing_rpc_protocol_versions_property_failure();
+  test_alts_peer_to_auth_context_success();
+
+  return 0;
+}
diff --git a/test/core/security/check_gcp_environment_linux_test.cc b/test/core/security/check_gcp_environment_linux_test.cc
new file mode 100644
index 0000000..6c436a3
--- /dev/null
+++ b/test/core/security/check_gcp_environment_linux_test.cc
@@ -0,0 +1,83 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/security/credentials/alts/check_gcp_environment.h"
+
+#if GPR_LINUX
+
+#include <stdio.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/gpr/tmpfile.h"
+
+static bool check_bios_data_linux_test(const char* data) {
+  /* Create a file with contents data. */
+  char* filename = nullptr;
+  FILE* fp = gpr_tmpfile("check_gcp_environment_test", &filename);
+  GPR_ASSERT(filename != nullptr);
+  GPR_ASSERT(fp != nullptr);
+  GPR_ASSERT(fwrite(data, 1, strlen(data), fp) == strlen(data));
+  fclose(fp);
+  bool result = grpc_core::internal::check_bios_data(
+      reinterpret_cast<const char*>(filename));
+  /* Cleanup. */
+  remove(filename);
+  gpr_free(filename);
+  return result;
+}
+
+static void test_gcp_environment_check_success() {
+  /* Exact match. */
+  GPR_ASSERT(check_bios_data_linux_test("Google"));
+  GPR_ASSERT(check_bios_data_linux_test("Google Compute Engine"));
+  /* With leading and trailing whitespaces. */
+  GPR_ASSERT(check_bios_data_linux_test(" Google  "));
+  GPR_ASSERT(check_bios_data_linux_test("Google  "));
+  GPR_ASSERT(check_bios_data_linux_test("   Google"));
+  GPR_ASSERT(check_bios_data_linux_test("  Google Compute Engine  "));
+  GPR_ASSERT(check_bios_data_linux_test("Google Compute Engine  "));
+  GPR_ASSERT(check_bios_data_linux_test("  Google Compute Engine"));
+  /* With leading and trailing \t and \n. */
+  GPR_ASSERT(check_bios_data_linux_test("\t\tGoogle Compute Engine\t"));
+  GPR_ASSERT(check_bios_data_linux_test("Google Compute Engine\n"));
+  GPR_ASSERT(check_bios_data_linux_test("\n\n\tGoogle Compute Engine \n\t\t"));
+}
+
+static void test_gcp_environment_check_failure() {
+  GPR_ASSERT(!check_bios_data_linux_test("non_existing-file"));
+  GPR_ASSERT(!check_bios_data_linux_test("Google-Chrome"));
+  GPR_ASSERT(!check_bios_data_linux_test("Amazon"));
+  GPR_ASSERT(!check_bios_data_linux_test("Google-Chrome\t\t"));
+  GPR_ASSERT(!check_bios_data_linux_test("Amazon"));
+}
+
+int main(int argc, char** argv) {
+  /* Tests. */
+  test_gcp_environment_check_success();
+  test_gcp_environment_check_failure();
+  return 0;
+}
+
+#else  // GPR_LINUX
+
+int main(int argc, char** argv) { return 0; }
+
+#endif  // GPR_LINUX
diff --git a/test/core/security/check_gcp_environment_windows_test.cc b/test/core/security/check_gcp_environment_windows_test.cc
new file mode 100644
index 0000000..46179b7
--- /dev/null
+++ b/test/core/security/check_gcp_environment_windows_test.cc
@@ -0,0 +1,71 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/security/credentials/alts/check_gcp_environment.h"
+
+#ifdef GPR_WINDOWS
+
+#include <stdio.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include "src/core/lib/gpr/tmpfile.h"
+
+static bool check_bios_data_windows_test(const char* data) {
+  /* Create a file with contents data. */
+  char* filename = nullptr;
+  FILE* fp = gpr_tmpfile("check_gcp_environment_test", &filename);
+  GPR_ASSERT(filename != nullptr);
+  GPR_ASSERT(fp != nullptr);
+  GPR_ASSERT(fwrite(data, 1, strlen(data), fp) == strlen(data));
+  fclose(fp);
+  bool result = grpc_core::internal::check_bios_data(
+      reinterpret_cast<const char*>(filename));
+  /* Cleanup. */
+  remove(filename);
+  gpr_free(filename);
+  return result;
+}
+
+static void test_gcp_environment_check_success() {
+  GPR_ASSERT(check_bios_data_windows_test("Google"));
+  GPR_ASSERT(check_bios_data_windows_test("Google\n"));
+  GPR_ASSERT(check_bios_data_windows_test("Google\r"));
+  GPR_ASSERT(check_bios_data_windows_test("Google\r\n"));
+  GPR_ASSERT(check_bios_data_windows_test("   Google   \r\n"));
+  GPR_ASSERT(check_bios_data_windows_test(" \t\t Google\r\n"));
+  GPR_ASSERT(check_bios_data_windows_test(" \t\t Google\t\t  \r\n"));
+}
+
+static void test_gcp_environment_check_failure() {
+  GPR_ASSERT(!check_bios_data_windows_test("\t\tAmazon\n"));
+  GPR_ASSERT(!check_bios_data_windows_test("  Amazon\r\n"));
+}
+
+int main(int argc, char** argv) {
+  /* Tests. */
+  test_gcp_environment_check_success();
+  test_gcp_environment_check_failure();
+  return 0;
+}
+#else  // GPR_WINDOWS
+
+int main(int argc, char** argv) { return 0; }
+
+#endif  // GPR_WINDOWS
diff --git a/test/core/security/grpc_alts_credentials_options_test.cc b/test/core/security/grpc_alts_credentials_options_test.cc
new file mode 100644
index 0000000..1217065
--- /dev/null
+++ b/test/core/security/grpc_alts_credentials_options_test.cc
@@ -0,0 +1,118 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <grpc/grpc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h"
+
+#define ALTS_CLIENT_OPTIONS_TEST_TARGET_SERVICE_ACCOUNT_1 "abc@google.com"
+#define ALTS_CLIENT_OPTIONS_TEST_TARGET_SERVICE_ACCOUNT_2 "def@google.com"
+
+const size_t kTargetServiceAccountNum = 2;
+
+static void test_add_target_service_account_failure() {
+  /* Initialization. */
+  grpc_alts_credentials_options* options =
+      grpc_alts_credentials_client_options_create();
+  auto client_options =
+      reinterpret_cast<grpc_alts_credentials_client_options*>(options);
+
+  /* Test. */
+  GPR_ASSERT(!grpc_alts_credentials_client_options_add_target_service_account(
+      client_options, nullptr));
+  GPR_ASSERT(!grpc_alts_credentials_client_options_add_target_service_account(
+      nullptr, ALTS_CLIENT_OPTIONS_TEST_TARGET_SERVICE_ACCOUNT_1));
+
+  /* Cleanup. */
+  grpc_alts_credentials_options_destroy(options);
+}
+
+static void test_copy_client_options_failure() {
+  /* Initialization. */
+  grpc_alts_credentials_options* options =
+      grpc_alts_credentials_client_options_create();
+
+  /* Test. */
+  GPR_ASSERT(grpc_alts_credentials_options_copy(nullptr) == nullptr);
+
+  /* Cleanup. */
+  grpc_alts_credentials_options_destroy(options);
+}
+
+static size_t get_target_service_account_num(
+    grpc_alts_credentials_client_options* options) {
+  size_t num = 0;
+  target_service_account* node = options->target_account_list_head;
+  while (node != nullptr) {
+    num++;
+    node = node->next;
+  }
+  return num;
+}
+
+static void test_client_options_api_success() {
+  /* Initialization. */
+  grpc_alts_credentials_options* options =
+      grpc_alts_credentials_client_options_create();
+  auto client_options =
+      reinterpret_cast<grpc_alts_credentials_client_options*>(options);
+
+  /* Set client options fields. */
+  grpc_alts_credentials_client_options_add_target_service_account(
+      client_options, ALTS_CLIENT_OPTIONS_TEST_TARGET_SERVICE_ACCOUNT_1);
+  grpc_alts_credentials_client_options_add_target_service_account(
+      client_options, ALTS_CLIENT_OPTIONS_TEST_TARGET_SERVICE_ACCOUNT_2);
+
+  /* Validate client option fields. */
+  GPR_ASSERT(get_target_service_account_num(client_options) ==
+             kTargetServiceAccountNum);
+  GPR_ASSERT(strcmp(client_options->target_account_list_head->data,
+                    ALTS_CLIENT_OPTIONS_TEST_TARGET_SERVICE_ACCOUNT_2) == 0);
+  GPR_ASSERT(strcmp(client_options->target_account_list_head->next->data,
+                    ALTS_CLIENT_OPTIONS_TEST_TARGET_SERVICE_ACCOUNT_1) == 0);
+
+  /* Perform a copy operation and validate its correctness. */
+  grpc_alts_credentials_options* new_options =
+      grpc_alts_credentials_options_copy(options);
+  auto new_client_options =
+      reinterpret_cast<grpc_alts_credentials_client_options*>(new_options);
+
+  GPR_ASSERT(get_target_service_account_num(new_client_options) ==
+             kTargetServiceAccountNum);
+  GPR_ASSERT(strcmp(new_client_options->target_account_list_head->data,
+                    ALTS_CLIENT_OPTIONS_TEST_TARGET_SERVICE_ACCOUNT_2) == 0);
+  GPR_ASSERT(strcmp(new_client_options->target_account_list_head->next->data,
+                    ALTS_CLIENT_OPTIONS_TEST_TARGET_SERVICE_ACCOUNT_1) == 0);
+
+  /* Cleanup.*/
+  grpc_alts_credentials_options_destroy(options);
+  grpc_alts_credentials_options_destroy(new_options);
+}
+
+int main(int argc, char** argv) {
+  /* Test. */
+  test_add_target_service_account_failure();
+  test_copy_client_options_failure();
+  test_client_options_api_success();
+  return 0;
+}
diff --git a/test/core/tsi/BUILD b/test/core/tsi/BUILD
index e28c0b5..8ac3e76 100644
--- a/test/core/tsi/BUILD
+++ b/test/core/tsi/BUILD
@@ -16,7 +16,7 @@
 
 licenses(["notice"])  # Apache v2
 
-grpc_package(name = "test/core/tsi")
+grpc_package(name = "test/core/tsi", visibility = "public")
 
 grpc_cc_library(
     name = "transport_security_test_lib",
diff --git a/test/core/tsi/alts/crypt/BUILD b/test/core/tsi/alts/crypt/BUILD
new file mode 100644
index 0000000..0057d7f
--- /dev/null
+++ b/test/core/tsi/alts/crypt/BUILD
@@ -0,0 +1,38 @@
+# Copyright 2018 gRPC authors.
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+load("//bazel:grpc_build_system.bzl", "grpc_cc_library", "grpc_cc_test", "grpc_package")
+
+licenses(["notice"])  # Apache v2
+
+grpc_package(name = "crypt", visibility = "public")
+
+grpc_cc_library(
+    name = "alts_crypt_test_util",
+    srcs = ["gsec_test_util.cc"],
+    hdrs = ["gsec_test_util.h"],
+    deps = [
+        "//:grpc",
+    ],
+)
+
+grpc_cc_test(
+    name = "alts_crypt_test",
+    srcs = ["aes_gcm_test.cc"],
+    language = "C++",
+    deps = [
+        ":alts_crypt_test_util",
+        "//:grpc",
+    ],
+)
diff --git a/test/core/tsi/alts/crypt/aes_gcm_test.cc b/test/core/tsi/alts/crypt/aes_gcm_test.cc
new file mode 100644
index 0000000..576dd8f
--- /dev/null
+++ b/test/core/tsi/alts/crypt/aes_gcm_test.cc
@@ -0,0 +1,2105 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/tsi/alts/crypt/gsec.h"
+#include "test/core/tsi/alts/crypt/gsec_test_util.h"
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+const size_t kTestMinTagLengthForCorruption = 8;
+const size_t kTestNumCrypters = 3;
+const size_t kTestMaxSlices = 5;
+const size_t kTestMaxLength = 1024;
+const size_t kTestNumEncryptions = 100;
+
+/* Struct for pre-generated test vector */
+typedef struct gsec_aead_test_vector {
+  uint8_t* nonce;
+  uint8_t* aad;
+  uint8_t* key;
+  uint8_t* plaintext;
+  uint8_t* ciphertext_and_tag;
+  size_t nonce_length;
+  size_t aad_length;
+  size_t key_length;
+  size_t plaintext_length;
+  size_t ciphertext_and_tag_length;
+} gsec_aead_test_vector;
+
+static void gsec_randomly_slice(uint8_t* input, size_t input_length,
+                                struct iovec** output, size_t* output_length) {
+  if (input_length == 0) {
+    *output = nullptr;
+    *output_length = 0;
+    return;
+  }
+  *output_length = gsec_test_bias_random_uint32(kTestMaxSlices) + 1;
+  *output =
+      static_cast<struct iovec*>(malloc(*output_length * sizeof(**output)));
+  size_t i;
+  for (i = 0; i < *output_length - 1; i++) {
+    size_t slice_length =
+        gsec_test_bias_random_uint32(static_cast<uint32_t>(input_length));
+    struct iovec slice = {input, slice_length};
+    (*output)[i] = slice;
+    input += slice_length;
+    input_length -= slice_length;
+  }
+  struct iovec slice = {input, input_length};
+  (*output)[*output_length - 1] = slice;
+}
+
+static void gsec_assert_ok(grpc_status_code status, const char* error_detail) {
+  char empty_string[] = "";
+  if (error_detail == nullptr) {
+    error_detail = empty_string;
+  }
+  if (status != GRPC_STATUS_OK) {
+    fprintf(stderr, "Status is not ok: %s\n", error_detail);
+  }
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+}
+
+static void gsec_test_random_encrypt_decrypt(gsec_aead_crypter* crypter,
+                                             size_t aad_length,
+                                             size_t message_length) {
+  GPR_ASSERT(crypter != nullptr);
+  size_t nonce_length, tag_length;
+  uint8_t *nonce, *aad, *message;
+  gsec_aead_crypter_nonce_length(crypter, &nonce_length, nullptr);
+  gsec_aead_crypter_tag_length(crypter, &tag_length, nullptr);
+
+  gsec_test_random_array(&nonce, nonce_length);
+  gsec_test_random_array(&aad, aad_length);
+  gsec_test_random_array(&message, message_length);
+
+  /* Test encryption  */
+  size_t ciphertext_and_tag_length, ciphertext_bytes_written = 0;
+  gsec_aead_crypter_max_ciphertext_and_tag_length(
+      crypter, message_length, &ciphertext_and_tag_length, nullptr);
+
+  uint8_t* ciphertext_and_tag =
+      static_cast<uint8_t*>(gpr_malloc(ciphertext_and_tag_length));
+
+  char* error_buffer = nullptr;
+  gsec_assert_ok(
+      gsec_aead_crypter_encrypt(crypter, nonce, nonce_length, aad, aad_length,
+                                message, message_length, ciphertext_and_tag,
+                                ciphertext_and_tag_length,
+                                &ciphertext_bytes_written, &error_buffer),
+      error_buffer);
+  GPR_ASSERT(message_length + tag_length == ciphertext_and_tag_length);
+  GPR_ASSERT(ciphertext_bytes_written == ciphertext_and_tag_length);
+
+  /* Test decryption */
+  size_t plaintext_length, plaintext_bytes_written = 0;
+  gsec_aead_crypter_max_plaintext_length(crypter, ciphertext_bytes_written,
+                                         &plaintext_length, nullptr);
+  uint8_t* plaintext = static_cast<uint8_t*>(gpr_malloc(plaintext_length));
+  grpc_status_code status = gsec_aead_crypter_decrypt(
+      crypter, nonce, nonce_length, aad, aad_length, ciphertext_and_tag,
+      ciphertext_bytes_written, plaintext, plaintext_length,
+      &plaintext_bytes_written, nullptr);
+
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(message_length == plaintext_bytes_written);
+  GPR_ASSERT(memcmp(message, plaintext, message_length) == 0);
+
+  /**
+   * The returned plaintext will be zeroed if there was an authentication error.
+   */
+  uint8_t* zero_message = static_cast<uint8_t*>(gpr_zalloc(plaintext_length));
+  if (tag_length >= kTestMinTagLengthForCorruption) {
+    char* error_message;
+    /* Corrupt nonce */
+    if (nonce_length > 0) {
+      plaintext_bytes_written = 0;
+      uint8_t* corrupt_nonce;
+      gsec_test_copy_and_alter_random_byte(nonce, &corrupt_nonce, nonce_length);
+      status = gsec_aead_crypter_decrypt(
+          crypter, corrupt_nonce, nonce_length, aad, aad_length,
+          ciphertext_and_tag, ciphertext_bytes_written, plaintext,
+          plaintext_length, &plaintext_bytes_written, &error_message);
+
+      GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+          status, GRPC_STATUS_FAILED_PRECONDITION, "Checking tag failed.",
+          error_message));
+      GPR_ASSERT(plaintext_bytes_written == 0);
+      GPR_ASSERT(memcmp(zero_message, plaintext, plaintext_length) == 0);
+      gpr_free(corrupt_nonce);
+      gpr_free(error_message);
+    }
+
+    /* Corrupt ciphertext_and_tag */
+    plaintext_bytes_written = 0;
+    uint8_t* corrupt_ciphertext_and_tag;
+    gsec_test_copy_and_alter_random_byte(ciphertext_and_tag,
+                                         &corrupt_ciphertext_and_tag,
+                                         ciphertext_and_tag_length);
+    status = gsec_aead_crypter_decrypt(
+        crypter, nonce, nonce_length, aad, aad_length,
+        corrupt_ciphertext_and_tag, ciphertext_bytes_written, plaintext,
+        plaintext_length, &plaintext_bytes_written, &error_message);
+
+    GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+        status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+        "Checking tag failed"));
+    GPR_ASSERT(plaintext_bytes_written == 0);
+    GPR_ASSERT(memcmp(zero_message, plaintext, plaintext_length) == 0);
+    gpr_free(error_message);
+    gpr_free(corrupt_ciphertext_and_tag);
+
+    /* Corrupt start of ciphertext_and_tag */
+    plaintext_bytes_written = 0;
+    gsec_test_copy(ciphertext_and_tag, &corrupt_ciphertext_and_tag,
+                   ciphertext_and_tag_length);
+    (*corrupt_ciphertext_and_tag)++;
+    status = gsec_aead_crypter_decrypt(
+        crypter, nonce, nonce_length, aad, aad_length,
+        corrupt_ciphertext_and_tag, ciphertext_bytes_written, plaintext,
+        plaintext_length, &plaintext_bytes_written, &error_message);
+    GPR_ASSERT(plaintext_bytes_written == 0);
+    GPR_ASSERT(memcmp(zero_message, plaintext, plaintext_length) == 0);
+    GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+        status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+        "Checking tag failed"));
+    gpr_free(error_message);
+    gpr_free(corrupt_ciphertext_and_tag);
+
+    /* Corrupt end of ciphertext_and_tag */
+    plaintext_bytes_written = 0;
+    gsec_test_copy(ciphertext_and_tag, &corrupt_ciphertext_and_tag,
+                   ciphertext_and_tag_length);
+    (*(corrupt_ciphertext_and_tag + ciphertext_and_tag_length - 1))++;
+
+    status = gsec_aead_crypter_decrypt(
+        crypter, nonce, nonce_length, aad, aad_length,
+        corrupt_ciphertext_and_tag, ciphertext_bytes_written, plaintext,
+        plaintext_length, &plaintext_bytes_written, &error_message);
+
+    GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+        status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+        "Checking tag failed"));
+    GPR_ASSERT(plaintext_bytes_written == 0);
+    GPR_ASSERT(memcmp(zero_message, plaintext, plaintext_length) == 0);
+    gpr_free(error_message);
+    gpr_free(corrupt_ciphertext_and_tag);
+  }
+
+  gpr_free(zero_message);
+  gpr_free(nonce);
+  gpr_free(aad);
+  gpr_free(message);
+  gpr_free(plaintext);
+  gpr_free(ciphertext_and_tag);
+}
+
+static void gsec_test_encrypt_decrypt(gsec_aead_crypter* crypter) {
+  GPR_ASSERT(crypter != nullptr);
+  size_t aad_length, message_length;
+  aad_length = gsec_test_bias_random_uint32(kTestMaxLength);
+  message_length = gsec_test_bias_random_uint32(kTestMaxLength);
+  gsec_test_random_encrypt_decrypt(crypter, aad_length, message_length);
+  gsec_test_random_encrypt_decrypt(crypter, 0, message_length);
+  gsec_test_random_encrypt_decrypt(crypter, aad_length, 0);
+}
+
+static void gsec_test_multiple_random_encrypt_decrypt(
+    gsec_aead_crypter* crypter, size_t* aad_lengths, size_t* message_lengths,
+    size_t count) {
+  GPR_ASSERT(crypter != nullptr);
+  size_t nonce_length, tag_length;
+  uint8_t **nonces, **aads, **messages;
+  nonces = static_cast<uint8_t**>(gpr_malloc(sizeof(uint8_t*) * count));
+  aads = static_cast<uint8_t**>(gpr_malloc(sizeof(uint8_t*) * count));
+  messages = static_cast<uint8_t**>(gpr_malloc(sizeof(uint8_t*) * count));
+
+  gsec_aead_crypter_nonce_length(crypter, &nonce_length, nullptr);
+  gsec_aead_crypter_tag_length(crypter, &tag_length, nullptr);
+
+  size_t ind;
+  for (ind = 0; ind < count; ind++) {
+    size_t aad_length = (aad_lengths == nullptr) ? 0 : aad_lengths[ind];
+    size_t message_length =
+        (message_lengths == nullptr) ? 0 : message_lengths[ind];
+    gsec_test_random_array(&(nonces[ind]), nonce_length);
+    gsec_test_random_array(&(aads[ind]), aad_length);
+    gsec_test_random_array(&(messages[ind]), message_length);
+  }
+
+  size_t* ciphertext_and_tag_lengths =
+      static_cast<size_t*>(gpr_malloc(sizeof(size_t) * count));
+  size_t* ciphertext_bytes_writtens =
+      static_cast<size_t*>(gpr_malloc(sizeof(size_t) * count));
+  size_t* plaintext_lengths =
+      static_cast<size_t*>(gpr_malloc(sizeof(size_t) * count));
+  size_t* plaintext_bytes_writtens =
+      static_cast<size_t*>(gpr_malloc(sizeof(size_t) * count));
+  uint8_t** ciphertext_and_tags =
+      static_cast<uint8_t**>(gpr_malloc(sizeof(uint8_t*) * count));
+  uint8_t** plaintexts =
+      static_cast<uint8_t**>(gpr_malloc(sizeof(uint8_t*) * count));
+
+  /* Do encryption */
+  for (ind = 0; ind < count; ind++) {
+    size_t aad_length = (aad_lengths == nullptr) ? 0 : aad_lengths[ind];
+    size_t message_length =
+        (message_lengths == nullptr) ? 0 : message_lengths[ind];
+    gsec_aead_crypter_max_ciphertext_and_tag_length(
+        crypter, message_length, &(ciphertext_and_tag_lengths[ind]), nullptr);
+    ciphertext_and_tags[ind] =
+        static_cast<uint8_t*>(gpr_malloc(ciphertext_and_tag_lengths[ind]));
+    grpc_status_code status = gsec_aead_crypter_encrypt(
+        crypter, nonces[ind], nonce_length, aads[ind], aad_length,
+        messages[ind], message_length, ciphertext_and_tags[ind],
+        ciphertext_and_tag_lengths[ind], &(ciphertext_bytes_writtens[ind]),
+        nullptr);
+    GPR_ASSERT(status == GRPC_STATUS_OK);
+    GPR_ASSERT(message_length + tag_length == ciphertext_and_tag_lengths[ind]);
+    GPR_ASSERT(ciphertext_bytes_writtens[ind] ==
+               ciphertext_and_tag_lengths[ind]);
+  }
+  /* Do Decryption */
+  for (ind = 0; ind < count; ind++) {
+    size_t aad_length = (aad_lengths == nullptr) ? 0 : aad_lengths[ind];
+    size_t message_length =
+        (message_lengths == nullptr) ? 0 : message_lengths[ind];
+    gsec_aead_crypter_max_plaintext_length(crypter,
+                                           ciphertext_bytes_writtens[ind],
+                                           &(plaintext_lengths[ind]), nullptr);
+    plaintexts[ind] = static_cast<uint8_t*>(gpr_malloc(plaintext_lengths[ind]));
+    grpc_status_code status = gsec_aead_crypter_decrypt(
+        crypter, nonces[ind], nonce_length, aads[ind], aad_length,
+        ciphertext_and_tags[ind], ciphertext_bytes_writtens[ind],
+        plaintexts[ind], plaintext_lengths[ind],
+        &(plaintext_bytes_writtens[ind]), nullptr);
+    GPR_ASSERT(status == GRPC_STATUS_OK);
+    GPR_ASSERT(message_length == plaintext_bytes_writtens[ind]);
+    GPR_ASSERT(memcmp(messages[ind], plaintexts[ind], message_length) == 0);
+  }
+
+  /* Slice the plaintext and encrypt with iovecs */
+  for (ind = 0; ind < count; ind++) {
+    size_t aad_length = (aad_lengths == nullptr) ? 0 : aad_lengths[ind];
+    struct iovec* aad_vecs = nullptr;
+    size_t aad_vecs_length = 0;
+    gsec_randomly_slice(aads[ind], aad_length, &aad_vecs, &aad_vecs_length);
+    size_t message_length =
+        (message_lengths == nullptr) ? 0 : message_lengths[ind];
+    struct iovec* message_vecs = nullptr;
+    size_t message_vecs_length = 0;
+    gsec_randomly_slice(messages[ind], message_length, &message_vecs,
+                        &message_vecs_length);
+
+    size_t ciphertext_length = ciphertext_and_tag_lengths[ind];
+    uint8_t* another_ciphertext =
+        static_cast<uint8_t*>(malloc(ciphertext_length));
+    struct iovec another_ciphertext_vec = {another_ciphertext,
+                                           ciphertext_length};
+
+    char* error_details = nullptr;
+    size_t ciphertext_bytes_written = 0;
+    gsec_assert_ok(
+        gsec_aead_crypter_encrypt_iovec(
+            crypter, nonces[ind], nonce_length, aad_vecs, aad_vecs_length,
+            message_vecs, message_vecs_length, another_ciphertext_vec,
+            &ciphertext_bytes_written, &error_details),
+        error_details);
+    GPR_ASSERT(memcmp(ciphertext_and_tags[ind], another_ciphertext_vec.iov_base,
+                      ciphertext_length) == 0);
+    free(another_ciphertext);
+    free(aad_vecs);
+    free(message_vecs);
+  }
+
+  /* Slice the ciphertext and decrypt with iovecs */
+  for (ind = 0; ind < count; ind++) {
+    size_t message_length =
+        (message_lengths == nullptr) ? 0 : message_lengths[ind];
+    message_length = message_length + 0;
+
+    size_t aad_length = (aad_lengths == nullptr) ? 0 : aad_lengths[ind];
+
+    struct iovec* aad_vecs = nullptr;
+    size_t aad_vecs_length = 0;
+    gsec_randomly_slice(aads[ind], aad_length, &aad_vecs, &aad_vecs_length);
+
+    struct iovec* ciphertext_vecs = nullptr;
+    size_t ciphertext_vecs_length = 0;
+    gsec_randomly_slice(ciphertext_and_tags[ind],
+                        ciphertext_bytes_writtens[ind], &ciphertext_vecs,
+                        &ciphertext_vecs_length);
+
+    size_t decrypted_length = plaintext_lengths[ind];
+    uint8_t* decrypted = static_cast<uint8_t*>(malloc(decrypted_length));
+    struct iovec decrypted_vec = {decrypted, decrypted_length};
+
+    char* error_details = nullptr;
+    gsec_assert_ok(gsec_aead_crypter_decrypt_iovec(
+                       crypter, nonces[ind], nonce_length, aad_vecs,
+                       aad_vecs_length, ciphertext_vecs, ciphertext_vecs_length,
+                       decrypted_vec, &decrypted_length, &error_details),
+                   error_details);
+    GPR_ASSERT(decrypted_vec.iov_len == message_length);
+    GPR_ASSERT(memcmp(decrypted_vec.iov_base, messages[ind], message_length) ==
+               0);
+    free(decrypted);
+    free(aad_vecs);
+    free(ciphertext_vecs);
+  }
+
+  for (ind = 0; ind < count; ind++) {
+    gpr_free(nonces[ind]);
+    gpr_free(aads[ind]);
+    gpr_free(messages[ind]);
+    gpr_free(ciphertext_and_tags[ind]);
+    gpr_free(plaintexts[ind]);
+  }
+  gpr_free(nonces);
+  gpr_free(aads);
+  gpr_free(messages);
+  gpr_free(ciphertext_and_tag_lengths);
+  gpr_free(ciphertext_bytes_writtens);
+  gpr_free(plaintext_lengths);
+  gpr_free(plaintext_bytes_writtens);
+  gpr_free(ciphertext_and_tags);
+  gpr_free(plaintexts);
+}
+
+static void gsec_test_multiple_encrypt_decrypt(gsec_aead_crypter* crypter) {
+  GPR_ASSERT(crypter != nullptr);
+  size_t count = kTestNumEncryptions;
+  size_t* aad_lengths =
+      static_cast<size_t*>(gpr_malloc(sizeof(size_t) * count));
+  size_t* message_lengths =
+      static_cast<size_t*>(gpr_malloc(sizeof(size_t) * count));
+  size_t ind;
+  for (ind = 0; ind < count; ind++) {
+    aad_lengths[ind] = gsec_test_bias_random_uint32(kTestMaxLength);
+    message_lengths[ind] = gsec_test_bias_random_uint32(kTestMaxLength);
+  }
+  gsec_test_multiple_random_encrypt_decrypt(crypter, aad_lengths,
+                                            message_lengths, count);
+  gsec_test_multiple_random_encrypt_decrypt(crypter, aad_lengths, nullptr,
+                                            count);
+  gsec_test_multiple_random_encrypt_decrypt(crypter, nullptr, message_lengths,
+                                            count);
+  gpr_free(aad_lengths);
+  gpr_free(message_lengths);
+}
+
+static void gsec_test_encryption_failure(gsec_aead_crypter* crypter) {
+  GPR_ASSERT(crypter != nullptr);
+  size_t aad_length = kTestMaxLength;
+  size_t message_length = kTestMaxLength;
+  size_t nonce_length;
+
+  char* error_message;
+  uint8_t *nonce, *aad, *message;
+
+  gsec_aead_crypter_nonce_length(crypter, &nonce_length, nullptr);
+  gsec_test_random_array(&nonce, nonce_length);
+  gsec_test_random_array(&aad, aad_length);
+  gsec_test_random_array(&message, message_length);
+
+  size_t ciphertext_and_tag_length, ciphertext_bytes_written = 0;
+  gsec_aead_crypter_max_ciphertext_and_tag_length(
+      crypter, message_length, &ciphertext_and_tag_length, nullptr);
+  uint8_t* ciphertext_and_tag =
+      static_cast<uint8_t*>(gpr_malloc(ciphertext_and_tag_length));
+
+  /* nullptr nonce */
+  grpc_status_code status = gsec_aead_crypter_encrypt(
+      crypter, nullptr, nonce_length, aad, aad_length, message, message_length,
+      ciphertext_and_tag, ciphertext_and_tag_length, &ciphertext_bytes_written,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Nonce buffer is nullptr."));
+  gpr_free(error_message);
+
+  /* Big nonce */
+  status = gsec_aead_crypter_encrypt(
+      crypter, nonce, nonce_length + 1, aad, aad_length, message,
+      message_length, ciphertext_and_tag, ciphertext_and_tag_length,
+      &ciphertext_bytes_written, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Nonce buffer has the wrong length."));
+  gpr_free(error_message);
+
+  /* Small nonce */
+  status = gsec_aead_crypter_encrypt(
+      crypter, nonce, nonce_length - 1, aad, aad_length, message,
+      message_length, ciphertext_and_tag, ciphertext_and_tag_length,
+      &ciphertext_bytes_written, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Nonce buffer has the wrong length."));
+  gpr_free(error_message);
+
+  /* nullptr aad */
+  status = gsec_aead_crypter_encrypt(
+      crypter, nonce, nonce_length, nullptr, aad_length, message,
+      message_length, ciphertext_and_tag, ciphertext_and_tag_length,
+      &ciphertext_bytes_written, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message, "aad is nullptr."));
+  gpr_free(error_message);
+
+  /* nullptr aad with zero length */
+  gsec_assert_ok(
+      gsec_aead_crypter_encrypt(crypter, nonce, nonce_length, nullptr, 0,
+                                message, message_length, ciphertext_and_tag,
+                                ciphertext_and_tag_length,
+                                &ciphertext_bytes_written, &error_message),
+      error_message);
+
+  /* nullptr plaintext */
+  status = gsec_aead_crypter_encrypt(
+      crypter, nonce, nonce_length, aad, aad_length, nullptr, message_length,
+      ciphertext_and_tag, ciphertext_and_tag_length, &ciphertext_bytes_written,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "plaintext is nullptr."));
+  gpr_free(error_message);
+
+  /* nullptr ciphertext */
+  status = gsec_aead_crypter_encrypt(crypter, nonce, nonce_length, aad,
+                                     aad_length, message, message_length,
+                                     nullptr, ciphertext_and_tag_length,
+                                     &ciphertext_bytes_written, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "ciphertext is nullptr."));
+  gpr_free(error_message);
+
+  /* Short ciphertext */
+  status = gsec_aead_crypter_encrypt(
+      crypter, nonce, nonce_length, aad, aad_length, message, message_length,
+      ciphertext_and_tag, ciphertext_and_tag_length - 1,
+      &ciphertext_bytes_written, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "ciphertext is too small to hold a tag."));
+  gpr_free(error_message);
+
+  /* nullptr ciphertext_bytes_written */
+  status = gsec_aead_crypter_encrypt(
+      crypter, nonce, nonce_length, aad, aad_length, message, message_length,
+      ciphertext_and_tag, ciphertext_and_tag_length, nullptr, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "bytes_written is nullptr."));
+  gpr_free(error_message);
+
+  /* nullptr plaintext/ciphertext encrypt with zero length */
+  gsec_assert_ok(gsec_aead_crypter_encrypt(
+                     crypter, nonce, nonce_length, aad, aad_length, nullptr, 0,
+                     ciphertext_and_tag, ciphertext_and_tag_length,
+                     &ciphertext_bytes_written, &error_message),
+                 error_message);
+
+  /* Success */
+  status = gsec_aead_crypter_encrypt(
+      crypter, nonce, nonce_length, aad, aad_length, message, message_length,
+      ciphertext_and_tag, ciphertext_and_tag_length, &ciphertext_bytes_written,
+      &error_message);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+
+  gpr_free(message);
+  gpr_free(aad);
+  gpr_free(nonce);
+  gpr_free(ciphertext_and_tag);
+}
+
+static void gsec_test_decryption_failure(gsec_aead_crypter* crypter) {
+  GPR_ASSERT(crypter != nullptr);
+  size_t aad_length = kTestMaxLength;
+  size_t message_length = kTestMaxLength;
+  size_t nonce_length, tag_length;
+  uint8_t *nonce, *aad, *message;
+
+  gsec_aead_crypter_nonce_length(crypter, &nonce_length, nullptr);
+  gsec_aead_crypter_tag_length(crypter, &tag_length, nullptr);
+  gsec_test_random_array(&nonce, nonce_length);
+  gsec_test_random_array(&aad, aad_length);
+  gsec_test_random_array(&message, message_length);
+
+  /* Test encryption */
+  size_t ciphertext_and_tag_length, ciphertext_bytes_written = 0;
+  gsec_aead_crypter_max_ciphertext_and_tag_length(
+      crypter, message_length, &ciphertext_and_tag_length, nullptr);
+  uint8_t* ciphertext_and_tag =
+      static_cast<uint8_t*>(gpr_malloc(ciphertext_and_tag_length));
+
+  grpc_status_code status = gsec_aead_crypter_encrypt(
+      crypter, nonce, nonce_length, aad, aad_length, message, message_length,
+      ciphertext_and_tag, ciphertext_and_tag_length, &ciphertext_bytes_written,
+      nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(ciphertext_bytes_written == ciphertext_and_tag_length);
+
+  size_t plaintext_length, plaintext_bytes_written = 0;
+  gsec_aead_crypter_max_plaintext_length(crypter, ciphertext_bytes_written,
+                                         &plaintext_length, nullptr);
+  uint8_t* plaintext = static_cast<uint8_t*>(gpr_malloc(plaintext_length));
+
+  char* error_message;
+  /* nullptr nonce */
+  status = gsec_aead_crypter_decrypt(
+      crypter, nullptr, nonce_length, aad, aad_length, ciphertext_and_tag,
+      ciphertext_and_tag_length, plaintext, plaintext_length,
+      &plaintext_bytes_written, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Nonce buffer is nullptr."));
+  gpr_free(error_message);
+
+  /* Big nonce */
+  status = gsec_aead_crypter_decrypt(
+      crypter, nonce, nonce_length + 1, aad, aad_length, ciphertext_and_tag,
+      ciphertext_and_tag_length, plaintext, plaintext_length,
+      &plaintext_bytes_written, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Nonce buffer has the wrong length."));
+  gpr_free(error_message);
+
+  /* Small nonce */
+  status = gsec_aead_crypter_decrypt(
+      crypter, nonce, nonce_length - 1, aad, aad_length, ciphertext_and_tag,
+      ciphertext_and_tag_length, plaintext, plaintext_length,
+      &plaintext_bytes_written, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Nonce buffer has the wrong length."));
+  gpr_free(error_message);
+
+  /* nullptr aad */
+  status = gsec_aead_crypter_decrypt(
+      crypter, nonce, nonce_length, nullptr, aad_length, ciphertext_and_tag,
+      ciphertext_and_tag_length, plaintext, plaintext_length,
+      &plaintext_bytes_written, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message, "aad is nullptr."));
+  gpr_free(error_message);
+
+  /* nullptr aad with zero length */
+  status = gsec_aead_crypter_encrypt(
+      crypter, nonce, nonce_length, nullptr, 0, message, message_length,
+      ciphertext_and_tag, ciphertext_and_tag_length, &ciphertext_bytes_written,
+      &error_message);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+
+  status = gsec_aead_crypter_decrypt(
+      crypter, nonce, nonce_length, nullptr, 0, ciphertext_and_tag,
+      ciphertext_and_tag_length, plaintext, plaintext_length,
+      &plaintext_bytes_written, &error_message);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+
+  /* Small ciphertext */
+  if (tag_length > 0) {
+    status = gsec_aead_crypter_decrypt(
+        crypter, nonce, nonce_length, aad, aad_length, ciphertext_and_tag,
+        tag_length - 1, plaintext, plaintext_length, &plaintext_bytes_written,
+        &error_message);
+
+    GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+        status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+        "ciphertext is too small to hold a tag."));
+    gpr_free(error_message);
+  }
+
+  /* nullptr ciphertext */
+  status = gsec_aead_crypter_decrypt(
+      crypter, nonce, nonce_length, aad, aad_length, nullptr,
+      ciphertext_and_tag_length, plaintext, plaintext_length,
+      &plaintext_bytes_written, &error_message);
+
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "ciphertext is nullptr."));
+  gpr_free(error_message);
+
+  /* nullptr plaintext */
+  status = gsec_aead_crypter_decrypt(
+      crypter, nonce, nonce_length, aad, aad_length, ciphertext_and_tag,
+      ciphertext_and_tag_length, nullptr, plaintext_length,
+      &plaintext_bytes_written, &error_message);
+
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "plaintext is nullptr, but plaintext_length is positive."));
+  gpr_free(error_message);
+
+  /* Short plaintext */
+  status = gsec_aead_crypter_decrypt(
+      crypter, nonce, nonce_length, aad, aad_length, ciphertext_and_tag,
+      ciphertext_and_tag_length, plaintext, plaintext_length - 1,
+      &plaintext_bytes_written, &error_message);
+
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Not enough plaintext buffer to hold encrypted ciphertext."));
+  gpr_free(error_message);
+
+  /* nullptr plaintext_bytes_written */
+  status = gsec_aead_crypter_decrypt(crypter, nonce, nonce_length, aad,
+                                     aad_length, ciphertext_and_tag,
+                                     ciphertext_and_tag_length, plaintext,
+                                     plaintext_length, nullptr, &error_message);
+
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "bytes_written is nullptr."));
+  gpr_free(error_message);
+
+  gpr_free(message);
+  gpr_free(plaintext);
+  gpr_free(ciphertext_and_tag);
+  gpr_free(aad);
+  gpr_free(nonce);
+}
+
+static void gsec_test_encrypt_decrypt_test_vector(
+    gsec_aead_crypter* crypter, gsec_aead_test_vector* test_vector) {
+  GPR_ASSERT(crypter != nullptr);
+  /* Test byte-based encryption interface. */
+  size_t ciphertext_and_tag_length, ciphertext_bytes_written = 0;
+  gsec_aead_crypter_max_ciphertext_and_tag_length(
+      crypter, test_vector->plaintext_length, &ciphertext_and_tag_length,
+      nullptr);
+  uint8_t* ciphertext_and_tag_bytes =
+      static_cast<uint8_t*>(gpr_malloc(ciphertext_and_tag_length));
+  grpc_status_code status = gsec_aead_crypter_encrypt(
+      crypter, test_vector->nonce, test_vector->nonce_length, test_vector->aad,
+      test_vector->aad_length, test_vector->plaintext,
+      test_vector->plaintext_length, ciphertext_and_tag_bytes,
+      ciphertext_and_tag_length, &ciphertext_bytes_written, nullptr);
+
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(ciphertext_bytes_written == ciphertext_and_tag_length);
+  GPR_ASSERT(memcmp(test_vector->ciphertext_and_tag, ciphertext_and_tag_bytes,
+                    ciphertext_and_tag_length) == 0);
+
+  /* Test byte-based decryption interface */
+  size_t plaintext_length, plaintext_bytes_written = 0;
+  gsec_aead_crypter_max_plaintext_length(crypter, ciphertext_and_tag_length,
+                                         &plaintext_length, nullptr);
+  uint8_t* plaintext_bytes =
+      static_cast<uint8_t*>(gpr_malloc(plaintext_length));
+  status = gsec_aead_crypter_decrypt(
+      crypter, test_vector->nonce, test_vector->nonce_length, test_vector->aad,
+      test_vector->aad_length, test_vector->ciphertext_and_tag,
+      test_vector->ciphertext_and_tag_length, plaintext_bytes, plaintext_length,
+      &plaintext_bytes_written, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(memcmp(test_vector->plaintext, plaintext_bytes,
+                    plaintext_bytes_written) == 0);
+
+  gpr_free(ciphertext_and_tag_bytes);
+  gpr_free(plaintext_bytes);
+}
+
+static void gsec_test_get_crypter_from_test_vector(
+    gsec_aead_crypter** crypter, gsec_aead_test_vector* test_vector,
+    bool rekey = false) {
+  size_t key_length = test_vector->key_length;
+  GPR_ASSERT(key_length == kAes128GcmKeyLength ||
+             key_length == kAes256GcmKeyLength ||
+             key_length == kAes128GcmRekeyKeyLength);
+  size_t nonce_length = test_vector->nonce_length;
+  GPR_ASSERT(nonce_length == kAesGcmNonceLength);
+  size_t plaintext_length = test_vector->plaintext_length;
+  size_t ciphertext_and_tag_length = test_vector->ciphertext_and_tag_length;
+  GPR_ASSERT(ciphertext_and_tag_length == plaintext_length + kAesGcmTagLength);
+  size_t tag_length = ciphertext_and_tag_length - plaintext_length;
+  gsec_aes_gcm_aead_crypter_create(test_vector->key, key_length, nonce_length,
+                                   tag_length, rekey, crypter, nullptr);
+}
+
+static void gsec_test_verify_crypter_on_test_vector(
+    gsec_aead_test_vector* test_vector, bool rekey = false) {
+  gsec_aead_crypter* crypter;
+  gsec_test_get_crypter_from_test_vector(&crypter, test_vector, rekey);
+  gsec_test_encrypt_decrypt_test_vector(crypter, test_vector);
+  gsec_aead_crypter_destroy(crypter);
+}
+
+static void gsec_aead_malloc_test_vector(
+    gsec_aead_test_vector** test_vector, const uint8_t* key, size_t key_length,
+    const uint8_t* nonce, size_t nonce_length, const uint8_t* aad,
+    size_t aad_length, const uint8_t* plaintext, size_t plaintext_length,
+    const uint8_t* ciphertext_and_tag, size_t ciphertext_and_tag_length) {
+  *test_vector = static_cast<gsec_aead_test_vector*>(
+      gpr_malloc(sizeof(gsec_aead_test_vector)));
+  (*test_vector)->key_length = key_length;
+  (*test_vector)->nonce_length = nonce_length;
+  (*test_vector)->aad_length = aad_length;
+  (*test_vector)->plaintext_length = plaintext_length;
+  (*test_vector)->ciphertext_and_tag_length = ciphertext_and_tag_length;
+  gsec_test_copy(key, &((*test_vector)->key), key_length);
+  gsec_test_copy(nonce, &((*test_vector)->nonce), nonce_length);
+  gsec_test_copy(aad, &((*test_vector)->aad), aad_length);
+  gsec_test_copy(plaintext, &((*test_vector)->plaintext), plaintext_length);
+  gsec_test_copy(ciphertext_and_tag, &((*test_vector)->ciphertext_and_tag),
+                 ciphertext_and_tag_length);
+}
+
+static void gsec_aead_free_test_vector(gsec_aead_test_vector* test_vector) {
+  gpr_free(test_vector->key);
+  gpr_free(test_vector->nonce);
+  gpr_free(test_vector->aad);
+  gpr_free(test_vector->plaintext);
+  gpr_free(test_vector->ciphertext_and_tag);
+  gpr_free(test_vector);
+}
+
+static void gsec_test_create_random_aes_gcm_crypter(gsec_aead_crypter** crypter,
+                                                    size_t key_length,
+                                                    size_t nonce_length,
+                                                    size_t tag_length,
+                                                    bool rekey) {
+  uint8_t* key;
+  gsec_test_random_array(&key, key_length);
+  gsec_aes_gcm_aead_crypter_create(key, key_length, nonce_length, tag_length,
+                                   rekey, crypter, nullptr);
+  gpr_free(key);
+}
+
+static void gsec_test_get_random_aes_gcm_crypters(
+    gsec_aead_crypter*** crypters) {
+  *crypters = static_cast<gsec_aead_crypter**>(
+      gpr_malloc(sizeof(gsec_aead_crypter*) * kTestNumCrypters));
+  gsec_test_create_random_aes_gcm_crypter(
+      &((*crypters)[0]), kAes128GcmKeyLength, kAesGcmNonceLength,
+      kAesGcmTagLength, /*rekey=*/false);
+  gsec_test_create_random_aes_gcm_crypter(
+      &((*crypters)[1]), kAes256GcmKeyLength, kAesGcmNonceLength,
+      kAesGcmTagLength, /*rekey=*/false);
+  gsec_test_create_random_aes_gcm_crypter(
+      &((*crypters)[2]), kAes128GcmRekeyKeyLength, kAesGcmNonceLength,
+      kAesGcmTagLength, /*rekey=*/true);
+}
+
+static void gsec_test_do_generic_crypter_tests() {
+  gsec_aead_crypter** crypters;
+  gsec_test_get_random_aes_gcm_crypters(&crypters);
+  size_t ind;
+  for (ind = 0; ind < kTestNumCrypters; ind++) {
+    gsec_test_encrypt_decrypt(crypters[ind]);
+    gsec_test_multiple_encrypt_decrypt(crypters[ind]);
+    gsec_test_encryption_failure(crypters[ind]);
+    gsec_test_decryption_failure(crypters[ind]);
+  }
+  for (ind = 0; ind < kTestNumCrypters; ind++) {
+    gsec_aead_crypter_destroy(crypters[ind]);
+  }
+  gpr_free(crypters);
+}
+
+static void gsec_test_do_vector_tests_rekey_nist() {
+  // NIST vectors from:
+  // http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/proposedmodes/gcm/gcm-revised-spec.pdf
+  //
+  // IEEE vectors from:
+  // http://www.ieee802.org/1/files/public/docs2011/bn-randall-test-vectors-0511-v1.pdf
+  //
+  // Key expanded by setting expandedKey = (key||(key ^ {0x01, .., 0x01})||key ^
+  // {0x02,..,0x02}))[0:44].
+
+  gsec_aead_test_vector vec;
+
+  // Derived from NIST test vector 1
+  uint8_t nonce_0[] = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+                       0x0, 0x0, 0x0, 0x0, 0x0, 0x0};
+  uint8_t aad_0[1] = {};
+  uint8_t key_0[] = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+                     0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1,
+                     0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x2,
+                     0x2, 0x2, 0x2, 0x2, 0x2, 0x2, 0x2, 0x2, 0x2, 0x2, 0x2};
+  uint8_t plaintext_0[1] = {};
+  uint8_t ciphertext_0[] = {0x85, 0xE8, 0x73, 0xE0, 0x2,  0xF6, 0xEB, 0xDC,
+                            0x40, 0x60, 0x95, 0x4E, 0xB8, 0x67, 0x55, 0x8};
+  vec = {nonce_0, aad_0, key_0, plaintext_0, ciphertext_0, 12, 0, 44, 0, 16};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from NIST test vector 2
+  uint8_t nonce_1[] = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+                       0x0, 0x0, 0x0, 0x0, 0x0, 0x0};
+  uint8_t aad_1[1] = {};
+  uint8_t key_1[] = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+                     0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1,
+                     0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x2,
+                     0x2, 0x2, 0x2, 0x2, 0x2, 0x2, 0x2, 0x2, 0x2, 0x2, 0x2};
+  uint8_t plaintext_1[] = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+                           0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0};
+  uint8_t ciphertext_1[] = {0x51, 0xE9, 0xA8, 0xCB, 0x23, 0xCA, 0x25, 0x12,
+                            0xC8, 0x25, 0x6A, 0xFF, 0xF8, 0xE7, 0x2D, 0x68,
+                            0x1A, 0xCA, 0x19, 0xA1, 0x14, 0x8A, 0xC1, 0x15,
+                            0xE8, 0x3D, 0xF4, 0x88, 0x8C, 0xC0, 0xD,  0x11};
+  vec = {nonce_1, aad_1, key_1, plaintext_1, ciphertext_1, 12, 0, 44, 16, 32};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from NIST test vector 3
+  uint8_t nonce_2[] = {0xCA, 0xFE, 0xBA, 0xBE, 0xFA, 0xCE,
+                       0xDB, 0xAD, 0xDE, 0xCA, 0xF8, 0x88};
+  uint8_t aad_2[1] = {};
+  uint8_t key_2[] = {0xFE, 0xFF, 0xE9, 0x92, 0x86, 0x65, 0x73, 0x1C, 0x6D,
+                     0x6A, 0x8F, 0x94, 0x67, 0x30, 0x83, 0x8,  0xFF, 0xFE,
+                     0xE8, 0x93, 0x87, 0x64, 0x72, 0x1D, 0x6C, 0x6B, 0x8E,
+                     0x95, 0x66, 0x31, 0x82, 0x9,  0xFC, 0xFD, 0xEB, 0x90,
+                     0x84, 0x67, 0x71, 0x1E, 0x6F, 0x68, 0x8D, 0x96};
+  uint8_t plaintext_2[] = {
+      0xD9, 0x31, 0x32, 0x25, 0xF8, 0x84, 0x6,  0xE5, 0xA5, 0x59, 0x9,
+      0xC5, 0xAF, 0xF5, 0x26, 0x9A, 0x86, 0xA7, 0xA9, 0x53, 0x15, 0x34,
+      0xF7, 0xDA, 0x2E, 0x4C, 0x30, 0x3D, 0x8A, 0x31, 0x8A, 0x72, 0x1C,
+      0x3C, 0xC,  0x95, 0x95, 0x68, 0x9,  0x53, 0x2F, 0xCF, 0xE,  0x24,
+      0x49, 0xA6, 0xB5, 0x25, 0xB1, 0x6A, 0xED, 0xF5, 0xAA, 0xD,  0xE6,
+      0x57, 0xBA, 0x63, 0x7B, 0x39, 0x1A, 0xAF, 0xD2, 0x55};
+  uint8_t ciphertext_2[] = {
+      0x10, 0x18, 0xED, 0x5A, 0x14, 0x2,  0xA8, 0x65, 0x16, 0xD6, 0x57, 0x6D,
+      0x70, 0xB2, 0xFF, 0xCC, 0xCA, 0x26, 0x1B, 0x94, 0xDF, 0x88, 0xB5, 0x8F,
+      0x53, 0xB6, 0x4D, 0xFB, 0xA4, 0x35, 0xD1, 0x8B, 0x2F, 0x6E, 0x3B, 0x78,
+      0x69, 0xF9, 0x35, 0x3D, 0x4A, 0xC8, 0xCF, 0x9,  0xAF, 0xB1, 0x66, 0x3D,
+      0xAA, 0x7B, 0x40, 0x17, 0xE6, 0xFC, 0x2C, 0x17, 0x7C, 0xC,  0x8,  0x7C,
+      0xD,  0xF1, 0x16, 0x21, 0x29, 0x95, 0x22, 0x13, 0xCE, 0xE1, 0xBC, 0x6E,
+      0x9C, 0x84, 0x95, 0xDD, 0x70, 0x5E, 0x1F, 0x3D};
+  vec = {nonce_2, aad_2, key_2, plaintext_2, ciphertext_2, 12, 0, 44, 64, 80};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from NIST test vector 4
+  uint8_t nonce_3[] = {0xCA, 0xFE, 0xBA, 0xBE, 0xFA, 0xCE,
+                       0xDB, 0xAD, 0xDE, 0xCA, 0xF8, 0x88};
+  uint8_t aad_3[] = {0xFE, 0xED, 0xFA, 0xCE, 0xDE, 0xAD, 0xBE,
+                     0xEF, 0xFE, 0xED, 0xFA, 0xCE, 0xDE, 0xAD,
+                     0xBE, 0xEF, 0xAB, 0xAD, 0xDA, 0xD2};
+  uint8_t key_3[] = {0xFE, 0xFF, 0xE9, 0x92, 0x86, 0x65, 0x73, 0x1C, 0x6D,
+                     0x6A, 0x8F, 0x94, 0x67, 0x30, 0x83, 0x8,  0xFF, 0xFE,
+                     0xE8, 0x93, 0x87, 0x64, 0x72, 0x1D, 0x6C, 0x6B, 0x8E,
+                     0x95, 0x66, 0x31, 0x82, 0x9,  0xFC, 0xFD, 0xEB, 0x90,
+                     0x84, 0x67, 0x71, 0x1E, 0x6F, 0x68, 0x8D, 0x96};
+  uint8_t plaintext_3[] = {
+      0xD9, 0x31, 0x32, 0x25, 0xF8, 0x84, 0x6,  0xE5, 0xA5, 0x59, 0x9,  0xC5,
+      0xAF, 0xF5, 0x26, 0x9A, 0x86, 0xA7, 0xA9, 0x53, 0x15, 0x34, 0xF7, 0xDA,
+      0x2E, 0x4C, 0x30, 0x3D, 0x8A, 0x31, 0x8A, 0x72, 0x1C, 0x3C, 0xC,  0x95,
+      0x95, 0x68, 0x9,  0x53, 0x2F, 0xCF, 0xE,  0x24, 0x49, 0xA6, 0xB5, 0x25,
+      0xB1, 0x6A, 0xED, 0xF5, 0xAA, 0xD,  0xE6, 0x57, 0xBA, 0x63, 0x7B, 0x39};
+  uint8_t ciphertext_3[] = {
+      0x10, 0x18, 0xED, 0x5A, 0x14, 0x2,  0xA8, 0x65, 0x16, 0xD6, 0x57,
+      0x6D, 0x70, 0xB2, 0xFF, 0xCC, 0xCA, 0x26, 0x1B, 0x94, 0xDF, 0x88,
+      0xB5, 0x8F, 0x53, 0xB6, 0x4D, 0xFB, 0xA4, 0x35, 0xD1, 0x8B, 0x2F,
+      0x6E, 0x3B, 0x78, 0x69, 0xF9, 0x35, 0x3D, 0x4A, 0xC8, 0xCF, 0x9,
+      0xAF, 0xB1, 0x66, 0x3D, 0xAA, 0x7B, 0x40, 0x17, 0xE6, 0xFC, 0x2C,
+      0x17, 0x7C, 0xC,  0x8,  0x7C, 0x47, 0x64, 0x56, 0x5D, 0x7,  0x7E,
+      0x91, 0x24, 0x0,  0x1D, 0xDB, 0x27, 0xFC, 0x8,  0x48, 0xC5};
+  vec = {nonce_3, aad_3, key_3, plaintext_3, ciphertext_3, 12, 20, 44, 60, 76};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from adapted NIST test vector 4 for KDF counter boundary (flip
+  // nonce bit 15)
+  uint8_t nonce_4[] = {0xCA, 0x7E, 0xBA, 0xBE, 0xFA, 0xCE,
+                       0xDB, 0xAD, 0xDE, 0xCA, 0xF8, 0x88};
+  uint8_t aad_4[] = {0xFE, 0xED, 0xFA, 0xCE, 0xDE, 0xAD, 0xBE,
+                     0xEF, 0xFE, 0xED, 0xFA, 0xCE, 0xDE, 0xAD,
+                     0xBE, 0xEF, 0xAB, 0xAD, 0xDA, 0xD2};
+  uint8_t key_4[] = {0xFE, 0xFF, 0xE9, 0x92, 0x86, 0x65, 0x73, 0x1C, 0x6D,
+                     0x6A, 0x8F, 0x94, 0x67, 0x30, 0x83, 0x8,  0xFF, 0xFE,
+                     0xE8, 0x93, 0x87, 0x64, 0x72, 0x1D, 0x6C, 0x6B, 0x8E,
+                     0x95, 0x66, 0x31, 0x82, 0x9,  0xFC, 0xFD, 0xEB, 0x90,
+                     0x84, 0x67, 0x71, 0x1E, 0x6F, 0x68, 0x8D, 0x96};
+  uint8_t plaintext_4[] = {
+      0xD9, 0x31, 0x32, 0x25, 0xF8, 0x84, 0x6,  0xE5, 0xA5, 0x59, 0x9,  0xC5,
+      0xAF, 0xF5, 0x26, 0x9A, 0x86, 0xA7, 0xA9, 0x53, 0x15, 0x34, 0xF7, 0xDA,
+      0x2E, 0x4C, 0x30, 0x3D, 0x8A, 0x31, 0x8A, 0x72, 0x1C, 0x3C, 0xC,  0x95,
+      0x95, 0x68, 0x9,  0x53, 0x2F, 0xCF, 0xE,  0x24, 0x49, 0xA6, 0xB5, 0x25,
+      0xB1, 0x6A, 0xED, 0xF5, 0xAA, 0xD,  0xE6, 0x57, 0xBA, 0x63, 0x7B, 0x39};
+  uint8_t ciphertext_4[] = {
+      0xE6, 0x50, 0xD3, 0xC0, 0xFB, 0x87, 0x93, 0x27, 0xF2, 0xD0, 0x32,
+      0x87, 0xFA, 0x93, 0xCD, 0x7,  0x34, 0x2B, 0x13, 0x62, 0x15, 0xAD,
+      0xBC, 0xA0, 0xC,  0x3B, 0xD5, 0x9,  0x9E, 0xC4, 0x18, 0x32, 0xB1,
+      0xD1, 0x8E, 0x4,  0x23, 0xED, 0x26, 0xBB, 0x12, 0xC6, 0xCD, 0x9,
+      0xDE, 0xBB, 0x29, 0x23, 0xA,  0x94, 0xC0, 0xCE, 0xE1, 0x59, 0x3,
+      0x65, 0x6F, 0x85, 0xED, 0xB6, 0xFC, 0x50, 0x9B, 0x1B, 0x28, 0x21,
+      0x63, 0x82, 0x17, 0x2E, 0xCB, 0xCC, 0x31, 0xE1, 0xE9, 0xB1};
+  vec = {nonce_4, aad_4, key_4, plaintext_4, ciphertext_4, 12, 20, 44, 60, 76};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from adapted NIST test vector 4 for KDF counter boundary (flip
+  // nonce bit 16)
+  uint8_t nonce_5[] = {0xCA, 0xFE, 0xBB, 0xBE, 0xFA, 0xCE,
+                       0xDB, 0xAD, 0xDE, 0xCA, 0xF8, 0x88};
+  uint8_t aad_5[] = {0xFE, 0xED, 0xFA, 0xCE, 0xDE, 0xAD, 0xBE,
+                     0xEF, 0xFE, 0xED, 0xFA, 0xCE, 0xDE, 0xAD,
+                     0xBE, 0xEF, 0xAB, 0xAD, 0xDA, 0xD2};
+  uint8_t key_5[] = {0xFE, 0xFF, 0xE9, 0x92, 0x86, 0x65, 0x73, 0x1C, 0x6D,
+                     0x6A, 0x8F, 0x94, 0x67, 0x30, 0x83, 0x8,  0xFF, 0xFE,
+                     0xE8, 0x93, 0x87, 0x64, 0x72, 0x1D, 0x6C, 0x6B, 0x8E,
+                     0x95, 0x66, 0x31, 0x82, 0x9,  0xFC, 0xFD, 0xEB, 0x90,
+                     0x84, 0x67, 0x71, 0x1E, 0x6F, 0x68, 0x8D, 0x96};
+  uint8_t plaintext_5[] = {
+      0xD9, 0x31, 0x32, 0x25, 0xF8, 0x84, 0x6,  0xE5, 0xA5, 0x59, 0x9,  0xC5,
+      0xAF, 0xF5, 0x26, 0x9A, 0x86, 0xA7, 0xA9, 0x53, 0x15, 0x34, 0xF7, 0xDA,
+      0x2E, 0x4C, 0x30, 0x3D, 0x8A, 0x31, 0x8A, 0x72, 0x1C, 0x3C, 0xC,  0x95,
+      0x95, 0x68, 0x9,  0x53, 0x2F, 0xCF, 0xE,  0x24, 0x49, 0xA6, 0xB5, 0x25,
+      0xB1, 0x6A, 0xED, 0xF5, 0xAA, 0xD,  0xE6, 0x57, 0xBA, 0x63, 0x7B, 0x39};
+  uint8_t ciphertext_5[] = {
+      0xC0, 0x12, 0x1E, 0x6C, 0x95, 0x4D, 0x7,  0x67, 0xF9, 0x66, 0x30,
+      0xC3, 0x34, 0x50, 0x99, 0x97, 0x91, 0xB2, 0xDA, 0x2A, 0xD0, 0x5C,
+      0x41, 0x90, 0x16, 0x9C, 0xCA, 0xD9, 0xAC, 0x86, 0xFF, 0x1C, 0x72,
+      0x1E, 0x3D, 0x82, 0xF2, 0xAD, 0x22, 0xAB, 0x46, 0x3B, 0xAB, 0x4A,
+      0x7,  0x54, 0xB7, 0xDD, 0x68, 0xCA, 0x4D, 0xE7, 0xEA, 0x25, 0x31,
+      0xB6, 0x25, 0xED, 0xA0, 0x1F, 0x89, 0x31, 0x2B, 0x2A, 0xB9, 0x57,
+      0xD5, 0xC7, 0xF8, 0x56, 0x8D, 0xD9, 0x5F, 0xCD, 0xCD, 0x1F};
+  vec = {nonce_5, aad_5, key_5, plaintext_5, ciphertext_5, 12, 20, 44, 60, 76};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from adapted NIST test vector 4 for KDF counter boundary (flip
+  // nonce bit 63)
+  uint8_t nonce_6[] = {0xCA, 0xFE, 0xBA, 0xBE, 0xFA, 0xCE,
+                       0xDB, 0x2D, 0xDE, 0xCA, 0xF8, 0x88};
+  uint8_t aad_6[] = {0xFE, 0xED, 0xFA, 0xCE, 0xDE, 0xAD, 0xBE,
+                     0xEF, 0xFE, 0xED, 0xFA, 0xCE, 0xDE, 0xAD,
+                     0xBE, 0xEF, 0xAB, 0xAD, 0xDA, 0xD2};
+  uint8_t key_6[] = {0xFE, 0xFF, 0xE9, 0x92, 0x86, 0x65, 0x73, 0x1C, 0x6D,
+                     0x6A, 0x8F, 0x94, 0x67, 0x30, 0x83, 0x8,  0xFF, 0xFE,
+                     0xE8, 0x93, 0x87, 0x64, 0x72, 0x1D, 0x6C, 0x6B, 0x8E,
+                     0x95, 0x66, 0x31, 0x82, 0x9,  0xFC, 0xFD, 0xEB, 0x90,
+                     0x84, 0x67, 0x71, 0x1E, 0x6F, 0x68, 0x8D, 0x96};
+  uint8_t plaintext_6[] = {
+      0xD9, 0x31, 0x32, 0x25, 0xF8, 0x84, 0x6,  0xE5, 0xA5, 0x59, 0x9,  0xC5,
+      0xAF, 0xF5, 0x26, 0x9A, 0x86, 0xA7, 0xA9, 0x53, 0x15, 0x34, 0xF7, 0xDA,
+      0x2E, 0x4C, 0x30, 0x3D, 0x8A, 0x31, 0x8A, 0x72, 0x1C, 0x3C, 0xC,  0x95,
+      0x95, 0x68, 0x9,  0x53, 0x2F, 0xCF, 0xE,  0x24, 0x49, 0xA6, 0xB5, 0x25,
+      0xB1, 0x6A, 0xED, 0xF5, 0xAA, 0xD,  0xE6, 0x57, 0xBA, 0x63, 0x7B, 0x39};
+  uint8_t ciphertext_6[] = {
+      0x8A, 0xF3, 0x7E, 0xA5, 0x68, 0x4A, 0x4D, 0x81, 0xD4, 0xFD, 0x81,
+      0x72, 0x61, 0xFD, 0x97, 0x43, 0x9,  0x9E, 0x7E, 0x6A, 0x2,  0x5E,
+      0xAA, 0xCF, 0x8E, 0x54, 0xB1, 0x24, 0xFB, 0x57, 0x43, 0x14, 0x9E,
+      0x5,  0xCB, 0x89, 0xF4, 0xA4, 0x94, 0x67, 0xFE, 0x2E, 0x5E, 0x59,
+      0x65, 0xF2, 0x9A, 0x19, 0xF9, 0x94, 0x16, 0xB0, 0x1,  0x6B, 0x54,
+      0x58, 0x5D, 0x12, 0x55, 0x37, 0x83, 0xBA, 0x59, 0xE9, 0xF7, 0x82,
+      0xE8, 0x2E, 0x9,  0x7C, 0x33, 0x6B, 0xF7, 0x98, 0x9F, 0x8};
+  vec = {nonce_6, aad_6, key_6, plaintext_6, ciphertext_6, 12, 20, 44, 60, 76};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from adapted NIST test vector 4 for KDF counter boundary (flip
+  // nonce bit 64)
+  uint8_t nonce_7[] = {0xCA, 0xFE, 0xBA, 0xBE, 0xFA, 0xCE,
+                       0xDB, 0xAD, 0xDF, 0xCA, 0xF8, 0x88};
+  uint8_t aad_7[] = {0xFE, 0xED, 0xFA, 0xCE, 0xDE, 0xAD, 0xBE,
+                     0xEF, 0xFE, 0xED, 0xFA, 0xCE, 0xDE, 0xAD,
+                     0xBE, 0xEF, 0xAB, 0xAD, 0xDA, 0xD2};
+  uint8_t key_7[] = {0xFE, 0xFF, 0xE9, 0x92, 0x86, 0x65, 0x73, 0x1C, 0x6D,
+                     0x6A, 0x8F, 0x94, 0x67, 0x30, 0x83, 0x8,  0xFF, 0xFE,
+                     0xE8, 0x93, 0x87, 0x64, 0x72, 0x1D, 0x6C, 0x6B, 0x8E,
+                     0x95, 0x66, 0x31, 0x82, 0x9,  0xFC, 0xFD, 0xEB, 0x90,
+                     0x84, 0x67, 0x71, 0x1E, 0x6F, 0x68, 0x8D, 0x96};
+  uint8_t plaintext_7[] = {
+      0xD9, 0x31, 0x32, 0x25, 0xF8, 0x84, 0x6,  0xE5, 0xA5, 0x59, 0x9,  0xC5,
+      0xAF, 0xF5, 0x26, 0x9A, 0x86, 0xA7, 0xA9, 0x53, 0x15, 0x34, 0xF7, 0xDA,
+      0x2E, 0x4C, 0x30, 0x3D, 0x8A, 0x31, 0x8A, 0x72, 0x1C, 0x3C, 0xC,  0x95,
+      0x95, 0x68, 0x9,  0x53, 0x2F, 0xCF, 0xE,  0x24, 0x49, 0xA6, 0xB5, 0x25,
+      0xB1, 0x6A, 0xED, 0xF5, 0xAA, 0xD,  0xE6, 0x57, 0xBA, 0x63, 0x7B, 0x39};
+  uint8_t ciphertext_7[] = {
+      0xFB, 0xD5, 0x28, 0x44, 0x8D, 0x3,  0x46, 0xBF, 0xA8, 0x78, 0x63,
+      0x48, 0x64, 0xD4, 0x7,  0xA3, 0x5A, 0x3,  0x9D, 0xE9, 0xDB, 0x2F,
+      0x1F, 0xEB, 0x8E, 0x96, 0x5B, 0x3A, 0xE9, 0x35, 0x6C, 0xE6, 0x28,
+      0x94, 0x41, 0xD7, 0x7F, 0x8F, 0xD,  0xF2, 0x94, 0x89, 0x1F, 0x37,
+      0xEA, 0x43, 0x8B, 0x22, 0x3E, 0x3B, 0xF2, 0xBD, 0xC5, 0x3D, 0x4C,
+      0x5A, 0x74, 0xFB, 0x68, 0xB,  0xB3, 0x12, 0xA8, 0xDE, 0xC6, 0xF7,
+      0x25, 0x2C, 0xBC, 0xD7, 0xF5, 0x79, 0x97, 0x50, 0xAD, 0x78};
+  vec = {nonce_7, aad_7, key_7, plaintext_7, ciphertext_7, 12, 20, 44, 60, 76};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+}
+
+static void gsec_test_do_vector_tests_rekey_ieee() {
+  // IEEE vectors from:
+  // http://www.ieee802.org/1/files/public/docs2011/bn-randall-test-vectors-0511-v1.pdf
+  //
+  // Key expanded by setting expandedKey = (key||(key ^ {0x01, .., 0x01})||key ^
+  // {0x02,..,0x02}))[0:44].
+
+  gsec_aead_test_vector vec;
+
+  // Derived from IEEE 2.1.1 54-byte auth
+  uint8_t nonce_8[] = {0x12, 0x15, 0x35, 0x24, 0xC0, 0x89,
+                       0x5E, 0x81, 0xB2, 0xC2, 0x84, 0x65};
+  uint8_t aad_8[] = {0xD6, 0x9,  0xB1, 0xF0, 0x56, 0x63, 0x7A, 0xD,  0x46, 0xDF,
+                     0x99, 0x8D, 0x88, 0xE5, 0x22, 0x2A, 0xB2, 0xC2, 0x84, 0x65,
+                     0x12, 0x15, 0x35, 0x24, 0xC0, 0x89, 0x5E, 0x81, 0x8,  0x0,
+                     0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
+                     0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22,
+                     0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C,
+                     0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x0,  0x1};
+  uint8_t key_8[] = {0xAD, 0x7A, 0x2B, 0xD0, 0x3E, 0xAC, 0x83, 0x5A, 0x6F,
+                     0x62, 0xF,  0xDC, 0xB5, 0x6,  0xB3, 0x45, 0xAC, 0x7B,
+                     0x2A, 0xD1, 0x3F, 0xAD, 0x82, 0x5B, 0x6E, 0x63, 0xE,
+                     0xDD, 0xB4, 0x7,  0xB2, 0x44, 0xAF, 0x78, 0x29, 0xD2,
+                     0x3C, 0xAE, 0x81, 0x58, 0x6D, 0x60, 0xD,  0xDE};
+  uint8_t plaintext_8[1] = {};
+  uint8_t ciphertext_8[] = {0x3E, 0xA0, 0xB5, 0x84, 0xF3, 0xC8, 0x5E, 0x93,
+                            0xF9, 0x32, 0xE,  0xA5, 0x91, 0x69, 0x9E, 0xFB};
+  vec = {nonce_8, aad_8, key_8, plaintext_8, ciphertext_8, 12, 70, 44, 0, 16};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.1.2 54-byte auth
+  uint8_t nonce_9[] = {0x12, 0x15, 0x35, 0x24, 0xC0, 0x89,
+                       0x5E, 0x81, 0xB2, 0xC2, 0x84, 0x65};
+  uint8_t aad_9[] = {0xD6, 0x9,  0xB1, 0xF0, 0x56, 0x63, 0x7A, 0xD,  0x46, 0xDF,
+                     0x99, 0x8D, 0x88, 0xE5, 0x22, 0x2A, 0xB2, 0xC2, 0x84, 0x65,
+                     0x12, 0x15, 0x35, 0x24, 0xC0, 0x89, 0x5E, 0x81, 0x8,  0x0,
+                     0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
+                     0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22,
+                     0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C,
+                     0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x0,  0x1};
+  uint8_t key_9[] = {0xE3, 0xC0, 0x8A, 0x8F, 0x6,  0xC6, 0xE3, 0xAD, 0x95,
+                     0xA7, 0x5,  0x57, 0xB2, 0x3F, 0x75, 0x48, 0x3C, 0xE3,
+                     0x30, 0x21, 0xA9, 0xC7, 0x2B, 0x70, 0x25, 0x66, 0x62,
+                     0x4,  0xC6, 0x9C, 0xB,  0x72, 0xE1, 0xC2, 0x88, 0x8D,
+                     0x4,  0xC4, 0xE1, 0xAF, 0x97, 0xA5, 0x7,  0x55};
+  uint8_t plaintext_9[1] = {};
+  uint8_t ciphertext_9[] = {0x29, 0x4E, 0x2,  0x8B, 0xF1, 0xFE, 0x6F, 0x14,
+                            0xC4, 0xE8, 0xF7, 0x30, 0x5C, 0x93, 0x3E, 0xB5};
+  vec = {nonce_9, aad_9, key_9, plaintext_9, ciphertext_9, 12, 70, 44, 0, 16};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.2.1 60-byte crypt
+  uint8_t nonce_10[] = {0x12, 0x15, 0x35, 0x24, 0xC0, 0x89,
+                        0x5E, 0x81, 0xB2, 0xC2, 0x84, 0x65};
+  uint8_t aad_10[] = {0xD6, 0x9,  0xB1, 0xF0, 0x56, 0x63, 0x7A,
+                      0xD,  0x46, 0xDF, 0x99, 0x8D, 0x88, 0xE5,
+                      0x2E, 0x0,  0xB2, 0xC2, 0x84, 0x65, 0x12,
+                      0x15, 0x35, 0x24, 0xC0, 0x89, 0x5E, 0x81};
+  uint8_t key_10[] = {0xAD, 0x7A, 0x2B, 0xD0, 0x3E, 0xAC, 0x83, 0x5A, 0x6F,
+                      0x62, 0xF,  0xDC, 0xB5, 0x6,  0xB3, 0x45, 0xAC, 0x7B,
+                      0x2A, 0xD1, 0x3F, 0xAD, 0x82, 0x5B, 0x6E, 0x63, 0xE,
+                      0xDD, 0xB4, 0x7,  0xB2, 0x44, 0xAF, 0x78, 0x29, 0xD2,
+                      0x3C, 0xAE, 0x81, 0x58, 0x6D, 0x60, 0xD,  0xDE};
+  uint8_t plaintext_10[] = {
+      0x8,  0x0,  0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
+      0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24,
+      0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30,
+      0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x0,  0x2};
+  uint8_t ciphertext_10[] = {
+      0xDB, 0x3D, 0x25, 0x71, 0x9C, 0x6B, 0xA,  0x3C, 0xA6, 0x14, 0x5C,
+      0x15, 0x9D, 0x5C, 0x6E, 0xD9, 0xAF, 0xF9, 0xC6, 0xE0, 0xB7, 0x9F,
+      0x17, 0x1,  0x9E, 0xA9, 0x23, 0xB8, 0x66, 0x5D, 0xDF, 0x52, 0x13,
+      0x7A, 0xD6, 0x11, 0xF0, 0xD1, 0xBF, 0x41, 0x7A, 0x7C, 0xA8, 0x5E,
+      0x45, 0xAF, 0xE1, 0x6,  0xFF, 0x9C, 0x75, 0x69, 0xD3, 0x35, 0xD0,
+      0x86, 0xAE, 0x6C, 0x3,  0xF0, 0x9,  0x87, 0xCC, 0xD6};
+  vec = {nonce_10, aad_10, key_10, plaintext_10, ciphertext_10,
+         12,       28,     44,     48,           64};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.2.2 60-byte crypt
+  uint8_t nonce_11[] = {0x12, 0x15, 0x35, 0x24, 0xC0, 0x89,
+                        0x5E, 0x81, 0xB2, 0xC2, 0x84, 0x65};
+  uint8_t aad_11[] = {0xD6, 0x9,  0xB1, 0xF0, 0x56, 0x63, 0x7A,
+                      0xD,  0x46, 0xDF, 0x99, 0x8D, 0x88, 0xE5,
+                      0x2E, 0x0,  0xB2, 0xC2, 0x84, 0x65, 0x12,
+                      0x15, 0x35, 0x24, 0xC0, 0x89, 0x5E, 0x81};
+  uint8_t key_11[] = {0xE3, 0xC0, 0x8A, 0x8F, 0x6,  0xC6, 0xE3, 0xAD, 0x95,
+                      0xA7, 0x5,  0x57, 0xB2, 0x3F, 0x75, 0x48, 0x3C, 0xE3,
+                      0x30, 0x21, 0xA9, 0xC7, 0x2B, 0x70, 0x25, 0x66, 0x62,
+                      0x4,  0xC6, 0x9C, 0xB,  0x72, 0xE1, 0xC2, 0x88, 0x8D,
+                      0x4,  0xC4, 0xE1, 0xAF, 0x97, 0xA5, 0x7,  0x55};
+  uint8_t plaintext_11[] = {
+      0x8,  0x0,  0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
+      0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24,
+      0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30,
+      0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x0,  0x2};
+  uint8_t ciphertext_11[] = {
+      0x16, 0x41, 0xF2, 0x8E, 0xC1, 0x3A, 0xFC, 0xC8, 0xF7, 0x90, 0x33,
+      0x89, 0x78, 0x72, 0x1,  0x5,  0x16, 0x44, 0x91, 0x49, 0x33, 0xE9,
+      0x20, 0x2B, 0xB9, 0xD0, 0x6A, 0xA0, 0x20, 0xC2, 0xA6, 0x7E, 0xF5,
+      0x1D, 0xFE, 0x7B, 0xC0, 0xA,  0x85, 0x6C, 0x55, 0xB8, 0xF8, 0x13,
+      0x3E, 0x77, 0xF6, 0x59, 0x13, 0x25, 0x2,  0xBA, 0xD6, 0x3F, 0x57,
+      0x13, 0xD5, 0x7D, 0xC,  0x11, 0xE0, 0xF8, 0x71, 0xED};
+  vec = {nonce_11, aad_11, key_11, plaintext_11, ciphertext_11,
+         12,       28,     44,     48,           64};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.3.1 60-byte auth
+  uint8_t nonce_12[] = {0xF0, 0x76, 0x1E, 0x8D, 0xCD, 0x3D,
+                        0x0,  0x1,  0x76, 0xD4, 0x57, 0xED};
+  uint8_t aad_12[] = {
+      0xE2, 0x1,  0x6,  0xD7, 0xCD, 0xD,  0xF0, 0x76, 0x1E, 0x8D, 0xCD, 0x3D,
+      0x88, 0xE5, 0x40, 0x0,  0x76, 0xD4, 0x57, 0xED, 0x8,  0x0,  0xF,  0x10,
+      0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C,
+      0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
+      0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34,
+      0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x0,  0x3};
+  uint8_t key_12[] = {0x7,  0x1B, 0x11, 0x3B, 0xC,  0xA7, 0x43, 0xFE, 0xCC,
+                      0xCF, 0x3D, 0x5,  0x1F, 0x73, 0x73, 0x82, 0x6,  0x1A,
+                      0x10, 0x3A, 0xD,  0xA6, 0x42, 0xFF, 0xCD, 0xCE, 0x3C,
+                      0x4,  0x1E, 0x72, 0x72, 0x83, 0x5,  0x19, 0x13, 0x39,
+                      0xE,  0xA5, 0x41, 0xFC, 0xCE, 0xCD, 0x3F, 0x7};
+  uint8_t plaintext_12[1] = {};
+  uint8_t ciphertext_12[] = {0x58, 0x83, 0x7A, 0x10, 0x56, 0x2B, 0xF,  0x1F,
+                             0x8E, 0xDB, 0xE5, 0x8C, 0xA5, 0x58, 0x11, 0xD3};
+  vec = {nonce_12, aad_12, key_12, plaintext_12, ciphertext_12, 12, 68,
+         44,       0,      16};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.3.2 60-byte auth
+  uint8_t nonce_13[] = {0xF0, 0x76, 0x1E, 0x8D, 0xCD, 0x3D,
+                        0x0,  0x1,  0x76, 0xD4, 0x57, 0xED};
+  uint8_t aad_13[] = {
+      0xE2, 0x1,  0x6,  0xD7, 0xCD, 0xD,  0xF0, 0x76, 0x1E, 0x8D, 0xCD, 0x3D,
+      0x88, 0xE5, 0x40, 0x0,  0x76, 0xD4, 0x57, 0xED, 0x8,  0x0,  0xF,  0x10,
+      0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C,
+      0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
+      0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34,
+      0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x0,  0x3};
+  uint8_t key_13[] = {0x69, 0x1D, 0x3E, 0xE9, 0x9,  0xD7, 0xF5, 0x41, 0x67,
+                      0xFD, 0x1C, 0xA0, 0xB5, 0xD7, 0x69, 0x8,  0x1F, 0x2B,
+                      0xDE, 0x1A, 0xEE, 0x65, 0x5F, 0xDB, 0xAB, 0x80, 0xBD,
+                      0x52, 0x95, 0xAE, 0x6B, 0xE7, 0x6B, 0x1F, 0x3C, 0xEB,
+                      0xB,  0xD5, 0xF7, 0x43, 0x65, 0xFF, 0x1E, 0xA2};
+  uint8_t plaintext_13[1] = {};
+  uint8_t ciphertext_13[] = {0xC2, 0x72, 0x2F, 0xF6, 0xCA, 0x29, 0xA2, 0x57,
+                             0x71, 0x8A, 0x52, 0x9D, 0x1F, 0xC,  0x6A, 0x3B};
+  vec = {nonce_13, aad_13, key_13, plaintext_13, ciphertext_13, 12, 68,
+         44,       0,      16};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.4.1 54-byte crypt
+  uint8_t nonce_14[] = {0xF0, 0x76, 0x1E, 0x8D, 0xCD, 0x3D,
+                        0x0,  0x1,  0x76, 0xD4, 0x57, 0xED};
+  uint8_t aad_14[] = {0xE2, 0x1,  0x6,  0xD7, 0xCD, 0xD,  0xF0,
+                      0x76, 0x1E, 0x8D, 0xCD, 0x3D, 0x88, 0xE5,
+                      0x4C, 0x2A, 0x76, 0xD4, 0x57, 0xED};
+  uint8_t key_14[] = {0x7,  0x1B, 0x11, 0x3B, 0xC,  0xA7, 0x43, 0xFE, 0xCC,
+                      0xCF, 0x3D, 0x5,  0x1F, 0x73, 0x73, 0x82, 0x6,  0x1A,
+                      0x10, 0x3A, 0xD,  0xA6, 0x42, 0xFF, 0xCD, 0xCE, 0x3C,
+                      0x4,  0x1E, 0x72, 0x72, 0x83, 0x5,  0x19, 0x13, 0x39,
+                      0xE,  0xA5, 0x41, 0xFC, 0xCE, 0xCD, 0x3F, 0x7};
+  uint8_t plaintext_14[] = {
+      0x8,  0x0,  0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+      0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22,
+      0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D,
+      0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x0,  0x4};
+  uint8_t ciphertext_14[] = {
+      0xFD, 0x96, 0xB7, 0x15, 0xB9, 0x3A, 0x13, 0x34, 0x6A, 0xF5, 0x1E, 0x8A,
+      0xCD, 0xF7, 0x92, 0xCD, 0xC7, 0xB2, 0x68, 0x6F, 0x85, 0x74, 0xC7, 0xE,
+      0x6B, 0xC,  0xBF, 0x16, 0x29, 0x1D, 0xED, 0x42, 0x7A, 0xD7, 0x3F, 0xEC,
+      0x48, 0xCD, 0x29, 0x8E, 0x5,  0x28, 0xA1, 0xF4, 0xC6, 0x44, 0xA9, 0x49,
+      0xFC, 0x31, 0xDC, 0x92, 0x79, 0x70, 0x6D, 0xDB, 0xA3, 0x3F};
+  vec = {nonce_14, aad_14, key_14, plaintext_14, ciphertext_14,
+         12,       20,     44,     42,           58};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.4.2 54-byte crypt
+  uint8_t nonce_15[] = {0xF0, 0x76, 0x1E, 0x8D, 0xCD, 0x3D,
+                        0x0,  0x1,  0x76, 0xD4, 0x57, 0xED};
+  uint8_t aad_15[] = {0xE2, 0x1,  0x6,  0xD7, 0xCD, 0xD,  0xF0,
+                      0x76, 0x1E, 0x8D, 0xCD, 0x3D, 0x88, 0xE5,
+                      0x4C, 0x2A, 0x76, 0xD4, 0x57, 0xED};
+  uint8_t key_15[] = {0x69, 0x1D, 0x3E, 0xE9, 0x9,  0xD7, 0xF5, 0x41, 0x67,
+                      0xFD, 0x1C, 0xA0, 0xB5, 0xD7, 0x69, 0x8,  0x1F, 0x2B,
+                      0xDE, 0x1A, 0xEE, 0x65, 0x5F, 0xDB, 0xAB, 0x80, 0xBD,
+                      0x52, 0x95, 0xAE, 0x6B, 0xE7, 0x6B, 0x1F, 0x3C, 0xEB,
+                      0xB,  0xD5, 0xF7, 0x43, 0x65, 0xFF, 0x1E, 0xA2};
+  uint8_t plaintext_15[] = {
+      0x8,  0x0,  0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+      0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22,
+      0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D,
+      0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x0,  0x4};
+  uint8_t ciphertext_15[] = {
+      0xB6, 0x8F, 0x63, 0x0,  0xC2, 0xE9, 0xAE, 0x83, 0x3B, 0xDC, 0x7,  0xE,
+      0x24, 0x2,  0x1A, 0x34, 0x77, 0x11, 0x8E, 0x78, 0xCC, 0xF8, 0x4E, 0x11,
+      0xA4, 0x85, 0xD8, 0x61, 0x47, 0x6C, 0x30, 0xF,  0x17, 0x53, 0x53, 0xD5,
+      0xCD, 0xF9, 0x20, 0x8,  0xA4, 0xF8, 0x78, 0xE6, 0xCC, 0x35, 0x77, 0x76,
+      0x80, 0x85, 0xC5, 0xA,  0xE,  0x98, 0xFD, 0xA6, 0xCB, 0xB8};
+  vec = {nonce_15, aad_15, key_15, plaintext_15, ciphertext_15,
+         12,       20,     44,     42,           58};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.5.1 65-byte auth
+  uint8_t nonce_16[] = {0x7C, 0xFD, 0xE9, 0xF9, 0xE3, 0x37,
+                        0x24, 0xC6, 0x89, 0x32, 0xD6, 0x12};
+  uint8_t aad_16[] = {
+      0x84, 0xC5, 0xD5, 0x13, 0xD2, 0xAA, 0xF6, 0xE5, 0xBB, 0xD2, 0x72, 0x77,
+      0x88, 0xE5, 0x23, 0x0,  0x89, 0x32, 0xD6, 0x12, 0x7C, 0xFD, 0xE9, 0xF9,
+      0xE3, 0x37, 0x24, 0xC6, 0x8,  0x0,  0xF,  0x10, 0x11, 0x12, 0x13, 0x14,
+      0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20,
+      0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C,
+      0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+      0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x0,  0x5};
+  uint8_t key_16[] = {0x1,  0x3F, 0xE0, 0xB,  0x5F, 0x11, 0xBE, 0x7F, 0x86,
+                      0x6D, 0xC,  0xBB, 0xC5, 0x5A, 0x7A, 0x90, 0x0,  0x3E,
+                      0xE1, 0xA,  0x5E, 0x10, 0xBF, 0x7E, 0x87, 0x6C, 0xD,
+                      0xBA, 0xC4, 0x5B, 0x7B, 0x91, 0x3,  0x3D, 0xE2, 0x9,
+                      0x5D, 0x13, 0xBC, 0x7D, 0x84, 0x6F, 0xE,  0xB9};
+  uint8_t plaintext_16[1] = {};
+  uint8_t ciphertext_16[] = {0xCC, 0xA2, 0xE,  0xEC, 0xDA, 0x62, 0x83, 0xF0,
+                             0x9B, 0xB3, 0x54, 0x3D, 0xD9, 0x9E, 0xDB, 0x9B};
+  vec = {nonce_16, aad_16, key_16, plaintext_16, ciphertext_16, 12, 81,
+         44,       0,      16};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.5.2 65-byte auth
+  uint8_t nonce_17[] = {0x7C, 0xFD, 0xE9, 0xF9, 0xE3, 0x37,
+                        0x24, 0xC6, 0x89, 0x32, 0xD6, 0x12};
+  uint8_t aad_17[] = {
+      0x84, 0xC5, 0xD5, 0x13, 0xD2, 0xAA, 0xF6, 0xE5, 0xBB, 0xD2, 0x72, 0x77,
+      0x88, 0xE5, 0x23, 0x0,  0x89, 0x32, 0xD6, 0x12, 0x7C, 0xFD, 0xE9, 0xF9,
+      0xE3, 0x37, 0x24, 0xC6, 0x8,  0x0,  0xF,  0x10, 0x11, 0x12, 0x13, 0x14,
+      0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20,
+      0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C,
+      0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+      0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x0,  0x5};
+  uint8_t key_17[] = {0x83, 0xC0, 0x93, 0xB5, 0x8D, 0xE7, 0xFF, 0xE1, 0xC0,
+                      0xDA, 0x92, 0x6A, 0xC4, 0x3F, 0xB3, 0x60, 0x9A, 0xC1,
+                      0xC8, 0xF,  0xEE, 0x1B, 0x62, 0x44, 0x97, 0xEF, 0x94,
+                      0x2E, 0x2F, 0x79, 0xA8, 0x23, 0x81, 0xC2, 0x91, 0xB7,
+                      0x8F, 0xE5, 0xFD, 0xE3, 0xC2, 0xD8, 0x90, 0x68};
+  uint8_t plaintext_17[1] = {};
+  uint8_t ciphertext_17[] = {0xB2, 0x32, 0xCC, 0x1D, 0xA5, 0x11, 0x7B, 0xF1,
+                             0x50, 0x3,  0x73, 0x4F, 0xA5, 0x99, 0xD2, 0x71};
+  vec = {nonce_17, aad_17, key_17, plaintext_17, ciphertext_17, 12, 81,
+         44,       0,      16};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE  2.6.1 61-byte crypt
+  uint8_t nonce_18[] = {0x7C, 0xFD, 0xE9, 0xF9, 0xE3, 0x37,
+                        0x24, 0xC6, 0x89, 0x32, 0xD6, 0x12};
+  uint8_t aad_18[] = {0x84, 0xC5, 0xD5, 0x13, 0xD2, 0xAA, 0xF6,
+                      0xE5, 0xBB, 0xD2, 0x72, 0x77, 0x88, 0xE5,
+                      0x2F, 0x0,  0x89, 0x32, 0xD6, 0x12, 0x7C,
+                      0xFD, 0xE9, 0xF9, 0xE3, 0x37, 0x24, 0xC6};
+  uint8_t key_18[] = {0x1,  0x3F, 0xE0, 0xB,  0x5F, 0x11, 0xBE, 0x7F, 0x86,
+                      0x6D, 0xC,  0xBB, 0xC5, 0x5A, 0x7A, 0x90, 0x0,  0x3E,
+                      0xE1, 0xA,  0x5E, 0x10, 0xBF, 0x7E, 0x87, 0x6C, 0xD,
+                      0xBA, 0xC4, 0x5B, 0x7B, 0x91, 0x3,  0x3D, 0xE2, 0x9,
+                      0x5D, 0x13, 0xBC, 0x7D, 0x84, 0x6F, 0xE,  0xB9};
+  uint8_t plaintext_18[] = {
+      0x8,  0x0,  0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
+      0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20,
+      0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A,
+      0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34,
+      0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x0,  0x6};
+  uint8_t ciphertext_18[] = {
+      0xFF, 0x19, 0x10, 0xD3, 0x5A, 0xD7, 0xE5, 0x65, 0x78, 0x90, 0xC7,
+      0xC5, 0x60, 0x14, 0x6F, 0xD0, 0x38, 0x70, 0x7F, 0x20, 0x4B, 0x66,
+      0xED, 0xBC, 0x3D, 0x16, 0x1F, 0x8A, 0xCE, 0x24, 0x4B, 0x98, 0x59,
+      0x21, 0x2,  0x3C, 0x43, 0x6E, 0x3A, 0x1C, 0x35, 0x32, 0xEC, 0xD5,
+      0xD0, 0x9A, 0x5,  0x6D, 0x70, 0xBE, 0x58, 0x3F, 0xD,  0x10, 0x82,
+      0x9D, 0x93, 0x87, 0xD0, 0x7D, 0x33, 0xD8, 0x72, 0xE4, 0x90};
+  vec = {nonce_18, aad_18, key_18, plaintext_18, ciphertext_18,
+         12,       28,     44,     49,           65};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.6.2 61-byte crypt
+  uint8_t nonce_19[] = {0x7C, 0xFD, 0xE9, 0xF9, 0xE3, 0x37,
+                        0x24, 0xC6, 0x89, 0x32, 0xD6, 0x12};
+  uint8_t aad_19[] = {0x84, 0xC5, 0xD5, 0x13, 0xD2, 0xAA, 0xF6,
+                      0xE5, 0xBB, 0xD2, 0x72, 0x77, 0x88, 0xE5,
+                      0x2F, 0x0,  0x89, 0x32, 0xD6, 0x12, 0x7C,
+                      0xFD, 0xE9, 0xF9, 0xE3, 0x37, 0x24, 0xC6};
+  uint8_t key_19[] = {0x83, 0xC0, 0x93, 0xB5, 0x8D, 0xE7, 0xFF, 0xE1, 0xC0,
+                      0xDA, 0x92, 0x6A, 0xC4, 0x3F, 0xB3, 0x60, 0x9A, 0xC1,
+                      0xC8, 0xF,  0xEE, 0x1B, 0x62, 0x44, 0x97, 0xEF, 0x94,
+                      0x2E, 0x2F, 0x79, 0xA8, 0x23, 0x81, 0xC2, 0x91, 0xB7,
+                      0x8F, 0xE5, 0xFD, 0xE3, 0xC2, 0xD8, 0x90, 0x68};
+  uint8_t plaintext_19[] = {
+      0x8,  0x0,  0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
+      0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20,
+      0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A,
+      0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34,
+      0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x0,  0x6};
+  uint8_t ciphertext_19[] = {
+      0xD,  0xB4, 0xCF, 0x95, 0x6B, 0x5F, 0x97, 0xEC, 0xA4, 0xEA, 0xB8,
+      0x2A, 0x69, 0x55, 0x30, 0x7F, 0x9A, 0xE0, 0x2A, 0x32, 0xDD, 0x7D,
+      0x93, 0xF8, 0x3D, 0x66, 0xAD, 0x4,  0xE1, 0xCF, 0xDC, 0x51, 0x82,
+      0xAD, 0x12, 0xAB, 0xDE, 0xA5, 0xBB, 0xB6, 0x19, 0xA1, 0xBD, 0x5F,
+      0xB9, 0xA5, 0x73, 0x59, 0xF,  0xBA, 0x90, 0x8E, 0x9C, 0x7A, 0x46,
+      0xC1, 0xF7, 0xBA, 0x9,  0x5,  0xD1, 0xB5, 0x5F, 0xFD, 0xA4};
+  vec = {nonce_19, aad_19, key_19, plaintext_19, ciphertext_19,
+         12,       28,     44,     49,           65};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.7.1 79-byte crypt
+  uint8_t nonce_20[] = {0x7A, 0xE8, 0xE2, 0xCA, 0x4E, 0xC5,
+                        0x0,  0x1,  0x2E, 0x58, 0x49, 0x5C};
+  uint8_t aad_20[] = {
+      0x68, 0xF2, 0xE7, 0x76, 0x96, 0xCE, 0x7A, 0xE8, 0xE2, 0xCA, 0x4E,
+      0xC5, 0x88, 0xE5, 0x41, 0x0,  0x2E, 0x58, 0x49, 0x5C, 0x8,  0x0,
+      0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19,
+      0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24,
+      0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F,
+      0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A,
+      0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45,
+      0x46, 0x47, 0x48, 0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x0,  0x7};
+  uint8_t key_20[] = {0x88, 0xEE, 0x8,  0x7F, 0xD9, 0x5D, 0xA9, 0xFB, 0xF6,
+                      0x72, 0x5A, 0xA9, 0xD7, 0x57, 0xB0, 0xCD, 0x89, 0xEF,
+                      0x9,  0x7E, 0xD8, 0x5C, 0xA8, 0xFA, 0xF7, 0x73, 0x5B,
+                      0xA8, 0xD6, 0x56, 0xB1, 0xCC, 0x8A, 0xEC, 0xA,  0x7D,
+                      0xDB, 0x5F, 0xAB, 0xF9, 0xF4, 0x70, 0x58, 0xAB};
+  uint8_t plaintext_20[1] = {};
+  uint8_t ciphertext_20[] = {0x81, 0x3F, 0xE,  0x63, 0xF,  0x96, 0xFB, 0x2D,
+                             0x3,  0xF,  0x58, 0xD8, 0x3F, 0x5C, 0xDF, 0xD0};
+  vec = {nonce_20, aad_20, key_20, plaintext_20, ciphertext_20, 12, 87,
+         44,       0,      16};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.7.2 79-byte crypt
+  uint8_t nonce_21[] = {0x7A, 0xE8, 0xE2, 0xCA, 0x4E, 0xC5,
+                        0x0,  0x1,  0x2E, 0x58, 0x49, 0x5C};
+  uint8_t aad_21[] = {
+      0x68, 0xF2, 0xE7, 0x76, 0x96, 0xCE, 0x7A, 0xE8, 0xE2, 0xCA, 0x4E,
+      0xC5, 0x88, 0xE5, 0x41, 0x0,  0x2E, 0x58, 0x49, 0x5C, 0x8,  0x0,
+      0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19,
+      0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24,
+      0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F,
+      0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A,
+      0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45,
+      0x46, 0x47, 0x48, 0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x0,  0x7};
+  uint8_t key_21[] = {0x4C, 0x97, 0x3D, 0xBC, 0x73, 0x64, 0x62, 0x16, 0x74,
+                      0xF8, 0xB5, 0xB8, 0x9E, 0x5C, 0x15, 0x51, 0x1F, 0xCE,
+                      0xD9, 0x21, 0x64, 0x90, 0xFB, 0x1C, 0x1A, 0x2C, 0xAA,
+                      0xF,  0xFE, 0x4,  0x7,  0xE5, 0x4E, 0x95, 0x3F, 0xBE,
+                      0x71, 0x66, 0x60, 0x14, 0x76, 0xFA, 0xB7, 0xBA};
+  uint8_t plaintext_21[1] = {};
+  uint8_t ciphertext_21[] = {0x77, 0xE5, 0xA4, 0x4C, 0x21, 0xEB, 0x7, 0x18,
+                             0x8A, 0xAC, 0xBD, 0x74, 0xD1, 0x98, 0xE, 0x97};
+  vec = {nonce_21, aad_21, key_21, plaintext_21, ciphertext_21, 12, 87,
+         44,       0,      16};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.8.1 61-byte crypt
+  uint8_t nonce_22[] = {0x7A, 0xE8, 0xE2, 0xCA, 0x4E, 0xC5,
+                        0x0,  0x1,  0x2E, 0x58, 0x49, 0x5C};
+  uint8_t aad_22[] = {0x68, 0xF2, 0xE7, 0x76, 0x96, 0xCE, 0x7A,
+                      0xE8, 0xE2, 0xCA, 0x4E, 0xC5, 0x88, 0xE5,
+                      0x4D, 0x0,  0x2E, 0x58, 0x49, 0x5C};
+  uint8_t key_22[] = {0x88, 0xEE, 0x8,  0x7F, 0xD9, 0x5D, 0xA9, 0xFB, 0xF6,
+                      0x72, 0x5A, 0xA9, 0xD7, 0x57, 0xB0, 0xCD, 0x89, 0xEF,
+                      0x9,  0x7E, 0xD8, 0x5C, 0xA8, 0xFA, 0xF7, 0x73, 0x5B,
+                      0xA8, 0xD6, 0x56, 0xB1, 0xCC, 0x8A, 0xEC, 0xA,  0x7D,
+                      0xDB, 0x5F, 0xAB, 0xF9, 0xF4, 0x70, 0x58, 0xAB};
+  uint8_t plaintext_22[] = {
+      0x8,  0x0,  0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+      0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22,
+      0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D,
+      0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+      0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x40, 0x41, 0x42, 0x43,
+      0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x0,  0x8};
+  uint8_t ciphertext_22[] = {
+      0x95, 0x8E, 0xC3, 0xF6, 0xD6, 0xA,  0xFE, 0xDA, 0x99, 0xEF, 0xD8, 0x88,
+      0xF1, 0x75, 0xE5, 0xFC, 0xD4, 0xC8, 0x7B, 0x9B, 0xCC, 0x5C, 0x2F, 0x54,
+      0x26, 0x25, 0x3A, 0x8B, 0x50, 0x62, 0x96, 0xC8, 0xC4, 0x33, 0x9,  0xAB,
+      0x2A, 0xDB, 0x59, 0x39, 0x46, 0x25, 0x41, 0xD9, 0x5E, 0x80, 0x81, 0x1E,
+      0x4,  0xE7, 0x6,  0xB1, 0x49, 0x8F, 0x2C, 0x40, 0x7C, 0x7F, 0xB2, 0x34,
+      0xF8, 0xCC, 0x1,  0xA6, 0x47, 0x55, 0xE,  0xE6, 0xB5, 0x57, 0xB3, 0x5A,
+      0x7E, 0x39, 0x45, 0x38, 0x18, 0x21, 0xF4};
+  vec = {nonce_22, aad_22, key_22, plaintext_22, ciphertext_22,
+         12,       20,     44,     63,           79};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+
+  // Derived from IEEE 2.8.2 61-byte crypt
+  uint8_t nonce_23[] = {0x7A, 0xE8, 0xE2, 0xCA, 0x4E, 0xC5,
+                        0x0,  0x1,  0x2E, 0x58, 0x49, 0x5C};
+  uint8_t aad_23[] = {0x68, 0xF2, 0xE7, 0x76, 0x96, 0xCE, 0x7A,
+                      0xE8, 0xE2, 0xCA, 0x4E, 0xC5, 0x88, 0xE5,
+                      0x4D, 0x0,  0x2E, 0x58, 0x49, 0x5C};
+  uint8_t key_23[] = {0x4C, 0x97, 0x3D, 0xBC, 0x73, 0x64, 0x62, 0x16, 0x74,
+                      0xF8, 0xB5, 0xB8, 0x9E, 0x5C, 0x15, 0x51, 0x1F, 0xCE,
+                      0xD9, 0x21, 0x64, 0x90, 0xFB, 0x1C, 0x1A, 0x2C, 0xAA,
+                      0xF,  0xFE, 0x4,  0x7,  0xE5, 0x4E, 0x95, 0x3F, 0xBE,
+                      0x71, 0x66, 0x60, 0x14, 0x76, 0xFA, 0xB7, 0xBA};
+  uint8_t plaintext_23[] = {
+      0x8,  0x0,  0xF,  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+      0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22,
+      0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D,
+      0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+      0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x40, 0x41, 0x42, 0x43,
+      0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x0,  0x8};
+  uint8_t ciphertext_23[] = {
+      0xB4, 0x4D, 0x7,  0x20, 0x11, 0xCD, 0x36, 0xD2, 0x72, 0xA9, 0xB7, 0xA9,
+      0x8D, 0xB9, 0xAA, 0x90, 0xCB, 0xC5, 0xC6, 0x7B, 0x93, 0xDD, 0xCE, 0x67,
+      0xC8, 0x54, 0x50, 0x32, 0x14, 0xE2, 0xE8, 0x96, 0xEC, 0x7E, 0x9D, 0xB6,
+      0x49, 0xED, 0x4B, 0xCF, 0x6F, 0x85, 0xA,  0xAC, 0x2,  0x23, 0xD0, 0xCF,
+      0x92, 0xC8, 0x3D, 0xB8, 0x7,  0x95, 0xC3, 0xA1, 0x7E, 0xCC, 0x12, 0x48,
+      0xBB, 0x0,  0x59, 0x17, 0x12, 0xB1, 0xAE, 0x71, 0xE2, 0x68, 0x16, 0x41,
+      0x96, 0x25, 0x21, 0x62, 0x81, 0xB,  0x0};
+  vec = {nonce_23, aad_23, key_23, plaintext_23, ciphertext_23,
+         12,       20,     44,     63,           79};
+  gsec_test_verify_crypter_on_test_vector(&vec, /*rekey=*/true);
+}
+
+static void gsec_test_do_vector_tests_nist() {
+  /**
+   * From:
+   * http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/proposedmodes/gcm/
+   * gcm-revised-spec.pdf
+   */
+
+  /* Test vector 1 */
+  gsec_aead_test_vector* test_vector_1;
+  const uint8_t test_vector_1_key[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                       0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                       0x00, 0x00, 0x00, 0x00};
+  const uint8_t test_vector_1_nonce[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+  const uint8_t test_vector_1_aad[1] = {};
+  const uint8_t test_vector_1_plaintext[1] = {};
+  const uint8_t test_vector_1_ciphertext_and_tag[] = {
+      0x58, 0xe2, 0xfc, 0xce, 0xfa, 0x7e, 0x30, 0x61,
+      0x36, 0x7f, 0x1d, 0x57, 0xa4, 0xe7, 0x45, 0x5a};
+  gsec_aead_malloc_test_vector(
+      &test_vector_1, test_vector_1_key,
+      sizeof(test_vector_1_key) / sizeof(uint8_t), test_vector_1_nonce,
+      sizeof(test_vector_1_nonce) / sizeof(uint8_t), test_vector_1_aad, 0,
+      test_vector_1_plaintext, 0, test_vector_1_ciphertext_and_tag,
+      sizeof(test_vector_1_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_1);
+  gsec_aead_free_test_vector(test_vector_1);
+
+  /* Test vector 2 */
+  gsec_aead_test_vector* test_vector_2;
+  const uint8_t test_vector_2_key[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                       0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                       0x00, 0x00, 0x00, 0x00};
+  const uint8_t test_vector_2_nonce[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+  const uint8_t test_vector_2_aad[1] = {};
+  const uint8_t test_vector_2_plaintext[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                             0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                             0x00, 0x00, 0x00, 0x00};
+  const uint8_t test_vector_2_ciphertext_and_tag[] = {
+      0x03, 0x88, 0xda, 0xce, 0x60, 0xb6, 0xa3, 0x92, 0xf3, 0x28, 0xc2,
+      0xb9, 0x71, 0xb2, 0xfe, 0x78, 0xab, 0x6e, 0x47, 0xd4, 0x2c, 0xec,
+      0x13, 0xbd, 0xf5, 0x3a, 0x67, 0xb2, 0x12, 0x57, 0xbd, 0xdf};
+  gsec_aead_malloc_test_vector(
+      &test_vector_2, test_vector_2_key,
+      sizeof(test_vector_2_key) / sizeof(uint8_t), test_vector_2_nonce,
+      sizeof(test_vector_2_nonce) / sizeof(uint8_t), test_vector_2_aad, 0,
+      test_vector_2_plaintext,
+      sizeof(test_vector_2_plaintext) / sizeof(uint8_t),
+      test_vector_2_ciphertext_and_tag,
+      sizeof(test_vector_2_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_2);
+  gsec_aead_free_test_vector(test_vector_2);
+
+  /* Test vector 3 */
+  gsec_aead_test_vector* test_vector_3;
+  const uint8_t test_vector_3_key[] = {0xfe, 0xff, 0xe9, 0x92, 0x86, 0x65,
+                                       0x73, 0x1c, 0x6d, 0x6a, 0x8f, 0x94,
+                                       0x67, 0x30, 0x83, 0x08};
+  const uint8_t test_vector_3_nonce[] = {0xca, 0xfe, 0xba, 0xbe, 0xfa, 0xce,
+                                         0xdb, 0xad, 0xde, 0xca, 0xf8, 0x88};
+  const uint8_t test_vector_3_aad[1] = {};
+  const uint8_t test_vector_3_plaintext[] = {
+      0xd9, 0x31, 0x32, 0x25, 0xf8, 0x84, 0x06, 0xe5, 0xa5, 0x59, 0x09,
+      0xc5, 0xaf, 0xf5, 0x26, 0x9a, 0x86, 0xa7, 0xa9, 0x53, 0x15, 0x34,
+      0xf7, 0xda, 0x2e, 0x4c, 0x30, 0x3d, 0x8a, 0x31, 0x8a, 0x72, 0x1c,
+      0x3c, 0x0c, 0x95, 0x95, 0x68, 0x09, 0x53, 0x2f, 0xcf, 0x0e, 0x24,
+      0x49, 0xa6, 0xb5, 0x25, 0xb1, 0x6a, 0xed, 0xf5, 0xaa, 0x0d, 0xe6,
+      0x57, 0xba, 0x63, 0x7b, 0x39, 0x1a, 0xaf, 0xd2, 0x55};
+  const uint8_t test_vector_3_ciphertext_and_tag[] = {
+      0x42, 0x83, 0x1e, 0xc2, 0x21, 0x77, 0x74, 0x24, 0x4b, 0x72, 0x21, 0xb7,
+      0x84, 0xd0, 0xd4, 0x9c, 0xe3, 0xaa, 0x21, 0x2f, 0x2c, 0x02, 0xa4, 0xe0,
+      0x35, 0xc1, 0x7e, 0x23, 0x29, 0xac, 0xa1, 0x2e, 0x21, 0xd5, 0x14, 0xb2,
+      0x54, 0x66, 0x93, 0x1c, 0x7d, 0x8f, 0x6a, 0x5a, 0xac, 0x84, 0xaa, 0x05,
+      0x1b, 0xa3, 0x0b, 0x39, 0x6a, 0x0a, 0xac, 0x97, 0x3d, 0x58, 0xe0, 0x91,
+      0x47, 0x3f, 0x59, 0x85, 0x4d, 0x5c, 0x2a, 0xf3, 0x27, 0xcd, 0x64, 0xa6,
+      0x2c, 0xf3, 0x5a, 0xbd, 0x2b, 0xa6, 0xfa, 0xb4};
+  gsec_aead_malloc_test_vector(
+      &test_vector_3, test_vector_3_key,
+      sizeof(test_vector_3_key) / sizeof(uint8_t), test_vector_3_nonce,
+      sizeof(test_vector_3_nonce) / sizeof(uint8_t), test_vector_3_aad, 0,
+      test_vector_3_plaintext,
+      sizeof(test_vector_3_plaintext) / sizeof(uint8_t),
+      test_vector_3_ciphertext_and_tag,
+      sizeof(test_vector_3_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_3);
+  gsec_aead_free_test_vector(test_vector_3);
+
+  /* Test vector 4 */
+  gsec_aead_test_vector* test_vector_4;
+  const uint8_t test_vector_4_key[] = {0xfe, 0xff, 0xe9, 0x92, 0x86, 0x65,
+                                       0x73, 0x1c, 0x6d, 0x6a, 0x8f, 0x94,
+                                       0x67, 0x30, 0x83, 0x08};
+  const uint8_t test_vector_4_nonce[] = {0xca, 0xfe, 0xba, 0xbe, 0xfa, 0xce,
+                                         0xdb, 0xad, 0xde, 0xca, 0xf8, 0x88};
+  const uint8_t test_vector_4_aad[] = {0xfe, 0xed, 0xfa, 0xce, 0xde, 0xad, 0xbe,
+                                       0xef, 0xfe, 0xed, 0xfa, 0xce, 0xde, 0xad,
+                                       0xbe, 0xef, 0xab, 0xad, 0xda, 0xd2};
+  const uint8_t test_vector_4_plaintext[] = {
+      0xd9, 0x31, 0x32, 0x25, 0xf8, 0x84, 0x06, 0xe5, 0xa5, 0x59, 0x09, 0xc5,
+      0xaf, 0xf5, 0x26, 0x9a, 0x86, 0xa7, 0xa9, 0x53, 0x15, 0x34, 0xf7, 0xda,
+      0x2e, 0x4c, 0x30, 0x3d, 0x8a, 0x31, 0x8a, 0x72, 0x1c, 0x3c, 0x0c, 0x95,
+      0x95, 0x68, 0x09, 0x53, 0x2f, 0xcf, 0x0e, 0x24, 0x49, 0xa6, 0xb5, 0x25,
+      0xb1, 0x6a, 0xed, 0xf5, 0xaa, 0x0d, 0xe6, 0x57, 0xba, 0x63, 0x7b, 0x39};
+  const uint8_t test_vector_4_ciphertext_and_tag[] = {
+      0x42, 0x83, 0x1e, 0xc2, 0x21, 0x77, 0x74, 0x24, 0x4b, 0x72, 0x21,
+      0xb7, 0x84, 0xd0, 0xd4, 0x9c, 0xe3, 0xaa, 0x21, 0x2f, 0x2c, 0x02,
+      0xa4, 0xe0, 0x35, 0xc1, 0x7e, 0x23, 0x29, 0xac, 0xa1, 0x2e, 0x21,
+      0xd5, 0x14, 0xb2, 0x54, 0x66, 0x93, 0x1c, 0x7d, 0x8f, 0x6a, 0x5a,
+      0xac, 0x84, 0xaa, 0x05, 0x1b, 0xa3, 0x0b, 0x39, 0x6a, 0x0a, 0xac,
+      0x97, 0x3d, 0x58, 0xe0, 0x91, 0x5b, 0xc9, 0x4f, 0xbc, 0x32, 0x21,
+      0xa5, 0xdb, 0x94, 0xfa, 0xe9, 0x5a, 0xe7, 0x12, 0x1a, 0x47};
+  gsec_aead_malloc_test_vector(
+      &test_vector_4, test_vector_4_key,
+      sizeof(test_vector_4_key) / sizeof(uint8_t), test_vector_4_nonce,
+      sizeof(test_vector_4_nonce) / sizeof(uint8_t), test_vector_4_aad,
+      sizeof(test_vector_4_aad) / sizeof(uint8_t), test_vector_4_plaintext,
+      sizeof(test_vector_4_plaintext) / sizeof(uint8_t),
+      test_vector_4_ciphertext_and_tag,
+      sizeof(test_vector_4_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_4);
+  gsec_aead_free_test_vector(test_vector_4);
+}
+
+static void gsec_test_do_vector_tests_ieee() {
+  /**
+   * From:
+   * http://www.ieee802.org/1/files/public/docs2011/
+   * bn-randall-test-vectors-0511-v1.pdf
+   */
+
+  /* 2.1.1 54-byte auth */
+  gsec_aead_test_vector* test_vector_5;
+  const uint8_t test_vector_5_key[] = {0xad, 0x7a, 0x2b, 0xd0, 0x3e, 0xac,
+                                       0x83, 0x5a, 0x6f, 0x62, 0x0f, 0xdc,
+                                       0xb5, 0x06, 0xb3, 0x45};
+  const uint8_t test_vector_5_nonce[] = {0x12, 0x15, 0x35, 0x24, 0xc0, 0x89,
+                                         0x5e, 0x81, 0xb2, 0xc2, 0x84, 0x65};
+  const uint8_t test_vector_5_aad[] = {
+      0xd6, 0x09, 0xb1, 0xf0, 0x56, 0x63, 0x7a, 0x0d, 0x46, 0xdf, 0x99, 0x8d,
+      0x88, 0xe5, 0x22, 0x2a, 0xb2, 0xc2, 0x84, 0x65, 0x12, 0x15, 0x35, 0x24,
+      0xc0, 0x89, 0x5e, 0x81, 0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14,
+      0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
+      0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c,
+      0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x00, 0x01};
+  const uint8_t test_vector_5_plaintext[1] = {};
+  const uint8_t test_vector_5_ciphertext_and_tag[] = {
+      0xf0, 0x94, 0x78, 0xa9, 0xb0, 0x90, 0x07, 0xd0,
+      0x6f, 0x46, 0xe9, 0xb6, 0xa1, 0xda, 0x25, 0xdd};
+  gsec_aead_malloc_test_vector(
+      &test_vector_5, test_vector_5_key,
+      sizeof(test_vector_5_key) / sizeof(uint8_t), test_vector_5_nonce,
+      sizeof(test_vector_5_nonce) / sizeof(uint8_t), test_vector_5_aad,
+      sizeof(test_vector_5_aad) / sizeof(uint8_t), test_vector_5_plaintext, 0,
+      test_vector_5_ciphertext_and_tag,
+      sizeof(test_vector_5_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_5);
+  gsec_aead_free_test_vector(test_vector_5);
+
+  /* 2.1.2 54-byte auth */
+  gsec_aead_test_vector* test_vector_6;
+  const uint8_t test_vector_6_key[] = {
+      0xe3, 0xc0, 0x8a, 0x8f, 0x06, 0xc6, 0xe3, 0xad, 0x95, 0xa7, 0x05,
+      0x57, 0xb2, 0x3f, 0x75, 0x48, 0x3c, 0xe3, 0x30, 0x21, 0xa9, 0xc7,
+      0x2b, 0x70, 0x25, 0x66, 0x62, 0x04, 0xc6, 0x9c, 0x0b, 0x72};
+
+  const uint8_t test_vector_6_nonce[] = {0x12, 0x15, 0x35, 0x24, 0xc0, 0x89,
+                                         0x5e, 0x81, 0xb2, 0xc2, 0x84, 0x65};
+  const uint8_t test_vector_6_aad[] = {
+      0xd6, 0x09, 0xb1, 0xf0, 0x56, 0x63, 0x7a, 0x0d, 0x46, 0xdf, 0x99, 0x8d,
+      0x88, 0xe5, 0x22, 0x2a, 0xb2, 0xc2, 0x84, 0x65, 0x12, 0x15, 0x35, 0x24,
+      0xc0, 0x89, 0x5e, 0x81, 0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14,
+      0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
+      0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c,
+      0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x00, 0x01};
+  const uint8_t test_vector_6_plaintext[1] = {};
+  const uint8_t test_vector_6_ciphertext_and_tag[] = {
+      0x2f, 0x0b, 0xc5, 0xaf, 0x40, 0x9e, 0x06, 0xd6,
+      0x09, 0xea, 0x8b, 0x7d, 0x0f, 0xa5, 0xea, 0x50};
+  gsec_aead_malloc_test_vector(
+      &test_vector_6, test_vector_6_key,
+      sizeof(test_vector_6_key) / sizeof(uint8_t), test_vector_6_nonce,
+      sizeof(test_vector_6_nonce) / sizeof(uint8_t), test_vector_6_aad,
+      sizeof(test_vector_6_aad) / sizeof(uint8_t), test_vector_6_plaintext, 0,
+      test_vector_6_ciphertext_and_tag,
+      sizeof(test_vector_6_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_6);
+  gsec_aead_free_test_vector(test_vector_6);
+
+  /* 2.2.1 60-byte crypt */
+  gsec_aead_test_vector* test_vector_7;
+  const uint8_t test_vector_7_key[] = {0xad, 0x7a, 0x2b, 0xd0, 0x3e, 0xac,
+                                       0x83, 0x5a, 0x6f, 0x62, 0x0f, 0xdc,
+                                       0xb5, 0x06, 0xb3, 0x45};
+
+  const uint8_t test_vector_7_nonce[] = {0x12, 0x15, 0x35, 0x24, 0xc0, 0x89,
+                                         0x5e, 0x81, 0xb2, 0xc2, 0x84, 0x65};
+  const uint8_t test_vector_7_aad[] = {
+      0xd6, 0x09, 0xb1, 0xf0, 0x56, 0x63, 0x7a, 0x0d, 0x46, 0xdf,
+      0x99, 0x8d, 0x88, 0xe5, 0x2e, 0x00, 0xb2, 0xc2, 0x84, 0x65,
+      0x12, 0x15, 0x35, 0x24, 0xc0, 0x89, 0x5e, 0x81};
+  const uint8_t test_vector_7_plaintext[] = {
+      0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
+      0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24,
+      0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30,
+      0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x00, 0x02};
+  const uint8_t test_vector_7_ciphertext_and_tag[] = {
+      0x70, 0x1a, 0xfa, 0x1c, 0xc0, 0x39, 0xc0, 0xd7, 0x65, 0x12, 0x8a,
+      0x66, 0x5d, 0xab, 0x69, 0x24, 0x38, 0x99, 0xbf, 0x73, 0x18, 0xcc,
+      0xdc, 0x81, 0xc9, 0x93, 0x1d, 0xa1, 0x7f, 0xbe, 0x8e, 0xdd, 0x7d,
+      0x17, 0xcb, 0x8b, 0x4c, 0x26, 0xfc, 0x81, 0xe3, 0x28, 0x4f, 0x2b,
+      0x7f, 0xba, 0x71, 0x3d, 0x4f, 0x8d, 0x55, 0xe7, 0xd3, 0xf0, 0x6f,
+      0xd5, 0xa1, 0x3c, 0x0c, 0x29, 0xb9, 0xd5, 0xb8, 0x80};
+  gsec_aead_malloc_test_vector(
+      &test_vector_7, test_vector_7_key,
+      sizeof(test_vector_7_key) / sizeof(uint8_t), test_vector_7_nonce,
+      sizeof(test_vector_7_nonce) / sizeof(uint8_t), test_vector_7_aad,
+      sizeof(test_vector_7_aad) / sizeof(uint8_t), test_vector_7_plaintext,
+      sizeof(test_vector_7_plaintext) / sizeof(uint8_t),
+      test_vector_7_ciphertext_and_tag,
+      sizeof(test_vector_7_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_7);
+  gsec_aead_free_test_vector(test_vector_7);
+
+  /* 2.2.2 60-byte crypt */
+  gsec_aead_test_vector* test_vector_8;
+  const uint8_t test_vector_8_key[] = {
+      0xe3, 0xc0, 0x8a, 0x8f, 0x06, 0xc6, 0xe3, 0xad, 0x95, 0xa7, 0x05,
+      0x57, 0xb2, 0x3f, 0x75, 0x48, 0x3c, 0xe3, 0x30, 0x21, 0xa9, 0xc7,
+      0x2b, 0x70, 0x25, 0x66, 0x62, 0x04, 0xc6, 0x9c, 0x0b, 0x72};
+  const uint8_t test_vector_8_nonce[] = {0x12, 0x15, 0x35, 0x24, 0xc0, 0x89,
+                                         0x5e, 0x81, 0xb2, 0xc2, 0x84, 0x65};
+  const uint8_t test_vector_8_aad[] = {
+      0xd6, 0x09, 0xb1, 0xf0, 0x56, 0x63, 0x7a, 0x0d, 0x46, 0xdf,
+      0x99, 0x8d, 0x88, 0xe5, 0x2e, 0x00, 0xb2, 0xc2, 0x84, 0x65,
+      0x12, 0x15, 0x35, 0x24, 0xc0, 0x89, 0x5e, 0x81};
+  const uint8_t test_vector_8_plaintext[] = {
+      0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
+      0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24,
+      0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30,
+      0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x00, 0x02};
+  const uint8_t test_vector_8_ciphertext_and_tag[] = {
+      0xe2, 0x00, 0x6e, 0xb4, 0x2f, 0x52, 0x77, 0x02, 0x2d, 0x9b, 0x19,
+      0x92, 0x5b, 0xc4, 0x19, 0xd7, 0xa5, 0x92, 0x66, 0x6c, 0x92, 0x5f,
+      0xe2, 0xef, 0x71, 0x8e, 0xb4, 0xe3, 0x08, 0xef, 0xea, 0xa7, 0xc5,
+      0x27, 0x3b, 0x39, 0x41, 0x18, 0x86, 0x0a, 0x5b, 0xe2, 0xa9, 0x7f,
+      0x56, 0xab, 0x78, 0x36, 0x5c, 0xa5, 0x97, 0xcd, 0xbb, 0x3e, 0xdb,
+      0x8d, 0x1a, 0x11, 0x51, 0xea, 0x0a, 0xf7, 0xb4, 0x36};
+  gsec_aead_malloc_test_vector(
+      &test_vector_8, test_vector_8_key,
+      sizeof(test_vector_8_key) / sizeof(uint8_t), test_vector_8_nonce,
+      sizeof(test_vector_8_nonce) / sizeof(uint8_t), test_vector_8_aad,
+      sizeof(test_vector_8_aad) / sizeof(uint8_t), test_vector_8_plaintext,
+      sizeof(test_vector_8_plaintext) / sizeof(uint8_t),
+      test_vector_8_ciphertext_and_tag,
+      sizeof(test_vector_8_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_8);
+  gsec_aead_free_test_vector(test_vector_8);
+
+  /* 2.3.1 60-byte auth */
+  gsec_aead_test_vector* test_vector_9;
+  const uint8_t test_vector_9_key[] = {0x07, 0x1b, 0x11, 0x3b, 0x0c, 0xa7,
+                                       0x43, 0xfe, 0xcc, 0xcf, 0x3d, 0x05,
+                                       0x1f, 0x73, 0x73, 0x82};
+  const uint8_t test_vector_9_nonce[] = {0xf0, 0x76, 0x1e, 0x8d, 0xcd, 0x3d,
+                                         0x00, 0x01, 0x76, 0xd4, 0x57, 0xed};
+  const uint8_t test_vector_9_aad[] = {
+      0xe2, 0x01, 0x06, 0xd7, 0xcd, 0x0d, 0xf0, 0x76, 0x1e, 0x8d, 0xcd, 0x3d,
+      0x88, 0xe5, 0x40, 0x00, 0x76, 0xd4, 0x57, 0xed, 0x08, 0x00, 0x0f, 0x10,
+      0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c,
+      0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
+      0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34,
+      0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x00, 0x03};
+  const uint8_t test_vector_9_plaintext[1] = {};
+  const uint8_t test_vector_9_ciphertext_and_tag[] = {
+      0x0c, 0x01, 0x7b, 0xc7, 0x3b, 0x22, 0x7d, 0xfc,
+      0xc9, 0xba, 0xfa, 0x1c, 0x41, 0xac, 0xc3, 0x53};
+  gsec_aead_malloc_test_vector(
+      &test_vector_9, test_vector_9_key,
+      sizeof(test_vector_9_key) / sizeof(uint8_t), test_vector_9_nonce,
+      sizeof(test_vector_9_nonce) / sizeof(uint8_t), test_vector_9_aad,
+      sizeof(test_vector_9_aad) / sizeof(uint8_t), test_vector_9_plaintext, 0,
+      test_vector_9_ciphertext_and_tag,
+      sizeof(test_vector_9_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_9);
+  gsec_aead_free_test_vector(test_vector_9);
+
+  /* 2.3.2 60-byte auth */
+  gsec_aead_test_vector* test_vector_10;
+  const uint8_t test_vector_10_key[] = {
+      0x69, 0x1d, 0x3e, 0xe9, 0x09, 0xd7, 0xf5, 0x41, 0x67, 0xfd, 0x1c,
+      0xa0, 0xb5, 0xd7, 0x69, 0x08, 0x1f, 0x2b, 0xde, 0x1a, 0xee, 0x65,
+      0x5f, 0xdb, 0xab, 0x80, 0xbd, 0x52, 0x95, 0xae, 0x6b, 0xe7};
+  const uint8_t test_vector_10_nonce[] = {0xf0, 0x76, 0x1e, 0x8d, 0xcd, 0x3d,
+                                          0x00, 0x01, 0x76, 0xd4, 0x57, 0xed};
+  const uint8_t test_vector_10_aad[] = {
+      0xe2, 0x01, 0x06, 0xd7, 0xcd, 0x0d, 0xf0, 0x76, 0x1e, 0x8d, 0xcd, 0x3d,
+      0x88, 0xe5, 0x40, 0x00, 0x76, 0xd4, 0x57, 0xed, 0x08, 0x00, 0x0f, 0x10,
+      0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c,
+      0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
+      0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34,
+      0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x00, 0x03};
+  const uint8_t test_vector_10_plaintext[1] = {};
+  const uint8_t test_vector_10_ciphertext_and_tag[] = {
+      0x35, 0x21, 0x7c, 0x77, 0x4b, 0xbc, 0x31, 0xb6,
+      0x31, 0x66, 0xbc, 0xf9, 0xd4, 0xab, 0xed, 0x07};
+  gsec_aead_malloc_test_vector(
+      &test_vector_10, test_vector_10_key,
+      sizeof(test_vector_10_key) / sizeof(uint8_t), test_vector_10_nonce,
+      sizeof(test_vector_10_nonce) / sizeof(uint8_t), test_vector_10_aad,
+      sizeof(test_vector_10_aad) / sizeof(uint8_t), test_vector_10_plaintext, 0,
+      test_vector_10_ciphertext_and_tag,
+      sizeof(test_vector_10_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_10);
+  gsec_aead_free_test_vector(test_vector_10);
+
+  /* 2.4.1 54-byte crypt */
+  gsec_aead_test_vector* test_vector_11;
+  const uint8_t test_vector_11_key[] = {0x07, 0x1b, 0x11, 0x3b, 0x0c, 0xa7,
+                                        0x43, 0xfe, 0xcc, 0xcf, 0x3d, 0x05,
+                                        0x1f, 0x73, 0x73, 0x82};
+  const uint8_t test_vector_11_nonce[] = {0xf0, 0x76, 0x1e, 0x8d, 0xcd, 0x3d,
+                                          0x00, 0x01, 0x76, 0xd4, 0x57, 0xed};
+  const uint8_t test_vector_11_aad[] = {
+      0xe2, 0x01, 0x06, 0xd7, 0xcd, 0x0d, 0xf0, 0x76, 0x1e, 0x8d,
+      0xcd, 0x3d, 0x88, 0xe5, 0x4c, 0x2a, 0x76, 0xd4, 0x57, 0xed};
+  const uint8_t test_vector_11_plaintext[] = {
+      0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+      0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22,
+      0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d,
+      0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x00, 0x04};
+  const uint8_t test_vector_11_ciphertext_and_tag[] = {
+      0x13, 0xb4, 0xc7, 0x2b, 0x38, 0x9d, 0xc5, 0x01, 0x8e, 0x72, 0xa1, 0x71,
+      0xdd, 0x85, 0xa5, 0xd3, 0x75, 0x22, 0x74, 0xd3, 0xa0, 0x19, 0xfb, 0xca,
+      0xed, 0x09, 0xa4, 0x25, 0xcd, 0x9b, 0x2e, 0x1c, 0x9b, 0x72, 0xee, 0xe7,
+      0xc9, 0xde, 0x7d, 0x52, 0xb3, 0xf3, 0xd6, 0xa5, 0x28, 0x4f, 0x4a, 0x6d,
+      0x3f, 0xe2, 0x2a, 0x5d, 0x6c, 0x2b, 0x96, 0x04, 0x94, 0xc3};
+  gsec_aead_malloc_test_vector(
+      &test_vector_11, test_vector_11_key,
+      sizeof(test_vector_11_key) / sizeof(uint8_t), test_vector_11_nonce,
+      sizeof(test_vector_11_nonce) / sizeof(uint8_t), test_vector_11_aad,
+      sizeof(test_vector_11_aad) / sizeof(uint8_t), test_vector_11_plaintext,
+      sizeof(test_vector_11_plaintext) / sizeof(uint8_t),
+      test_vector_11_ciphertext_and_tag,
+      sizeof(test_vector_11_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_11);
+  gsec_aead_free_test_vector(test_vector_11);
+
+  /* 2.4.2 54-byte crypt */
+  gsec_aead_test_vector* test_vector_12;
+  const uint8_t test_vector_12_key[] = {
+      0x69, 0x1d, 0x3e, 0xe9, 0x09, 0xd7, 0xf5, 0x41, 0x67, 0xfd, 0x1c,
+      0xa0, 0xb5, 0xd7, 0x69, 0x08, 0x1f, 0x2b, 0xde, 0x1a, 0xee, 0x65,
+      0x5f, 0xdb, 0xab, 0x80, 0xbd, 0x52, 0x95, 0xae, 0x6b, 0xe7};
+  const uint8_t test_vector_12_nonce[] = {0xf0, 0x76, 0x1e, 0x8d, 0xcd, 0x3d,
+                                          0x00, 0x01, 0x76, 0xd4, 0x57, 0xed};
+  const uint8_t test_vector_12_aad[] = {
+      0xe2, 0x01, 0x06, 0xd7, 0xcd, 0x0d, 0xf0, 0x76, 0x1e, 0x8d,
+      0xcd, 0x3d, 0x88, 0xe5, 0x4c, 0x2a, 0x76, 0xd4, 0x57, 0xed};
+  const uint8_t test_vector_12_plaintext[] = {
+      0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+      0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22,
+      0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d,
+      0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x00, 0x04};
+  const uint8_t test_vector_12_ciphertext_and_tag[] = {
+      0xc1, 0x62, 0x3f, 0x55, 0x73, 0x0c, 0x93, 0x53, 0x30, 0x97, 0xad, 0xda,
+      0xd2, 0x56, 0x64, 0x96, 0x61, 0x25, 0x35, 0x2b, 0x43, 0xad, 0xac, 0xbd,
+      0x61, 0xc5, 0xef, 0x3a, 0xc9, 0x0b, 0x5b, 0xee, 0x92, 0x9c, 0xe4, 0x63,
+      0x0e, 0xa7, 0x9f, 0x6c, 0xe5, 0x19, 0x12, 0xaf, 0x39, 0xc2, 0xd1, 0xfd,
+      0xc2, 0x05, 0x1f, 0x8b, 0x7b, 0x3c, 0x9d, 0x39, 0x7e, 0xf2};
+  gsec_aead_malloc_test_vector(
+      &test_vector_12, test_vector_12_key,
+      sizeof(test_vector_12_key) / sizeof(uint8_t), test_vector_12_nonce,
+      sizeof(test_vector_12_nonce) / sizeof(uint8_t), test_vector_12_aad,
+      sizeof(test_vector_12_aad) / sizeof(uint8_t), test_vector_12_plaintext,
+      sizeof(test_vector_12_plaintext) / sizeof(uint8_t),
+      test_vector_12_ciphertext_and_tag,
+      sizeof(test_vector_12_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_12);
+  gsec_aead_free_test_vector(test_vector_12);
+
+  /* 2.5.1 65-byte auth */
+  gsec_aead_test_vector* test_vector_13;
+  const uint8_t test_vector_13_key[] = {0x01, 0x3f, 0xe0, 0x0b, 0x5f, 0x11,
+                                        0xbe, 0x7f, 0x86, 0x6d, 0x0c, 0xbb,
+                                        0xc5, 0x5a, 0x7a, 0x90};
+  const uint8_t test_vector_13_nonce[] = {0x7c, 0xfd, 0xe9, 0xf9, 0xe3, 0x37,
+                                          0x24, 0xc6, 0x89, 0x32, 0xd6, 0x12};
+  const uint8_t test_vector_13_aad[] = {
+      0x84, 0xc5, 0xd5, 0x13, 0xd2, 0xaa, 0xf6, 0xe5, 0xbb, 0xd2, 0x72, 0x77,
+      0x88, 0xe5, 0x23, 0x00, 0x89, 0x32, 0xd6, 0x12, 0x7c, 0xfd, 0xe9, 0xf9,
+      0xe3, 0x37, 0x24, 0xc6, 0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14,
+      0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
+      0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c,
+      0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+      0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x00, 0x05};
+  const uint8_t test_vector_13_plaintext[1] = {};
+  const uint8_t test_vector_13_ciphertext_and_tag[] = {
+      0x21, 0x78, 0x67, 0xe5, 0x0c, 0x2d, 0xad, 0x74,
+      0xc2, 0x8c, 0x3b, 0x50, 0xab, 0xdf, 0x69, 0x5a};
+  gsec_aead_malloc_test_vector(
+      &test_vector_13, test_vector_13_key,
+      sizeof(test_vector_13_key) / sizeof(uint8_t), test_vector_13_nonce,
+      sizeof(test_vector_13_nonce) / sizeof(uint8_t), test_vector_13_aad,
+      sizeof(test_vector_13_aad) / sizeof(uint8_t), test_vector_13_plaintext, 0,
+      test_vector_13_ciphertext_and_tag,
+      sizeof(test_vector_13_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_13);
+  gsec_aead_free_test_vector(test_vector_13);
+
+  /* 2.5.2 65-byte auth */
+  gsec_aead_test_vector* test_vector_14;
+  const uint8_t test_vector_14_key[] = {
+      0x83, 0xc0, 0x93, 0xb5, 0x8d, 0xe7, 0xff, 0xe1, 0xc0, 0xda, 0x92,
+      0x6a, 0xc4, 0x3f, 0xb3, 0x60, 0x9a, 0xc1, 0xc8, 0x0f, 0xee, 0x1b,
+      0x62, 0x44, 0x97, 0xef, 0x94, 0x2e, 0x2f, 0x79, 0xa8, 0x23};
+  const uint8_t test_vector_14_nonce[] = {0x7c, 0xfd, 0xe9, 0xf9, 0xe3, 0x37,
+                                          0x24, 0xc6, 0x89, 0x32, 0xd6, 0x12};
+  const uint8_t test_vector_14_aad[] = {
+      0x84, 0xc5, 0xd5, 0x13, 0xd2, 0xaa, 0xf6, 0xe5, 0xbb, 0xd2, 0x72, 0x77,
+      0x88, 0xe5, 0x23, 0x00, 0x89, 0x32, 0xd6, 0x12, 0x7c, 0xfd, 0xe9, 0xf9,
+      0xe3, 0x37, 0x24, 0xc6, 0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14,
+      0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
+      0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c,
+      0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+      0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x00, 0x05};
+  const uint8_t test_vector_14_plaintext[1] = {};
+  const uint8_t test_vector_14_ciphertext_and_tag[] = {
+      0x6e, 0xe1, 0x60, 0xe8, 0xfa, 0xec, 0xa4, 0xb3,
+      0x6c, 0x86, 0xb2, 0x34, 0x92, 0x0c, 0xa9, 0x75};
+  gsec_aead_malloc_test_vector(
+      &test_vector_14, test_vector_14_key,
+      sizeof(test_vector_14_key) / sizeof(uint8_t), test_vector_14_nonce,
+      sizeof(test_vector_14_nonce) / sizeof(uint8_t), test_vector_14_aad,
+      sizeof(test_vector_14_aad) / sizeof(uint8_t), test_vector_14_plaintext, 0,
+      test_vector_14_ciphertext_and_tag,
+      sizeof(test_vector_14_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_14);
+  gsec_aead_free_test_vector(test_vector_14);
+
+  /* 2.6.1 61-byte crypt */
+  gsec_aead_test_vector* test_vector_15;
+  const uint8_t test_vector_15_key[] = {0x01, 0x3f, 0xe0, 0x0b, 0x5f, 0x11,
+                                        0xbe, 0x7f, 0x86, 0x6d, 0x0c, 0xbb,
+                                        0xc5, 0x5a, 0x7a, 0x90};
+  const uint8_t test_vector_15_nonce[] = {0x7c, 0xfd, 0xe9, 0xf9, 0xe3, 0x37,
+                                          0x24, 0xc6, 0x89, 0x32, 0xd6, 0x12};
+  const uint8_t test_vector_15_aad[] = {
+      0x84, 0xc5, 0xd5, 0x13, 0xd2, 0xaa, 0xf6, 0xe5, 0xbb, 0xd2,
+      0x72, 0x77, 0x88, 0xe5, 0x2f, 0x00, 0x89, 0x32, 0xd6, 0x12,
+      0x7c, 0xfd, 0xe9, 0xf9, 0xe3, 0x37, 0x24, 0xc6};
+  const uint8_t test_vector_15_plaintext[] = {
+      0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
+      0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
+      0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a,
+      0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34,
+      0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x00, 0x06};
+  const uint8_t test_vector_15_ciphertext_and_tag[] = {
+      0x3a, 0x4d, 0xe6, 0xfa, 0x32, 0x19, 0x10, 0x14, 0xdb, 0xb3, 0x03,
+      0xd9, 0x2e, 0xe3, 0xa9, 0xe8, 0xa1, 0xb5, 0x99, 0xc1, 0x4d, 0x22,
+      0xfb, 0x08, 0x00, 0x96, 0xe1, 0x38, 0x11, 0x81, 0x6a, 0x3c, 0x9c,
+      0x9b, 0xcf, 0x7c, 0x1b, 0x9b, 0x96, 0xda, 0x80, 0x92, 0x04, 0xe2,
+      0x9d, 0x0e, 0x2a, 0x76, 0x42, 0xbf, 0xd3, 0x10, 0xa4, 0x83, 0x7c,
+      0x81, 0x6c, 0xcf, 0xa5, 0xac, 0x23, 0xab, 0x00, 0x39, 0x88};
+  gsec_aead_malloc_test_vector(
+      &test_vector_15, test_vector_15_key,
+      sizeof(test_vector_15_key) / sizeof(uint8_t), test_vector_15_nonce,
+      sizeof(test_vector_15_nonce) / sizeof(uint8_t), test_vector_15_aad,
+      sizeof(test_vector_15_aad) / sizeof(uint8_t), test_vector_15_plaintext,
+      sizeof(test_vector_15_plaintext) / sizeof(uint8_t),
+      test_vector_15_ciphertext_and_tag,
+      sizeof(test_vector_15_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_15);
+  gsec_aead_free_test_vector(test_vector_15);
+
+  /* 2.6.2 61-byte crypt */
+  gsec_aead_test_vector* test_vector_16;
+  const uint8_t test_vector_16_key[] = {
+      0x83, 0xc0, 0x93, 0xb5, 0x8d, 0xe7, 0xff, 0xe1, 0xc0, 0xda, 0x92,
+      0x6a, 0xc4, 0x3f, 0xb3, 0x60, 0x9a, 0xc1, 0xc8, 0x0f, 0xee, 0x1b,
+      0x62, 0x44, 0x97, 0xef, 0x94, 0x2e, 0x2f, 0x79, 0xa8, 0x23};
+  const uint8_t test_vector_16_nonce[] = {0x7c, 0xfd, 0xe9, 0xf9, 0xe3, 0x37,
+                                          0x24, 0xc6, 0x89, 0x32, 0xd6, 0x12};
+  const uint8_t test_vector_16_aad[] = {
+      0x84, 0xc5, 0xd5, 0x13, 0xd2, 0xaa, 0xf6, 0xe5, 0xbb, 0xd2,
+      0x72, 0x77, 0x88, 0xe5, 0x2f, 0x00, 0x89, 0x32, 0xd6, 0x12,
+      0x7c, 0xfd, 0xe9, 0xf9, 0xe3, 0x37, 0x24, 0xc6};
+  const uint8_t test_vector_16_plaintext[] = {
+      0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
+      0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
+      0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a,
+      0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34,
+      0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x00, 0x06};
+  const uint8_t test_vector_16_ciphertext_and_tag[] = {
+      0x11, 0x02, 0x22, 0xff, 0x80, 0x50, 0xcb, 0xec, 0xe6, 0x6a, 0x81,
+      0x3a, 0xd0, 0x9a, 0x73, 0xed, 0x7a, 0x9a, 0x08, 0x9c, 0x10, 0x6b,
+      0x95, 0x93, 0x89, 0x16, 0x8e, 0xd6, 0xe8, 0x69, 0x8e, 0xa9, 0x02,
+      0xeb, 0x12, 0x77, 0xdb, 0xec, 0x2e, 0x68, 0xe4, 0x73, 0x15, 0x5a,
+      0x15, 0xa7, 0xda, 0xee, 0xd4, 0xa1, 0x0f, 0x4e, 0x05, 0x13, 0x9c,
+      0x23, 0xdf, 0x00, 0xb3, 0xaa, 0xdc, 0x71, 0xf0, 0x59, 0x6a};
+  gsec_aead_malloc_test_vector(
+      &test_vector_16, test_vector_16_key,
+      sizeof(test_vector_16_key) / sizeof(uint8_t), test_vector_16_nonce,
+      sizeof(test_vector_16_nonce) / sizeof(uint8_t), test_vector_16_aad,
+      sizeof(test_vector_16_aad) / sizeof(uint8_t), test_vector_16_plaintext,
+      sizeof(test_vector_16_plaintext) / sizeof(uint8_t),
+      test_vector_16_ciphertext_and_tag,
+      sizeof(test_vector_16_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_16);
+  gsec_aead_free_test_vector(test_vector_16);
+
+  /* 2.7.1 79-byte crypt */
+  gsec_aead_test_vector* test_vector_17;
+  const uint8_t test_vector_17_key[] = {0x88, 0xee, 0x08, 0x7f, 0xd9, 0x5d,
+                                        0xa9, 0xfb, 0xf6, 0x72, 0x5a, 0xa9,
+                                        0xd7, 0x57, 0xb0, 0xcd};
+  const uint8_t test_vector_17_nonce[] = {0x7a, 0xe8, 0xe2, 0xca, 0x4e, 0xc5,
+                                          0x00, 0x01, 0x2e, 0x58, 0x49, 0x5c};
+  const uint8_t test_vector_17_aad[] = {
+      0x68, 0xf2, 0xe7, 0x76, 0x96, 0xce, 0x7a, 0xe8, 0xe2, 0xca, 0x4e,
+      0xc5, 0x88, 0xe5, 0x41, 0x00, 0x2e, 0x58, 0x49, 0x5c, 0x08, 0x00,
+      0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19,
+      0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24,
+      0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
+      0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a,
+      0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45,
+      0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x00, 0x07};
+  const uint8_t test_vector_17_plaintext[1] = {};
+  const uint8_t test_vector_17_ciphertext_and_tag[] = {
+      0x07, 0x92, 0x2b, 0x8e, 0xbc, 0xf1, 0x0b, 0xb2,
+      0x29, 0x75, 0x88, 0xca, 0x4c, 0x61, 0x45, 0x23};
+  gsec_aead_malloc_test_vector(
+      &test_vector_17, test_vector_17_key,
+      sizeof(test_vector_17_key) / sizeof(uint8_t), test_vector_17_nonce,
+      sizeof(test_vector_17_nonce) / sizeof(uint8_t), test_vector_17_aad,
+      sizeof(test_vector_17_aad) / sizeof(uint8_t), test_vector_17_plaintext, 0,
+      test_vector_17_ciphertext_and_tag,
+      sizeof(test_vector_17_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_17);
+  gsec_aead_free_test_vector(test_vector_17);
+
+  /* 2.7.2 79-byte crypt */
+  gsec_aead_test_vector* test_vector_18;
+  const uint8_t test_vector_18_key[] = {
+      0x4c, 0x97, 0x3d, 0xbc, 0x73, 0x64, 0x62, 0x16, 0x74, 0xf8, 0xb5,
+      0xb8, 0x9e, 0x5c, 0x15, 0x51, 0x1f, 0xce, 0xd9, 0x21, 0x64, 0x90,
+      0xfb, 0x1c, 0x1a, 0x2c, 0xaa, 0x0f, 0xfe, 0x04, 0x07, 0xe5};
+  const uint8_t test_vector_18_nonce[] = {0x7a, 0xe8, 0xe2, 0xca, 0x4e, 0xc5,
+                                          0x00, 0x01, 0x2e, 0x58, 0x49, 0x5c};
+  const uint8_t test_vector_18_aad[] = {
+      0x68, 0xf2, 0xe7, 0x76, 0x96, 0xce, 0x7a, 0xe8, 0xe2, 0xca, 0x4e,
+      0xc5, 0x88, 0xe5, 0x41, 0x00, 0x2e, 0x58, 0x49, 0x5c, 0x08, 0x00,
+      0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19,
+      0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24,
+      0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
+      0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a,
+      0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45,
+      0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x00, 0x07};
+  const uint8_t test_vector_18_plaintext[1] = {};
+  const uint8_t test_vector_18_ciphertext_and_tag[] = {
+      0x00, 0xbd, 0xa1, 0xb7, 0xe8, 0x76, 0x08, 0xbc,
+      0xbf, 0x47, 0x0f, 0x12, 0x15, 0x7f, 0x4c, 0x07};
+  gsec_aead_malloc_test_vector(
+      &test_vector_18, test_vector_18_key,
+      sizeof(test_vector_18_key) / sizeof(uint8_t), test_vector_18_nonce,
+      sizeof(test_vector_18_nonce) / sizeof(uint8_t), test_vector_18_aad,
+      sizeof(test_vector_18_aad) / sizeof(uint8_t), test_vector_18_plaintext, 0,
+      test_vector_18_ciphertext_and_tag,
+      sizeof(test_vector_18_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_18);
+  gsec_aead_free_test_vector(test_vector_18);
+
+  /* 2.8.1 61-byte crypt */
+  gsec_aead_test_vector* test_vector_19;
+  const uint8_t test_vector_19_key[] = {0x88, 0xee, 0x08, 0x7f, 0xd9, 0x5d,
+                                        0xa9, 0xfb, 0xf6, 0x72, 0x5a, 0xa9,
+                                        0xd7, 0x57, 0xb0, 0xcd};
+  const uint8_t test_vector_19_nonce[] = {0x7a, 0xe8, 0xe2, 0xca, 0x4e, 0xc5,
+                                          0x00, 0x01, 0x2e, 0x58, 0x49, 0x5c};
+  const uint8_t test_vector_19_aad[] = {
+      0x68, 0xf2, 0xe7, 0x76, 0x96, 0xce, 0x7a, 0xe8, 0xe2, 0xca,
+      0x4e, 0xc5, 0x88, 0xe5, 0x4d, 0x00, 0x2e, 0x58, 0x49, 0x5c};
+  const uint8_t test_vector_19_plaintext[] = {
+      0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+      0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22,
+      0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d,
+      0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+      0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x40, 0x41, 0x42, 0x43,
+      0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x00, 0x08};
+  const uint8_t test_vector_19_ciphertext_and_tag[] = {
+      0xc3, 0x1f, 0x53, 0xd9, 0x9e, 0x56, 0x87, 0xf7, 0x36, 0x51, 0x19, 0xb8,
+      0x32, 0xd2, 0xaa, 0xe7, 0x07, 0x41, 0xd5, 0x93, 0xf1, 0xf9, 0xe2, 0xab,
+      0x34, 0x55, 0x77, 0x9b, 0x07, 0x8e, 0xb8, 0xfe, 0xac, 0xdf, 0xec, 0x1f,
+      0x8e, 0x3e, 0x52, 0x77, 0xf8, 0x18, 0x0b, 0x43, 0x36, 0x1f, 0x65, 0x12,
+      0xad, 0xb1, 0x6d, 0x2e, 0x38, 0x54, 0x8a, 0x2c, 0x71, 0x9d, 0xba, 0x72,
+      0x28, 0xd8, 0x40, 0x88, 0xf8, 0x75, 0x7a, 0xdb, 0x8a, 0xa7, 0x88, 0xd8,
+      0xf6, 0x5a, 0xd6, 0x68, 0xbe, 0x70, 0xe7};
+  gsec_aead_malloc_test_vector(
+      &test_vector_19, test_vector_19_key,
+      sizeof(test_vector_19_key) / sizeof(uint8_t), test_vector_19_nonce,
+      sizeof(test_vector_19_nonce) / sizeof(uint8_t), test_vector_19_aad,
+      sizeof(test_vector_19_aad) / sizeof(uint8_t), test_vector_19_plaintext,
+      sizeof(test_vector_19_plaintext) / sizeof(uint8_t),
+      test_vector_19_ciphertext_and_tag,
+      sizeof(test_vector_19_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_19);
+  gsec_aead_free_test_vector(test_vector_19);
+
+  /* 2.8.2 61-byte crypt */
+  gsec_aead_test_vector* test_vector_20;
+  const uint8_t test_vector_20_key[] = {
+      0x4c, 0x97, 0x3d, 0xbc, 0x73, 0x64, 0x62, 0x16, 0x74, 0xf8, 0xb5,
+      0xb8, 0x9e, 0x5c, 0x15, 0x51, 0x1f, 0xce, 0xd9, 0x21, 0x64, 0x90,
+      0xfb, 0x1c, 0x1a, 0x2c, 0xaa, 0x0f, 0xfe, 0x04, 0x07, 0xe5};
+  const uint8_t test_vector_20_nonce[] = {0x7a, 0xe8, 0xe2, 0xca, 0x4e, 0xc5,
+                                          0x00, 0x01, 0x2e, 0x58, 0x49, 0x5c};
+  const uint8_t test_vector_20_aad[] = {
+      0x68, 0xf2, 0xe7, 0x76, 0x96, 0xce, 0x7a, 0xe8, 0xe2, 0xca,
+      0x4e, 0xc5, 0x88, 0xe5, 0x4d, 0x00, 0x2e, 0x58, 0x49, 0x5c};
+  const uint8_t test_vector_20_plaintext[] = {
+      0x08, 0x00, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+      0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22,
+      0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d,
+      0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+      0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x40, 0x41, 0x42, 0x43,
+      0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x00, 0x08};
+  const uint8_t test_vector_20_ciphertext_and_tag[] = {
+      0xba, 0x8a, 0xe3, 0x1b, 0xc5, 0x06, 0x48, 0x6d, 0x68, 0x73, 0xe4, 0xfc,
+      0xe4, 0x60, 0xe7, 0xdc, 0x57, 0x59, 0x1f, 0xf0, 0x06, 0x11, 0xf3, 0x1c,
+      0x38, 0x34, 0xfe, 0x1c, 0x04, 0xad, 0x80, 0xb6, 0x68, 0x03, 0xaf, 0xcf,
+      0x5b, 0x27, 0xe6, 0x33, 0x3f, 0xa6, 0x7c, 0x99, 0xda, 0x47, 0xc2, 0xf0,
+      0xce, 0xd6, 0x8d, 0x53, 0x1b, 0xd7, 0x41, 0xa9, 0x43, 0xcf, 0xf7, 0xa6,
+      0x71, 0x3b, 0xd0, 0x26, 0x11, 0xcd, 0x7d, 0xaa, 0x01, 0xd6, 0x1c, 0x5c,
+      0x88, 0x6d, 0xc1, 0xa8, 0x17, 0x01, 0x07};
+  gsec_aead_malloc_test_vector(
+      &test_vector_20, test_vector_20_key,
+      sizeof(test_vector_20_key) / sizeof(uint8_t), test_vector_20_nonce,
+      sizeof(test_vector_20_nonce) / sizeof(uint8_t), test_vector_20_aad,
+      sizeof(test_vector_20_aad) / sizeof(uint8_t), test_vector_20_plaintext,
+      sizeof(test_vector_20_plaintext) / sizeof(uint8_t),
+      test_vector_20_ciphertext_and_tag,
+      sizeof(test_vector_20_ciphertext_and_tag) / sizeof(uint8_t));
+  gsec_test_verify_crypter_on_test_vector(test_vector_20);
+  gsec_aead_free_test_vector(test_vector_20);
+}
+
+int main(int argc, char** argv) {
+  grpc_init();
+  gsec_test_do_generic_crypter_tests();
+  gsec_test_do_vector_tests_nist();
+  gsec_test_do_vector_tests_ieee();
+  gsec_test_do_vector_tests_rekey_nist();
+  gsec_test_do_vector_tests_rekey_ieee();
+  grpc_shutdown();
+  return 0;
+}
diff --git a/test/core/tsi/alts/crypt/gsec_test_util.cc b/test/core/tsi/alts/crypt/gsec_test_util.cc
new file mode 100644
index 0000000..992c91e
--- /dev/null
+++ b/test/core/tsi/alts/crypt/gsec_test_util.cc
@@ -0,0 +1,87 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "test/core/tsi/alts/crypt/gsec_test_util.h"
+
+#include <grpc/support/alloc.h>
+
+void gsec_test_random_bytes(uint8_t* bytes, size_t length) {
+  if (!RAND_bytes(bytes, static_cast<int>(length))) {
+    fprintf(stderr,
+            "Random bytes generation failed in gsec_test_random_bytes().");
+    abort();
+  }
+}
+
+void gsec_test_random_array(uint8_t** bytes, size_t length) {
+  if (bytes != nullptr) {
+    *bytes = static_cast<uint8_t*>(gpr_malloc(length));
+    gsec_test_random_bytes(*bytes, length);
+  } else {
+    fprintf(stderr, "bytes buffer is nullptr in gsec_test_random_array().");
+    abort();
+  }
+}
+
+uint32_t gsec_test_bias_random_uint32(uint32_t max_length) {
+  uint32_t value;
+  gsec_test_random_bytes((uint8_t*)(&value), sizeof(value));
+  return value % max_length;
+}
+
+void gsec_test_copy(const uint8_t* src, uint8_t** des, size_t source_len) {
+  if (src != nullptr && des != nullptr) {
+    *des = static_cast<uint8_t*>(gpr_malloc(source_len));
+    memcpy(*des, src, source_len);
+  } else {
+    fprintf(stderr, "Either src or des buffer is nullptr in gsec_test_copy().");
+    abort();
+  }
+}
+
+void gsec_test_copy_and_alter_random_byte(const uint8_t* src, uint8_t** des,
+                                          size_t source_len) {
+  if (src != nullptr && des != nullptr) {
+    *des = static_cast<uint8_t*>(gpr_malloc(source_len));
+    memcpy(*des, src, source_len);
+    uint32_t offset;
+    offset = gsec_test_bias_random_uint32(static_cast<uint32_t>(source_len));
+    (*(*des + offset))++;
+  } else {
+    fprintf(stderr,
+            "Either src or des is nullptr in "
+            "gsec_test_copy_and_alter_random_byte().");
+    abort();
+  }
+}
+
+int gsec_test_expect_compare_code_and_substr(grpc_status_code status1,
+                                             grpc_status_code status2,
+                                             const char* msg1,
+                                             const char* msg2) {
+  int failure = 1;
+  if (status1 != status2) {
+    fprintf(stderr, "Status %d does not equal %d.\n", status1, status2);
+    failure = 0;
+  }
+  if (strstr(msg1, msg2) == nullptr) {
+    fprintf(stderr, "Status message <%s> does not contain <%s>.\n", msg1, msg2);
+    failure = 0;
+  }
+  return failure;
+}
diff --git a/test/core/tsi/alts/crypt/gsec_test_util.h b/test/core/tsi/alts/crypt/gsec_test_util.h
new file mode 100644
index 0000000..206ae2f
--- /dev/null
+++ b/test/core/tsi/alts/crypt/gsec_test_util.h
@@ -0,0 +1,91 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_TEST_CORE_TSI_ALTS_CRYPT_GSEC_TEST_UTIL_H_
+#define GRPC_TEST_CORE_TSI_ALTS_CRYPT_GSEC_TEST_UTIL_H_
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <openssl/rand.h>
+
+#include <grpc/grpc.h>
+
+/**
+ * This method returns random bytes of certain length.
+ *
+ * - bytes: buffer to hold random bytes.
+ * - length: length of buffer to be populated.
+ */
+void gsec_test_random_bytes(uint8_t* bytes, size_t length);
+
+/**
+ * This method returns an array of random bytes.
+ *
+ * - bytes: array to hold random bytes.
+ * - length: length of array to be populated.
+ */
+void gsec_test_random_array(uint8_t** bytes, size_t length);
+
+/**
+ * This method returns a uint32 that's not quite uniformly random, but good
+ * enough for tests.
+ *
+ * - max_length: a max value the returned random number can choose.
+ */
+uint32_t gsec_test_bias_random_uint32(uint32_t max_length);
+
+/**
+ * This method copies data from a source to a destination buffer.
+ *
+ * - src: a source buffer.
+ * - des: a destination buffer.
+ * - length: the length of source buffer to be copied from its beginning.
+ */
+void gsec_test_copy(const uint8_t* src, uint8_t** des, size_t length);
+
+/**
+ * This method copies data from a source to a destination buffer, and flips one
+ * byte in the destination buffer randomly.
+ *
+ * - src: a source buffer.
+ * - des: a destination buffer.
+ * - length: the length of source buffer to be copied from its beginning.
+ */
+void gsec_test_copy_and_alter_random_byte(const uint8_t* src, uint8_t** des,
+                                          size_t source_len);
+
+/**
+ * This method compares two grpc_status_code values, and verifies if one string
+ * is a substring of the other.
+ *
+ * - status1: the first grpc_status_code to be compared.
+ * - status2: the second grpc_status_code to be compared.
+ * - msg1: a string to be scanned.
+ * - msg2: a small string to be searched within msg1.
+ *
+ * If both checks succeed, the method returns 1 and otherwise, it returns 0.
+ */
+int gsec_test_expect_compare_code_and_substr(grpc_status_code status1,
+                                             grpc_status_code status2,
+                                             const char* msg1,
+                                             const char* msg2);
+
+#endif  // GRPC_TEST_CORE_TSI_ALTS_CRYPT_GSEC_TEST_UTIL_H_ */
diff --git a/test/core/tsi/alts/frame_protector/BUILD b/test/core/tsi/alts/frame_protector/BUILD
new file mode 100644
index 0000000..8bbc8c6
--- /dev/null
+++ b/test/core/tsi/alts/frame_protector/BUILD
@@ -0,0 +1,60 @@
+# Copyright 2018 gRPC authors.
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("//bazel:grpc_build_system.bzl", "grpc_cc_library", "grpc_cc_test", "grpc_package")
+
+licenses(["notice"])  # Apache v2
+
+grpc_package(name = "frame_protector")
+
+grpc_cc_test(
+    name = "alts_counter_test",
+    srcs = ["alts_counter_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+        "//test/core/tsi/alts/crypt:alts_crypt_test_util",
+    ],
+)
+
+grpc_cc_test(
+    name = "alts_crypter_test",
+    srcs = ["alts_crypter_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+        "//test/core/tsi/alts/crypt:alts_crypt_test_util",
+    ],
+)
+
+grpc_cc_test(
+    name = "alts_frame_protector_test",
+    srcs = ["alts_frame_protector_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+        "//test/core/tsi/alts/crypt:alts_crypt_test_util",
+        "//test/core/tsi:transport_security_test_lib",
+    ],
+)
+
+grpc_cc_test(
+    name = "frame_handler_test",
+    srcs = ["frame_handler_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+        "//test/core/tsi/alts/crypt:alts_crypt_test_util",
+    ],
+)
diff --git a/test/core/tsi/alts/frame_protector/alts_counter_test.cc b/test/core/tsi/alts/frame_protector/alts_counter_test.cc
new file mode 100644
index 0000000..49ff821
--- /dev/null
+++ b/test/core/tsi/alts/frame_protector/alts_counter_test.cc
@@ -0,0 +1,180 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/tsi/alts/frame_protector/alts_counter.h"
+#include "test/core/tsi/alts/crypt/gsec_test_util.h"
+
+const size_t kSmallCounterSize = 4;
+const size_t kSmallOverflowSize = 1;
+const size_t kGcmCounterSize = 12;
+const size_t kGcmOverflowSize = 5;
+
+static bool do_bytes_represent_client(alts_counter* ctr, unsigned char* counter,
+                                      size_t size) {
+  return (ctr->counter[size - 1] & 0x80) == 0x80;
+}
+
+static void alts_counter_test_input_sanity_check(size_t counter_size,
+                                                 size_t overflow_size) {
+  alts_counter* ctr = nullptr;
+  char* error_details = nullptr;
+
+  /* Input sanity check on alts_counter_create(). */
+  /* Invalid counter size. */
+  grpc_status_code status =
+      alts_counter_create(true, 0, overflow_size, &ctr, &error_details);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_details,
+      "counter_size is invalid."));
+  gpr_free(error_details);
+
+  /* Invalid overflow size. */
+  status = alts_counter_create(true, counter_size, 0, &ctr, &error_details);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_details,
+      "overflow_size is invalid."));
+  gpr_free(error_details);
+
+  /* alts_counter is nullptr. */
+  status = alts_counter_create(true, counter_size, overflow_size, nullptr,
+                               &error_details);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_details,
+      "crypter_counter is nullptr."));
+  gpr_free(error_details);
+
+  status = alts_counter_create(true, counter_size, overflow_size, &ctr,
+                               &error_details);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+
+  /* Input sanity check on alts_counter_increment(). */
+  /* crypter_counter is nullptr. */
+  bool is_overflow = false;
+  status = alts_counter_increment(nullptr, &is_overflow, &error_details);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_details,
+      "crypter_counter is nullptr."));
+  gpr_free(error_details);
+  /* is_overflow is nullptr. */
+  status = alts_counter_increment(ctr, nullptr, &error_details);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_details,
+      "is_overflow is nullptr."));
+  gpr_free(error_details);
+  alts_counter_destroy(ctr);
+}
+
+static void alts_counter_test_overflow_full_range(bool is_client,
+                                                  size_t counter_size,
+                                                  size_t overflow_size) {
+  alts_counter* ctr = nullptr;
+  char* error_details = nullptr;
+  grpc_status_code status = alts_counter_create(
+      is_client, counter_size, overflow_size, &ctr, &error_details);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  unsigned char* expected =
+      static_cast<unsigned char*>(gpr_zalloc(counter_size));
+  if (is_client) {
+    expected[counter_size - 1] = 0x80;
+  }
+  /* Do a single iteration to ensure the counter is initialized as expected. */
+  GPR_ASSERT(do_bytes_represent_client(ctr, alts_counter_get_counter(ctr),
+                                       counter_size) == is_client);
+  GPR_ASSERT(memcmp(alts_counter_get_counter(ctr), expected, counter_size) ==
+             0);
+  bool is_overflow = false;
+  GPR_ASSERT(alts_counter_increment(ctr, &is_overflow, &error_details) ==
+             GRPC_STATUS_OK);
+  GPR_ASSERT(!is_overflow);
+  /**
+   * The counter can return 2^{overflow_size * 8} counters. The
+   * high-order bit is fixed to the client/server. The last call will yield a
+   * useable counter, but overflow the counter object.
+   */
+  int iterations = 1 << (overflow_size * 8);
+  int ind = 1;
+  for (ind = 1; ind < iterations - 1; ind++) {
+    GPR_ASSERT(do_bytes_represent_client(ctr, alts_counter_get_counter(ctr),
+                                         counter_size) == is_client);
+    GPR_ASSERT(alts_counter_increment(ctr, &is_overflow, &error_details) ==
+               GRPC_STATUS_OK);
+    GPR_ASSERT(!is_overflow);
+  }
+  GPR_ASSERT(do_bytes_represent_client(ctr, alts_counter_get_counter(ctr),
+                                       counter_size) == is_client);
+  GPR_ASSERT(alts_counter_increment(ctr, &is_overflow, &error_details) ==
+             GRPC_STATUS_FAILED_PRECONDITION);
+  GPR_ASSERT(is_overflow);
+  gpr_free(expected);
+  alts_counter_destroy(ctr);
+}
+
+/* Set the counter manually and make sure it overflows as expected. */
+static void alts_counter_test_overflow_single_increment(bool is_client,
+                                                        size_t counter_size,
+                                                        size_t overflow_size) {
+  alts_counter* ctr = nullptr;
+  char* error_details = nullptr;
+  grpc_status_code status = alts_counter_create(
+      is_client, counter_size, overflow_size, &ctr, &error_details);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  unsigned char* expected =
+      static_cast<unsigned char*>(gpr_zalloc(counter_size));
+  memset(expected, 0xFF, overflow_size);
+  expected[0] = 0xFE;
+
+  if (is_client) {
+    expected[counter_size - 1] = 0x80;
+  }
+  memcpy(ctr->counter, expected, counter_size);
+  GPR_ASSERT(do_bytes_represent_client(ctr, alts_counter_get_counter(ctr),
+                                       counter_size) == is_client);
+  GPR_ASSERT(memcmp(expected, alts_counter_get_counter(ctr), counter_size) ==
+             0);
+  bool is_overflow = false;
+  GPR_ASSERT(alts_counter_increment(ctr, &is_overflow, &error_details) ==
+             GRPC_STATUS_OK);
+  GPR_ASSERT(!is_overflow);
+  GPR_ASSERT(do_bytes_represent_client(ctr, alts_counter_get_counter(ctr),
+                                       counter_size) == is_client);
+  expected[0] = static_cast<unsigned char>(expected[0] + 1);
+  GPR_ASSERT(memcmp(expected, alts_counter_get_counter(ctr), counter_size) ==
+             0);
+  GPR_ASSERT(alts_counter_increment(ctr, &is_overflow, &error_details) ==
+             GRPC_STATUS_FAILED_PRECONDITION);
+  GPR_ASSERT(is_overflow);
+  gpr_free(expected);
+  alts_counter_destroy(ctr);
+}
+
+int main(int argc, char** argv) {
+  alts_counter_test_input_sanity_check(kGcmCounterSize, kGcmOverflowSize);
+  alts_counter_test_overflow_full_range(true, kSmallCounterSize,
+                                        kSmallOverflowSize);
+  alts_counter_test_overflow_full_range(false, kSmallCounterSize,
+                                        kSmallOverflowSize);
+  alts_counter_test_overflow_single_increment(true, kGcmCounterSize,
+                                              kGcmOverflowSize);
+  alts_counter_test_overflow_single_increment(false, kGcmCounterSize,
+                                              kGcmOverflowSize);
+
+  return 0;
+}
diff --git a/test/core/tsi/alts/frame_protector/alts_crypter_test.cc b/test/core/tsi/alts/frame_protector/alts_crypter_test.cc
new file mode 100644
index 0000000..0ad616b
--- /dev/null
+++ b/test/core/tsi/alts/frame_protector/alts_crypter_test.cc
@@ -0,0 +1,493 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/tsi/alts/frame_protector/alts_crypter.h"
+#include "test/core/tsi/alts/crypt/gsec_test_util.h"
+
+static void alts_crypter_test_random_seal_unseal(alts_crypter* server_seal,
+                                                 alts_crypter* server_unseal,
+                                                 alts_crypter* client_seal,
+                                                 alts_crypter* client_unseal) {
+  size_t data_size = gsec_test_bias_random_uint32(1024) + 1;
+  size_t num_overhead_bytes = alts_crypter_num_overhead_bytes(server_seal);
+  size_t protected_data_size = data_size + num_overhead_bytes;
+  uint8_t* data_buffer = static_cast<uint8_t*>(gpr_malloc(protected_data_size));
+  gsec_test_random_bytes(data_buffer, data_size);
+  uint8_t* duplicate_buffer = nullptr;
+  gsec_test_copy(data_buffer, &duplicate_buffer, data_size);
+
+  /* Client seal and server unseal */
+  size_t size = data_size;
+  grpc_status_code status = alts_crypter_process_in_place(
+      client_seal, data_buffer, protected_data_size, size, &size, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size == protected_data_size);
+  status = alts_crypter_process_in_place(
+      server_unseal, data_buffer, protected_data_size, size, &size, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(memcmp(data_buffer, duplicate_buffer, data_size) == 0);
+  GPR_ASSERT(size == data_size);
+  /* Server seal and client unseal */
+  status = alts_crypter_process_in_place(
+      server_seal, data_buffer, protected_data_size, size, &size, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size == protected_data_size);
+  status = alts_crypter_process_in_place(
+      client_unseal, data_buffer, protected_data_size, size, &size, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(memcmp(data_buffer, duplicate_buffer, data_size) == 0);
+  GPR_ASSERT(size == data_size);
+  gpr_free(data_buffer);
+  gpr_free(duplicate_buffer);
+}
+
+static void alts_crypter_test_multiple_random_seal_unseal(
+    alts_crypter* server_seal, alts_crypter* server_unseal,
+    alts_crypter* client_seal, alts_crypter* client_unseal) {
+  size_t data_size = gsec_test_bias_random_uint32(1024) + 1;
+  size_t num_overhead_bytes = alts_crypter_num_overhead_bytes(server_seal);
+  size_t protected_data_size = data_size + num_overhead_bytes;
+
+  uint8_t* data_buffer1 =
+      static_cast<uint8_t*>(gpr_malloc(protected_data_size));
+  uint8_t* data_buffer2 =
+      static_cast<uint8_t*>(gpr_malloc(protected_data_size));
+  uint8_t* duplicate_buffer1 = nullptr;
+  uint8_t* duplicate_buffer2 = nullptr;
+  gsec_test_random_bytes(data_buffer1, data_size);
+  gsec_test_random_bytes(data_buffer2, data_size);
+  gsec_test_copy(data_buffer1, &duplicate_buffer1, data_size);
+  gsec_test_copy(data_buffer2, &duplicate_buffer2, data_size);
+
+  /* Client seal and server unseal */
+  size_t size1 = data_size, size2 = data_size;
+  grpc_status_code status = alts_crypter_process_in_place(
+      client_seal, data_buffer1, protected_data_size, size1, &size1, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size1 == protected_data_size);
+  status = alts_crypter_process_in_place(
+      client_seal, data_buffer2, protected_data_size, size2, &size2, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size2 == protected_data_size);
+  status = alts_crypter_process_in_place(
+      server_unseal, data_buffer1, protected_data_size, size1, &size1, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(memcmp(data_buffer1, duplicate_buffer1, data_size) == 0);
+  GPR_ASSERT(size1 == data_size);
+  status = alts_crypter_process_in_place(
+      server_unseal, data_buffer2, protected_data_size, size2, &size2, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(memcmp(data_buffer2, duplicate_buffer2, data_size) == 0);
+  GPR_ASSERT(size2 == data_size);
+
+  /* Server seal and client unseal */
+  status = alts_crypter_process_in_place(
+      server_seal, data_buffer1, protected_data_size, size1, &size1, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size1 == protected_data_size);
+  status = alts_crypter_process_in_place(
+      server_seal, data_buffer2, protected_data_size, size2, &size2, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size2 == protected_data_size);
+  status = alts_crypter_process_in_place(
+      client_unseal, data_buffer1, protected_data_size, size1, &size1, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(memcmp(data_buffer1, duplicate_buffer1, data_size) == 0);
+  GPR_ASSERT(size1 == data_size);
+  status = alts_crypter_process_in_place(
+      client_unseal, data_buffer2, protected_data_size, size2, &size2, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(memcmp(data_buffer2, duplicate_buffer2, data_size) == 0);
+  GPR_ASSERT(size2 == data_size);
+
+  gpr_free(data_buffer1);
+  gpr_free(data_buffer2);
+  gpr_free(duplicate_buffer1);
+  gpr_free(duplicate_buffer2);
+}
+
+static void alts_crypter_test_corrupted_unseal(alts_crypter* server_seal,
+                                               alts_crypter* server_unseal,
+                                               alts_crypter* client_seal,
+                                               alts_crypter* client_unseal) {
+  size_t data_size = gsec_test_bias_random_uint32(1024) + 1;
+  size_t num_overhead_bytes = alts_crypter_num_overhead_bytes(server_seal);
+  size_t protected_data_size = data_size + num_overhead_bytes;
+  auto* data_buffer = static_cast<uint8_t*>(gpr_malloc(protected_data_size));
+  auto* zero_buffer = static_cast<uint8_t*>(gpr_zalloc(data_size));
+
+  /* Corrupt a random byte in protected data. */
+  size_t size = data_size;
+  gsec_test_random_bytes(data_buffer, data_size);
+  grpc_status_code status = alts_crypter_process_in_place(
+      client_seal, data_buffer, protected_data_size, size, &size, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size == protected_data_size);
+  uint8_t* corrupted_data_buffer;
+  char* error_message = nullptr;
+  gsec_test_copy_and_alter_random_byte(data_buffer, &corrupted_data_buffer,
+                                       protected_data_size);
+  status = alts_crypter_process_in_place(server_unseal, corrupted_data_buffer,
+                                         protected_data_size, size, &size,
+                                         &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+      "Checking tag failed"));
+  GPR_ASSERT(memcmp(corrupted_data_buffer, zero_buffer, data_size) == 0);
+  gpr_free(corrupted_data_buffer);
+  gpr_free(error_message);
+
+  /* Corrupt the beginning of protected data. */
+  size = data_size;
+  gsec_test_random_bytes(data_buffer, data_size);
+  status = alts_crypter_process_in_place(
+      client_seal, data_buffer, protected_data_size, size, &size, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size == protected_data_size);
+  gsec_test_copy(data_buffer, &corrupted_data_buffer, protected_data_size);
+  (*corrupted_data_buffer)++;
+  status = alts_crypter_process_in_place(server_unseal, corrupted_data_buffer,
+                                         protected_data_size, size, &size,
+                                         &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+      "Checking tag failed"));
+  GPR_ASSERT(memcmp(corrupted_data_buffer, zero_buffer, data_size) == 0);
+  gpr_free(corrupted_data_buffer);
+  gpr_free(error_message);
+
+  /* Corrupt the end of protected data. */
+  size = data_size;
+  gsec_test_random_bytes(data_buffer, data_size);
+  status = alts_crypter_process_in_place(
+      client_seal, data_buffer, protected_data_size, size, &size, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size == protected_data_size);
+  gsec_test_copy(data_buffer, &corrupted_data_buffer, protected_data_size);
+  (*(corrupted_data_buffer + protected_data_size - 1))++;
+  status = alts_crypter_process_in_place(server_unseal, corrupted_data_buffer,
+                                         protected_data_size, size, &size,
+                                         &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+      "Checking tag failed"));
+  GPR_ASSERT(memcmp(corrupted_data_buffer, zero_buffer, data_size) == 0);
+  gpr_free(corrupted_data_buffer);
+  gpr_free(error_message);
+
+  gpr_free(data_buffer);
+  gpr_free(zero_buffer);
+}
+
+static void alts_crypter_test_unsync_seal_unseal(alts_crypter* server_seal,
+                                                 alts_crypter* server_unseal,
+                                                 alts_crypter* client_seal,
+                                                 alts_crypter* client_unseal) {
+  size_t data_size = gsec_test_bias_random_uint32(1024) + 1;
+  size_t num_overhead_bytes = alts_crypter_num_overhead_bytes(server_seal);
+  size_t protected_data_size = data_size + num_overhead_bytes;
+  auto* data_buffer = static_cast<uint8_t*>(gpr_malloc(protected_data_size));
+  auto* zero_buffer = static_cast<uint8_t*>(gpr_zalloc(data_size));
+
+  /* Perform two seals at client, one unseal at server. */
+  size_t size = data_size;
+  gsec_test_random_bytes(data_buffer, data_size);
+  grpc_status_code status = alts_crypter_process_in_place(
+      client_seal, data_buffer, protected_data_size, size, &size, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size == protected_data_size);
+
+  size = data_size;
+  gsec_test_random_bytes(data_buffer, data_size);
+  status = alts_crypter_process_in_place(
+      client_seal, data_buffer, protected_data_size, size, &size, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size == protected_data_size);
+
+  char* error_message = nullptr;
+  status = alts_crypter_process_in_place(server_unseal, data_buffer,
+                                         protected_data_size, size, &size,
+                                         &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+      "Checking tag failed"));
+  GPR_ASSERT(memcmp(data_buffer, zero_buffer, data_size) == 0);
+  gpr_free(error_message);
+
+  /* Perform two seals at server, one unseal at client. */
+  size = data_size;
+  gsec_test_random_bytes(data_buffer, data_size);
+  status = alts_crypter_process_in_place(
+      server_seal, data_buffer, protected_data_size, size, &size, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size == protected_data_size);
+
+  size = data_size;
+  gsec_test_random_bytes(data_buffer, data_size);
+  status = alts_crypter_process_in_place(
+      server_seal, data_buffer, protected_data_size, size, &size, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(size == protected_data_size);
+
+  status = alts_crypter_process_in_place(client_unseal, data_buffer,
+                                         protected_data_size, size, &size,
+                                         &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+      "Checking tag failed"));
+  GPR_ASSERT(memcmp(data_buffer, zero_buffer, data_size) == 0);
+  gpr_free(error_message);
+  gpr_free(data_buffer);
+  gpr_free(zero_buffer);
+}
+
+static void alts_crypter_test_input_sanity_check(alts_crypter* crypter_seal,
+                                                 alts_crypter* crypter_unseal) {
+  size_t data_size = gsec_test_bias_random_uint32(1024) + 1;
+  size_t num_overhead_bytes = alts_crypter_num_overhead_bytes(crypter_seal);
+  size_t protected_data_size = data_size + num_overhead_bytes;
+  auto* data_buffer = static_cast<uint8_t*>(gpr_malloc(protected_data_size));
+  gsec_test_random_bytes(data_buffer, data_size);
+  char* error_message = nullptr;
+  size_t size = data_size;
+
+  /* Crypter is nullptr. */
+  grpc_status_code status = alts_crypter_process_in_place(
+      nullptr, data_buffer, protected_data_size, size, &size, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "crypter or crypter->vtable has not been initialized properly."));
+  gpr_free(error_message);
+
+  /* Seal data is nullptr. */
+  size = data_size;
+  status = alts_crypter_process_in_place(
+      crypter_seal, nullptr, protected_data_size, size, &size, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message, "data is nullptr."));
+  gpr_free(error_message);
+
+  /* Seal data size is 0. */
+  size = 0;
+  status = alts_crypter_process_in_place(crypter_seal, data_buffer,
+                                         protected_data_size, size, &size,
+                                         &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "data_size is zero."));
+  gpr_free(error_message);
+
+  /* Seal data buffer has a size smaller than the required. */
+  size = data_size;
+  status = alts_crypter_process_in_place(crypter_seal, data_buffer,
+                                         protected_data_size - 1, size, &size,
+                                         &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "data_allocated_size is smaller than sum of data_size and "
+      "num_overhead_bytes."));
+  gpr_free(error_message);
+
+  /* Unseal data is nullptr. */
+  size = data_size;
+  status = alts_crypter_process_in_place(crypter_unseal, nullptr,
+                                         protected_data_size, size, &size,
+                                         &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message, "data is nullptr."));
+  gpr_free(error_message);
+
+  /* Unseal data size is 0. */
+  size = 0;
+  status = alts_crypter_process_in_place(crypter_unseal, data_buffer,
+                                         protected_data_size, size, &size,
+                                         &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "data_size is smaller than num_overhead_bytes."));
+  gpr_free(error_message);
+
+  /* Unseal data size is smaller than number of overhead bytes. */
+  size = num_overhead_bytes - 1;
+  status = alts_crypter_process_in_place(crypter_unseal, data_buffer,
+                                         protected_data_size, size, &size,
+                                         &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "data_size is smaller than num_overhead_bytes."));
+  gpr_free(error_message);
+  gpr_free(data_buffer);
+}
+
+static void create_random_alts_seal_crypter(
+    alts_crypter** server_seal, alts_crypter** server_unseal,
+    alts_crypter** client_seal, alts_crypter** client_unseal,
+    gsec_aead_crypter** server_crypter_seal,
+    gsec_aead_crypter** server_crypter_unseal,
+    gsec_aead_crypter** client_crypter_seal,
+    gsec_aead_crypter** client_crypter_unseal, bool rekey) {
+  size_t key_length = rekey ? kAes128GcmRekeyKeyLength : kAes128GcmKeyLength;
+  uint8_t* key;
+  gsec_test_random_array(&key, key_length);
+  gsec_aes_gcm_aead_crypter_create(key, key_length, kAesGcmNonceLength,
+                                   kAesGcmTagLength, rekey, server_crypter_seal,
+                                   nullptr);
+  gsec_aes_gcm_aead_crypter_create(key, key_length, kAesGcmNonceLength,
+                                   kAesGcmTagLength, rekey,
+                                   server_crypter_unseal, nullptr);
+  gsec_aes_gcm_aead_crypter_create(key, key_length, kAesGcmNonceLength,
+                                   kAesGcmTagLength, rekey, client_crypter_seal,
+                                   nullptr);
+  gsec_aes_gcm_aead_crypter_create(key, key_length, kAesGcmNonceLength,
+                                   kAesGcmTagLength, rekey,
+                                   client_crypter_unseal, nullptr);
+
+  size_t overflow_size = rekey ? 8 : 5;
+  alts_seal_crypter_create(*client_crypter_seal, /*is_client=*/true,
+                           overflow_size, client_seal, nullptr);
+  alts_unseal_crypter_create(*client_crypter_unseal, /*is_client=*/true,
+                             overflow_size, client_unseal, nullptr);
+  alts_seal_crypter_create(*server_crypter_seal, /*is_client=*/false,
+                           overflow_size, server_seal, nullptr);
+  alts_unseal_crypter_create(*server_crypter_unseal, /*is_client=*/false,
+                             overflow_size, server_unseal, nullptr);
+  gpr_free(key);
+}
+
+static void destroy_random_alts_seal_crypter(alts_crypter* server_seal,
+                                             alts_crypter* server_unseal,
+                                             alts_crypter* client_seal,
+                                             alts_crypter* client_unseal) {
+  alts_crypter_destroy(server_seal);
+  alts_crypter_destroy(server_unseal);
+  alts_crypter_destroy(client_seal);
+  alts_crypter_destroy(client_unseal);
+}
+
+static void alts_crypter_do_generic_tests() {
+  alts_crypter *server_seal = nullptr, *server_unseal = nullptr,
+               *client_seal = nullptr, *client_unseal = nullptr;
+  gsec_aead_crypter *server_crypter_seal = nullptr,
+                    *server_crypter_unseal = nullptr,
+                    *client_crypter_seal = nullptr,
+                    *client_crypter_unseal = nullptr;
+  /* Random seal and unseal tests */
+  create_random_alts_seal_crypter(&server_seal, &server_unseal, &client_seal,
+                                  &client_unseal, &server_crypter_seal,
+                                  &server_crypter_unseal, &client_crypter_seal,
+                                  &client_crypter_unseal, /*rekey=*/false);
+  alts_crypter_test_random_seal_unseal(server_seal, server_unseal, client_seal,
+                                       client_unseal);
+  destroy_random_alts_seal_crypter(server_seal, server_unseal, client_seal,
+                                   client_unseal);
+
+  create_random_alts_seal_crypter(&server_seal, &server_unseal, &client_seal,
+                                  &client_unseal, &server_crypter_seal,
+                                  &server_crypter_unseal, &client_crypter_seal,
+                                  &client_crypter_unseal, /*rekey=*/true);
+  alts_crypter_test_random_seal_unseal(server_seal, server_unseal, client_seal,
+                                       client_unseal);
+  destroy_random_alts_seal_crypter(server_seal, server_unseal, client_seal,
+                                   client_unseal);
+
+  /* Multiple random seal and unseal tests */
+  create_random_alts_seal_crypter(&server_seal, &server_unseal, &client_seal,
+                                  &client_unseal, &server_crypter_seal,
+                                  &server_crypter_unseal, &client_crypter_seal,
+                                  &client_crypter_unseal, /*rekey=*/false);
+  alts_crypter_test_multiple_random_seal_unseal(server_seal, server_unseal,
+                                                client_seal, client_unseal);
+  destroy_random_alts_seal_crypter(server_seal, server_unseal, client_seal,
+                                   client_unseal);
+
+  create_random_alts_seal_crypter(&server_seal, &server_unseal, &client_seal,
+                                  &client_unseal, &server_crypter_seal,
+                                  &server_crypter_unseal, &client_crypter_seal,
+                                  &client_crypter_unseal, /*rekey=*/true);
+  alts_crypter_test_multiple_random_seal_unseal(server_seal, server_unseal,
+                                                client_seal, client_unseal);
+  destroy_random_alts_seal_crypter(server_seal, server_unseal, client_seal,
+                                   client_unseal);
+
+  /* Corrupted unseal tests */
+  create_random_alts_seal_crypter(&server_seal, &server_unseal, &client_seal,
+                                  &client_unseal, &server_crypter_seal,
+                                  &server_crypter_unseal, &client_crypter_seal,
+                                  &client_crypter_unseal, /*rekey=*/false);
+  alts_crypter_test_corrupted_unseal(server_seal, server_unseal, client_seal,
+                                     client_unseal);
+  destroy_random_alts_seal_crypter(server_seal, server_unseal, client_seal,
+                                   client_unseal);
+
+  create_random_alts_seal_crypter(&server_seal, &server_unseal, &client_seal,
+                                  &client_unseal, &server_crypter_seal,
+                                  &server_crypter_unseal, &client_crypter_seal,
+                                  &client_crypter_unseal, /*rekey=*/true);
+  alts_crypter_test_corrupted_unseal(server_seal, server_unseal, client_seal,
+                                     client_unseal);
+  destroy_random_alts_seal_crypter(server_seal, server_unseal, client_seal,
+                                   client_unseal);
+
+  /* Unsync seal and unseal tests */
+  create_random_alts_seal_crypter(&server_seal, &server_unseal, &client_seal,
+                                  &client_unseal, &server_crypter_seal,
+                                  &server_crypter_unseal, &client_crypter_seal,
+                                  &client_crypter_unseal, /*rekey=*/false);
+  alts_crypter_test_unsync_seal_unseal(server_seal, server_unseal, client_seal,
+                                       client_unseal);
+  destroy_random_alts_seal_crypter(server_seal, server_unseal, client_seal,
+                                   client_unseal);
+
+  create_random_alts_seal_crypter(&server_seal, &server_unseal, &client_seal,
+                                  &client_unseal, &server_crypter_seal,
+                                  &server_crypter_unseal, &client_crypter_seal,
+                                  &client_crypter_unseal, /*rekey=*/true);
+  alts_crypter_test_unsync_seal_unseal(server_seal, server_unseal, client_seal,
+                                       client_unseal);
+  destroy_random_alts_seal_crypter(server_seal, server_unseal, client_seal,
+                                   client_unseal);
+
+  /* Input sanity check tests */
+  create_random_alts_seal_crypter(&server_seal, &server_unseal, &client_seal,
+                                  &client_unseal, &server_crypter_seal,
+                                  &server_crypter_unseal, &client_crypter_seal,
+                                  &client_crypter_unseal, /*rekey=*/false);
+  alts_crypter_test_input_sanity_check(server_seal, server_unseal);
+  destroy_random_alts_seal_crypter(server_seal, server_unseal, client_seal,
+                                   client_unseal);
+
+  create_random_alts_seal_crypter(&server_seal, &server_unseal, &client_seal,
+                                  &client_unseal, &server_crypter_seal,
+                                  &server_crypter_unseal, &client_crypter_seal,
+                                  &client_crypter_unseal, /*rekey=*/true);
+  alts_crypter_test_input_sanity_check(server_seal, server_unseal);
+  destroy_random_alts_seal_crypter(server_seal, server_unseal, client_seal,
+                                   client_unseal);
+}
+
+int main(int argc, char** argv) {
+  alts_crypter_do_generic_tests();
+  return 0;
+}
diff --git a/test/core/tsi/alts/frame_protector/alts_frame_protector_test.cc b/test/core/tsi/alts/frame_protector/alts_frame_protector_test.cc
new file mode 100644
index 0000000..2bd4958
--- /dev/null
+++ b/test/core/tsi/alts/frame_protector/alts_frame_protector_test.cc
@@ -0,0 +1,394 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include <stdbool.h>
+
+#include "src/core/tsi/alts/crypt/gsec.h"
+#include "src/core/tsi/alts/frame_protector/alts_frame_protector.h"
+#include "src/core/tsi/transport_security_interface.h"
+#include "test/core/tsi/alts/crypt/gsec_test_util.h"
+#include "test/core/tsi/transport_security_test_lib.h"
+
+const size_t kChannelSize = 32768;
+
+static void alts_test_do_round_trip_check_frames(
+    tsi_test_frame_protector_fixture* fixture, const uint8_t* key,
+    const size_t key_size, bool rekey, const uint8_t* client_message,
+    const size_t client_message_size, const uint8_t* client_expected_frames,
+    const size_t client_frame_size, const uint8_t* server_message,
+    const size_t server_message_size, const uint8_t* server_expected_frames,
+    const size_t server_frame_size) {
+  GPR_ASSERT(fixture != nullptr);
+  GPR_ASSERT(fixture->config != nullptr);
+  tsi_frame_protector* client_frame_protector = nullptr;
+  tsi_frame_protector* server_frame_protector = nullptr;
+  tsi_test_frame_protector_config* config = fixture->config;
+  tsi_test_channel* channel = fixture->channel;
+  /* Create a client frame protector. */
+  size_t client_max_output_protected_frame_size =
+      config->client_max_output_protected_frame_size;
+  GPR_ASSERT(
+      alts_create_frame_protector(key, key_size, /*is_client=*/true, rekey,
+                                  client_max_output_protected_frame_size == 0
+                                      ? nullptr
+                                      : &client_max_output_protected_frame_size,
+                                  &client_frame_protector) == TSI_OK);
+  /* Create a server frame protector. */
+  size_t server_max_output_protected_frame_size =
+      config->server_max_output_protected_frame_size;
+  GPR_ASSERT(
+      alts_create_frame_protector(key, key_size, /*is_client=*/false, rekey,
+                                  server_max_output_protected_frame_size == 0
+                                      ? nullptr
+                                      : &server_max_output_protected_frame_size,
+                                  &server_frame_protector) == TSI_OK);
+  tsi_test_frame_protector_fixture_init(fixture, client_frame_protector,
+                                        server_frame_protector);
+  /* Client sends a message to server. */
+  uint8_t* saved_client_message = config->client_message;
+  config->client_message = const_cast<uint8_t*>(client_message);
+  config->client_message_size = client_message_size;
+  tsi_test_frame_protector_send_message_to_peer(config, channel,
+                                                client_frame_protector,
+                                                /*is_client=*/true);
+  /* Verify if the generated frame is the same as the expected. */
+  GPR_ASSERT(channel->bytes_written_to_server_channel == client_frame_size);
+  GPR_ASSERT(memcmp(client_expected_frames, channel->server_channel,
+                    client_frame_size) == 0);
+  unsigned char* server_received_message =
+      static_cast<unsigned char*>(gpr_malloc(kChannelSize));
+  size_t server_received_message_size = 0;
+  tsi_test_frame_protector_receive_message_from_peer(
+      config, channel, server_frame_protector, server_received_message,
+      &server_received_message_size, /*is_client=*/false);
+  GPR_ASSERT(config->client_message_size == server_received_message_size);
+  GPR_ASSERT(memcmp(config->client_message, server_received_message,
+                    server_received_message_size) == 0);
+  /* Server sends a message to client. */
+  uint8_t* saved_server_message = config->server_message;
+  config->server_message = const_cast<uint8_t*>(server_message);
+  config->server_message_size = server_message_size;
+  tsi_test_frame_protector_send_message_to_peer(config, channel,
+                                                server_frame_protector,
+                                                /*is_client=*/false);
+  /* Verify if the generated frame is the same as the expected. */
+  GPR_ASSERT(channel->bytes_written_to_client_channel == server_frame_size);
+  GPR_ASSERT(memcmp(server_expected_frames, channel->client_channel,
+                    server_frame_size) == 0);
+  unsigned char* client_received_message =
+      static_cast<unsigned char*>(gpr_malloc(kChannelSize));
+  size_t client_received_message_size = 0;
+  tsi_test_frame_protector_receive_message_from_peer(
+      config, channel, client_frame_protector, client_received_message,
+      &client_received_message_size,
+      /*is_client=*/true);
+  GPR_ASSERT(config->server_message_size == client_received_message_size);
+  GPR_ASSERT(memcmp(config->server_message, client_received_message,
+                    client_received_message_size) == 0);
+  config->client_message = saved_client_message;
+  config->server_message = saved_server_message;
+  /* Destroy server and client frame protectors. */
+  gpr_free(server_received_message);
+  gpr_free(client_received_message);
+}
+
+static void alts_test_do_round_trip_vector_tests() {
+  const uint8_t key[] = {0xfe, 0xff, 0xe9, 0x92, 0x86, 0x65, 0x73, 0x1c,
+                         0x6d, 0x6a, 0x8f, 0x94, 0x67, 0x30, 0x83, 0x08};
+  const char small_message[] = {'C', 'h', 'a', 'p', 'i', ' ',
+                                'C', 'h', 'a', 'p', 'o'};
+  const uint8_t large_message[] = {
+      0xd9, 0x31, 0x32, 0x25, 0xf8, 0x84, 0x06, 0xe5, 0xa5, 0x59, 0x09, 0xc5,
+      0xaf, 0xf5, 0x26, 0x9a, 0x86, 0xa7, 0xa9, 0x53, 0x15, 0x34, 0xf7, 0xda,
+      0x2e, 0x4c, 0x30, 0x3d, 0x8a, 0x31, 0x8a, 0x72, 0x1c, 0x3c, 0x0c, 0x95,
+      0x95, 0x68, 0x09, 0x53, 0x2f, 0xcf, 0x0e, 0x24, 0x49, 0xa6, 0xb5, 0x25,
+      0xb1, 0x6a, 0xed, 0xf5, 0xaa, 0x0d, 0xe6, 0x57, 0xba, 0x63, 0x7b, 0x39,
+      0x1a, 0xaf, 0xd2, 0x55, 0xd6, 0x09, 0xb1, 0xf0, 0x56, 0x63, 0x7a, 0x0d,
+      0x46, 0xdf, 0x99, 0x8d, 0x88, 0xe5, 0x22, 0x2a, 0xb2, 0xc2, 0x84, 0x65,
+      0x12, 0x15, 0x35, 0x24, 0xc0, 0x89, 0x5e, 0x81, 0x08, 0x06, 0x0f, 0x10,
+      0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c,
+      0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
+      0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30};
+  const size_t small_message_size = sizeof(small_message) / sizeof(uint8_t);
+  const size_t large_message_size = sizeof(large_message) / sizeof(uint8_t);
+  /* Test small client message and large server message. */
+  const uint8_t client_expected_frame1[] = {
+      0x1f, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x09, 0xd8, 0xd5, 0x92,
+      0x4d, 0x50, 0x32, 0xb7, 0x1f, 0xb8, 0xf2, 0xbb, 0x43, 0xc7, 0xe2, 0x94,
+      0x3d, 0x3e, 0x9a, 0x78, 0x76, 0xaa, 0x0a, 0x6b, 0xfa, 0x98, 0x3a};
+  const uint8_t server_expected_frame1[] = {
+      0x94, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0xa9, 0x4b, 0xf8, 0xc8,
+      0xe7, 0x8f, 0x1a, 0x26, 0x37, 0x44, 0xa2, 0x5c, 0x55, 0x94, 0x30, 0x4e,
+      0x3e, 0x16, 0xe7, 0x9e, 0x96, 0xe8, 0x1b, 0xc0, 0xdd, 0x52, 0x30, 0x06,
+      0xc2, 0x72, 0x9a, 0xa1, 0x0b, 0xdb, 0xdc, 0x19, 0x8c, 0x93, 0x5e, 0x84,
+      0x1f, 0x4b, 0x97, 0x26, 0xf0, 0x73, 0x85, 0x59, 0x00, 0x95, 0xc1, 0xc5,
+      0x22, 0x2f, 0x70, 0x85, 0x68, 0x2c, 0x4f, 0xfe, 0x30, 0x26, 0x91, 0xde,
+      0x62, 0x55, 0x1d, 0x35, 0x01, 0x96, 0x1c, 0xe7, 0xa2, 0x8b, 0x14, 0x8a,
+      0x5e, 0x1b, 0x4a, 0x3b, 0x4f, 0x65, 0x0f, 0xca, 0x79, 0x10, 0xb4, 0xdd,
+      0xf7, 0xa4, 0x8b, 0x64, 0x2f, 0x00, 0x39, 0x60, 0x03, 0xfc, 0xe1, 0x8b,
+      0x5c, 0x19, 0xba, 0xcc, 0x46, 0xba, 0x88, 0xdd, 0x40, 0x42, 0x27, 0x4f,
+      0xe4, 0x1a, 0x6a, 0x31, 0x6c, 0x1c, 0xb0, 0xb6, 0x5c, 0x3e, 0xca, 0x84,
+      0x9b, 0x5f, 0x04, 0x84, 0x11, 0xa9, 0xf8, 0x39, 0xe7, 0xe7, 0xc5, 0xc4,
+      0x33, 0x9f, 0x63, 0x21, 0x9a, 0x7c, 0x9c, 0x64};
+  const size_t client_frame_size1 =
+      sizeof(client_expected_frame1) / sizeof(uint8_t);
+  const size_t server_frame_size1 =
+      sizeof(server_expected_frame1) / sizeof(uint8_t);
+  tsi_test_frame_protector_fixture* fixture =
+      tsi_test_frame_protector_fixture_create();
+  alts_test_do_round_trip_check_frames(
+      fixture, key, kAes128GcmKeyLength, /*rekey=*/false,
+      reinterpret_cast<const uint8_t*>(small_message), small_message_size,
+      client_expected_frame1, client_frame_size1, large_message,
+      large_message_size, server_expected_frame1, server_frame_size1);
+  tsi_test_frame_protector_fixture_destroy(fixture);
+  /**
+   * Test large client message, small server message, and small
+   * message_buffer_allocated_size.
+   */
+  const uint8_t client_expected_frame2[] = {
+      0x94, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x93, 0x81, 0x86, 0xc7,
+      0xdc, 0xf4, 0x77, 0x3a, 0xdb, 0x91, 0x94, 0x61, 0xba, 0xed, 0xd5, 0x37,
+      0x47, 0x53, 0x0c, 0xe1, 0xbf, 0x59, 0x23, 0x20, 0xde, 0x8b, 0x25, 0x13,
+      0x72, 0xe7, 0x8a, 0x4f, 0x32, 0x61, 0xc6, 0xda, 0xc3, 0xe9, 0xff, 0x31,
+      0x33, 0x53, 0x4a, 0xf8, 0xc9, 0x98, 0xe4, 0x19, 0x71, 0x9c, 0x5e, 0x72,
+      0xc7, 0x35, 0x97, 0x78, 0x30, 0xf2, 0xc4, 0xd1, 0x53, 0xd5, 0x6e, 0x8f,
+      0x4f, 0xd9, 0x28, 0x5a, 0xfd, 0x22, 0x57, 0x7f, 0x95, 0xb4, 0x8a, 0x5e,
+      0x7c, 0x47, 0xa8, 0xcf, 0x64, 0x3d, 0x83, 0xa5, 0xcf, 0xc3, 0xfe, 0x54,
+      0xc2, 0x6a, 0x40, 0xc4, 0xfb, 0x8e, 0x07, 0x77, 0x70, 0x8f, 0x99, 0x94,
+      0xb1, 0xd5, 0xa7, 0xf9, 0x0d, 0xc7, 0x11, 0xc5, 0x6f, 0x4a, 0x4f, 0x56,
+      0xd5, 0xe2, 0x9c, 0xbb, 0x95, 0x7a, 0xd0, 0x9f, 0x30, 0x54, 0xca, 0x6d,
+      0x5c, 0x8e, 0x83, 0xa0, 0x04, 0x5e, 0xd0, 0x22, 0x8c, 0x2a, 0x7f, 0xdb,
+      0xfe, 0xb3, 0x2e, 0xae, 0x22, 0xe6, 0xf4, 0xb7};
+  const uint8_t server_expected_frame2[] = {
+      0x1f, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x33, 0x12, 0xab, 0x9d,
+      0x76, 0x2b, 0x5f, 0xab, 0xf3, 0x6d, 0xc4, 0xaa, 0xe5, 0x1e, 0x63, 0xc1,
+      0x7b, 0x7b, 0x10, 0xd5, 0x63, 0x0f, 0x29, 0xad, 0x17, 0x33, 0x73};
+  const size_t client_frame_size2 =
+      sizeof(client_expected_frame2) / sizeof(uint8_t);
+  const size_t server_frame_size2 =
+      sizeof(server_expected_frame2) / sizeof(uint8_t);
+  fixture = tsi_test_frame_protector_fixture_create();
+  alts_test_do_round_trip_check_frames(
+      fixture, key, kAes128GcmKeyLength, /*rekey=*/false, large_message,
+      large_message_size, client_expected_frame2, client_frame_size2,
+      reinterpret_cast<const uint8_t*>(small_message), small_message_size,
+      server_expected_frame2, server_frame_size2);
+  tsi_test_frame_protector_fixture_destroy(fixture);
+  /**
+   * Test large client message, small server message, and small
+   * protected_buffer_size.
+   */
+  const uint8_t client_expected_frame3[] = {
+      0x94, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x93, 0x81, 0x86, 0xc7,
+      0xdc, 0xf4, 0x77, 0x3a, 0xdb, 0x91, 0x94, 0x61, 0xba, 0xed, 0xd5, 0x37,
+      0x47, 0x53, 0x0c, 0xe1, 0xbf, 0x59, 0x23, 0x20, 0xde, 0x8b, 0x25, 0x13,
+      0x72, 0xe7, 0x8a, 0x4f, 0x32, 0x61, 0xc6, 0xda, 0xc3, 0xe9, 0xff, 0x31,
+      0x33, 0x53, 0x4a, 0xf8, 0xc9, 0x98, 0xe4, 0x19, 0x71, 0x9c, 0x5e, 0x72,
+      0xc7, 0x35, 0x97, 0x78, 0x30, 0xf2, 0xc4, 0xd1, 0x53, 0xd5, 0x6e, 0x8f,
+      0x4f, 0xd9, 0x28, 0x5a, 0xfd, 0x22, 0x57, 0x7f, 0x95, 0xb4, 0x8a, 0x5e,
+      0x7c, 0x47, 0xa8, 0xcf, 0x64, 0x3d, 0x83, 0xa5, 0xcf, 0xc3, 0xfe, 0x54,
+      0xc2, 0x6a, 0x40, 0xc4, 0xfb, 0x8e, 0x07, 0x77, 0x70, 0x8f, 0x99, 0x94,
+      0xb1, 0xd5, 0xa7, 0xf9, 0x0d, 0xc7, 0x11, 0xc5, 0x6f, 0x4a, 0x4f, 0x56,
+      0xd5, 0xe2, 0x9c, 0xbb, 0x95, 0x7a, 0xd0, 0x9f, 0x30, 0x54, 0xca, 0x6d,
+      0x5c, 0x8e, 0x83, 0xa0, 0x04, 0x5e, 0xd0, 0x22, 0x8c, 0x2a, 0x7f, 0xdb,
+      0xfe, 0xb3, 0x2e, 0xae, 0x22, 0xe6, 0xf4, 0xb7};
+  const uint8_t server_expected_frame3[] = {
+      0x1f, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x33, 0x12, 0xab, 0x9d,
+      0x76, 0x2b, 0x5f, 0xab, 0xf3, 0x6d, 0xc4, 0xaa, 0xe5, 0x1e, 0x63, 0xc1,
+      0x7b, 0x7b, 0x10, 0xd5, 0x63, 0x0f, 0x29, 0xad, 0x17, 0x33, 0x73};
+  const size_t client_frame_size3 =
+      sizeof(client_expected_frame3) / sizeof(uint8_t);
+  const size_t server_frame_size3 =
+      sizeof(server_expected_frame3) / sizeof(uint8_t);
+  fixture = tsi_test_frame_protector_fixture_create();
+  alts_test_do_round_trip_check_frames(
+      fixture, key, kAes128GcmKeyLength, /*rekey=*/false, large_message,
+      large_message_size, client_expected_frame3, client_frame_size3,
+      reinterpret_cast<const uint8_t*>(small_message), small_message_size,
+      server_expected_frame3, server_frame_size3);
+  tsi_test_frame_protector_fixture_destroy(fixture);
+  /**
+   * Test large client message, small server message, and small
+   * read_buffer_allocated_size.
+   */
+  const uint8_t client_expected_frame4[] = {
+      0x94, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x93, 0x81, 0x86, 0xc7,
+      0xdc, 0xf4, 0x77, 0x3a, 0xdb, 0x91, 0x94, 0x61, 0xba, 0xed, 0xd5, 0x37,
+      0x47, 0x53, 0x0c, 0xe1, 0xbf, 0x59, 0x23, 0x20, 0xde, 0x8b, 0x25, 0x13,
+      0x72, 0xe7, 0x8a, 0x4f, 0x32, 0x61, 0xc6, 0xda, 0xc3, 0xe9, 0xff, 0x31,
+      0x33, 0x53, 0x4a, 0xf8, 0xc9, 0x98, 0xe4, 0x19, 0x71, 0x9c, 0x5e, 0x72,
+      0xc7, 0x35, 0x97, 0x78, 0x30, 0xf2, 0xc4, 0xd1, 0x53, 0xd5, 0x6e, 0x8f,
+      0x4f, 0xd9, 0x28, 0x5a, 0xfd, 0x22, 0x57, 0x7f, 0x95, 0xb4, 0x8a, 0x5e,
+      0x7c, 0x47, 0xa8, 0xcf, 0x64, 0x3d, 0x83, 0xa5, 0xcf, 0xc3, 0xfe, 0x54,
+      0xc2, 0x6a, 0x40, 0xc4, 0xfb, 0x8e, 0x07, 0x77, 0x70, 0x8f, 0x99, 0x94,
+      0xb1, 0xd5, 0xa7, 0xf9, 0x0d, 0xc7, 0x11, 0xc5, 0x6f, 0x4a, 0x4f, 0x56,
+      0xd5, 0xe2, 0x9c, 0xbb, 0x95, 0x7a, 0xd0, 0x9f, 0x30, 0x54, 0xca, 0x6d,
+      0x5c, 0x8e, 0x83, 0xa0, 0x04, 0x5e, 0xd0, 0x22, 0x8c, 0x2a, 0x7f, 0xdb,
+      0xfe, 0xb3, 0x2e, 0xae, 0x22, 0xe6, 0xf4, 0xb7};
+  const uint8_t server_expected_frame4[] = {
+      0x1f, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x33, 0x12, 0xab, 0x9d,
+      0x76, 0x2b, 0x5f, 0xab, 0xf3, 0x6d, 0xc4, 0xaa, 0xe5, 0x1e, 0x63, 0xc1,
+      0x7b, 0x7b, 0x10, 0xd5, 0x63, 0x0f, 0x29, 0xad, 0x17, 0x33, 0x73};
+  const size_t client_frame_size4 =
+      sizeof(client_expected_frame4) / sizeof(uint8_t);
+  const size_t server_frame_size4 =
+      sizeof(server_expected_frame4) / sizeof(uint8_t);
+  fixture = tsi_test_frame_protector_fixture_create();
+  alts_test_do_round_trip_check_frames(
+      fixture, key, kAes128GcmKeyLength, /*rekey=*/false, large_message,
+      large_message_size, client_expected_frame4, client_frame_size4,
+      reinterpret_cast<const uint8_t*>(small_message), small_message_size,
+      server_expected_frame4, server_frame_size4);
+  tsi_test_frame_protector_fixture_destroy(fixture);
+  /**
+   * Test large client message, small server message, and small
+   * client_max_output_protected_frame_size.
+   */
+  const uint8_t client_expected_frame5[] = {
+      0x94, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x93, 0x81, 0x86, 0xc7,
+      0xdc, 0xf4, 0x77, 0x3a, 0xdb, 0x91, 0x94, 0x61, 0xba, 0xed, 0xd5, 0x37,
+      0x47, 0x53, 0x0c, 0xe1, 0xbf, 0x59, 0x23, 0x20, 0xde, 0x8b, 0x25, 0x13,
+      0x72, 0xe7, 0x8a, 0x4f, 0x32, 0x61, 0xc6, 0xda, 0xc3, 0xe9, 0xff, 0x31,
+      0x33, 0x53, 0x4a, 0xf8, 0xc9, 0x98, 0xe4, 0x19, 0x71, 0x9c, 0x5e, 0x72,
+      0xc7, 0x35, 0x97, 0x78, 0x30, 0xf2, 0xc4, 0xd1, 0x53, 0xd5, 0x6e, 0x8f,
+      0x4f, 0xd9, 0x28, 0x5a, 0xfd, 0x22, 0x57, 0x7f, 0x95, 0xb4, 0x8a, 0x5e,
+      0x7c, 0x47, 0xa8, 0xcf, 0x64, 0x3d, 0x83, 0xa5, 0xcf, 0xc3, 0xfe, 0x54,
+      0xc2, 0x6a, 0x40, 0xc4, 0xfb, 0x8e, 0x07, 0x77, 0x70, 0x8f, 0x99, 0x94,
+      0xb1, 0xd5, 0xa7, 0xf9, 0x0d, 0xc7, 0x11, 0xc5, 0x6f, 0x4a, 0x4f, 0x56,
+      0xd5, 0xe2, 0x9c, 0xbb, 0x95, 0x7a, 0xd0, 0x9f, 0x30, 0x54, 0xca, 0x6d,
+      0x5c, 0x8e, 0x83, 0xa0, 0x04, 0x5e, 0xd0, 0x22, 0x8c, 0x2a, 0x7f, 0xdb,
+      0xfe, 0xb3, 0x2e, 0xae, 0x22, 0xe6, 0xf4, 0xb7};
+  const uint8_t server_expected_frame5[] = {
+      0x1f, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x33, 0x12, 0xab, 0x9d,
+      0x76, 0x2b, 0x5f, 0xab, 0xf3, 0x6d, 0xc4, 0xaa, 0xe5, 0x1e, 0x63, 0xc1,
+      0x7b, 0x7b, 0x10, 0xd5, 0x63, 0x0f, 0x29, 0xad, 0x17, 0x33, 0x73};
+  const size_t client_frame_size5 =
+      sizeof(client_expected_frame5) / sizeof(uint8_t);
+  const size_t server_frame_size5 =
+      sizeof(server_expected_frame5) / sizeof(uint8_t);
+  fixture = tsi_test_frame_protector_fixture_create();
+  alts_test_do_round_trip_check_frames(
+      fixture, key, kAes128GcmKeyLength, /*rekey=*/false, large_message,
+      large_message_size, client_expected_frame5, client_frame_size5,
+      reinterpret_cast<const uint8_t*>(small_message), small_message_size,
+      server_expected_frame5, server_frame_size5);
+  tsi_test_frame_protector_fixture_destroy(fixture);
+  /**
+   * Test small client message, large server message, and small
+   * server_max_output_protected_frame_size.
+   */
+  const uint8_t client_expected_frame6[] = {
+      0x1f, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x09, 0xd8, 0xd5, 0x92,
+      0x4d, 0x50, 0x32, 0xb7, 0x1f, 0xb8, 0xf2, 0xbb, 0x43, 0xc7, 0xe2, 0x94,
+      0x3d, 0x3e, 0x9a, 0x78, 0x76, 0xaa, 0x0a, 0x6b, 0xfa, 0x98, 0x3a};
+  const uint8_t server_expected_frame6[] = {
+      0x94, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0xa9, 0x4b, 0xf8, 0xc8,
+      0xe7, 0x8f, 0x1a, 0x26, 0x37, 0x44, 0xa2, 0x5c, 0x55, 0x94, 0x30, 0x4e,
+      0x3e, 0x16, 0xe7, 0x9e, 0x96, 0xe8, 0x1b, 0xc0, 0xdd, 0x52, 0x30, 0x06,
+      0xc2, 0x72, 0x9a, 0xa1, 0x0b, 0xdb, 0xdc, 0x19, 0x8c, 0x93, 0x5e, 0x84,
+      0x1f, 0x4b, 0x97, 0x26, 0xf0, 0x73, 0x85, 0x59, 0x00, 0x95, 0xc1, 0xc5,
+      0x22, 0x2f, 0x70, 0x85, 0x68, 0x2c, 0x4f, 0xfe, 0x30, 0x26, 0x91, 0xde,
+      0x62, 0x55, 0x1d, 0x35, 0x01, 0x96, 0x1c, 0xe7, 0xa2, 0x8b, 0x14, 0x8a,
+      0x5e, 0x1b, 0x4a, 0x3b, 0x4f, 0x65, 0x0f, 0xca, 0x79, 0x10, 0xb4, 0xdd,
+      0xf7, 0xa4, 0x8b, 0x64, 0x2f, 0x00, 0x39, 0x60, 0x03, 0xfc, 0xe1, 0x8b,
+      0x5c, 0x19, 0xba, 0xcc, 0x46, 0xba, 0x88, 0xdd, 0x40, 0x42, 0x27, 0x4f,
+      0xe4, 0x1a, 0x6a, 0x31, 0x6c, 0x1c, 0xb0, 0xb6, 0x5c, 0x3e, 0xca, 0x84,
+      0x9b, 0x5f, 0x04, 0x84, 0x11, 0xa9, 0xf8, 0x39, 0xe7, 0xe7, 0xc5, 0xc4,
+      0x33, 0x9f, 0x63, 0x21, 0x9a, 0x7c, 0x9c, 0x64};
+  const size_t client_frame_size6 =
+      sizeof(client_expected_frame6) / sizeof(uint8_t);
+  const size_t server_frame_size6 =
+      sizeof(server_expected_frame6) / sizeof(uint8_t);
+  fixture = tsi_test_frame_protector_fixture_create();
+  alts_test_do_round_trip_check_frames(
+      fixture, key, kAes128GcmKeyLength, /*rekey=*/false,
+      reinterpret_cast<const uint8_t*>(small_message), small_message_size,
+      client_expected_frame6, client_frame_size6, large_message,
+      large_message_size, server_expected_frame6, server_frame_size6);
+  tsi_test_frame_protector_fixture_destroy(fixture);
+}
+
+static void alts_test_do_round_trip(tsi_test_frame_protector_fixture* fixture,
+                                    bool rekey) {
+  GPR_ASSERT(fixture != nullptr);
+  GPR_ASSERT(fixture->config != nullptr);
+  tsi_frame_protector* client_frame_protector = nullptr;
+  tsi_frame_protector* server_frame_protector = nullptr;
+  tsi_test_frame_protector_config* config = fixture->config;
+  /* Create a key to be used by both client and server. */
+  uint8_t* key = nullptr;
+  size_t key_length = rekey ? kAes128GcmRekeyKeyLength : kAes128GcmKeyLength;
+  gsec_test_random_array(&key, key_length);
+  /* Create a client frame protector. */
+  size_t client_max_output_protected_frame_size =
+      config->client_max_output_protected_frame_size;
+  GPR_ASSERT(
+      alts_create_frame_protector(key, key_length, /*is_client=*/true, rekey,
+                                  client_max_output_protected_frame_size == 0
+                                      ? nullptr
+                                      : &client_max_output_protected_frame_size,
+                                  &client_frame_protector) == TSI_OK);
+  /* Create a server frame protector. */
+  size_t server_max_output_protected_frame_size =
+      config->server_max_output_protected_frame_size;
+  GPR_ASSERT(
+      alts_create_frame_protector(key, key_length, /*is_client=*/false, rekey,
+                                  server_max_output_protected_frame_size == 0
+                                      ? nullptr
+                                      : &server_max_output_protected_frame_size,
+                                  &server_frame_protector) == TSI_OK);
+  tsi_test_frame_protector_fixture_init(fixture, client_frame_protector,
+                                        server_frame_protector);
+  tsi_test_frame_protector_do_round_trip_no_handshake(fixture);
+  gpr_free(key);
+}
+
+/* Run all combinations of different arguments of test config. */
+static void alts_test_do_round_trip_all(bool rekey) {
+  unsigned int* bit_array = static_cast<unsigned int*>(
+      gpr_malloc(sizeof(unsigned int) * TSI_TEST_NUM_OF_ARGUMENTS));
+  unsigned int mask = 1U << (TSI_TEST_NUM_OF_ARGUMENTS - 1);
+  unsigned int val = 0, ind = 0;
+  for (val = 0; val < TSI_TEST_NUM_OF_COMBINATIONS; val++) {
+    unsigned int v = val;
+    for (ind = 0; ind < TSI_TEST_NUM_OF_ARGUMENTS; ind++) {
+      bit_array[ind] = (v & mask) ? 1 : 0;
+      v <<= 1;
+    }
+    tsi_test_frame_protector_fixture* fixture =
+        tsi_test_frame_protector_fixture_create();
+    tsi_test_frame_protector_config_destroy(fixture->config);
+    fixture->config = tsi_test_frame_protector_config_create(
+        bit_array[0], bit_array[1], bit_array[2], bit_array[3], bit_array[4],
+        bit_array[5], bit_array[6]);
+    alts_test_do_round_trip(fixture, rekey);
+    tsi_test_frame_protector_fixture_destroy(fixture);
+  }
+  gpr_free(bit_array);
+}
+
+int main(int argc, char** argv) {
+  alts_test_do_round_trip_vector_tests();
+  alts_test_do_round_trip_all(/*rekey=*/false);
+  alts_test_do_round_trip_all(/*rekey=*/true);
+  return 0;
+}
diff --git a/test/core/tsi/alts/frame_protector/frame_handler_test.cc b/test/core/tsi/alts/frame_protector/frame_handler_test.cc
new file mode 100644
index 0000000..6434ea1
--- /dev/null
+++ b/test/core/tsi/alts/frame_protector/frame_handler_test.cc
@@ -0,0 +1,244 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/gpr/useful.h"
+#include "src/core/tsi/alts/frame_protector/frame_handler.h"
+#include "test/core/tsi/alts/crypt/gsec_test_util.h"
+
+const size_t kFrameHandlerTestBufferSize = 1024;
+
+typedef struct frame_handler {
+  alts_frame_writer* writer;
+  alts_frame_reader* reader;
+  unsigned char* buffer;
+  size_t buffer_size;
+} frame_handler;
+
+static size_t frame_length(size_t payload_length) {
+  return payload_length + kFrameHeaderSize;
+}
+
+static frame_handler* create_frame_handler() {
+  frame_handler* handler =
+      static_cast<frame_handler*>(gpr_malloc(sizeof(frame_handler)));
+  handler->writer = alts_create_frame_writer();
+  handler->reader = alts_create_frame_reader();
+  handler->buffer = nullptr;
+  handler->buffer_size = 0;
+  return handler;
+}
+
+static void destroy_frame_handler(frame_handler* handler) {
+  if (handler != nullptr) {
+    alts_destroy_frame_reader(handler->reader);
+    alts_destroy_frame_writer(handler->writer);
+    if (handler->buffer != nullptr) gpr_free(handler->buffer);
+    gpr_free(handler);
+  }
+}
+
+static void frame(frame_handler* handler, unsigned char* payload,
+                  size_t payload_length, size_t write_length) {
+  handler->buffer_size = frame_length(payload_length);
+  handler->buffer =
+      static_cast<unsigned char*>(gpr_malloc(handler->buffer_size));
+  GPR_ASSERT(alts_reset_frame_writer(handler->writer, payload, payload_length));
+  size_t offset = 0;
+  while (offset < handler->buffer_size &&
+         !alts_is_frame_writer_done(handler->writer)) {
+    size_t bytes_written = GPR_MIN(write_length, handler->buffer_size - offset);
+    GPR_ASSERT(alts_write_frame_bytes(handler->writer, handler->buffer + offset,
+                                      &bytes_written));
+    offset += bytes_written;
+  }
+  GPR_ASSERT(alts_is_frame_writer_done(handler->writer));
+  GPR_ASSERT(handler->buffer_size == offset);
+}
+
+static size_t deframe(frame_handler* handler, unsigned char* bytes,
+                      size_t read_length) {
+  GPR_ASSERT(alts_reset_frame_reader(handler->reader, bytes));
+  size_t offset = 0;
+  while (offset < handler->buffer_size &&
+         !alts_is_frame_reader_done(handler->reader)) {
+    size_t bytes_read = GPR_MIN(read_length, handler->buffer_size - offset);
+    GPR_ASSERT(alts_read_frame_bytes(handler->reader, handler->buffer + offset,
+                                     &bytes_read));
+    offset += bytes_read;
+  }
+  GPR_ASSERT(alts_is_frame_reader_done(handler->reader));
+  GPR_ASSERT(handler->buffer_size == offset);
+  return offset - handler->reader->header_bytes_read;
+}
+
+static void frame_n_deframe(frame_handler* handler, unsigned char* payload,
+                            size_t payload_length, size_t write_length,
+                            size_t read_length) {
+  frame(handler, payload, payload_length, write_length);
+  unsigned char* bytes =
+      static_cast<unsigned char*>(gpr_malloc(kFrameHandlerTestBufferSize));
+  size_t deframed_payload_length = deframe(handler, bytes, read_length);
+  GPR_ASSERT(payload_length == deframed_payload_length);
+  GPR_ASSERT(memcmp(payload, bytes, payload_length) == 0);
+  gpr_free(bytes);
+}
+
+static void frame_handler_test_frame_deframe() {
+  unsigned char payload[] = "hello world";
+  size_t payload_length = strlen((char*)payload) + 1;
+  frame_handler* handler = create_frame_handler();
+  frame_n_deframe(handler, payload, payload_length,
+                  frame_length(payload_length), frame_length(payload_length));
+  destroy_frame_handler(handler);
+}
+
+static void frame_handler_test_small_buffer() {
+  unsigned char payload[] = "hello world";
+  size_t payload_length = strlen(reinterpret_cast<char*>(payload)) + 1;
+  frame_handler* handler = create_frame_handler();
+  frame_n_deframe(handler, payload, payload_length, 1, 1);
+  destroy_frame_handler(handler);
+}
+
+static void frame_handler_test_null_input_stream() {
+  frame_handler* handler = create_frame_handler();
+  GPR_ASSERT(!alts_reset_frame_writer(handler->writer, nullptr, 0));
+  destroy_frame_handler(handler);
+}
+
+static void frame_handler_test_bad_input_length() {
+  unsigned char payload[] = "hello world";
+  frame_handler* handler = create_frame_handler();
+  GPR_ASSERT(!alts_reset_frame_writer(handler->writer, payload, SIZE_MAX));
+  destroy_frame_handler(handler);
+}
+
+static void frame_handler_test_null_writer_byte_length() {
+  unsigned char payload[] = "hello world";
+  size_t payload_length = strlen(reinterpret_cast<char*>(payload)) + 1;
+  frame_handler* handler = create_frame_handler();
+  GPR_ASSERT(alts_reset_frame_writer(handler->writer, payload, payload_length));
+  GPR_ASSERT(
+      !alts_write_frame_bytes(handler->writer, handler->buffer, nullptr));
+  destroy_frame_handler(handler);
+}
+
+static void frame_handler_test_null_writer_bytes() {
+  unsigned char payload[] = "hello world";
+  size_t payload_length = strlen(reinterpret_cast<char*>(payload)) + 1;
+  frame_handler* handler = create_frame_handler();
+  GPR_ASSERT(alts_reset_frame_writer(handler->writer, payload, payload_length));
+  GPR_ASSERT(
+      !alts_write_frame_bytes(handler->writer, nullptr, &payload_length));
+  destroy_frame_handler(handler);
+}
+
+static void frame_handler_test_bad_frame_length() {
+  unsigned char payload[] = "hello world";
+  size_t payload_length = strlen(reinterpret_cast<char*>(payload)) + 1;
+  frame_handler* handler = create_frame_handler();
+  frame(handler, payload, payload_length, payload_length);
+  memset(handler->buffer, 0x00, kFrameLengthFieldSize);
+  unsigned char* bytes =
+      static_cast<unsigned char*>(gpr_malloc(kFrameHandlerTestBufferSize));
+  GPR_ASSERT(alts_reset_frame_reader(handler->reader, bytes));
+  size_t bytes_read = handler->buffer_size;
+  GPR_ASSERT(
+      !alts_read_frame_bytes(handler->reader, handler->buffer, &bytes_read));
+  GPR_ASSERT(alts_is_frame_reader_done(handler->reader));
+  GPR_ASSERT(bytes_read == 0);
+  gpr_free(bytes);
+  destroy_frame_handler(handler);
+}
+
+static void frame_handler_test_unsupported_message_type() {
+  unsigned char payload[] = "hello world";
+  size_t payload_length = strlen(reinterpret_cast<char*>(payload)) + 1;
+  frame_handler* handler = create_frame_handler();
+  frame(handler, payload, payload_length, payload_length);
+  memset(handler->buffer + kFrameLengthFieldSize, 0x00,
+         kFrameMessageTypeFieldSize);
+  unsigned char* bytes =
+      static_cast<unsigned char*>(gpr_malloc(kFrameHandlerTestBufferSize));
+  GPR_ASSERT(alts_reset_frame_reader(handler->reader, bytes));
+  size_t bytes_read = handler->buffer_size;
+  GPR_ASSERT(
+      !alts_read_frame_bytes(handler->reader, handler->buffer, &bytes_read));
+  GPR_ASSERT(alts_is_frame_reader_done(handler->reader));
+  GPR_ASSERT(bytes_read == 0);
+  gpr_free(bytes);
+  destroy_frame_handler(handler);
+}
+
+static void frame_handler_test_null_output_stream() {
+  unsigned char payload[] = "hello world";
+  size_t payload_length = strlen(reinterpret_cast<char*>(payload)) + 1;
+  frame_handler* handler = create_frame_handler();
+  frame(handler, payload, payload_length, payload_length);
+  GPR_ASSERT(!alts_reset_frame_reader(handler->reader, nullptr));
+  destroy_frame_handler(handler);
+}
+
+static void frame_handler_test_null_reader_byte_length() {
+  unsigned char payload[] = "hello world";
+  size_t payload_length = strlen(reinterpret_cast<char*>(payload)) + 1;
+  frame_handler* handler = create_frame_handler();
+  frame(handler, payload, payload_length, payload_length);
+  unsigned char* bytes =
+      static_cast<unsigned char*>(gpr_malloc(kFrameHandlerTestBufferSize));
+  GPR_ASSERT(alts_reset_frame_reader(handler->reader, bytes));
+  GPR_ASSERT(!alts_read_frame_bytes(handler->reader, handler->buffer, nullptr));
+  gpr_free(bytes);
+  destroy_frame_handler(handler);
+}
+
+static void frame_handler_test_null_reader_bytes() {
+  unsigned char payload[] = "hello world";
+  size_t payload_length = strlen(reinterpret_cast<char*>(payload)) + 1;
+  frame_handler* handler = create_frame_handler();
+  frame(handler, payload, payload_length, payload_length);
+  unsigned char* bytes =
+      static_cast<unsigned char*>(gpr_malloc(kFrameHandlerTestBufferSize));
+  GPR_ASSERT(alts_reset_frame_reader(handler->reader, bytes));
+  size_t bytes_read = handler->buffer_size;
+  GPR_ASSERT(!alts_read_frame_bytes(handler->reader, nullptr, &bytes_read));
+  gpr_free(bytes);
+  destroy_frame_handler(handler);
+}
+
+int main(int argc, char** argv) {
+  frame_handler_test_frame_deframe();
+  frame_handler_test_small_buffer();
+  frame_handler_test_null_input_stream();
+  frame_handler_test_bad_input_length();
+  frame_handler_test_null_writer_byte_length();
+  frame_handler_test_null_writer_bytes();
+  frame_handler_test_bad_frame_length();
+  frame_handler_test_unsupported_message_type();
+  frame_handler_test_null_output_stream();
+  frame_handler_test_null_reader_byte_length();
+  frame_handler_test_null_reader_bytes();
+  return 0;
+}
diff --git a/test/core/tsi/alts/handshaker/BUILD b/test/core/tsi/alts/handshaker/BUILD
new file mode 100644
index 0000000..db39732
--- /dev/null
+++ b/test/core/tsi/alts/handshaker/BUILD
@@ -0,0 +1,78 @@
+# Copyright 2018 gRPC authors.
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("//bazel:grpc_build_system.bzl", "grpc_cc_library", "grpc_cc_test", "grpc_package")
+
+licenses(["notice"])  # Apache v2 
+         
+grpc_package(name = "handshaker")
+         
+grpc_cc_library(
+    name = "alts_handshaker_service_api_test_lib",
+    srcs = ["alts_handshaker_service_api_test_lib.cc"],
+    hdrs = ["alts_handshaker_service_api_test_lib.h"],
+    deps = [
+        "//:grpc",
+    ], 
+)
+
+grpc_cc_test(
+    name = "alts_handshaker_client_test",
+    srcs = ["alts_handshaker_client_test.cc"],
+    language = "C++",
+    deps = [
+        ":alts_handshaker_service_api_test_lib",
+        "//:grpc",
+    ],
+)
+
+grpc_cc_test(
+    name = "alts_handshaker_service_api_test",
+    srcs = ["alts_handshaker_service_api_test.cc"],
+    language = "C++",
+    deps = [
+        ":alts_handshaker_service_api_test_lib",
+        "//:grpc",
+    ],
+)
+
+grpc_cc_test(
+    name = "alts_tsi_handshaker_test",
+    srcs = ["alts_tsi_handshaker_test.cc"],
+    language = "C++",
+    deps = [
+        ":alts_handshaker_service_api_test_lib",
+        "//:grpc",
+    ],
+)
+
+grpc_cc_test(
+    name = "alts_tsi_utils_test",
+    srcs = ["alts_tsi_utils_test.cc"],
+    language = "C++",
+    deps = [
+        ":alts_handshaker_service_api_test_lib",
+        "//:grpc",
+    ],
+)
+
+grpc_cc_test(
+    name = "transport_security_common_api_test",
+    srcs = ["transport_security_common_api_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+    ],
+)
+
diff --git a/test/core/tsi/alts/handshaker/alts_handshaker_client_test.cc b/test/core/tsi/alts/handshaker/alts_handshaker_client_test.cc
new file mode 100644
index 0000000..7072be6
--- /dev/null
+++ b/test/core/tsi/alts/handshaker/alts_handshaker_client_test.cc
@@ -0,0 +1,412 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/grpc.h>
+
+#include "src/core/tsi/alts/handshaker/alts_handshaker_client.h"
+#include "src/core/tsi/alts/handshaker/alts_tsi_event.h"
+#include "src/core/tsi/alts/handshaker/alts_tsi_handshaker.h"
+#include "src/core/tsi/transport_security.h"
+#include "src/core/tsi/transport_security_interface.h"
+#include "test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.h"
+
+#define ALTS_HANDSHAKER_CLIENT_TEST_OUT_FRAME "Hello Google"
+#define ALTS_HANDSHAKER_CLIENT_TEST_HANDSHAKER_SERVICE_URL "lame"
+#define ALTS_HANDSHAKER_CLIENT_TEST_TARGET_NAME "bigtable.google.api.com"
+#define ALTS_HANDSHAKER_CLIENT_TEST_TARGET_SERVICE_ACCOUNT1 "A@google.com"
+#define ALTS_HANDSHAKER_CLIENT_TEST_TARGET_SERVICE_ACCOUNT2 "B@google.com"
+
+const size_t kHandshakerClientOpNum = 4;
+const size_t kMaxRpcVersionMajor = 3;
+const size_t kMaxRpcVersionMinor = 2;
+const size_t kMinRpcVersionMajor = 2;
+const size_t kMinRpcVersionMinor = 1;
+
+using grpc_core::internal::alts_handshaker_client_set_grpc_caller_for_testing;
+
+typedef struct alts_handshaker_client_test_config {
+  grpc_channel* channel;
+  grpc_completion_queue* cq;
+  alts_handshaker_client* client;
+  grpc_slice out_frame;
+} alts_handshaker_client_test_config;
+
+static alts_tsi_event* alts_tsi_event_create_for_testing(bool is_client) {
+  alts_tsi_event* e = static_cast<alts_tsi_event*>(gpr_zalloc(sizeof(*e)));
+  grpc_metadata_array_init(&e->initial_metadata);
+  grpc_metadata_array_init(&e->trailing_metadata);
+  e->options = is_client ? grpc_alts_credentials_client_options_create()
+                         : grpc_alts_credentials_server_options_create();
+  if (is_client) {
+    grpc_alts_credentials_client_options_add_target_service_account(
+        reinterpret_cast<grpc_alts_credentials_client_options*>(e->options),
+        ALTS_HANDSHAKER_CLIENT_TEST_TARGET_SERVICE_ACCOUNT1);
+    grpc_alts_credentials_client_options_add_target_service_account(
+        reinterpret_cast<grpc_alts_credentials_client_options*>(e->options),
+        ALTS_HANDSHAKER_CLIENT_TEST_TARGET_SERVICE_ACCOUNT2);
+  }
+  grpc_gcp_rpc_protocol_versions* versions = &e->options->rpc_versions;
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_max(
+      versions, kMaxRpcVersionMajor, kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_min(
+      versions, kMinRpcVersionMajor, kMinRpcVersionMinor));
+  e->target_name =
+      grpc_slice_from_static_string(ALTS_HANDSHAKER_CLIENT_TEST_TARGET_NAME);
+  return e;
+}
+
+static void validate_rpc_protocol_versions(
+    grpc_gcp_rpc_protocol_versions* versions) {
+  GPR_ASSERT(versions != nullptr);
+  GPR_ASSERT(versions->max_rpc_version.major == kMaxRpcVersionMajor);
+  GPR_ASSERT(versions->max_rpc_version.minor == kMaxRpcVersionMinor);
+  GPR_ASSERT(versions->min_rpc_version.major == kMinRpcVersionMajor);
+  GPR_ASSERT(versions->min_rpc_version.minor == kMinRpcVersionMinor);
+}
+
+static void validate_target_identities(
+    const repeated_field* target_identity_head) {
+  grpc_gcp_identity* target_identity1 = static_cast<grpc_gcp_identity*>(
+      const_cast<void*>(target_identity_head->next->data));
+  grpc_gcp_identity* target_identity2 = static_cast<grpc_gcp_identity*>(
+      const_cast<void*>(target_identity_head->data));
+  grpc_slice* service_account1 =
+      static_cast<grpc_slice*>(target_identity1->service_account.arg);
+  grpc_slice* service_account2 =
+      static_cast<grpc_slice*>(target_identity2->service_account.arg);
+  GPR_ASSERT(memcmp(GRPC_SLICE_START_PTR(*service_account1),
+                    ALTS_HANDSHAKER_CLIENT_TEST_TARGET_SERVICE_ACCOUNT1,
+                    GRPC_SLICE_LENGTH(*service_account1)) == 0);
+  GPR_ASSERT(strlen(ALTS_HANDSHAKER_CLIENT_TEST_TARGET_SERVICE_ACCOUNT1) ==
+             GRPC_SLICE_LENGTH(*service_account1));
+  GPR_ASSERT(memcmp(GRPC_SLICE_START_PTR(*service_account2),
+                    ALTS_HANDSHAKER_CLIENT_TEST_TARGET_SERVICE_ACCOUNT2,
+                    GRPC_SLICE_LENGTH(*service_account2)) == 0);
+  GPR_ASSERT(strlen(ALTS_HANDSHAKER_CLIENT_TEST_TARGET_SERVICE_ACCOUNT2) ==
+             GRPC_SLICE_LENGTH(*service_account2));
+}
+
+/**
+ * Validate if grpc operation data is correctly populated with the fields of
+ * ALTS TSI event.
+ */
+static bool validate_op(alts_tsi_event* event, const grpc_op* op, size_t nops,
+                        bool is_start) {
+  GPR_ASSERT(event != nullptr && op != nullptr && nops != 0);
+  bool ok = true;
+  grpc_op* start_op = const_cast<grpc_op*>(op);
+  if (is_start) {
+    ok &= (op->op == GRPC_OP_SEND_INITIAL_METADATA);
+    ok &= (op->data.send_initial_metadata.count == 0);
+    op++;
+    GPR_ASSERT((size_t)(op - start_op) <= kHandshakerClientOpNum);
+
+    ok &= (op->op == GRPC_OP_RECV_INITIAL_METADATA);
+    ok &= (op->data.recv_initial_metadata.recv_initial_metadata ==
+           &event->initial_metadata);
+    op++;
+    GPR_ASSERT((size_t)(op - start_op) <= kHandshakerClientOpNum);
+  }
+  ok &= (op->op == GRPC_OP_SEND_MESSAGE);
+  ok &= (op->data.send_message.send_message == event->send_buffer);
+  op++;
+  GPR_ASSERT((size_t)(op - start_op) <= kHandshakerClientOpNum);
+
+  ok &= (op->op == GRPC_OP_RECV_MESSAGE);
+  ok &= (op->data.recv_message.recv_message == &event->recv_buffer);
+  op++;
+  GPR_ASSERT((size_t)(op - start_op) <= kHandshakerClientOpNum);
+
+  return ok;
+}
+
+static grpc_gcp_handshaker_req* deserialize_handshaker_req(
+    grpc_gcp_handshaker_req_type type, grpc_byte_buffer* buffer) {
+  GPR_ASSERT(buffer != nullptr);
+  grpc_gcp_handshaker_req* req = grpc_gcp_handshaker_decoded_req_create(type);
+  grpc_byte_buffer_reader bbr;
+  GPR_ASSERT(grpc_byte_buffer_reader_init(&bbr, buffer));
+  grpc_slice slice = grpc_byte_buffer_reader_readall(&bbr);
+  GPR_ASSERT(grpc_gcp_handshaker_req_decode(slice, req));
+  grpc_slice_unref(slice);
+  grpc_byte_buffer_reader_destroy(&bbr);
+  return req;
+}
+
+/**
+ * A mock grpc_caller used to check if client_start, server_start, and next
+ * operations correctly handle invalid arguments. It should not be called.
+ */
+static grpc_call_error check_must_not_be_called(grpc_call* call,
+                                                const grpc_op* ops, size_t nops,
+                                                void* tag) {
+  GPR_ASSERT(0);
+}
+
+/**
+ * A mock grpc_caller used to check correct execution of client_start operation.
+ * It checks if the client_start handshaker request is populated with correct
+ * handshake_security_protocol, application_protocol, and record_protocol, and
+ * op is correctly populated.
+ */
+static grpc_call_error check_client_start_success(grpc_call* call,
+                                                  const grpc_op* op,
+                                                  size_t nops, void* tag) {
+  alts_tsi_event* event = static_cast<alts_tsi_event*>(tag);
+  grpc_gcp_handshaker_req* req =
+      deserialize_handshaker_req(CLIENT_START_REQ, event->send_buffer);
+  GPR_ASSERT(req->client_start.handshake_security_protocol ==
+             grpc_gcp_HandshakeProtocol_ALTS);
+  const void* data = (static_cast<repeated_field*>(
+                          req->client_start.application_protocols.arg))
+                         ->data;
+  GPR_ASSERT(data != nullptr);
+  grpc_slice* application_protocol = (grpc_slice*)data;
+  data = (static_cast<repeated_field*>(req->client_start.record_protocols.arg))
+             ->data;
+  grpc_slice* record_protocol = (grpc_slice*)data;
+  GPR_ASSERT(memcmp(GRPC_SLICE_START_PTR(*application_protocol),
+                    ALTS_APPLICATION_PROTOCOL,
+                    GRPC_SLICE_LENGTH(*application_protocol)) == 0);
+  GPR_ASSERT(memcmp(GRPC_SLICE_START_PTR(*record_protocol),
+                    ALTS_RECORD_PROTOCOL,
+                    GRPC_SLICE_LENGTH(*record_protocol)) == 0);
+  validate_rpc_protocol_versions(&req->client_start.rpc_versions);
+  validate_target_identities(
+      static_cast<repeated_field*>(req->client_start.target_identities.arg));
+  grpc_slice* target_name =
+      static_cast<grpc_slice*>(req->client_start.target_name.arg);
+  GPR_ASSERT(memcmp(GRPC_SLICE_START_PTR(*target_name),
+                    ALTS_HANDSHAKER_CLIENT_TEST_TARGET_NAME,
+                    GRPC_SLICE_LENGTH(*target_name)) == 0);
+  GPR_ASSERT(GRPC_SLICE_LENGTH(*target_name) ==
+             strlen(ALTS_HANDSHAKER_CLIENT_TEST_TARGET_NAME));
+  GPR_ASSERT(validate_op(event, op, nops, true /* is_start */));
+  grpc_gcp_handshaker_req_destroy(req);
+  return GRPC_CALL_OK;
+}
+
+/**
+ * A mock grpc_caller used to check correct execution of server_start operation.
+ * It checks if the server_start handshaker request is populated with correct
+ * handshake_security_protocol, application_protocol, and record_protocol, and
+ * op is correctly populated.
+ */
+static grpc_call_error check_server_start_success(grpc_call* call,
+                                                  const grpc_op* op,
+                                                  size_t nops, void* tag) {
+  alts_tsi_event* event = static_cast<alts_tsi_event*>(tag);
+  grpc_gcp_handshaker_req* req =
+      deserialize_handshaker_req(SERVER_START_REQ, event->send_buffer);
+  const void* data = (static_cast<repeated_field*>(
+                          req->server_start.application_protocols.arg))
+                         ->data;
+  GPR_ASSERT(data != nullptr);
+  grpc_slice* application_protocol = (grpc_slice*)data;
+  GPR_ASSERT(memcmp(GRPC_SLICE_START_PTR(*application_protocol),
+                    ALTS_APPLICATION_PROTOCOL,
+                    GRPC_SLICE_LENGTH(*application_protocol)) == 0);
+  GPR_ASSERT(req->server_start.handshake_parameters_count == 1);
+  GPR_ASSERT(req->server_start.handshake_parameters[0].key ==
+             grpc_gcp_HandshakeProtocol_ALTS);
+  data = (static_cast<repeated_field*>(req->server_start.handshake_parameters[0]
+                                           .value.record_protocols.arg))
+             ->data;
+  GPR_ASSERT(data != nullptr);
+  grpc_slice* record_protocol = (grpc_slice*)data;
+  GPR_ASSERT(memcmp(GRPC_SLICE_START_PTR(*record_protocol),
+                    ALTS_RECORD_PROTOCOL,
+                    GRPC_SLICE_LENGTH(*record_protocol)) == 0);
+  validate_rpc_protocol_versions(&req->server_start.rpc_versions);
+  GPR_ASSERT(validate_op(event, op, nops, true /* is_start */));
+  grpc_gcp_handshaker_req_destroy(req);
+  return GRPC_CALL_OK;
+}
+
+/**
+ * A mock grpc_caller used to check correct execution of next operation. It
+ * checks if the next handshaker request is populated with correct information,
+ * and op is correctly populated.
+ */
+static grpc_call_error check_next_success(grpc_call* call, const grpc_op* op,
+                                          size_t nops, void* tag) {
+  alts_tsi_event* event = static_cast<alts_tsi_event*>(tag);
+  grpc_gcp_handshaker_req* req =
+      deserialize_handshaker_req(NEXT_REQ, event->send_buffer);
+  grpc_slice* in_bytes = static_cast<grpc_slice*>(req->next.in_bytes.arg);
+  GPR_ASSERT(in_bytes != nullptr);
+  GPR_ASSERT(memcmp(GRPC_SLICE_START_PTR(*in_bytes),
+                    ALTS_HANDSHAKER_CLIENT_TEST_OUT_FRAME,
+                    GRPC_SLICE_LENGTH(*in_bytes)) == 0);
+  GPR_ASSERT(validate_op(event, op, nops, false /* is_start */));
+  grpc_gcp_handshaker_req_destroy(req);
+  return GRPC_CALL_OK;
+}
+/**
+ * A mock grpc_caller used to check if client_start, server_start, and next
+ * operations correctly handle the situation when the grpc call made to the
+ * handshaker service fails.
+ */
+static grpc_call_error check_grpc_call_failure(grpc_call* call,
+                                               const grpc_op* op, size_t nops,
+                                               void* tag) {
+  return GRPC_CALL_ERROR;
+}
+
+static alts_handshaker_client_test_config* create_config() {
+  alts_handshaker_client_test_config* config =
+      static_cast<alts_handshaker_client_test_config*>(
+          gpr_zalloc(sizeof(*config)));
+  config->channel = grpc_insecure_channel_create(
+      ALTS_HANDSHAKER_CLIENT_TEST_HANDSHAKER_SERVICE_URL, nullptr, nullptr);
+  config->cq = grpc_completion_queue_create_for_next(nullptr);
+  config->client = alts_grpc_handshaker_client_create(
+      config->channel, config->cq,
+      ALTS_HANDSHAKER_CLIENT_TEST_HANDSHAKER_SERVICE_URL);
+  GPR_ASSERT(config->client != nullptr);
+  config->out_frame =
+      grpc_slice_from_static_string(ALTS_HANDSHAKER_CLIENT_TEST_OUT_FRAME);
+  return config;
+}
+
+static void destroy_config(alts_handshaker_client_test_config* config) {
+  if (config == nullptr) {
+    return;
+  }
+  grpc_completion_queue_destroy(config->cq);
+  grpc_channel_destroy(config->channel);
+  alts_handshaker_client_destroy(config->client);
+  grpc_slice_unref(config->out_frame);
+  gpr_free(config);
+}
+
+static void schedule_request_invalid_arg_test() {
+  /* Initialization. */
+  alts_handshaker_client_test_config* config = create_config();
+  alts_tsi_event* event = nullptr;
+
+  /* Tests. */
+  alts_handshaker_client_set_grpc_caller_for_testing(config->client,
+                                                     check_must_not_be_called);
+  event = alts_tsi_event_create_for_testing(true /* is_client */);
+  /* Check client_start. */
+  GPR_ASSERT(alts_handshaker_client_start_client(nullptr, event) ==
+             TSI_INVALID_ARGUMENT);
+  GPR_ASSERT(alts_handshaker_client_start_client(config->client, nullptr) ==
+             TSI_INVALID_ARGUMENT);
+
+  /* Check server_start. */
+  GPR_ASSERT(alts_handshaker_client_start_server(
+                 config->client, event, nullptr) == TSI_INVALID_ARGUMENT);
+  GPR_ASSERT(alts_handshaker_client_start_server(config->client, nullptr,
+                                                 &config->out_frame) ==
+             TSI_INVALID_ARGUMENT);
+  GPR_ASSERT(alts_handshaker_client_start_server(
+                 nullptr, event, &config->out_frame) == TSI_INVALID_ARGUMENT);
+
+  /* Check next. */
+  GPR_ASSERT(alts_handshaker_client_next(config->client, event, nullptr) ==
+             TSI_INVALID_ARGUMENT);
+  GPR_ASSERT(alts_handshaker_client_next(config->client, nullptr,
+                                         &config->out_frame) ==
+             TSI_INVALID_ARGUMENT);
+  GPR_ASSERT(alts_handshaker_client_next(nullptr, event, &config->out_frame) ==
+             TSI_INVALID_ARGUMENT);
+
+  /* Cleanup. */
+  alts_tsi_event_destroy(event);
+  destroy_config(config);
+}
+
+static void schedule_request_success_test() {
+  /* Initialization. */
+  alts_handshaker_client_test_config* config = create_config();
+  alts_tsi_event* event = nullptr;
+
+  /* Check client_start success. */
+  alts_handshaker_client_set_grpc_caller_for_testing(
+      config->client, check_client_start_success);
+  event = alts_tsi_event_create_for_testing(true /* is_client. */);
+  GPR_ASSERT(alts_handshaker_client_start_client(config->client, event) ==
+             TSI_OK);
+  alts_tsi_event_destroy(event);
+
+  /* Check server_start success. */
+  alts_handshaker_client_set_grpc_caller_for_testing(
+      config->client, check_server_start_success);
+  event = alts_tsi_event_create_for_testing(false /* is_client. */);
+  GPR_ASSERT(alts_handshaker_client_start_server(config->client, event,
+                                                 &config->out_frame) == TSI_OK);
+  alts_tsi_event_destroy(event);
+
+  /* Check next success. */
+  alts_handshaker_client_set_grpc_caller_for_testing(config->client,
+                                                     check_next_success);
+  event = alts_tsi_event_create_for_testing(true /* is_client. */);
+  GPR_ASSERT(alts_handshaker_client_next(config->client, event,
+                                         &config->out_frame) == TSI_OK);
+  alts_tsi_event_destroy(event);
+
+  /* Cleanup. */
+  destroy_config(config);
+}
+
+static void schedule_request_grpc_call_failure_test() {
+  /* Initialization. */
+  alts_handshaker_client_test_config* config = create_config();
+  alts_tsi_event* event = nullptr;
+
+  /* Check client_start failure. */
+  alts_handshaker_client_set_grpc_caller_for_testing(config->client,
+                                                     check_grpc_call_failure);
+  event = alts_tsi_event_create_for_testing(true /* is_client. */);
+  GPR_ASSERT(alts_handshaker_client_start_client(config->client, event) ==
+             TSI_INTERNAL_ERROR);
+  alts_tsi_event_destroy(event);
+
+  /* Check server_start failure. */
+  event = alts_tsi_event_create_for_testing(false /* is_client. */);
+  GPR_ASSERT(alts_handshaker_client_start_server(config->client, event,
+                                                 &config->out_frame) ==
+             TSI_INTERNAL_ERROR);
+  alts_tsi_event_destroy(event);
+
+  /* Check next failure. */
+  event = alts_tsi_event_create_for_testing(true /* is_cleint. */);
+  GPR_ASSERT(
+      alts_handshaker_client_next(config->client, event, &config->out_frame) ==
+      TSI_INTERNAL_ERROR);
+  alts_tsi_event_destroy(event);
+
+  /* Cleanup. */
+  destroy_config(config);
+}
+
+int main(int argc, char** argv) {
+  /* Initialization. */
+  grpc_init();
+
+  /* Tests. */
+  schedule_request_invalid_arg_test();
+  schedule_request_success_test();
+  schedule_request_grpc_call_failure_test();
+
+  /* Cleanup. */
+  grpc_shutdown();
+  return 0;
+}
diff --git a/test/core/tsi/alts/handshaker/alts_handshaker_service_api_test.cc b/test/core/tsi/alts/handshaker/alts_handshaker_service_api_test.cc
new file mode 100644
index 0000000..3506264
--- /dev/null
+++ b/test/core/tsi/alts/handshaker/alts_handshaker_service_api_test.cc
@@ -0,0 +1,149 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.h"
+
+int main(int argc, char** argv) {
+  const char in_bytes[] = "HELLO GOOGLE!";
+  const char out_frames[] = "HELLO WORLD!";
+  const char key_data[] = "THIS IS KEY DATA.";
+  const char details[] = "DETAILS NEED TO BE POPULATED";
+  const uint32_t max_rpc_version_major = 3;
+  const uint32_t max_rpc_version_minor = 2;
+  const uint32_t min_rpc_version_major = 2;
+  const uint32_t min_rpc_version_minor = 1;
+
+  /* handshaker_req_next. */
+  grpc_gcp_handshaker_req* req = grpc_gcp_handshaker_req_create(NEXT_REQ);
+  grpc_gcp_handshaker_req* decoded_req =
+      grpc_gcp_handshaker_decoded_req_create(NEXT_REQ);
+  GPR_ASSERT(
+      grpc_gcp_handshaker_req_set_in_bytes(req, in_bytes, strlen(in_bytes)));
+  grpc_slice encoded_req;
+  GPR_ASSERT(grpc_gcp_handshaker_req_encode(req, &encoded_req));
+  GPR_ASSERT(grpc_gcp_handshaker_req_decode(encoded_req, decoded_req));
+  GPR_ASSERT(grpc_gcp_handshaker_req_equals(req, decoded_req));
+  grpc_gcp_handshaker_req_destroy(req);
+  grpc_gcp_handshaker_req_destroy(decoded_req);
+  grpc_slice_unref(encoded_req);
+
+  /* handshaker_req_client_start. */
+  req = grpc_gcp_handshaker_req_create(CLIENT_START_REQ);
+  decoded_req = grpc_gcp_handshaker_decoded_req_create(CLIENT_START_REQ);
+  GPR_ASSERT(grpc_gcp_handshaker_req_set_handshake_protocol(
+      req, grpc_gcp_HandshakeProtocol_TLS));
+  GPR_ASSERT(grpc_gcp_handshaker_req_set_local_identity_hostname(
+      req, "www.google.com"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_set_local_endpoint(
+      req, "2001:db8::8:800:200C:417a", 9876, grpc_gcp_NetworkProtocol_TCP));
+  GPR_ASSERT(grpc_gcp_handshaker_req_set_remote_endpoint(
+      req, "2001:db8::bac5::fed0:84a2", 1234, grpc_gcp_NetworkProtocol_TCP));
+  GPR_ASSERT(grpc_gcp_handshaker_req_add_application_protocol(req, "grpc"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_add_application_protocol(req, "http2"));
+  GPR_ASSERT(
+      grpc_gcp_handshaker_req_add_record_protocol(req, "ALTSRP_GCM_AES256"));
+  GPR_ASSERT(
+      grpc_gcp_handshaker_req_add_record_protocol(req, "ALTSRP_GCM_AES384"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_add_target_identity_service_account(
+      req, "foo@google.com"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_set_target_name(
+      req, "google.example.library.service"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_set_rpc_versions(
+      req, max_rpc_version_major, max_rpc_version_minor, min_rpc_version_major,
+      min_rpc_version_minor));
+  GPR_ASSERT(grpc_gcp_handshaker_req_encode(req, &encoded_req));
+  GPR_ASSERT(grpc_gcp_handshaker_req_decode(encoded_req, decoded_req));
+  GPR_ASSERT(grpc_gcp_handshaker_req_equals(req, decoded_req));
+  grpc_gcp_handshaker_req_destroy(req);
+  grpc_gcp_handshaker_req_destroy(decoded_req);
+  grpc_slice_unref(encoded_req);
+
+  /* handshaker_req_server_start. */
+  req = grpc_gcp_handshaker_req_create(SERVER_START_REQ);
+  decoded_req = grpc_gcp_handshaker_decoded_req_create(SERVER_START_REQ);
+  GPR_ASSERT(grpc_gcp_handshaker_req_add_application_protocol(req, "grpc"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_add_application_protocol(req, "http2"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_set_local_endpoint(
+      req, "2001:db8::8:800:200C:417a", 9876, grpc_gcp_NetworkProtocol_TCP));
+  GPR_ASSERT(grpc_gcp_handshaker_req_set_remote_endpoint(
+      req, "2001:db8::bac5::fed0:84a2", 1234, grpc_gcp_NetworkProtocol_UDP));
+  GPR_ASSERT(
+      grpc_gcp_handshaker_req_set_in_bytes(req, in_bytes, strlen(in_bytes)));
+  GPR_ASSERT(grpc_gcp_handshaker_req_param_add_record_protocol(
+      req, grpc_gcp_HandshakeProtocol_TLS, "ALTSRP_GCM_AES128"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_param_add_local_identity_service_account(
+      req, grpc_gcp_HandshakeProtocol_TLS, "foo@google.com"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_param_add_local_identity_hostname(
+      req, grpc_gcp_HandshakeProtocol_TLS, "yihuaz0.mtv.corp.google.com"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_param_add_record_protocol(
+      req, grpc_gcp_HandshakeProtocol_ALTS, "ALTSRP_GCM_AES128"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_param_add_local_identity_hostname(
+      req, grpc_gcp_HandshakeProtocol_ALTS, "www.amazon.com"));
+  GPR_ASSERT(grpc_gcp_handshaker_req_set_rpc_versions(
+      req, max_rpc_version_major, max_rpc_version_minor, min_rpc_version_major,
+      min_rpc_version_minor));
+
+  GPR_ASSERT(grpc_gcp_handshaker_req_encode(req, &encoded_req));
+  GPR_ASSERT(grpc_gcp_handshaker_req_decode(encoded_req, decoded_req));
+  GPR_ASSERT(grpc_gcp_handshaker_req_equals(req, decoded_req));
+  grpc_gcp_handshaker_req_destroy(req);
+  grpc_gcp_handshaker_req_destroy(decoded_req);
+  grpc_slice_unref(encoded_req);
+
+  /* handshaker_resp. */
+  grpc_gcp_handshaker_resp* resp = grpc_gcp_handshaker_resp_create();
+  grpc_gcp_handshaker_resp* decoded_resp = grpc_gcp_handshaker_resp_create();
+  GPR_ASSERT(grpc_gcp_handshaker_resp_set_out_frames(resp, out_frames,
+                                                     strlen(out_frames)));
+  GPR_ASSERT(grpc_gcp_handshaker_resp_set_bytes_consumed(resp, 1024));
+  GPR_ASSERT(grpc_gcp_handshaker_resp_set_application_protocol(resp, "http"));
+  GPR_ASSERT(
+      grpc_gcp_handshaker_resp_set_record_protocol(resp, "ALTSRP_GCM_AES128"));
+  GPR_ASSERT(
+      grpc_gcp_handshaker_resp_set_key_data(resp, key_data, strlen(key_data)));
+  GPR_ASSERT(grpc_gcp_handshaker_resp_set_local_identity_hostname(
+      resp, "www.faceboook.com"));
+  GPR_ASSERT(grpc_gcp_handshaker_resp_set_peer_identity_hostname(
+      resp, "www.amazon.com"));
+  GPR_ASSERT(grpc_gcp_handshaker_resp_set_channel_open(
+      resp, false /* channel_open */));
+  GPR_ASSERT(grpc_gcp_handshaker_resp_set_code(resp, 1023));
+  GPR_ASSERT(grpc_gcp_handshaker_resp_set_details(resp, details));
+  GPR_ASSERT(grpc_gcp_handshaker_resp_set_peer_rpc_versions(
+      resp, max_rpc_version_major, max_rpc_version_minor, min_rpc_version_major,
+      min_rpc_version_minor));
+  grpc_slice encoded_resp;
+  GPR_ASSERT(grpc_gcp_handshaker_resp_encode(resp, &encoded_resp));
+  GPR_ASSERT(grpc_gcp_handshaker_resp_decode(encoded_resp, decoded_resp));
+  GPR_ASSERT(grpc_gcp_handshaker_resp_equals(resp, decoded_resp));
+  grpc_gcp_handshaker_resp_destroy(resp);
+  grpc_gcp_handshaker_resp_destroy(decoded_resp);
+  grpc_slice_unref(encoded_resp);
+  /* Test invalid arguments. */
+  GPR_ASSERT(!grpc_gcp_handshaker_req_set_in_bytes(nullptr, in_bytes,
+                                                   strlen(in_bytes)));
+  GPR_ASSERT(!grpc_gcp_handshaker_req_param_add_record_protocol(
+      req, grpc_gcp_HandshakeProtocol_TLS, nullptr));
+  GPR_ASSERT(!grpc_gcp_handshaker_req_param_add_local_identity_service_account(
+      nullptr, grpc_gcp_HandshakeProtocol_TLS, nullptr));
+  GPR_ASSERT(!grpc_gcp_handshaker_resp_set_record_protocol(nullptr, nullptr));
+}
diff --git a/test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.cc b/test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.cc
new file mode 100644
index 0000000..ecca04d
--- /dev/null
+++ b/test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.cc
@@ -0,0 +1,642 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.h"
+
+const size_t kHandshakeProtocolNum = 3;
+
+grpc_gcp_handshaker_req* grpc_gcp_handshaker_decoded_req_create(
+    grpc_gcp_handshaker_req_type type) {
+  grpc_gcp_handshaker_req* req =
+      static_cast<grpc_gcp_handshaker_req*>(gpr_zalloc(sizeof(*req)));
+  switch (type) {
+    case CLIENT_START_REQ:
+      req->has_client_start = true;
+      req->client_start.target_identities.funcs.decode =
+          decode_repeated_identity_cb;
+      req->client_start.application_protocols.funcs.decode =
+          decode_repeated_string_cb;
+      req->client_start.record_protocols.funcs.decode =
+          decode_repeated_string_cb;
+      req->client_start.local_identity.hostname.funcs.decode =
+          decode_string_or_bytes_cb;
+      req->client_start.local_identity.service_account.funcs.decode =
+          decode_string_or_bytes_cb;
+      req->client_start.local_endpoint.ip_address.funcs.decode =
+          decode_string_or_bytes_cb;
+      req->client_start.remote_endpoint.ip_address.funcs.decode =
+          decode_string_or_bytes_cb;
+      req->client_start.target_name.funcs.decode = decode_string_or_bytes_cb;
+      break;
+    case SERVER_START_REQ:
+      req->has_server_start = true;
+      req->server_start.application_protocols.funcs.decode =
+          &decode_repeated_string_cb;
+      for (size_t i = 0; i < kHandshakeProtocolNum; i++) {
+        req->server_start.handshake_parameters[i]
+            .value.local_identities.funcs.decode = &decode_repeated_identity_cb;
+        req->server_start.handshake_parameters[i]
+            .value.record_protocols.funcs.decode = &decode_repeated_string_cb;
+      }
+      req->server_start.in_bytes.funcs.decode = decode_string_or_bytes_cb;
+      req->server_start.local_endpoint.ip_address.funcs.decode =
+          decode_string_or_bytes_cb;
+      req->server_start.remote_endpoint.ip_address.funcs.decode =
+          decode_string_or_bytes_cb;
+      break;
+    case NEXT_REQ:
+      req->has_next = true;
+      break;
+  }
+  return req;
+}
+
+bool grpc_gcp_handshaker_resp_set_application_protocol(
+    grpc_gcp_handshaker_resp* resp, const char* application_protocol) {
+  if (resp == nullptr || application_protocol == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "handshaker_resp_set_application_protocol().");
+    return false;
+  }
+  resp->has_result = true;
+  grpc_slice* slice =
+      create_slice(application_protocol, strlen(application_protocol));
+  resp->result.application_protocol.arg = slice;
+  resp->result.application_protocol.funcs.encode = encode_string_or_bytes_cb;
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_set_record_protocol(
+    grpc_gcp_handshaker_resp* resp, const char* record_protocol) {
+  if (resp == nullptr || record_protocol == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "handshaker_resp_set_record_protocol().");
+    return false;
+  }
+  resp->has_result = true;
+  grpc_slice* slice = create_slice(record_protocol, strlen(record_protocol));
+  resp->result.record_protocol.arg = slice;
+  resp->result.record_protocol.funcs.encode = encode_string_or_bytes_cb;
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_set_key_data(grpc_gcp_handshaker_resp* resp,
+                                           const char* key_data, size_t size) {
+  if (resp == nullptr || key_data == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to handshaker_resp_set_key_data().");
+    return false;
+  }
+  resp->has_result = true;
+  grpc_slice* slice = create_slice(key_data, size);
+  resp->result.key_data.arg = slice;
+  resp->result.key_data.funcs.encode = encode_string_or_bytes_cb;
+  return true;
+}
+
+static void set_identity_hostname(grpc_gcp_identity* identity,
+                                  const char* hostname) {
+  grpc_slice* slice = create_slice(hostname, strlen(hostname));
+  identity->hostname.arg = slice;
+  identity->hostname.funcs.encode = encode_string_or_bytes_cb;
+}
+
+static void set_identity_service_account(grpc_gcp_identity* identity,
+                                         const char* service_account) {
+  grpc_slice* slice = create_slice(service_account, strlen(service_account));
+  identity->service_account.arg = slice;
+  identity->service_account.funcs.encode = encode_string_or_bytes_cb;
+}
+
+bool grpc_gcp_handshaker_resp_set_local_identity_hostname(
+    grpc_gcp_handshaker_resp* resp, const char* hostname) {
+  if (resp == nullptr || hostname == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_handshaker_resp_set_local_identity_hostname().");
+    return false;
+  }
+  resp->has_result = true;
+  resp->result.has_local_identity = true;
+  set_identity_hostname(&resp->result.local_identity, hostname);
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_set_local_identity_service_account(
+    grpc_gcp_handshaker_resp* resp, const char* service_account) {
+  if (resp == nullptr || service_account == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_handshaker_resp_set_local_identity_service_account().");
+    return false;
+  }
+  resp->has_result = true;
+  resp->result.has_local_identity = true;
+  set_identity_service_account(&resp->result.local_identity, service_account);
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_set_peer_identity_hostname(
+    grpc_gcp_handshaker_resp* resp, const char* hostname) {
+  if (resp == nullptr || hostname == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_handshaker_resp_set_peer_identity_hostname().");
+    return false;
+  }
+  resp->has_result = true;
+  resp->result.has_peer_identity = true;
+  set_identity_hostname(&resp->result.peer_identity, hostname);
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_set_peer_identity_service_account(
+    grpc_gcp_handshaker_resp* resp, const char* service_account) {
+  if (resp == nullptr || service_account == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_handshaker_resp_set_peer_identity_service_account().");
+    return false;
+  }
+  resp->has_result = true;
+  resp->result.has_peer_identity = true;
+  set_identity_service_account(&resp->result.peer_identity, service_account);
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_set_channel_open(grpc_gcp_handshaker_resp* resp,
+                                               bool keep_channel_open) {
+  if (resp == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr argument to "
+            "grpc_gcp_handshaker_resp_set_channel_open().");
+    return false;
+  }
+  resp->has_result = true;
+  resp->result.has_keep_channel_open = true;
+  resp->result.keep_channel_open = keep_channel_open;
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_set_code(grpc_gcp_handshaker_resp* resp,
+                                       uint32_t code) {
+  if (resp == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr argument to grpc_gcp_handshaker_resp_set_code().");
+    return false;
+  }
+  resp->has_status = true;
+  resp->status.has_code = true;
+  resp->status.code = code;
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_set_details(grpc_gcp_handshaker_resp* resp,
+                                          const char* details) {
+  if (resp == nullptr || details == nullptr) {
+    gpr_log(
+        GPR_ERROR,
+        "Invalid nullptr arguments to grpc_gcp_handshaker_resp_set_details().");
+    return false;
+  }
+  resp->has_status = true;
+  grpc_slice* slice = create_slice(details, strlen(details));
+  resp->status.details.arg = slice;
+  resp->status.details.funcs.encode = encode_string_or_bytes_cb;
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_set_out_frames(grpc_gcp_handshaker_resp* resp,
+                                             const char* out_frames,
+                                             size_t size) {
+  if (resp == nullptr || out_frames == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to "
+            "grpc_gcp_handshaker_resp_set_out_frames().");
+    return false;
+  }
+  grpc_slice* slice = create_slice(out_frames, size);
+  resp->out_frames.arg = slice;
+  resp->out_frames.funcs.encode = encode_string_or_bytes_cb;
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_set_bytes_consumed(grpc_gcp_handshaker_resp* resp,
+                                                 int32_t bytes_consumed) {
+  if (resp == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr argument to "
+            "grpc_gcp_handshaker_resp_set_bytes_consumed().");
+    return false;
+  }
+  resp->has_bytes_consumed = true;
+  resp->bytes_consumed = bytes_consumed;
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_set_peer_rpc_versions(
+    grpc_gcp_handshaker_resp* resp, uint32_t max_major, uint32_t max_minor,
+    uint32_t min_major, uint32_t min_minor) {
+  if (resp == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr argument to "
+            "grpc_gcp_handshaker_resp_set_peer_rpc_versions().");
+    return false;
+  }
+  resp->has_result = true;
+  resp->result.has_peer_rpc_versions = true;
+  grpc_gcp_rpc_protocol_versions* versions = &resp->result.peer_rpc_versions;
+  versions->has_max_rpc_version = true;
+  versions->has_min_rpc_version = true;
+  versions->max_rpc_version.has_major = true;
+  versions->max_rpc_version.has_minor = true;
+  versions->min_rpc_version.has_major = true;
+  versions->min_rpc_version.has_minor = true;
+  versions->max_rpc_version.major = max_major;
+  versions->max_rpc_version.minor = max_minor;
+  versions->min_rpc_version.major = min_major;
+  versions->min_rpc_version.minor = min_minor;
+  return true;
+}
+
+bool grpc_gcp_handshaker_resp_encode(grpc_gcp_handshaker_resp* resp,
+                                     grpc_slice* slice) {
+  if (resp == nullptr || slice == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr arguments to grpc_gcp_handshaker_resp_encode().");
+    return false;
+  }
+  pb_ostream_t size_stream;
+  memset(&size_stream, 0, sizeof(pb_ostream_t));
+  if (!pb_encode(&size_stream, grpc_gcp_HandshakerResp_fields, resp)) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&size_stream));
+    return false;
+  }
+  size_t encoded_length = size_stream.bytes_written;
+  *slice = grpc_slice_malloc(encoded_length);
+  pb_ostream_t output_stream =
+      pb_ostream_from_buffer(GRPC_SLICE_START_PTR(*slice), encoded_length);
+  if (!pb_encode(&output_stream, grpc_gcp_HandshakerResp_fields, resp)) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&size_stream));
+    return false;
+  }
+  return true;
+}
+
+bool grpc_gcp_handshaker_req_decode(grpc_slice slice,
+                                    grpc_gcp_handshaker_req* req) {
+  if (req == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Invalid nullptr argument to grpc_gcp_handshaker_req_decode().");
+    return false;
+  }
+  pb_istream_t stream = pb_istream_from_buffer(GRPC_SLICE_START_PTR(slice),
+                                               GRPC_SLICE_LENGTH(slice));
+  req->next.in_bytes.funcs.decode = decode_string_or_bytes_cb;
+  if (!pb_decode(&stream, grpc_gcp_HandshakerReq_fields, req)) {
+    gpr_log(GPR_ERROR, "nanopb error: %s", PB_GET_ERROR(&stream));
+    return false;
+  }
+  return true;
+}
+
+/* Check equality of a pair of grpc_slice fields. */
+static bool slice_equals(grpc_slice* l_slice, grpc_slice* r_slice) {
+  if (l_slice == nullptr && r_slice == nullptr) {
+    return true;
+  }
+  if (l_slice != nullptr && r_slice != nullptr) {
+    return grpc_slice_eq(*l_slice, *r_slice);
+  }
+  return false;
+}
+
+/* Check equality of a pair of grpc_gcp_identity fields. */
+static bool handshaker_identity_equals(const grpc_gcp_identity* l_id,
+                                       const grpc_gcp_identity* r_id) {
+  if (!((l_id->hostname.arg != nullptr) != (r_id->hostname.arg != nullptr))) {
+    if (l_id->hostname.arg != nullptr) {
+      return slice_equals(static_cast<grpc_slice*>(l_id->hostname.arg),
+                          static_cast<grpc_slice*>(r_id->hostname.arg));
+    }
+  } else {
+    return false;
+  }
+  if (!((l_id->service_account.arg != nullptr) !=
+        (r_id->service_account.arg != nullptr))) {
+    if (l_id->service_account.arg != nullptr) {
+      return slice_equals(static_cast<grpc_slice*>(l_id->service_account.arg),
+                          static_cast<grpc_slice*>(r_id->service_account.arg));
+    }
+  } else {
+    return false;
+  }
+  return true;
+}
+
+static bool handshaker_rpc_versions_equals(
+    const grpc_gcp_rpc_protocol_versions* l_version,
+    const grpc_gcp_rpc_protocol_versions* r_version) {
+  bool result = true;
+  result &=
+      (l_version->max_rpc_version.major == r_version->max_rpc_version.major);
+  result &=
+      (l_version->max_rpc_version.minor == r_version->max_rpc_version.minor);
+  result &=
+      (l_version->min_rpc_version.major == r_version->min_rpc_version.major);
+  result &=
+      (l_version->min_rpc_version.minor == r_version->min_rpc_version.minor);
+  return result;
+}
+
+/* Check equality of a pair of grpc_gcp_endpoint fields. */
+static bool handshaker_endpoint_equals(const grpc_gcp_endpoint* l_end,
+                                       const grpc_gcp_endpoint* r_end) {
+  bool result = true;
+  result &= (l_end->port == r_end->port);
+  result &= (l_end->protocol == r_end->protocol);
+  if (!((l_end->ip_address.arg != nullptr) !=
+        (r_end->ip_address.arg != nullptr))) {
+    if (l_end->ip_address.arg != nullptr) {
+      result &= slice_equals(static_cast<grpc_slice*>(l_end->ip_address.arg),
+                             static_cast<grpc_slice*>(r_end->ip_address.arg));
+    }
+  } else {
+    return false;
+  }
+  return result;
+}
+/**
+ * Check if a specific repeated field (i.e., target) is contained in a repeated
+ * field list (i.e., head).
+ */
+static bool repeated_field_list_contains_identity(
+    const repeated_field* head, const repeated_field* target) {
+  repeated_field* field = const_cast<repeated_field*>(head);
+  while (field != nullptr) {
+    if (handshaker_identity_equals(
+            static_cast<const grpc_gcp_identity*>(field->data),
+            static_cast<const grpc_gcp_identity*>(target->data))) {
+      return true;
+    }
+    field = field->next;
+  }
+  return false;
+}
+
+static bool repeated_field_list_contains_string(const repeated_field* head,
+                                                const repeated_field* target) {
+  repeated_field* field = const_cast<repeated_field*>(head);
+  while (field != nullptr) {
+    if (slice_equals((grpc_slice*)field->data, (grpc_slice*)target->data)) {
+      return true;
+    }
+    field = field->next;
+  }
+  return false;
+}
+
+/* Return a length of repeated field list. */
+static size_t repeated_field_list_get_length(const repeated_field* head) {
+  repeated_field* field = const_cast<repeated_field*>(head);
+  size_t len = 0;
+  while (field != nullptr) {
+    len++;
+    field = field->next;
+  }
+  return len;
+}
+
+/**
+ * Check if a pair of repeated field lists contain the same set of repeated
+ * fields.
+ */
+static bool repeated_field_list_equals_identity(const repeated_field* l_head,
+                                                const repeated_field* r_head) {
+  if (repeated_field_list_get_length(l_head) !=
+      repeated_field_list_get_length(r_head)) {
+    return false;
+  }
+  repeated_field* field = const_cast<repeated_field*>(l_head);
+  repeated_field* head = const_cast<repeated_field*>(r_head);
+  while (field != nullptr) {
+    if (!repeated_field_list_contains_identity(head, field)) {
+      return false;
+    }
+    field = field->next;
+  }
+  return true;
+}
+
+static bool repeated_field_list_equals_string(const repeated_field* l_head,
+                                              const repeated_field* r_head) {
+  if (repeated_field_list_get_length(l_head) !=
+      repeated_field_list_get_length(r_head)) {
+    return false;
+  }
+  repeated_field* field = const_cast<repeated_field*>(l_head);
+  repeated_field* head = const_cast<repeated_field*>(r_head);
+  while (field != nullptr) {
+    if (!repeated_field_list_contains_string(head, field)) {
+      return false;
+    }
+    field = field->next;
+  }
+  return true;
+}
+
+/* Check equality of a pair of ALTS client_start handshake requests. */
+bool grpc_gcp_handshaker_client_start_req_equals(
+    grpc_gcp_start_client_handshake_req* l_req,
+    grpc_gcp_start_client_handshake_req* r_req) {
+  bool result = true;
+  /* Compare handshake_security_protocol. */
+  result &=
+      l_req->handshake_security_protocol == r_req->handshake_security_protocol;
+  /* Compare application_protocols, record_protocols, and target_identities. */
+  result &= repeated_field_list_equals_string(
+      static_cast<const repeated_field*>(l_req->application_protocols.arg),
+      static_cast<const repeated_field*>(r_req->application_protocols.arg));
+  result &= repeated_field_list_equals_string(
+      static_cast<const repeated_field*>(l_req->record_protocols.arg),
+      static_cast<const repeated_field*>(r_req->record_protocols.arg));
+  result &= repeated_field_list_equals_identity(
+      static_cast<const repeated_field*>(l_req->target_identities.arg),
+      static_cast<const repeated_field*>(r_req->target_identities.arg));
+  if ((l_req->has_local_identity ^ r_req->has_local_identity) |
+      (l_req->has_local_endpoint ^ r_req->has_local_endpoint) |
+      ((l_req->has_remote_endpoint ^ r_req->has_remote_endpoint)) |
+      (l_req->has_rpc_versions ^ r_req->has_rpc_versions)) {
+    return false;
+  }
+  /* Compare local_identity, local_endpoint, and remote_endpoint. */
+  if (l_req->has_local_identity) {
+    result &= handshaker_identity_equals(&l_req->local_identity,
+                                         &r_req->local_identity);
+  }
+  if (l_req->has_local_endpoint) {
+    result &= handshaker_endpoint_equals(&l_req->local_endpoint,
+                                         &r_req->local_endpoint);
+  }
+  if (l_req->has_remote_endpoint) {
+    result &= handshaker_endpoint_equals(&l_req->remote_endpoint,
+                                         &r_req->remote_endpoint);
+  }
+  if (l_req->has_rpc_versions) {
+    result &= handshaker_rpc_versions_equals(&l_req->rpc_versions,
+                                             &r_req->rpc_versions);
+  }
+  return result;
+}
+
+/* Check equality of a pair of ALTS server_start handshake requests. */
+bool grpc_gcp_handshaker_server_start_req_equals(
+    grpc_gcp_start_server_handshake_req* l_req,
+    grpc_gcp_start_server_handshake_req* r_req) {
+  bool result = true;
+  /* Compare application_protocols. */
+  result &= repeated_field_list_equals_string(
+      static_cast<const repeated_field*>(l_req->application_protocols.arg),
+      static_cast<const repeated_field*>(r_req->application_protocols.arg));
+  /* Compare handshake_parameters. */
+  size_t i = 0, j = 0;
+  result &=
+      (l_req->handshake_parameters_count == r_req->handshake_parameters_count);
+  for (i = 0; i < l_req->handshake_parameters_count; i++) {
+    bool found = false;
+    for (j = 0; j < r_req->handshake_parameters_count; j++) {
+      if (l_req->handshake_parameters[i].key ==
+          r_req->handshake_parameters[j].key) {
+        found = true;
+        result &= repeated_field_list_equals_string(
+            static_cast<const repeated_field*>(
+                l_req->handshake_parameters[i].value.record_protocols.arg),
+            static_cast<const repeated_field*>(
+                r_req->handshake_parameters[j].value.record_protocols.arg));
+        result &= repeated_field_list_equals_identity(
+            static_cast<const repeated_field*>(
+                l_req->handshake_parameters[i].value.local_identities.arg),
+            static_cast<const repeated_field*>(
+                r_req->handshake_parameters[j].value.local_identities.arg));
+      }
+    }
+    if (!found) {
+      return false;
+    }
+  }
+  /* Compare in_bytes, local_endpoint, remote_endpoint. */
+  result &= slice_equals(static_cast<grpc_slice*>(l_req->in_bytes.arg),
+                         static_cast<grpc_slice*>(r_req->in_bytes.arg));
+  if ((l_req->has_local_endpoint ^ r_req->has_local_endpoint) |
+      (l_req->has_remote_endpoint ^ r_req->has_remote_endpoint) |
+      (l_req->has_rpc_versions ^ r_req->has_rpc_versions))
+    return false;
+  if (l_req->has_local_endpoint) {
+    result &= handshaker_endpoint_equals(&l_req->local_endpoint,
+                                         &r_req->local_endpoint);
+  }
+  if (l_req->has_remote_endpoint) {
+    result &= handshaker_endpoint_equals(&l_req->remote_endpoint,
+                                         &r_req->remote_endpoint);
+  }
+  if (l_req->has_rpc_versions) {
+    result &= handshaker_rpc_versions_equals(&l_req->rpc_versions,
+                                             &r_req->rpc_versions);
+  }
+  return result;
+}
+
+/* Check equality of a pair of ALTS handshake requests. */
+bool grpc_gcp_handshaker_req_equals(grpc_gcp_handshaker_req* l_req,
+                                    grpc_gcp_handshaker_req* r_req) {
+  if (l_req->has_next && r_req->has_next) {
+    return slice_equals(static_cast<grpc_slice*>(l_req->next.in_bytes.arg),
+                        static_cast<grpc_slice*>(r_req->next.in_bytes.arg));
+  } else if (l_req->has_client_start && r_req->has_client_start) {
+    return grpc_gcp_handshaker_client_start_req_equals(&l_req->client_start,
+                                                       &r_req->client_start);
+  } else if (l_req->has_server_start && r_req->has_server_start) {
+    return grpc_gcp_handshaker_server_start_req_equals(&l_req->server_start,
+                                                       &r_req->server_start);
+  }
+  return false;
+}
+
+/* Check equality of a pair of ALTS handshake results. */
+bool grpc_gcp_handshaker_resp_result_equals(
+    grpc_gcp_handshaker_result* l_result,
+    grpc_gcp_handshaker_result* r_result) {
+  bool result = true;
+  /* Compare application_protocol, record_protocol, and key_data. */
+  result &= slice_equals(
+      static_cast<grpc_slice*>(l_result->application_protocol.arg),
+      static_cast<grpc_slice*>(r_result->application_protocol.arg));
+  result &=
+      slice_equals(static_cast<grpc_slice*>(l_result->record_protocol.arg),
+                   static_cast<grpc_slice*>(r_result->record_protocol.arg));
+  result &= slice_equals(static_cast<grpc_slice*>(l_result->key_data.arg),
+                         static_cast<grpc_slice*>(r_result->key_data.arg));
+  /* Compare local_identity, peer_identity, and keep_channel_open. */
+  if ((l_result->has_local_identity ^ r_result->has_local_identity) |
+      (l_result->has_peer_identity ^ r_result->has_peer_identity) |
+      (l_result->has_peer_rpc_versions ^ r_result->has_peer_rpc_versions)) {
+    return false;
+  }
+  if (l_result->has_local_identity) {
+    result &= handshaker_identity_equals(&l_result->local_identity,
+                                         &r_result->local_identity);
+  }
+  if (l_result->has_peer_identity) {
+    result &= handshaker_identity_equals(&l_result->peer_identity,
+                                         &r_result->peer_identity);
+  }
+  if (l_result->has_peer_rpc_versions) {
+    result &= handshaker_rpc_versions_equals(&l_result->peer_rpc_versions,
+                                             &r_result->peer_rpc_versions);
+  }
+  result &= (l_result->keep_channel_open == r_result->keep_channel_open);
+  return result;
+}
+
+/* Check equality of a pair of ALTS handshake responses. */
+bool grpc_gcp_handshaker_resp_equals(grpc_gcp_handshaker_resp* l_resp,
+                                     grpc_gcp_handshaker_resp* r_resp) {
+  bool result = true;
+  /* Compare out_frames and bytes_consumed. */
+  result &= slice_equals(static_cast<grpc_slice*>(l_resp->out_frames.arg),
+                         static_cast<grpc_slice*>(r_resp->out_frames.arg));
+  result &= (l_resp->bytes_consumed == r_resp->bytes_consumed);
+  /* Compare result and status. */
+  if ((l_resp->has_result ^ r_resp->has_result) |
+      (l_resp->has_status ^ r_resp->has_status)) {
+    return false;
+  }
+  if (l_resp->has_result) {
+    result &= grpc_gcp_handshaker_resp_result_equals(&l_resp->result,
+                                                     &r_resp->result);
+  }
+  if (l_resp->has_status) {
+    result &= (l_resp->status.code == r_resp->status.code);
+    result &=
+        slice_equals(static_cast<grpc_slice*>(l_resp->status.details.arg),
+                     static_cast<grpc_slice*>(r_resp->status.details.arg));
+  }
+  return result;
+}
diff --git a/test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.h b/test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.h
new file mode 100644
index 0000000..2fcbb4e
--- /dev/null
+++ b/test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.h
@@ -0,0 +1,143 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_TEST_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_SERVICE_API_TEST_LIB_H
+#define GRPC_TEST_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_SERVICE_API_TEST_LIB_H
+
+#include "src/core/tsi/alts/handshaker/alts_handshaker_service_api.h"
+#include "src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h"
+#include "src/core/tsi/alts/handshaker/transport_security_common_api.h"
+
+/**
+ * The first part of this file contains function signatures for de-serializing
+ * ALTS handshake requests and setting/serializing ALTS handshake responses,
+ * which simulate the behaviour of grpc server that runs ALTS handshaker
+ * service.
+ */
+
+/**
+ * This method creates a ALTS handshaker request that is used to hold
+ * de-serialized result.
+ */
+grpc_gcp_handshaker_req* grpc_gcp_handshaker_decoded_req_create(
+    grpc_gcp_handshaker_req_type type);
+
+/* This method de-serializes a ALTS handshaker request. */
+bool grpc_gcp_handshaker_req_decode(grpc_slice slice,
+                                    grpc_gcp_handshaker_req* req);
+
+/* This method serializes a ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_encode(grpc_gcp_handshaker_resp* resp,
+                                     grpc_slice* slice);
+
+/* This method sets application protocol of ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_set_application_protocol(
+    grpc_gcp_handshaker_resp* resp, const char* application_protocol);
+
+/* This method sets record protocol of ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_set_record_protocol(
+    grpc_gcp_handshaker_resp* resp, const char* record_protocol);
+
+/* This method sets key_data of ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_set_key_data(grpc_gcp_handshaker_resp* resp,
+                                           const char* key_data, size_t size);
+
+/* This method sets local identity's hostname for ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_set_local_identity_hostname(
+    grpc_gcp_handshaker_resp* resp, const char* hostname);
+
+/**
+ * This method sets local identity's service account for ALTS handshaker
+ * response.
+ */
+bool grpc_gcp_handshaker_resp_set_local_identity_service_account(
+    grpc_gcp_handshaker_resp* resp, const char* service_account);
+
+/* This method sets peer identity's hostname for ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_set_peer_identity_hostname(
+    grpc_gcp_handshaker_resp* resp, const char* hostname);
+
+/**
+ * This method sets peer identity's service account for ALTS handshaker
+ * response.
+ */
+bool grpc_gcp_handshaker_resp_set_peer_identity_service_account(
+    grpc_gcp_handshaker_resp* resp, const char* service_account);
+
+/* This method sets keep_channel_open for ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_set_channel_open(grpc_gcp_handshaker_resp* resp,
+                                               bool keep_channel_open);
+
+/* This method sets code for ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_set_code(grpc_gcp_handshaker_resp* resp,
+                                       uint32_t code);
+
+/* This method sets details for ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_set_details(grpc_gcp_handshaker_resp* resp,
+                                          const char* details);
+
+/* This method sets out_frames for ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_set_out_frames(grpc_gcp_handshaker_resp* resp,
+                                             const char* out_frames,
+                                             size_t size);
+
+/* This method sets peer_rpc_versions for ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_set_peer_rpc_versions(
+    grpc_gcp_handshaker_resp* resp, uint32_t max_major, uint32_t max_minor,
+    uint32_t min_major, uint32_t min_minor);
+
+/* This method sets bytes_consumed for ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_set_bytes_consumed(grpc_gcp_handshaker_resp* resp,
+                                                 int32_t bytes_consumed);
+
+/* This method serializes ALTS handshaker response. */
+bool grpc_gcp_handshaker_resp_encode(grpc_gcp_handshaker_resp* resp,
+                                     grpc_slice* slice);
+
+/* This method de-serializes ALTS handshaker request. */
+bool grpc_gcp_handshaker_req_decode(grpc_slice slice,
+                                    grpc_gcp_handshaker_req* req);
+
+/**
+ * The second part contains function signatures for checking equality of a pair
+ * of ALTS handshake requests/responses.
+ */
+
+/* This method checks equality of two client_start handshaker requests. */
+bool grpc_gcp_handshaker_client_start_req_equals(
+    grpc_gcp_start_client_handshake_req* l_req,
+    grpc_gcp_start_client_handshake_req* r_req);
+
+/* This method checks equality of two server_start handshaker requests. */
+bool grpc_gcp_handshaker_server_start_req_equals(
+    grpc_gcp_start_server_handshake_req* l_req,
+    grpc_gcp_start_server_handshake_req* r_req);
+
+/* This method checks equality of two ALTS handshaker requests. */
+bool grpc_gcp_handshaker_req_equals(grpc_gcp_handshaker_req* l_req,
+                                    grpc_gcp_handshaker_req* r_req);
+
+/* This method checks equality of two handshaker response results. */
+bool grpc_gcp_handshaker_resp_result_equals(
+    grpc_gcp_handshaker_result* l_result, grpc_gcp_handshaker_result* r_result);
+
+/* This method checks equality of two ALTS handshaker responses. */
+bool grpc_gcp_handshaker_resp_equals(grpc_gcp_handshaker_resp* l_resp,
+                                     grpc_gcp_handshaker_resp* r_resp);
+
+#endif  // GRPC_TEST_CORE_TSI_ALTS_HANDSHAKER_ALTS_HANDSHAKER_SERVICE_API_TEST_LIB_H
diff --git a/test/core/tsi/alts/handshaker/alts_tsi_handshaker_test.cc b/test/core/tsi/alts/handshaker/alts_tsi_handshaker_test.cc
new file mode 100644
index 0000000..95724f8
--- /dev/null
+++ b/test/core/tsi/alts/handshaker/alts_tsi_handshaker_test.cc
@@ -0,0 +1,682 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <grpc/grpc.h>
+#include <grpc/support/sync.h>
+
+#include "src/core/lib/gprpp/thd.h"
+#include "src/core/tsi/alts/handshaker/alts_handshaker_client.h"
+#include "src/core/tsi/alts/handshaker/alts_tsi_event.h"
+#include "src/core/tsi/alts/handshaker/alts_tsi_handshaker.h"
+#include "src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h"
+#include "test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.h"
+
+#define ALTS_TSI_HANDSHAKER_TEST_RECV_BYTES "Hello World"
+#define ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME "Hello Google"
+#define ALTS_TSI_HANDSHAKER_TEST_CONSUMED_BYTES "Hello "
+#define ALTS_TSI_HANDSHAKER_TEST_REMAIN_BYTES "Google"
+#define ALTS_TSI_HANDSHAKER_TEST_PEER_IDENTITY "chapi@service.google.com"
+#define ALTS_TSI_HANDSHAKER_TEST_KEY_DATA \
+  "ABCDEFGHIJKLMNOPABCDEFGHIJKLMNOPABCDEFGHIJKL"
+#define ALTS_TSI_HANDSHAKER_TEST_BUFFER_SIZE 100
+#define ALTS_TSI_HANDSHAKER_TEST_SLEEP_TIME_IN_SECONDS 2
+#define ALTS_TSI_HANDSHAKER_TEST_MAX_RPC_VERSION_MAJOR 3
+#define ALTS_TSI_HANDSHAKER_TEST_MAX_RPC_VERSION_MINOR 2
+#define ALTS_TSI_HANDSHAKER_TEST_MIN_RPC_VERSION_MAJOR 2
+#define ALTS_TSI_HANDSHAKER_TEST_MIN_RPC_VERSION_MINOR 1
+
+using grpc_core::internal::
+    alts_tsi_handshaker_get_has_sent_start_message_for_testing;
+using grpc_core::internal::alts_tsi_handshaker_get_is_client_for_testing;
+using grpc_core::internal::alts_tsi_handshaker_get_recv_bytes_for_testing;
+using grpc_core::internal::alts_tsi_handshaker_set_client_for_testing;
+using grpc_core::internal::alts_tsi_handshaker_set_recv_bytes_for_testing;
+
+/* ALTS mock notification. */
+typedef struct notification {
+  gpr_cv cv;
+  gpr_mu mu;
+  bool notified;
+} notification;
+
+/* ALTS mock handshaker client. */
+typedef struct alts_mock_handshaker_client {
+  alts_handshaker_client base;
+  bool used_for_success_test;
+} alts_mock_handshaker_client;
+
+/* Type of ALTS handshaker response. */
+typedef enum {
+  INVALID,
+  FAILED,
+  CLIENT_START,
+  SERVER_START,
+  CLIENT_NEXT,
+  SERVER_NEXT,
+} alts_handshaker_response_type;
+
+static alts_tsi_event* client_start_event;
+static alts_tsi_event* client_next_event;
+static alts_tsi_event* server_start_event;
+static alts_tsi_event* server_next_event;
+static notification caller_to_tsi_notification;
+static notification tsi_to_caller_notification;
+
+static void notification_init(notification* n) {
+  gpr_mu_init(&n->mu);
+  gpr_cv_init(&n->cv);
+  n->notified = false;
+}
+
+static void notification_destroy(notification* n) {
+  gpr_mu_destroy(&n->mu);
+  gpr_cv_destroy(&n->cv);
+}
+
+static void signal(notification* n) {
+  gpr_mu_lock(&n->mu);
+  n->notified = true;
+  gpr_cv_signal(&n->cv);
+  gpr_mu_unlock(&n->mu);
+}
+
+static void wait(notification* n) {
+  gpr_mu_lock(&n->mu);
+  while (!n->notified) {
+    gpr_cv_wait(&n->cv, &n->mu, gpr_inf_future(GPR_CLOCK_REALTIME));
+  }
+  n->notified = false;
+  gpr_mu_unlock(&n->mu);
+}
+
+/**
+ * This method mocks ALTS handshaker service to generate handshaker response
+ * for a specific request.
+ */
+static grpc_byte_buffer* generate_handshaker_response(
+    alts_handshaker_response_type type) {
+  grpc_gcp_handshaker_resp* resp = grpc_gcp_handshaker_resp_create();
+  GPR_ASSERT(grpc_gcp_handshaker_resp_set_code(resp, 0));
+  switch (type) {
+    case INVALID:
+      break;
+    case CLIENT_START:
+    case SERVER_START:
+      GPR_ASSERT(grpc_gcp_handshaker_resp_set_out_frames(
+          resp, ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME,
+          strlen(ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME)));
+      break;
+    case CLIENT_NEXT:
+      GPR_ASSERT(grpc_gcp_handshaker_resp_set_out_frames(
+          resp, ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME,
+          strlen(ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME)));
+      GPR_ASSERT(grpc_gcp_handshaker_resp_set_peer_identity_service_account(
+          resp, ALTS_TSI_HANDSHAKER_TEST_PEER_IDENTITY));
+      GPR_ASSERT(grpc_gcp_handshaker_resp_set_bytes_consumed(
+          resp, strlen(ALTS_TSI_HANDSHAKER_TEST_CONSUMED_BYTES)));
+      GPR_ASSERT(grpc_gcp_handshaker_resp_set_key_data(
+          resp, ALTS_TSI_HANDSHAKER_TEST_KEY_DATA,
+          strlen(ALTS_TSI_HANDSHAKER_TEST_KEY_DATA)));
+      GPR_ASSERT(grpc_gcp_handshaker_resp_set_peer_rpc_versions(
+          resp, ALTS_TSI_HANDSHAKER_TEST_MAX_RPC_VERSION_MAJOR,
+          ALTS_TSI_HANDSHAKER_TEST_MAX_RPC_VERSION_MINOR,
+          ALTS_TSI_HANDSHAKER_TEST_MIN_RPC_VERSION_MAJOR,
+          ALTS_TSI_HANDSHAKER_TEST_MIN_RPC_VERSION_MINOR));
+      break;
+    case SERVER_NEXT:
+      GPR_ASSERT(grpc_gcp_handshaker_resp_set_peer_identity_service_account(
+          resp, ALTS_TSI_HANDSHAKER_TEST_PEER_IDENTITY));
+      GPR_ASSERT(grpc_gcp_handshaker_resp_set_bytes_consumed(
+          resp, strlen(ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME)));
+      GPR_ASSERT(grpc_gcp_handshaker_resp_set_key_data(
+          resp, ALTS_TSI_HANDSHAKER_TEST_KEY_DATA,
+          strlen(ALTS_TSI_HANDSHAKER_TEST_KEY_DATA)));
+      GPR_ASSERT(grpc_gcp_handshaker_resp_set_peer_rpc_versions(
+          resp, ALTS_TSI_HANDSHAKER_TEST_MAX_RPC_VERSION_MAJOR,
+          ALTS_TSI_HANDSHAKER_TEST_MAX_RPC_VERSION_MINOR,
+          ALTS_TSI_HANDSHAKER_TEST_MIN_RPC_VERSION_MAJOR,
+          ALTS_TSI_HANDSHAKER_TEST_MIN_RPC_VERSION_MINOR));
+      break;
+    case FAILED:
+      GPR_ASSERT(
+          grpc_gcp_handshaker_resp_set_code(resp, 3 /* INVALID ARGUMENT */));
+      break;
+  }
+  grpc_slice slice;
+  GPR_ASSERT(grpc_gcp_handshaker_resp_encode(resp, &slice));
+  if (type == INVALID) {
+    grpc_slice bad_slice =
+        grpc_slice_split_head(&slice, GRPC_SLICE_LENGTH(slice) - 1);
+    grpc_slice_unref(slice);
+    slice = grpc_slice_ref(bad_slice);
+    grpc_slice_unref(bad_slice);
+  }
+  grpc_byte_buffer* buffer =
+      grpc_raw_byte_buffer_create(&slice, 1 /* number of slices */);
+  grpc_slice_unref(slice);
+  grpc_gcp_handshaker_resp_destroy(resp);
+  return buffer;
+}
+
+static void check_must_not_be_called(tsi_result status, void* user_data,
+                                     const unsigned char* bytes_to_send,
+                                     size_t bytes_to_send_size,
+                                     tsi_handshaker_result* result) {
+  GPR_ASSERT(0);
+}
+
+static void on_client_start_success_cb(tsi_result status, void* user_data,
+                                       const unsigned char* bytes_to_send,
+                                       size_t bytes_to_send_size,
+                                       tsi_handshaker_result* result) {
+  GPR_ASSERT(status == TSI_OK);
+  GPR_ASSERT(user_data == nullptr);
+  GPR_ASSERT(bytes_to_send_size == strlen(ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME));
+  GPR_ASSERT(memcmp(bytes_to_send, ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME,
+                    bytes_to_send_size) == 0);
+  GPR_ASSERT(result == nullptr);
+  /* Validate peer identity. */
+  tsi_peer peer;
+  GPR_ASSERT(tsi_handshaker_result_extract_peer(result, &peer) ==
+             TSI_INVALID_ARGUMENT);
+  /* Validate frame protector. */
+  tsi_frame_protector* protector = nullptr;
+  GPR_ASSERT(tsi_handshaker_result_create_frame_protector(
+                 result, nullptr, &protector) == TSI_INVALID_ARGUMENT);
+  /* Validate unused bytes. */
+  const unsigned char* unused_bytes = nullptr;
+  size_t unused_bytes_size = 0;
+  GPR_ASSERT(tsi_handshaker_result_get_unused_bytes(result, &unused_bytes,
+                                                    &unused_bytes_size) ==
+             TSI_INVALID_ARGUMENT);
+  signal(&tsi_to_caller_notification);
+}
+
+static void on_server_start_success_cb(tsi_result status, void* user_data,
+                                       const unsigned char* bytes_to_send,
+                                       size_t bytes_to_send_size,
+                                       tsi_handshaker_result* result) {
+  GPR_ASSERT(status == TSI_OK);
+  GPR_ASSERT(user_data == nullptr);
+  GPR_ASSERT(bytes_to_send_size == strlen(ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME));
+  GPR_ASSERT(memcmp(bytes_to_send, ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME,
+                    bytes_to_send_size) == 0);
+  GPR_ASSERT(result == nullptr);
+  /* Validate peer identity. */
+  tsi_peer peer;
+  GPR_ASSERT(tsi_handshaker_result_extract_peer(result, &peer) ==
+             TSI_INVALID_ARGUMENT);
+  /* Validate frame protector. */
+  tsi_frame_protector* protector = nullptr;
+  GPR_ASSERT(tsi_handshaker_result_create_frame_protector(
+                 result, nullptr, &protector) == TSI_INVALID_ARGUMENT);
+  /* Validate unused bytes. */
+  const unsigned char* unused_bytes = nullptr;
+  size_t unused_bytes_size = 0;
+  GPR_ASSERT(tsi_handshaker_result_get_unused_bytes(result, &unused_bytes,
+                                                    &unused_bytes_size) ==
+             TSI_INVALID_ARGUMENT);
+  signal(&tsi_to_caller_notification);
+}
+
+static void on_client_next_success_cb(tsi_result status, void* user_data,
+                                      const unsigned char* bytes_to_send,
+                                      size_t bytes_to_send_size,
+                                      tsi_handshaker_result* result) {
+  GPR_ASSERT(status == TSI_OK);
+  GPR_ASSERT(user_data == nullptr);
+  GPR_ASSERT(bytes_to_send_size == strlen(ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME));
+  GPR_ASSERT(memcmp(bytes_to_send, ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME,
+                    bytes_to_send_size) == 0);
+  GPR_ASSERT(result != nullptr);
+  /* Validate peer identity. */
+  tsi_peer peer;
+  GPR_ASSERT(tsi_handshaker_result_extract_peer(result, &peer) == TSI_OK);
+  GPR_ASSERT(peer.property_count == kTsiAltsNumOfPeerProperties);
+  GPR_ASSERT(memcmp(TSI_ALTS_CERTIFICATE_TYPE, peer.properties[0].value.data,
+                    peer.properties[0].value.length) == 0);
+  GPR_ASSERT(memcmp(ALTS_TSI_HANDSHAKER_TEST_PEER_IDENTITY,
+                    peer.properties[1].value.data,
+                    peer.properties[1].value.length) == 0);
+  tsi_peer_destruct(&peer);
+  /* Validate unused bytes. */
+  const unsigned char* bytes = nullptr;
+  size_t bytes_size = 0;
+  GPR_ASSERT(tsi_handshaker_result_get_unused_bytes(result, &bytes,
+                                                    &bytes_size) == TSI_OK);
+  GPR_ASSERT(bytes_size == strlen(ALTS_TSI_HANDSHAKER_TEST_REMAIN_BYTES));
+  GPR_ASSERT(memcmp(bytes, ALTS_TSI_HANDSHAKER_TEST_REMAIN_BYTES, bytes_size) ==
+             0);
+  /* Validate frame protector. */
+  tsi_frame_protector* protector = nullptr;
+  GPR_ASSERT(tsi_handshaker_result_create_frame_protector(
+                 result, nullptr, &protector) == TSI_OK);
+  GPR_ASSERT(protector != nullptr);
+  tsi_frame_protector_destroy(protector);
+  tsi_handshaker_result_destroy(result);
+  signal(&tsi_to_caller_notification);
+}
+
+static void on_server_next_success_cb(tsi_result status, void* user_data,
+                                      const unsigned char* bytes_to_send,
+                                      size_t bytes_to_send_size,
+                                      tsi_handshaker_result* result) {
+  GPR_ASSERT(status == TSI_OK);
+  GPR_ASSERT(user_data == nullptr);
+  GPR_ASSERT(bytes_to_send_size == 0);
+  GPR_ASSERT(bytes_to_send == nullptr);
+  GPR_ASSERT(result != nullptr);
+  /* Validate peer identity. */
+  tsi_peer peer;
+  GPR_ASSERT(tsi_handshaker_result_extract_peer(result, &peer) == TSI_OK);
+  GPR_ASSERT(peer.property_count == kTsiAltsNumOfPeerProperties);
+  GPR_ASSERT(memcmp(TSI_ALTS_CERTIFICATE_TYPE, peer.properties[0].value.data,
+                    peer.properties[0].value.length) == 0);
+  GPR_ASSERT(memcmp(ALTS_TSI_HANDSHAKER_TEST_PEER_IDENTITY,
+                    peer.properties[1].value.data,
+                    peer.properties[1].value.length) == 0);
+  tsi_peer_destruct(&peer);
+  /* Validate unused bytes. */
+  const unsigned char* bytes = nullptr;
+  size_t bytes_size = 0;
+  GPR_ASSERT(tsi_handshaker_result_get_unused_bytes(result, &bytes,
+                                                    &bytes_size) == TSI_OK);
+  GPR_ASSERT(bytes_size == 0);
+  GPR_ASSERT(bytes == nullptr);
+  /* Validate frame protector. */
+  tsi_frame_protector* protector = nullptr;
+  GPR_ASSERT(tsi_handshaker_result_create_frame_protector(
+                 result, nullptr, &protector) == TSI_OK);
+  GPR_ASSERT(protector != nullptr);
+  tsi_frame_protector_destroy(protector);
+  tsi_handshaker_result_destroy(result);
+  signal(&tsi_to_caller_notification);
+}
+
+static tsi_result mock_client_start(alts_handshaker_client* self,
+                                    alts_tsi_event* event) {
+  alts_mock_handshaker_client* client =
+      reinterpret_cast<alts_mock_handshaker_client*>(self);
+  if (!client->used_for_success_test) {
+    alts_tsi_event_destroy(event);
+    return TSI_INTERNAL_ERROR;
+  }
+  GPR_ASSERT(event->cb == on_client_start_success_cb);
+  GPR_ASSERT(event->user_data == nullptr);
+  GPR_ASSERT(!alts_tsi_handshaker_get_has_sent_start_message_for_testing(
+      event->handshaker));
+  /* Populate handshaker response for client_start request. */
+  event->recv_buffer = generate_handshaker_response(CLIENT_START);
+  client_start_event = event;
+  signal(&caller_to_tsi_notification);
+  return TSI_OK;
+}
+
+static tsi_result mock_server_start(alts_handshaker_client* self,
+                                    alts_tsi_event* event,
+                                    grpc_slice* bytes_received) {
+  alts_mock_handshaker_client* client =
+      reinterpret_cast<alts_mock_handshaker_client*>(self);
+  if (!client->used_for_success_test) {
+    alts_tsi_event_destroy(event);
+    return TSI_INTERNAL_ERROR;
+  }
+  GPR_ASSERT(event->cb == on_server_start_success_cb);
+  GPR_ASSERT(event->user_data == nullptr);
+  grpc_slice slice = grpc_empty_slice();
+  GPR_ASSERT(grpc_slice_cmp(*bytes_received, slice) == 0);
+  GPR_ASSERT(!alts_tsi_handshaker_get_has_sent_start_message_for_testing(
+      event->handshaker));
+  /* Populate handshaker response for server_start request. */
+  event->recv_buffer = generate_handshaker_response(SERVER_START);
+  server_start_event = event;
+  grpc_slice_unref(slice);
+  signal(&caller_to_tsi_notification);
+  return TSI_OK;
+}
+
+static tsi_result mock_next(alts_handshaker_client* self, alts_tsi_event* event,
+                            grpc_slice* bytes_received) {
+  alts_mock_handshaker_client* client =
+      reinterpret_cast<alts_mock_handshaker_client*>(self);
+  if (!client->used_for_success_test) {
+    alts_tsi_event_destroy(event);
+    return TSI_INTERNAL_ERROR;
+  }
+  bool is_client =
+      alts_tsi_handshaker_get_is_client_for_testing(event->handshaker);
+  if (is_client) {
+    GPR_ASSERT(event->cb == on_client_next_success_cb);
+  } else {
+    GPR_ASSERT(event->cb == on_server_next_success_cb);
+  }
+  GPR_ASSERT(event->user_data == nullptr);
+  GPR_ASSERT(bytes_received != nullptr);
+  GPR_ASSERT(memcmp(GRPC_SLICE_START_PTR(*bytes_received),
+                    ALTS_TSI_HANDSHAKER_TEST_RECV_BYTES,
+                    GRPC_SLICE_LENGTH(*bytes_received)) == 0);
+  GPR_ASSERT(grpc_slice_cmp(alts_tsi_handshaker_get_recv_bytes_for_testing(
+                                event->handshaker),
+                            *bytes_received) == 0);
+  GPR_ASSERT(alts_tsi_handshaker_get_has_sent_start_message_for_testing(
+      event->handshaker));
+  /* Populate handshaker response for next request. */
+  grpc_slice out_frame =
+      grpc_slice_from_static_string(ALTS_TSI_HANDSHAKER_TEST_OUT_FRAME);
+  if (is_client) {
+    event->recv_buffer = generate_handshaker_response(CLIENT_NEXT);
+  } else {
+    event->recv_buffer = generate_handshaker_response(SERVER_NEXT);
+  }
+  alts_tsi_handshaker_set_recv_bytes_for_testing(event->handshaker, &out_frame);
+  if (is_client) {
+    client_next_event = event;
+  } else {
+    server_next_event = event;
+  }
+  signal(&caller_to_tsi_notification);
+  grpc_slice_unref(out_frame);
+  return TSI_OK;
+}
+
+static void mock_destruct(alts_handshaker_client* client) {}
+
+static const alts_handshaker_client_vtable vtable = {
+    mock_client_start, mock_server_start, mock_next, mock_destruct};
+
+static alts_handshaker_client* alts_mock_handshaker_client_create(
+    bool used_for_success_test) {
+  alts_mock_handshaker_client* client =
+      static_cast<alts_mock_handshaker_client*>(gpr_zalloc(sizeof(*client)));
+  client->base.vtable = &vtable;
+  client->used_for_success_test = used_for_success_test;
+  return &client->base;
+}
+
+static tsi_handshaker* create_test_handshaker(bool used_for_success_test,
+                                              bool is_client) {
+  tsi_handshaker* handshaker = nullptr;
+  alts_handshaker_client* client =
+      alts_mock_handshaker_client_create(used_for_success_test);
+  grpc_alts_credentials_options* options =
+      grpc_alts_credentials_client_options_create();
+  alts_tsi_handshaker_create(options, "target_name", "lame", is_client,
+                             &handshaker);
+  alts_tsi_handshaker* alts_handshaker =
+      reinterpret_cast<alts_tsi_handshaker*>(handshaker);
+  alts_tsi_handshaker_set_client_for_testing(alts_handshaker, client);
+  grpc_alts_credentials_options_destroy(options);
+  return handshaker;
+}
+
+static void check_handshaker_next_invalid_input() {
+  /* Initialization. */
+  tsi_handshaker* handshaker = create_test_handshaker(true, true);
+  /* Check nullptr handshaker. */
+  GPR_ASSERT(tsi_handshaker_next(nullptr, nullptr, 0, nullptr, nullptr, nullptr,
+                                 check_must_not_be_called,
+                                 nullptr) == TSI_INVALID_ARGUMENT);
+  /* Check nullptr callback. */
+  GPR_ASSERT(tsi_handshaker_next(handshaker, nullptr, 0, nullptr, nullptr,
+                                 nullptr, nullptr,
+                                 nullptr) == TSI_INVALID_ARGUMENT);
+  /* Cleanup. */
+  tsi_handshaker_destroy(handshaker);
+}
+
+static void check_handshaker_next_success() {
+  /**
+   * Create handshakers for which internal mock client is going to do
+   * correctness check.
+   */
+  tsi_handshaker* client_handshaker = create_test_handshaker(
+      true /* used_for_success_test */, true /* is_client */);
+  tsi_handshaker* server_handshaker = create_test_handshaker(
+      true /* used_for_success_test */, false /* is_client */);
+  /* Client start. */
+  GPR_ASSERT(tsi_handshaker_next(client_handshaker, nullptr, 0, nullptr,
+                                 nullptr, nullptr, on_client_start_success_cb,
+                                 nullptr) == TSI_ASYNC);
+  wait(&tsi_to_caller_notification);
+  /* Client next. */
+  GPR_ASSERT(tsi_handshaker_next(
+                 client_handshaker,
+                 (const unsigned char*)ALTS_TSI_HANDSHAKER_TEST_RECV_BYTES,
+                 strlen(ALTS_TSI_HANDSHAKER_TEST_RECV_BYTES), nullptr, nullptr,
+                 nullptr, on_client_next_success_cb, nullptr) == TSI_ASYNC);
+  wait(&tsi_to_caller_notification);
+  /* Server start. */
+  GPR_ASSERT(tsi_handshaker_next(server_handshaker, nullptr, 0, nullptr,
+                                 nullptr, nullptr, on_server_start_success_cb,
+                                 nullptr) == TSI_ASYNC);
+  wait(&tsi_to_caller_notification);
+  /* Server next. */
+  GPR_ASSERT(tsi_handshaker_next(
+                 server_handshaker,
+                 (const unsigned char*)ALTS_TSI_HANDSHAKER_TEST_RECV_BYTES,
+                 strlen(ALTS_TSI_HANDSHAKER_TEST_RECV_BYTES), nullptr, nullptr,
+                 nullptr, on_server_next_success_cb, nullptr) == TSI_ASYNC);
+  wait(&tsi_to_caller_notification);
+  /* Cleanup. */
+  tsi_handshaker_destroy(server_handshaker);
+  tsi_handshaker_destroy(client_handshaker);
+}
+
+static void check_handshaker_next_failure() {
+  /**
+   * Create handshakers for which internal mock client is always going to fail.
+   */
+  tsi_handshaker* client_handshaker = create_test_handshaker(
+      false /* used_for_success_test */, true /* is_client */);
+  tsi_handshaker* server_handshaker = create_test_handshaker(
+      false /* used_for_success_test */, false /* is_client */);
+  /* Client start. */
+  GPR_ASSERT(tsi_handshaker_next(client_handshaker, nullptr, 0, nullptr,
+                                 nullptr, nullptr, check_must_not_be_called,
+                                 nullptr) == TSI_INTERNAL_ERROR);
+  /* Server start. */
+  GPR_ASSERT(tsi_handshaker_next(server_handshaker, nullptr, 0, nullptr,
+                                 nullptr, nullptr, check_must_not_be_called,
+                                 nullptr) == TSI_INTERNAL_ERROR);
+  /* Server next. */
+  GPR_ASSERT(tsi_handshaker_next(
+                 server_handshaker,
+                 (const unsigned char*)ALTS_TSI_HANDSHAKER_TEST_RECV_BYTES,
+                 strlen(ALTS_TSI_HANDSHAKER_TEST_RECV_BYTES), nullptr, nullptr,
+                 nullptr, check_must_not_be_called,
+                 nullptr) == TSI_INTERNAL_ERROR);
+  /* Client next. */
+  GPR_ASSERT(tsi_handshaker_next(
+                 client_handshaker,
+                 (const unsigned char*)ALTS_TSI_HANDSHAKER_TEST_RECV_BYTES,
+                 strlen(ALTS_TSI_HANDSHAKER_TEST_RECV_BYTES), nullptr, nullptr,
+                 nullptr, check_must_not_be_called,
+                 nullptr) == TSI_INTERNAL_ERROR);
+  /* Cleanup. */
+  tsi_handshaker_destroy(server_handshaker);
+  tsi_handshaker_destroy(client_handshaker);
+}
+
+static void on_invalid_input_cb(tsi_result status, void* user_data,
+                                const unsigned char* bytes_to_send,
+                                size_t bytes_to_send_size,
+                                tsi_handshaker_result* result) {
+  GPR_ASSERT(status == TSI_INTERNAL_ERROR);
+  GPR_ASSERT(user_data == nullptr);
+  GPR_ASSERT(bytes_to_send == nullptr);
+  GPR_ASSERT(bytes_to_send_size == 0);
+  GPR_ASSERT(result == nullptr);
+}
+
+static void on_failed_grpc_call_cb(tsi_result status, void* user_data,
+                                   const unsigned char* bytes_to_send,
+                                   size_t bytes_to_send_size,
+                                   tsi_handshaker_result* result) {
+  GPR_ASSERT(status == TSI_INTERNAL_ERROR);
+  GPR_ASSERT(user_data == nullptr);
+  GPR_ASSERT(bytes_to_send == nullptr);
+  GPR_ASSERT(bytes_to_send_size == 0);
+  GPR_ASSERT(result == nullptr);
+}
+
+static void check_handle_response_invalid_input() {
+  /**
+   * Create a handshaker at the client side, for which internal mock client is
+   * always going to fail.
+   */
+  tsi_handshaker* handshaker = create_test_handshaker(
+      false /* used_for_success_test */, true /* is_client */);
+  alts_tsi_handshaker* alts_handshaker =
+      reinterpret_cast<alts_tsi_handshaker*>(handshaker);
+  grpc_byte_buffer recv_buffer;
+  /* Check nullptr handshaker. */
+  alts_tsi_handshaker_handle_response(nullptr, &recv_buffer, GRPC_STATUS_OK,
+                                      nullptr, on_invalid_input_cb, nullptr,
+                                      true);
+  /* Check nullptr recv_bytes. */
+  alts_tsi_handshaker_handle_response(alts_handshaker, nullptr, GRPC_STATUS_OK,
+                                      nullptr, on_invalid_input_cb, nullptr,
+                                      true);
+  /* Check failed grpc call made to handshaker service. */
+  alts_tsi_handshaker_handle_response(alts_handshaker, &recv_buffer,
+                                      GRPC_STATUS_UNKNOWN, nullptr,
+                                      on_failed_grpc_call_cb, nullptr, true);
+
+  alts_tsi_handshaker_handle_response(alts_handshaker, &recv_buffer,
+                                      GRPC_STATUS_OK, nullptr,
+                                      on_failed_grpc_call_cb, nullptr, false);
+
+  /* Cleanup. */
+  tsi_handshaker_destroy(handshaker);
+}
+
+static void on_invalid_resp_cb(tsi_result status, void* user_data,
+                               const unsigned char* bytes_to_send,
+                               size_t bytes_to_send_size,
+                               tsi_handshaker_result* result) {
+  GPR_ASSERT(status == TSI_DATA_CORRUPTED);
+  GPR_ASSERT(user_data == nullptr);
+  GPR_ASSERT(bytes_to_send == nullptr);
+  GPR_ASSERT(bytes_to_send_size == 0);
+  GPR_ASSERT(result == nullptr);
+}
+
+static void check_handle_response_invalid_resp() {
+  /**
+   * Create a handshaker at the client side, for which internal mock client is
+   * always going to fail.
+   */
+  tsi_handshaker* handshaker = create_test_handshaker(
+      false /* used_for_success_test */, true /* is_client */);
+  alts_tsi_handshaker* alts_handshaker =
+      reinterpret_cast<alts_tsi_handshaker*>(handshaker);
+  /* Tests. */
+  grpc_byte_buffer* recv_buffer = generate_handshaker_response(INVALID);
+  alts_tsi_handshaker_handle_response(alts_handshaker, recv_buffer,
+                                      GRPC_STATUS_OK, nullptr,
+                                      on_invalid_resp_cb, nullptr, true);
+  /* Cleanup. */
+  grpc_byte_buffer_destroy(recv_buffer);
+  tsi_handshaker_destroy(handshaker);
+}
+
+static void check_handle_response_success(void* unused) {
+  /* Client start. */
+  wait(&caller_to_tsi_notification);
+  alts_tsi_event_dispatch_to_handshaker(client_start_event, true /* is_ok */);
+  alts_tsi_event_destroy(client_start_event);
+  /* Client next. */
+  wait(&caller_to_tsi_notification);
+  alts_tsi_event_dispatch_to_handshaker(client_next_event, true /* is_ok */);
+  alts_tsi_event_destroy(client_next_event);
+  /* Server start. */
+  wait(&caller_to_tsi_notification);
+  alts_tsi_event_dispatch_to_handshaker(server_start_event, true /* is_ok */);
+  alts_tsi_event_destroy(server_start_event);
+  /* Server next. */
+  wait(&caller_to_tsi_notification);
+  alts_tsi_event_dispatch_to_handshaker(server_next_event, true /* is_ok */);
+  alts_tsi_event_destroy(server_next_event);
+}
+
+static void on_failed_resp_cb(tsi_result status, void* user_data,
+                              const unsigned char* bytes_to_send,
+                              size_t bytes_to_send_size,
+                              tsi_handshaker_result* result) {
+  GPR_ASSERT(status == TSI_INVALID_ARGUMENT);
+  GPR_ASSERT(user_data == nullptr);
+  GPR_ASSERT(bytes_to_send == nullptr);
+  GPR_ASSERT(bytes_to_send_size == 0);
+  GPR_ASSERT(result == nullptr);
+}
+
+static void check_handle_response_failure() {
+  /**
+   * Create a handshaker at the client side, for which internal mock client is
+   * always going to fail.
+   */
+  tsi_handshaker* handshaker = create_test_handshaker(
+      false /* used_for_success_test */, true /* is_client */);
+  alts_tsi_handshaker* alts_handshaker =
+      reinterpret_cast<alts_tsi_handshaker*>(handshaker);
+  /* Tests. */
+  grpc_byte_buffer* recv_buffer = generate_handshaker_response(FAILED);
+  alts_tsi_handshaker_handle_response(alts_handshaker, recv_buffer,
+                                      GRPC_STATUS_OK, nullptr,
+                                      on_failed_resp_cb, nullptr, true);
+  grpc_byte_buffer_destroy(recv_buffer);
+  /* Cleanup. */
+  tsi_handshaker_destroy(handshaker);
+}
+
+void check_handshaker_success() {
+  /* Initialization. */
+  notification_init(&caller_to_tsi_notification);
+  notification_init(&tsi_to_caller_notification);
+  client_start_event = nullptr;
+  client_next_event = nullptr;
+  server_start_event = nullptr;
+  server_next_event = nullptr;
+  /* Tests. */
+  grpc_core::Thread thd("alts_tsi_handshaker_test",
+                        &check_handle_response_success, nullptr);
+  thd.Start();
+  check_handshaker_next_success();
+  thd.Join();
+  /* Cleanup. */
+  notification_destroy(&caller_to_tsi_notification);
+  notification_destroy(&tsi_to_caller_notification);
+}
+
+int main(int argc, char** argv) {
+  /* Initialization. */
+  grpc_init();
+  /* Tests. */
+  check_handshaker_success();
+  check_handshaker_next_invalid_input();
+  check_handshaker_next_failure();
+  check_handle_response_invalid_input();
+  check_handle_response_invalid_resp();
+  check_handle_response_failure();
+  /* Cleanup. */
+  grpc_shutdown();
+  return 0;
+}
diff --git a/test/core/tsi/alts/handshaker/alts_tsi_utils_test.cc b/test/core/tsi/alts/handshaker/alts_tsi_utils_test.cc
new file mode 100644
index 0000000..98c5d23
--- /dev/null
+++ b/test/core/tsi/alts/handshaker/alts_tsi_utils_test.cc
@@ -0,0 +1,73 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/tsi/alts/handshaker/alts_tsi_utils.h"
+#include "test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.h"
+
+#define ALTS_TSI_UTILS_TEST_OUT_FRAME "Hello Google"
+
+static void convert_to_tsi_result_test() {
+  GPR_ASSERT(alts_tsi_utils_convert_to_tsi_result(GRPC_STATUS_OK) == TSI_OK);
+  GPR_ASSERT(alts_tsi_utils_convert_to_tsi_result(GRPC_STATUS_UNKNOWN) ==
+             TSI_UNKNOWN_ERROR);
+  GPR_ASSERT(alts_tsi_utils_convert_to_tsi_result(
+                 GRPC_STATUS_INVALID_ARGUMENT) == TSI_INVALID_ARGUMENT);
+  GPR_ASSERT(alts_tsi_utils_convert_to_tsi_result(GRPC_STATUS_OUT_OF_RANGE) ==
+             TSI_UNKNOWN_ERROR);
+  GPR_ASSERT(alts_tsi_utils_convert_to_tsi_result(GRPC_STATUS_INTERNAL) ==
+             TSI_INTERNAL_ERROR);
+  GPR_ASSERT(alts_tsi_utils_convert_to_tsi_result(GRPC_STATUS_NOT_FOUND) ==
+             TSI_NOT_FOUND);
+}
+
+static void deserialize_response_test() {
+  grpc_gcp_handshaker_resp* resp = grpc_gcp_handshaker_resp_create();
+  GPR_ASSERT(grpc_gcp_handshaker_resp_set_out_frames(
+      resp, ALTS_TSI_UTILS_TEST_OUT_FRAME,
+      strlen(ALTS_TSI_UTILS_TEST_OUT_FRAME)));
+  grpc_slice slice;
+  GPR_ASSERT(grpc_gcp_handshaker_resp_encode(resp, &slice));
+
+  /* Valid serialization. */
+  grpc_byte_buffer* buffer =
+      grpc_raw_byte_buffer_create(&slice, 1 /* number of slices */);
+  grpc_gcp_handshaker_resp* decoded_resp =
+      alts_tsi_utils_deserialize_response(buffer);
+  GPR_ASSERT(grpc_gcp_handshaker_resp_equals(resp, decoded_resp));
+  grpc_byte_buffer_destroy(buffer);
+
+  /* Invalid serializaiton. */
+  grpc_slice bad_slice =
+      grpc_slice_split_head(&slice, GRPC_SLICE_LENGTH(slice) - 1);
+  buffer = grpc_raw_byte_buffer_create(&bad_slice, 1 /* number of slices */);
+  GPR_ASSERT(alts_tsi_utils_deserialize_response(buffer) == nullptr);
+
+  /* Clean up. */
+  grpc_slice_unref(slice);
+  grpc_slice_unref(bad_slice);
+  grpc_byte_buffer_destroy(buffer);
+  grpc_gcp_handshaker_resp_destroy(resp);
+  grpc_gcp_handshaker_resp_destroy(decoded_resp);
+}
+
+int main(int argc, char** argv) {
+  /* Tests. */
+  deserialize_response_test();
+  convert_to_tsi_result_test();
+  return 0;
+}
diff --git a/test/core/tsi/alts/handshaker/transport_security_common_api_test.cc b/test/core/tsi/alts/handshaker/transport_security_common_api_test.cc
new file mode 100644
index 0000000..6ff1357
--- /dev/null
+++ b/test/core/tsi/alts/handshaker/transport_security_common_api_test.cc
@@ -0,0 +1,196 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "src/core/tsi/alts/handshaker/transport_security_common_api.h"
+
+const size_t kMaxRpcVersionMajor = 3;
+const size_t kMaxRpcVersionMinor = 2;
+const size_t kMinRpcVersionMajor = 2;
+const size_t kMinRpcVersionMinor = 1;
+
+static bool grpc_gcp_rpc_protocol_versions_equal(
+    grpc_gcp_rpc_protocol_versions* l_versions,
+    grpc_gcp_rpc_protocol_versions* r_versions) {
+  GPR_ASSERT(l_versions != nullptr && r_versions != nullptr);
+  if ((l_versions->has_max_rpc_version ^ r_versions->has_max_rpc_version) |
+      (l_versions->has_min_rpc_version ^ r_versions->has_min_rpc_version)) {
+    return false;
+  }
+  if (l_versions->has_max_rpc_version) {
+    if ((l_versions->max_rpc_version.major !=
+         r_versions->max_rpc_version.major) ||
+        (l_versions->max_rpc_version.minor !=
+         r_versions->max_rpc_version.minor)) {
+      return false;
+    }
+  }
+  if (l_versions->has_min_rpc_version) {
+    if ((l_versions->min_rpc_version.major !=
+         r_versions->min_rpc_version.major) ||
+        (l_versions->min_rpc_version.minor !=
+         r_versions->min_rpc_version.minor)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+static void test_success() {
+  grpc_gcp_rpc_protocol_versions version;
+  grpc_gcp_rpc_protocol_versions decoded_version;
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_max(
+      &version, kMaxRpcVersionMajor, kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_min(
+      &version, kMinRpcVersionMajor, kMinRpcVersionMinor));
+  /* Serializes to raw bytes. */
+  size_t encoded_length =
+      grpc_gcp_rpc_protocol_versions_encode_length(&version);
+  uint8_t* encoded_bytes = static_cast<uint8_t*>(gpr_malloc(encoded_length));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_encode_to_raw_bytes(
+      &version, encoded_bytes, encoded_length));
+  grpc_slice encoded_slice;
+  /* Serializes to grpc slice. */
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_encode(&version, &encoded_slice));
+  /* Checks serialized raw bytes and serialized grpc slice have same content. */
+  GPR_ASSERT(encoded_length == GRPC_SLICE_LENGTH(encoded_slice));
+  GPR_ASSERT(memcmp(encoded_bytes, GRPC_SLICE_START_PTR(encoded_slice),
+                    encoded_length) == 0);
+  /* Deserializes and compares with the original version. */
+  GPR_ASSERT(
+      grpc_gcp_rpc_protocol_versions_decode(encoded_slice, &decoded_version));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_equal(&version, &decoded_version));
+  grpc_slice_unref(encoded_slice);
+  gpr_free(encoded_bytes);
+}
+
+static void test_failure() {
+  grpc_gcp_rpc_protocol_versions version, decoded_version;
+  grpc_slice encoded_slice;
+  /* Test for invalid arguments. */
+  GPR_ASSERT(!grpc_gcp_rpc_protocol_versions_set_max(
+      nullptr, kMaxRpcVersionMajor, kMaxRpcVersionMinor));
+  GPR_ASSERT(!grpc_gcp_rpc_protocol_versions_set_min(
+      nullptr, kMinRpcVersionMajor, kMinRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_encode_length(nullptr) == 0);
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_max(
+      &version, kMaxRpcVersionMajor, kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_min(
+      &version, kMinRpcVersionMajor, kMinRpcVersionMinor));
+  size_t encoded_length =
+      grpc_gcp_rpc_protocol_versions_encode_length(&version);
+  uint8_t* encoded_bytes = static_cast<uint8_t*>(gpr_malloc(encoded_length));
+  GPR_ASSERT(!grpc_gcp_rpc_protocol_versions_encode_to_raw_bytes(
+      nullptr, encoded_bytes, encoded_length));
+  GPR_ASSERT(!grpc_gcp_rpc_protocol_versions_encode_to_raw_bytes(
+      &version, nullptr, encoded_length));
+  GPR_ASSERT(!grpc_gcp_rpc_protocol_versions_encode_to_raw_bytes(
+      &version, encoded_bytes, 0));
+  GPR_ASSERT(!grpc_gcp_rpc_protocol_versions_encode(nullptr, &encoded_slice));
+  GPR_ASSERT(!grpc_gcp_rpc_protocol_versions_encode(&version, nullptr));
+  GPR_ASSERT(!grpc_gcp_rpc_protocol_versions_decode(encoded_slice, nullptr));
+  /* Test for nanopb decode. */
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_encode(&version, &encoded_slice));
+  grpc_slice bad_slice = grpc_slice_split_head(
+      &encoded_slice, GRPC_SLICE_LENGTH(encoded_slice) - 1);
+  grpc_slice_unref(encoded_slice);
+  GPR_ASSERT(
+      !grpc_gcp_rpc_protocol_versions_decode(bad_slice, &decoded_version));
+  grpc_slice_unref(bad_slice);
+  gpr_free(encoded_bytes);
+}
+
+static void test_copy() {
+  grpc_gcp_rpc_protocol_versions src;
+  grpc_gcp_rpc_protocol_versions des;
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_max(&src, kMaxRpcVersionMajor,
+                                                    kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_min(&src, kMinRpcVersionMajor,
+                                                    kMinRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_copy(&src, &des));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_equal(&src, &des));
+}
+
+static void test_check_success() {
+  grpc_gcp_rpc_protocol_versions v1;
+  grpc_gcp_rpc_protocol_versions v2;
+  grpc_gcp_rpc_protocol_versions_version highest_common_version;
+  /* test equality. */
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_max(&v1, kMaxRpcVersionMajor,
+                                                    kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_min(&v1, kMaxRpcVersionMajor,
+                                                    kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_max(&v2, kMaxRpcVersionMajor,
+                                                    kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_min(&v2, kMaxRpcVersionMajor,
+                                                    kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_check(
+                 (const grpc_gcp_rpc_protocol_versions*)&v1,
+                 (const grpc_gcp_rpc_protocol_versions*)&v2,
+                 &highest_common_version) == 1);
+  GPR_ASSERT(grpc_core::internal::grpc_gcp_rpc_protocol_version_compare(
+                 &highest_common_version, &v1.max_rpc_version) == 0);
+
+  /* test inequality. */
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_max(&v1, kMaxRpcVersionMajor,
+                                                    kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_min(&v1, kMinRpcVersionMinor,
+                                                    kMinRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_max(&v2, kMaxRpcVersionMajor,
+                                                    kMinRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_min(&v2, kMinRpcVersionMajor,
+                                                    kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_check(
+                 (const grpc_gcp_rpc_protocol_versions*)&v1,
+                 (const grpc_gcp_rpc_protocol_versions*)&v2,
+                 &highest_common_version) == 1);
+  GPR_ASSERT(grpc_core::internal::grpc_gcp_rpc_protocol_version_compare(
+                 &highest_common_version, &v2.max_rpc_version) == 0);
+}
+
+static void test_check_failure() {
+  grpc_gcp_rpc_protocol_versions v1;
+  grpc_gcp_rpc_protocol_versions v2;
+  grpc_gcp_rpc_protocol_versions_version highest_common_version;
+
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_max(&v1, kMinRpcVersionMajor,
+                                                    kMinRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_min(&v1, kMinRpcVersionMajor,
+                                                    kMinRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_max(&v2, kMaxRpcVersionMajor,
+                                                    kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_set_min(&v2, kMaxRpcVersionMajor,
+                                                    kMaxRpcVersionMinor));
+  GPR_ASSERT(grpc_gcp_rpc_protocol_versions_check(
+                 (const grpc_gcp_rpc_protocol_versions*)&v1,
+                 (const grpc_gcp_rpc_protocol_versions*)&v2,
+                 &highest_common_version) == 0);
+}
+
+int main(int argc, char** argv) {
+  /* Run tests. */
+  test_success();
+  test_failure();
+  test_copy();
+  test_check_success();
+  test_check_failure();
+  return 0;
+}
diff --git a/test/core/tsi/alts/zero_copy_frame_protector/BUILD b/test/core/tsi/alts/zero_copy_frame_protector/BUILD
new file mode 100644
index 0000000..80f4572
--- /dev/null
+++ b/test/core/tsi/alts/zero_copy_frame_protector/BUILD
@@ -0,0 +1,49 @@
+# Copyright 2018 gRPC authors.
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("//bazel:grpc_build_system.bzl", "grpc_cc_test", "grpc_package")
+
+licenses(["notice"])  # Apache v2
+
+grpc_package(name = "zero_copy_frame_protector")
+
+grpc_cc_test(
+    name = "alts_grpc_record_protocol_test",
+    srcs = ["alts_grpc_record_protocol_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+        "//test/core/tsi/alts/crypt:alts_crypt_test_util",
+    ],
+)
+
+grpc_cc_test(
+    name = "alts_iovec_record_protocol_test",
+    srcs = ["alts_iovec_record_protocol_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+        "//test/core/tsi/alts/crypt:alts_crypt_test_util",
+    ],
+)
+
+grpc_cc_test(
+    name = "alts_zero_copy_grpc_protector_test",
+    srcs = ["alts_zero_copy_grpc_protector_test.cc"],
+    language = "C++",
+    deps = [
+        "//:grpc",
+        "//test/core/tsi/alts/crypt:alts_crypt_test_util",
+    ],
+)
diff --git a/test/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_test.cc b/test/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_test.cc
new file mode 100644
index 0000000..fbbea71
--- /dev/null
+++ b/test/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_test.cc
@@ -0,0 +1,449 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/slice/slice_internal.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h"
+#include "test/core/tsi/alts/crypt/gsec_test_util.h"
+
+constexpr size_t kMaxSliceLength = 256;
+constexpr size_t kMaxSlices = 10;
+constexpr size_t kSealRepeatTimes = 5;
+constexpr size_t kTagLength = 16;
+
+/* Test fixtures for each test cases.  */
+struct alts_grpc_record_protocol_test_fixture {
+  alts_grpc_record_protocol* client_protect;
+  alts_grpc_record_protocol* client_unprotect;
+  alts_grpc_record_protocol* server_protect;
+  alts_grpc_record_protocol* server_unprotect;
+};
+
+/* Test input variables for protect/unprotect operations.  */
+struct alts_grpc_record_protocol_test_var {
+  size_t header_length;
+  size_t tag_length;
+  grpc_slice_buffer original_sb;
+  grpc_slice_buffer duplicate_sb;
+  grpc_slice_buffer protected_sb;
+  grpc_slice_buffer unprotected_sb;
+};
+
+/* --- Test utility functions. --- */
+
+static void create_random_slice_buffer(grpc_slice_buffer* sb) {
+  GPR_ASSERT(sb != nullptr);
+  size_t slice_count = gsec_test_bias_random_uint32(kMaxSlices) + 1;
+  for (size_t i = 0; i < slice_count; i++) {
+    size_t slice_length = gsec_test_bias_random_uint32(kMaxSliceLength) + 1;
+    grpc_slice slice = GRPC_SLICE_MALLOC(slice_length);
+    gsec_test_random_bytes(GRPC_SLICE_START_PTR(slice), slice_length);
+    grpc_slice_buffer_add(sb, slice);
+  }
+}
+
+static uint8_t* pointer_to_nth_byte(grpc_slice_buffer* sb, size_t index) {
+  GPR_ASSERT(sb != nullptr);
+  GPR_ASSERT(index < sb->length);
+  for (size_t i = 0; i < sb->count; i++) {
+    if (index < GRPC_SLICE_LENGTH(sb->slices[i])) {
+      return GRPC_SLICE_START_PTR(sb->slices[i]) + index;
+    } else {
+      index -= GRPC_SLICE_LENGTH(sb->slices[i]);
+    }
+  }
+  return nullptr;
+}
+
+/* Checks if two slice buffer contents are the same. It is not super efficient,
+ * but OK for testing.  */
+static bool are_slice_buffers_equal(grpc_slice_buffer* first,
+                                    grpc_slice_buffer* second) {
+  GPR_ASSERT(first != nullptr);
+  GPR_ASSERT(second != nullptr);
+  if (first->length != second->length) {
+    return false;
+  }
+  for (size_t i = 0; i < first->length; i++) {
+    uint8_t* first_ptr = pointer_to_nth_byte(first, i);
+    uint8_t* second_ptr = pointer_to_nth_byte(second, i);
+    GPR_ASSERT(first_ptr != nullptr);
+    GPR_ASSERT(second_ptr != nullptr);
+    if ((*first_ptr) != (*second_ptr)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+static void alter_random_byte(grpc_slice_buffer* sb) {
+  GPR_ASSERT(sb != nullptr);
+  if (sb->length == 0) {
+    return;
+  }
+  uint32_t offset =
+      gsec_test_bias_random_uint32(static_cast<uint32_t>(sb->length));
+  uint8_t* ptr = pointer_to_nth_byte(sb, offset);
+  (*ptr)++;
+}
+
+static alts_grpc_record_protocol_test_fixture*
+test_fixture_integrity_only_create(bool rekey) {
+  alts_grpc_record_protocol_test_fixture* fixture =
+      static_cast<alts_grpc_record_protocol_test_fixture*>(
+          gpr_zalloc(sizeof(alts_grpc_record_protocol_test_fixture)));
+  size_t key_length = rekey ? kAes128GcmRekeyKeyLength : kAes128GcmKeyLength;
+  uint8_t* key;
+  gsec_test_random_array(&key, key_length);
+  gsec_aead_crypter* crypter = nullptr;
+
+  /* Create client record protocol for protect. */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_grpc_integrity_only_record_protocol_create(
+                 crypter, 8, /*is_client=*/true, /*is_protect=*/true,
+                 &fixture->client_protect) == TSI_OK);
+  /* Create client record protocol for unprotect.  */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_grpc_integrity_only_record_protocol_create(
+                 crypter, 8, /*is_client=*/true, /*is_protect=*/false,
+                 &fixture->client_unprotect) == TSI_OK);
+  /* Create server record protocol for protect.  */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_grpc_integrity_only_record_protocol_create(
+                 crypter, 8, /*is_client=*/false, /*is_protect=*/true,
+                 &fixture->server_protect) == TSI_OK);
+  /* Create server record protocol for unprotect.  */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_grpc_integrity_only_record_protocol_create(
+                 crypter, 8, /*is_client=*/false, /*is_protect=*/false,
+                 &fixture->server_unprotect) == TSI_OK);
+
+  gpr_free(key);
+  return fixture;
+}
+
+static alts_grpc_record_protocol_test_fixture*
+test_fixture_integrity_only_no_rekey_create() {
+  return test_fixture_integrity_only_create(false);
+}
+
+static alts_grpc_record_protocol_test_fixture*
+test_fixture_integrity_only_rekey_create() {
+  return test_fixture_integrity_only_create(true);
+}
+
+static alts_grpc_record_protocol_test_fixture*
+test_fixture_privacy_integrity_create(bool rekey) {
+  alts_grpc_record_protocol_test_fixture* fixture =
+      static_cast<alts_grpc_record_protocol_test_fixture*>(
+          gpr_zalloc(sizeof(alts_grpc_record_protocol_test_fixture)));
+  size_t key_length = rekey ? kAes128GcmRekeyKeyLength : kAes128GcmKeyLength;
+  uint8_t* key;
+  gsec_test_random_array(&key, key_length);
+  gsec_aead_crypter* crypter = nullptr;
+
+  /* Create client record protocol for protect. */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_grpc_privacy_integrity_record_protocol_create(
+                 crypter, 8, /*is_client=*/true, /*is_protect=*/true,
+                 &fixture->client_protect) == TSI_OK);
+  /* Create client record protocol for unprotect.  */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_grpc_privacy_integrity_record_protocol_create(
+                 crypter, 8, /*is_client=*/true, /*is_protect=*/false,
+                 &fixture->client_unprotect) == TSI_OK);
+  /* Create server record protocol for protect.  */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_grpc_privacy_integrity_record_protocol_create(
+                 crypter, 8, /*is_client=*/false, /*is_protect=*/true,
+                 &fixture->server_protect) == TSI_OK);
+  /* Create server record protocol for unprotect.  */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_grpc_privacy_integrity_record_protocol_create(
+                 crypter, 8, /*is_client=*/false, /*is_protect=*/false,
+                 &fixture->server_unprotect) == TSI_OK);
+
+  gpr_free(key);
+  return fixture;
+}
+
+static alts_grpc_record_protocol_test_fixture*
+test_fixture_privacy_integrity_no_rekey_create() {
+  return test_fixture_privacy_integrity_create(false);
+}
+
+static alts_grpc_record_protocol_test_fixture*
+test_fixture_privacy_integrity_rekey_create() {
+  return test_fixture_privacy_integrity_create(true);
+}
+
+static void alts_grpc_record_protocol_test_fixture_destroy(
+    alts_grpc_record_protocol_test_fixture* fixture) {
+  if (fixture == nullptr) {
+    return;
+  }
+  grpc_core::ExecCtx exec_ctx;
+  alts_grpc_record_protocol_destroy(fixture->client_protect);
+  alts_grpc_record_protocol_destroy(fixture->client_unprotect);
+  alts_grpc_record_protocol_destroy(fixture->server_protect);
+  alts_grpc_record_protocol_destroy(fixture->server_unprotect);
+  grpc_core::ExecCtx::Get()->Flush();
+  gpr_free(fixture);
+}
+
+static alts_grpc_record_protocol_test_var*
+alts_grpc_record_protocol_test_var_create() {
+  alts_grpc_record_protocol_test_var* var =
+      static_cast<alts_grpc_record_protocol_test_var*>(
+          gpr_zalloc(sizeof(alts_grpc_record_protocol_test_var)));
+  var->header_length = alts_iovec_record_protocol_get_header_length();
+  var->tag_length = kTagLength;
+  /* Initialized slice buffers.  */
+  grpc_slice_buffer_init(&var->original_sb);
+  grpc_slice_buffer_init(&var->duplicate_sb);
+  grpc_slice_buffer_init(&var->protected_sb);
+  grpc_slice_buffer_init(&var->unprotected_sb);
+  /* Randomly sets content of original_sb, and copies into duplicate_sb.  */
+  create_random_slice_buffer(&var->original_sb);
+  for (size_t i = 0; i < var->original_sb.count; i++) {
+    grpc_slice_buffer_add(&var->duplicate_sb,
+                          grpc_slice_ref(var->original_sb.slices[i]));
+  }
+  return var;
+}
+
+static void alts_grpc_record_protocol_test_var_destroy(
+    alts_grpc_record_protocol_test_var* var) {
+  if (var == nullptr) {
+    return;
+  }
+  grpc_slice_buffer_destroy_internal(&var->original_sb);
+  grpc_slice_buffer_destroy_internal(&var->duplicate_sb);
+  grpc_slice_buffer_destroy_internal(&var->protected_sb);
+  grpc_slice_buffer_destroy_internal(&var->unprotected_sb);
+  gpr_free(var);
+}
+
+/* --- alts grpc record protocol tests. --- */
+
+static void random_seal_unseal(alts_grpc_record_protocol* sender,
+                               alts_grpc_record_protocol* receiver) {
+  grpc_core::ExecCtx exec_ctx;
+  for (size_t i = 0; i < kSealRepeatTimes; i++) {
+    alts_grpc_record_protocol_test_var* var =
+        alts_grpc_record_protocol_test_var_create();
+    /* Seals and then unseals.  */
+    size_t data_length = var->original_sb.length;
+    tsi_result status = alts_grpc_record_protocol_protect(
+        sender, &var->original_sb, &var->protected_sb);
+    GPR_ASSERT(status == TSI_OK);
+    GPR_ASSERT(var->protected_sb.length ==
+               data_length + var->header_length + var->tag_length);
+    status = alts_grpc_record_protocol_unprotect(receiver, &var->protected_sb,
+                                                 &var->unprotected_sb);
+    GPR_ASSERT(status == TSI_OK);
+    GPR_ASSERT(
+        are_slice_buffers_equal(&var->unprotected_sb, &var->duplicate_sb));
+    alts_grpc_record_protocol_test_var_destroy(var);
+  }
+  grpc_core::ExecCtx::Get()->Flush();
+}
+
+static void empty_seal_unseal(alts_grpc_record_protocol* sender,
+                              alts_grpc_record_protocol* receiver) {
+  grpc_core::ExecCtx exec_ctx;
+  for (size_t i = 0; i < kSealRepeatTimes; i++) {
+    alts_grpc_record_protocol_test_var* var =
+        alts_grpc_record_protocol_test_var_create();
+    /* Seals and then unseals empty payload.  */
+    grpc_slice_buffer_reset_and_unref_internal(&var->original_sb);
+    grpc_slice_buffer_reset_and_unref_internal(&var->duplicate_sb);
+    tsi_result status = alts_grpc_record_protocol_protect(
+        sender, &var->original_sb, &var->protected_sb);
+    GPR_ASSERT(status == TSI_OK);
+    GPR_ASSERT(var->protected_sb.length ==
+               var->header_length + var->tag_length);
+    status = alts_grpc_record_protocol_unprotect(receiver, &var->protected_sb,
+                                                 &var->unprotected_sb);
+    GPR_ASSERT(status == TSI_OK);
+    GPR_ASSERT(
+        are_slice_buffers_equal(&var->unprotected_sb, &var->duplicate_sb));
+    alts_grpc_record_protocol_test_var_destroy(var);
+  }
+  grpc_core::ExecCtx::Get()->Flush();
+}
+
+static void unsync_seal_unseal(alts_grpc_record_protocol* sender,
+                               alts_grpc_record_protocol* receiver) {
+  grpc_core::ExecCtx exec_ctx;
+  tsi_result status;
+  alts_grpc_record_protocol_test_var* var =
+      alts_grpc_record_protocol_test_var_create();
+  /* Seals once.  */
+  status = alts_grpc_record_protocol_protect(sender, &var->original_sb,
+                                             &var->protected_sb);
+  GPR_ASSERT(status == TSI_OK);
+  grpc_slice_buffer_reset_and_unref_internal(&var->protected_sb);
+  /* Seals again.  */
+  status = alts_grpc_record_protocol_protect(sender, &var->duplicate_sb,
+                                             &var->protected_sb);
+  GPR_ASSERT(status == TSI_OK);
+  /* Unseals the second frame.  */
+  status = alts_grpc_record_protocol_unprotect(receiver, &var->protected_sb,
+                                               &var->unprotected_sb);
+  GPR_ASSERT(status == TSI_INTERNAL_ERROR);
+  alts_grpc_record_protocol_test_var_destroy(var);
+  grpc_core::ExecCtx::Get()->Flush();
+}
+
+static void corrupted_data(alts_grpc_record_protocol* sender,
+                           alts_grpc_record_protocol* receiver) {
+  grpc_core::ExecCtx exec_ctx;
+  tsi_result status;
+  alts_grpc_record_protocol_test_var* var =
+      alts_grpc_record_protocol_test_var_create();
+  /* Seals once.  */
+  status = alts_grpc_record_protocol_protect(sender, &var->original_sb,
+                                             &var->protected_sb);
+  GPR_ASSERT(status == TSI_OK);
+  /* Corrupts one byte in protected_sb and tries to unprotect.  */
+  alter_random_byte(&var->protected_sb);
+  status = alts_grpc_record_protocol_unprotect(receiver, &var->protected_sb,
+                                               &var->unprotected_sb);
+  GPR_ASSERT(status == TSI_INTERNAL_ERROR);
+  alts_grpc_record_protocol_test_var_destroy(var);
+  grpc_core::ExecCtx::Get()->Flush();
+}
+
+static void input_check(alts_grpc_record_protocol* rp) {
+  grpc_core::ExecCtx exec_ctx;
+  tsi_result status;
+  alts_grpc_record_protocol_test_var* var =
+      alts_grpc_record_protocol_test_var_create();
+  /* Protects with nullptr input.  */
+  status = alts_grpc_record_protocol_protect(rp, nullptr, &var->protected_sb);
+  GPR_ASSERT(status == TSI_INVALID_ARGUMENT);
+  status = alts_grpc_record_protocol_protect(rp, &var->original_sb, nullptr);
+  GPR_ASSERT(status == TSI_INVALID_ARGUMENT);
+  /* Unprotects with nullptr input.  */
+  status = alts_grpc_record_protocol_protect(rp, &var->original_sb,
+                                             &var->protected_sb);
+  GPR_ASSERT(status == TSI_OK);
+  status =
+      alts_grpc_record_protocol_unprotect(rp, nullptr, &var->unprotected_sb);
+  GPR_ASSERT(status == TSI_INVALID_ARGUMENT);
+  status = alts_grpc_record_protocol_unprotect(rp, &var->protected_sb, nullptr);
+  GPR_ASSERT(status == TSI_INVALID_ARGUMENT);
+  /* Unprotects on a temporary slice buffer which length is smaller than header
+   * length plus tag length.  */
+  grpc_slice_buffer temp_sb;
+  grpc_slice_buffer_init(&temp_sb);
+  grpc_slice_buffer_move_first(
+      &var->protected_sb, var->header_length + var->tag_length - 1, &temp_sb);
+  status =
+      alts_grpc_record_protocol_unprotect(rp, &temp_sb, &var->unprotected_sb);
+  GPR_ASSERT(status == TSI_INVALID_ARGUMENT);
+  grpc_slice_buffer_destroy_internal(&temp_sb);
+  alts_grpc_record_protocol_test_var_destroy(var);
+  grpc_core::ExecCtx::Get()->Flush();
+}
+
+/* --- Test cases. --- */
+
+static void alts_grpc_record_protocol_random_seal_unseal_tests(
+    alts_grpc_record_protocol_test_fixture* fixture) {
+  random_seal_unseal(fixture->client_protect, fixture->server_unprotect);
+  random_seal_unseal(fixture->server_protect, fixture->client_unprotect);
+}
+
+static void alts_grpc_record_protocol_empty_seal_unseal_tests(
+    alts_grpc_record_protocol_test_fixture* fixture) {
+  empty_seal_unseal(fixture->client_protect, fixture->server_unprotect);
+  empty_seal_unseal(fixture->server_protect, fixture->client_unprotect);
+}
+
+static void alts_grpc_record_protocol_unsync_seal_unseal_tests(
+    alts_grpc_record_protocol_test_fixture* fixture) {
+  unsync_seal_unseal(fixture->client_protect, fixture->server_unprotect);
+  unsync_seal_unseal(fixture->server_protect, fixture->client_unprotect);
+}
+
+static void alts_grpc_record_protocol_corrupted_data_tests(
+    alts_grpc_record_protocol_test_fixture* fixture) {
+  corrupted_data(fixture->client_protect, fixture->server_unprotect);
+  corrupted_data(fixture->server_protect, fixture->client_unprotect);
+}
+
+static void alts_grpc_record_protocol_input_check_tests(
+    alts_grpc_record_protocol_test_fixture* fixture) {
+  input_check(fixture->client_protect);
+}
+
+static void alts_grpc_record_protocol_tests(
+    alts_grpc_record_protocol_test_fixture* (*fixture_create)()) {
+  auto* fixture_1 = fixture_create();
+  alts_grpc_record_protocol_random_seal_unseal_tests(fixture_1);
+  alts_grpc_record_protocol_test_fixture_destroy(fixture_1);
+
+  auto* fixture_2 = fixture_create();
+  alts_grpc_record_protocol_empty_seal_unseal_tests(fixture_2);
+  alts_grpc_record_protocol_test_fixture_destroy(fixture_2);
+
+  auto* fixture_3 = fixture_create();
+  alts_grpc_record_protocol_unsync_seal_unseal_tests(fixture_3);
+  alts_grpc_record_protocol_test_fixture_destroy(fixture_3);
+
+  auto* fixture_4 = fixture_create();
+  alts_grpc_record_protocol_corrupted_data_tests(fixture_4);
+  alts_grpc_record_protocol_test_fixture_destroy(fixture_4);
+
+  auto* fixture_5 = fixture_create();
+  alts_grpc_record_protocol_input_check_tests(fixture_5);
+  alts_grpc_record_protocol_test_fixture_destroy(fixture_5);
+}
+
+int main(int argc, char** argv) {
+  alts_grpc_record_protocol_tests(&test_fixture_integrity_only_no_rekey_create);
+  alts_grpc_record_protocol_tests(&test_fixture_integrity_only_rekey_create);
+  alts_grpc_record_protocol_tests(
+      &test_fixture_privacy_integrity_no_rekey_create);
+  alts_grpc_record_protocol_tests(&test_fixture_privacy_integrity_rekey_create);
+
+  return 0;
+}
diff --git a/test/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol_test.cc b/test/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol_test.cc
new file mode 100644
index 0000000..db1934b
--- /dev/null
+++ b/test/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol_test.cc
@@ -0,0 +1,928 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h"
+#include "test/core/tsi/alts/crypt/gsec_test_util.h"
+
+constexpr size_t kMaxDataSize = 1024;
+constexpr size_t kMaxSlices = 10;
+constexpr size_t kSealRepeatTimes = 5;
+constexpr size_t kTagLength = 16;
+
+/* Test fixtures for each test cases.  */
+struct alts_iovec_record_protocol_test_fixture {
+  alts_iovec_record_protocol* client_protect;
+  alts_iovec_record_protocol* client_unprotect;
+  alts_iovec_record_protocol* server_protect;
+  alts_iovec_record_protocol* server_unprotect;
+};
+
+/* Test variables for protect/unprotect operations.  */
+struct alts_iovec_record_protocol_test_var {
+  uint8_t* header_buf;
+  size_t header_length;
+  iovec_t header_iovec;
+  uint8_t* tag_buf;
+  size_t tag_length;
+  iovec_t tag_iovec;
+  uint8_t* data_buf;
+  uint8_t* dup_buf;
+  size_t data_length;
+  iovec_t* data_iovec;
+  size_t data_iovec_length;
+  uint8_t* protected_buf;
+  iovec_t protected_iovec;
+  iovec_t unprotected_iovec;
+};
+
+/* --- Test utility functions. --- */
+
+static void randomly_slice(uint8_t* input, size_t input_length,
+                           iovec_t** output, size_t* output_length) {
+  if (input_length == 0) {
+    *output = nullptr;
+    *output_length = 0;
+    return;
+  }
+  *output_length = gsec_test_bias_random_uint32(kMaxSlices) + 1;
+  *output = static_cast<iovec_t*>(gpr_malloc(*output_length * sizeof(iovec_t)));
+  for (size_t i = 0; i < *output_length - 1; i++) {
+    size_t slice_length =
+        gsec_test_bias_random_uint32(static_cast<uint32_t>(input_length));
+    iovec_t slice = {input, slice_length};
+    (*output)[i] = slice;
+    input += slice_length;
+    input_length -= slice_length;
+  }
+  iovec_t slice = {input, input_length};
+  (*output)[*output_length - 1] = slice;
+}
+
+static size_t alter_random_byte(uint8_t* buf, size_t buf_length) {
+  GPR_ASSERT(buf != nullptr);
+  uint32_t offset =
+      gsec_test_bias_random_uint32(static_cast<uint32_t>(buf_length));
+  (*(buf + offset))++;
+  return offset;
+}
+
+static void revert_back_alter(uint8_t* buf, size_t offset) {
+  GPR_ASSERT(buf != nullptr);
+  (*(buf + offset))--;
+}
+
+static alts_iovec_record_protocol_test_fixture*
+alts_iovec_record_protocol_test_fixture_create(bool rekey,
+                                               bool integrity_only) {
+  alts_iovec_record_protocol_test_fixture* fixture =
+      static_cast<alts_iovec_record_protocol_test_fixture*>(
+          gpr_malloc(sizeof(alts_iovec_record_protocol_test_fixture)));
+  size_t overflow_size = 8;
+  size_t key_length = rekey ? kAes128GcmRekeyKeyLength : kAes128GcmKeyLength;
+  uint8_t* key;
+  gsec_test_random_array(&key, key_length);
+  gsec_aead_crypter* crypter = nullptr;
+  /* Create client record protocol for protect.  */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_iovec_record_protocol_create(
+                 crypter, overflow_size, /*is_client=*/true, integrity_only,
+                 /*is_protect=*/true, &fixture->client_protect,
+                 nullptr) == GRPC_STATUS_OK);
+  /* Create client record protocol for unprotect.  */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_iovec_record_protocol_create(
+                 crypter, overflow_size, /*is_client=*/true, integrity_only,
+                 /*is_protect=*/false, &fixture->client_unprotect,
+                 nullptr) == GRPC_STATUS_OK);
+  /* Create server record protocol for protect.  */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_iovec_record_protocol_create(
+                 crypter, overflow_size, /*is_client=*/false, integrity_only,
+                 /*is_protect=*/true, &fixture->server_protect,
+                 nullptr) == GRPC_STATUS_OK);
+  /* Create server record protocol for unprotect.  */
+  GPR_ASSERT(gsec_aes_gcm_aead_crypter_create(
+                 key, key_length, kAesGcmNonceLength, kAesGcmTagLength, rekey,
+                 &crypter, nullptr) == GRPC_STATUS_OK);
+  GPR_ASSERT(alts_iovec_record_protocol_create(
+                 crypter, overflow_size, /*is_client=*/false, integrity_only,
+                 /*is_protect=*/false, &fixture->server_unprotect,
+                 nullptr) == GRPC_STATUS_OK);
+
+  gpr_free(key);
+  return fixture;
+}
+
+static void alts_iovec_record_protocol_test_fixture_destroy(
+    alts_iovec_record_protocol_test_fixture* fixture) {
+  if (fixture == nullptr) {
+    return;
+  }
+  alts_iovec_record_protocol_destroy(fixture->client_protect);
+  alts_iovec_record_protocol_destroy(fixture->client_unprotect);
+  alts_iovec_record_protocol_destroy(fixture->server_protect);
+  alts_iovec_record_protocol_destroy(fixture->server_unprotect);
+  gpr_free(fixture);
+}
+
+static alts_iovec_record_protocol_test_var*
+alts_iovec_record_protocol_test_var_create() {
+  auto* var = static_cast<alts_iovec_record_protocol_test_var*>(
+      gpr_zalloc(sizeof(alts_iovec_record_protocol_test_var)));
+  /* Sets header buffer.  */
+  var->header_length = alts_iovec_record_protocol_get_header_length();
+  var->header_buf = static_cast<uint8_t*>(gpr_malloc(var->header_length));
+  var->header_iovec.iov_base = var->header_buf;
+  var->header_iovec.iov_len = var->header_length;
+  /* Sets tag buffer.  */
+  var->tag_length = kTagLength;
+  var->tag_buf = static_cast<uint8_t*>(gpr_malloc(var->tag_length));
+  var->tag_iovec.iov_base = var->tag_buf;
+  var->tag_iovec.iov_len = var->tag_length;
+  /* Randomly sets data buffer and duplicates to dup_buf.  */
+  var->data_length = gsec_test_bias_random_uint32(kMaxDataSize) + 1;
+  var->data_buf = static_cast<uint8_t*>(gpr_malloc(var->data_length));
+  gsec_test_random_bytes(var->data_buf, var->data_length);
+  gsec_test_copy(var->data_buf, &var->dup_buf, var->data_length);
+  var->data_iovec = nullptr;
+  var->data_iovec_length = 0;
+  randomly_slice(var->data_buf, var->data_length, &var->data_iovec,
+                 &var->data_iovec_length);
+  /* Sets protected iovec.  */
+  size_t protected_buf_length =
+      var->header_length + var->data_length + var->tag_length;
+  var->protected_buf = static_cast<uint8_t*>(gpr_malloc(protected_buf_length));
+  var->protected_iovec.iov_base = var->protected_buf;
+  var->protected_iovec.iov_len = protected_buf_length;
+  /* Unprotected iovec points to data_buf.  */
+  var->unprotected_iovec.iov_base = var->data_buf;
+  var->unprotected_iovec.iov_len = var->data_length;
+  return var;
+}
+
+static void alts_iovec_record_protocol_test_var_destroy(
+    alts_iovec_record_protocol_test_var* var) {
+  if (var == nullptr) {
+    return;
+  }
+  gpr_free(var->header_buf);
+  gpr_free(var->tag_buf);
+  gpr_free(var->data_buf);
+  gpr_free(var->dup_buf);
+  gpr_free(var->data_iovec);
+  gpr_free(var->protected_buf);
+  gpr_free(var);
+}
+
+/* --- Integrity-only protect/unprotect tests. --- */
+
+static void integrity_only_random_seal_unseal(
+    alts_iovec_record_protocol* sender, alts_iovec_record_protocol* receiver) {
+  for (size_t i = 0; i < kSealRepeatTimes; i++) {
+    alts_iovec_record_protocol_test_var* var =
+        alts_iovec_record_protocol_test_var_create();
+    /* Seals and then unseals.  */
+    grpc_status_code status = alts_iovec_record_protocol_integrity_only_protect(
+        sender, var->data_iovec, var->data_iovec_length, var->header_iovec,
+        var->tag_iovec, nullptr);
+    GPR_ASSERT(status == GRPC_STATUS_OK);
+    gpr_free(var->data_iovec);
+    /* Randomly slices data buffer again.  */
+    randomly_slice(var->data_buf, var->data_length, &var->data_iovec,
+                   &var->data_iovec_length);
+    status = alts_iovec_record_protocol_integrity_only_unprotect(
+        receiver, var->data_iovec, var->data_iovec_length, var->header_iovec,
+        var->tag_iovec, nullptr);
+    GPR_ASSERT(status == GRPC_STATUS_OK);
+    /* Makes sure data buffer has not been modified during
+     * seal/unseal.  */
+    GPR_ASSERT(memcmp(var->data_buf, var->dup_buf, var->data_length) == 0);
+    alts_iovec_record_protocol_test_var_destroy(var);
+  }
+}
+
+static void integrity_only_empty_seal_unseal(
+    alts_iovec_record_protocol* sender, alts_iovec_record_protocol* receiver) {
+  for (size_t i = 0; i < kSealRepeatTimes; i++) {
+    alts_iovec_record_protocol_test_var* var =
+        alts_iovec_record_protocol_test_var_create();
+    /* Seals and then unseals empty payload.  */
+    grpc_status_code status = alts_iovec_record_protocol_integrity_only_protect(
+        sender, nullptr, 0, var->header_iovec, var->tag_iovec, nullptr);
+    GPR_ASSERT(status == GRPC_STATUS_OK);
+    status = alts_iovec_record_protocol_integrity_only_unprotect(
+        receiver, nullptr, 0, var->header_iovec, var->tag_iovec, nullptr);
+    GPR_ASSERT(status == GRPC_STATUS_OK);
+    alts_iovec_record_protocol_test_var_destroy(var);
+  }
+}
+
+static void integrity_only_unsync_seal_unseal(
+    alts_iovec_record_protocol* sender, alts_iovec_record_protocol* receiver) {
+  /* Seals once.  */
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  grpc_status_code status = alts_iovec_record_protocol_integrity_only_protect(
+      sender, var->data_iovec, var->data_iovec_length, var->header_iovec,
+      var->tag_iovec, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  alts_iovec_record_protocol_test_var_destroy(var);
+  /* Seals again.  */
+  var = alts_iovec_record_protocol_test_var_create();
+  status = alts_iovec_record_protocol_integrity_only_protect(
+      sender, var->data_iovec, var->data_iovec_length, var->header_iovec,
+      var->tag_iovec, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  /* Unseals the second frame.  */
+  char* error_message = nullptr;
+  status = alts_iovec_record_protocol_integrity_only_unprotect(
+      receiver, var->data_iovec, var->data_iovec_length, var->header_iovec,
+      var->tag_iovec, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INTERNAL, error_message,
+      "Frame tag verification failed."));
+  gpr_free(error_message);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+static void integrity_only_corrupted_data(
+    alts_iovec_record_protocol* sender, alts_iovec_record_protocol* receiver) {
+  /* Seals the data first.  */
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  grpc_status_code status = alts_iovec_record_protocol_integrity_only_protect(
+      sender, var->data_iovec, var->data_iovec_length, var->header_iovec,
+      var->tag_iovec, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  /* Alter frame length field.  */
+  char* error_message = nullptr;
+  size_t offset =
+      alter_random_byte(var->header_buf, kZeroCopyFrameLengthFieldSize);
+  status = alts_iovec_record_protocol_integrity_only_unprotect(
+      receiver, var->data_iovec, var->data_iovec_length, var->header_iovec,
+      var->tag_iovec, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INTERNAL, error_message, "Bad frame length."));
+  gpr_free(error_message);
+  revert_back_alter(var->header_buf, offset);
+  /* Alter message type field.  */
+  offset = alter_random_byte(var->header_buf + kZeroCopyFrameLengthFieldSize,
+                             kZeroCopyFrameMessageTypeFieldSize);
+  status = alts_iovec_record_protocol_integrity_only_unprotect(
+      receiver, var->data_iovec, var->data_iovec_length, var->header_iovec,
+      var->tag_iovec, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INTERNAL, error_message,
+      "Unsupported message type."));
+  gpr_free(error_message);
+  revert_back_alter(var->header_buf + kZeroCopyFrameLengthFieldSize, offset);
+  /* Alter data.  */
+  offset = alter_random_byte(var->data_buf, var->data_length);
+  status = alts_iovec_record_protocol_integrity_only_unprotect(
+      receiver, var->data_iovec, var->data_iovec_length, var->header_iovec,
+      var->tag_iovec, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INTERNAL, error_message,
+      "Frame tag verification failed."));
+  gpr_free(error_message);
+  revert_back_alter(var->data_buf, offset);
+  /* Alter tag.  */
+  offset = alter_random_byte(var->tag_buf, var->tag_length);
+  status = alts_iovec_record_protocol_integrity_only_unprotect(
+      receiver, var->data_iovec, var->data_iovec_length, var->header_iovec,
+      var->tag_iovec, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INTERNAL, error_message,
+      "Frame tag verification failed."));
+  gpr_free(error_message);
+  revert_back_alter(var->tag_buf, offset);
+  /* Reverted protected data should be verified correctly.  */
+  status = alts_iovec_record_protocol_integrity_only_unprotect(
+      receiver, var->data_iovec, var->data_iovec_length, var->header_iovec,
+      var->tag_iovec, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(memcmp(var->data_buf, var->dup_buf, var->data_length) == 0);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+static void integrity_only_protect_input_check(alts_iovec_record_protocol* rp) {
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  char* error_message = nullptr;
+  /* Header buffer is nullptr.  */
+  iovec_t header_iovec = {nullptr, var->header_length};
+  grpc_status_code status = alts_iovec_record_protocol_integrity_only_protect(
+      rp, var->data_iovec, var->data_iovec_length, header_iovec, var->tag_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Header is nullptr."));
+  gpr_free(error_message);
+  /* Header buffer length is 0.  */
+  header_iovec.iov_base = var->header_buf;
+  header_iovec.iov_len = 0;
+  status = alts_iovec_record_protocol_integrity_only_protect(
+      rp, var->data_iovec, var->data_iovec_length, header_iovec, var->tag_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Header length is incorrect."));
+  gpr_free(error_message);
+  /* Tag buffer is nullptr.  */
+  iovec_t tag_iovec = {nullptr, var->tag_length};
+  status = alts_iovec_record_protocol_integrity_only_protect(
+      rp, var->data_iovec, var->data_iovec_length, var->header_iovec, tag_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message, "Tag is nullptr."));
+  gpr_free(error_message);
+  /* Tag buffer length is 0.  */
+  tag_iovec.iov_base = var->tag_buf;
+  tag_iovec.iov_len = 0;
+  status = alts_iovec_record_protocol_integrity_only_protect(
+      rp, var->data_iovec, var->data_iovec_length, var->header_iovec, tag_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Tag length is incorrect."));
+  gpr_free(error_message);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+static void integrity_only_unprotect_input_check(
+    alts_iovec_record_protocol* rp) {
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  char* error_message = nullptr;
+  /* Header buffer is nullptr.  */
+  iovec_t header_iovec = {nullptr, var->header_length};
+  grpc_status_code status = alts_iovec_record_protocol_integrity_only_unprotect(
+      rp, var->data_iovec, var->data_iovec_length, header_iovec, var->tag_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Header is nullptr."));
+  gpr_free(error_message);
+  /* Header buffer length is 0.  */
+  header_iovec.iov_base = var->header_buf;
+  header_iovec.iov_len = 0;
+  status = alts_iovec_record_protocol_integrity_only_unprotect(
+      rp, var->data_iovec, var->data_iovec_length, header_iovec, var->tag_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Header length is incorrect."));
+  gpr_free(error_message);
+  /* Tag buffer is nullptr.  */
+  iovec_t tag_iovec = {nullptr, var->tag_length};
+  status = alts_iovec_record_protocol_integrity_only_unprotect(
+      rp, var->data_iovec, var->data_iovec_length, var->header_iovec, tag_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message, "Tag is nullptr."));
+  gpr_free(error_message);
+  /* Tag buffer length is 0.  */
+  tag_iovec.iov_base = var->tag_buf;
+  tag_iovec.iov_len = 0;
+  status = alts_iovec_record_protocol_integrity_only_unprotect(
+      rp, var->data_iovec, var->data_iovec_length, var->header_iovec, tag_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Tag length is incorrect."));
+  gpr_free(error_message);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+/* --- Privacy-integrity protect/unprotect tests. --- */
+
+static void privacy_integrity_random_seal_unseal(
+    alts_iovec_record_protocol* sender, alts_iovec_record_protocol* receiver) {
+  for (size_t i = 0; i < kSealRepeatTimes; i++) {
+    alts_iovec_record_protocol_test_var* var =
+        alts_iovec_record_protocol_test_var_create();
+    /* Seals and then unseals.  */
+    grpc_status_code status =
+        alts_iovec_record_protocol_privacy_integrity_protect(
+            sender, var->data_iovec, var->data_iovec_length,
+            var->protected_iovec, nullptr);
+    GPR_ASSERT(status == GRPC_STATUS_OK);
+    iovec_t header_iovec = {var->protected_buf, var->header_length};
+    gpr_free(var->data_iovec);
+    /* Randomly slices protected buffer, excluding the header.  */
+    randomly_slice(var->protected_buf + var->header_length,
+                   var->data_length + var->tag_length, &var->data_iovec,
+                   &var->data_iovec_length);
+    status = alts_iovec_record_protocol_privacy_integrity_unprotect(
+        receiver, header_iovec, var->data_iovec, var->data_iovec_length,
+        var->unprotected_iovec, nullptr);
+    GPR_ASSERT(status == GRPC_STATUS_OK);
+    /* Makes sure unprotected data are the same as the original.  */
+    GPR_ASSERT(memcmp(var->data_buf, var->dup_buf, var->data_length) == 0);
+    alts_iovec_record_protocol_test_var_destroy(var);
+  }
+}
+
+static void privacy_integrity_empty_seal_unseal(
+    alts_iovec_record_protocol* sender, alts_iovec_record_protocol* receiver) {
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  size_t empty_payload_frame_size = var->header_length + var->tag_length;
+  auto* protected_buf =
+      static_cast<uint8_t*>(gpr_malloc(empty_payload_frame_size));
+  for (size_t i = 0; i < kSealRepeatTimes; i++) {
+    iovec_t protected_iovec = {protected_buf, empty_payload_frame_size};
+    iovec_t unprotected_iovec = {nullptr, 0};
+    iovec_t data_iovec = {protected_buf + var->header_length, var->tag_length};
+    /* Seals and then unseals empty payload.  */
+    grpc_status_code status =
+        alts_iovec_record_protocol_privacy_integrity_protect(
+            sender, nullptr, 0, protected_iovec, nullptr);
+    GPR_ASSERT(status == GRPC_STATUS_OK);
+    iovec_t header_iovec = {protected_buf, var->header_length};
+    status = alts_iovec_record_protocol_privacy_integrity_unprotect(
+        receiver, header_iovec, &data_iovec, 1, unprotected_iovec, nullptr);
+    GPR_ASSERT(status == GRPC_STATUS_OK);
+  }
+  gpr_free(protected_buf);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+static void privacy_integrity_unsync_seal_unseal(
+    alts_iovec_record_protocol* sender, alts_iovec_record_protocol* receiver) {
+  /* Seals once.  */
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  grpc_status_code status =
+      alts_iovec_record_protocol_privacy_integrity_protect(
+          sender, var->data_iovec, var->data_iovec_length, var->protected_iovec,
+          nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  alts_iovec_record_protocol_test_var_destroy(var);
+  /* Seals again.  */
+  var = alts_iovec_record_protocol_test_var_create();
+  status = alts_iovec_record_protocol_privacy_integrity_protect(
+      sender, var->data_iovec, var->data_iovec_length, var->protected_iovec,
+      nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  /* Unseals the second frame.  */
+  char* error_message = nullptr;
+  iovec_t header_iovec = {var->protected_buf, var->header_length};
+  iovec_t protected_iovec = {var->protected_buf + var->header_length,
+                             var->data_length + var->tag_length};
+  status = alts_iovec_record_protocol_privacy_integrity_unprotect(
+      receiver, header_iovec, &protected_iovec, 1, var->unprotected_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INTERNAL, error_message, "Frame decryption failed."));
+  gpr_free(error_message);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+static void privacy_integrity_corrupted_data(
+    alts_iovec_record_protocol* sender, alts_iovec_record_protocol* receiver) {
+  /* Seals the data first.  */
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  grpc_status_code status =
+      alts_iovec_record_protocol_privacy_integrity_protect(
+          sender, var->data_iovec, var->data_iovec_length, var->protected_iovec,
+          nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  char* error_message = nullptr;
+  uint8_t* header_buf = var->protected_buf;
+  size_t header_length = var->header_length;
+  iovec_t header_iovec = {header_buf, header_length};
+  /* The following protected_buf and protected_length excludes header.  */
+  uint8_t* protected_buf = var->protected_buf + var->header_length;
+  size_t protected_length = var->data_length + var->tag_length;
+  iovec_t protected_iovec = {protected_buf, protected_length};
+  /* Alter frame length field.  */
+  size_t offset = alter_random_byte(header_buf, kZeroCopyFrameLengthFieldSize);
+  status = alts_iovec_record_protocol_privacy_integrity_unprotect(
+      receiver, header_iovec, &protected_iovec, 1, var->unprotected_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INTERNAL, error_message, "Bad frame length."));
+  gpr_free(error_message);
+  revert_back_alter(header_buf, offset);
+  /* Alter message type field.  */
+  offset = alter_random_byte(header_buf + kZeroCopyFrameLengthFieldSize,
+                             kZeroCopyFrameMessageTypeFieldSize);
+  status = alts_iovec_record_protocol_privacy_integrity_unprotect(
+      receiver, header_iovec, &protected_iovec, 1, var->unprotected_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INTERNAL, error_message,
+      "Unsupported message type."));
+  gpr_free(error_message);
+  revert_back_alter(header_buf + kZeroCopyFrameLengthFieldSize, offset);
+  /* Alter protected data.  */
+  offset = alter_random_byte(protected_buf, protected_length);
+  status = alts_iovec_record_protocol_privacy_integrity_unprotect(
+      receiver, header_iovec, &protected_iovec, 1, var->unprotected_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INTERNAL, error_message, "Frame decryption failed."));
+  gpr_free(error_message);
+  revert_back_alter(protected_buf, offset);
+  /* Reverted protected data should be verified correctly.  */
+  status = alts_iovec_record_protocol_privacy_integrity_unprotect(
+      receiver, header_iovec, &protected_iovec, 1, var->unprotected_iovec,
+      nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  GPR_ASSERT(memcmp(var->data_buf, var->dup_buf, var->data_length) == 0);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+static void privacy_integrity_protect_input_check(
+    alts_iovec_record_protocol* rp) {
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  char* error_message = nullptr;
+  /* Protected output buffer is nullptr.  */
+  iovec_t protected_iovec = {nullptr, var->protected_iovec.iov_len};
+  grpc_status_code status =
+      alts_iovec_record_protocol_privacy_integrity_protect(
+          rp, var->data_iovec, var->data_iovec_length, protected_iovec,
+          &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Protected frame is nullptr."));
+  gpr_free(error_message);
+  /* Protected output buffer length incorrect.  */
+  protected_iovec.iov_base = var->protected_buf;
+  protected_iovec.iov_len = var->header_length + var->data_length;
+  status = alts_iovec_record_protocol_privacy_integrity_protect(
+      rp, var->data_iovec, var->data_iovec_length, protected_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Protected frame size is incorrect."));
+  gpr_free(error_message);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+static void privacy_integrity_unprotect_input_check(
+    alts_iovec_record_protocol* rp) {
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  char* error_message = nullptr;
+  /* Header buffer is nullptr.  */
+  iovec_t header_iovec = {var->protected_buf, var->header_length};
+  iovec_t protected_iovec = {var->protected_buf + var->header_length,
+                             var->data_length + var->tag_length};
+  header_iovec.iov_base = nullptr;
+  grpc_status_code status =
+      alts_iovec_record_protocol_privacy_integrity_unprotect(
+          rp, header_iovec, &protected_iovec, 1, var->unprotected_iovec,
+          &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Header is nullptr."));
+  gpr_free(error_message);
+  header_iovec.iov_base = var->protected_buf;
+  /* Header buffer length is 0.  */
+  header_iovec.iov_len = 0;
+  status = alts_iovec_record_protocol_privacy_integrity_unprotect(
+      rp, header_iovec, &protected_iovec, 1, var->unprotected_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Header length is incorrect."));
+  gpr_free(error_message);
+  header_iovec.iov_len = var->header_length;
+  /* Unprotected output buffer length is incorrect.  */
+  iovec_t unprotected_iovec = {var->data_buf, var->data_length - 1};
+  status = alts_iovec_record_protocol_privacy_integrity_unprotect(
+      rp, header_iovec, &protected_iovec, 1, unprotected_iovec, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INVALID_ARGUMENT, error_message,
+      "Unprotected data size is incorrect."));
+  gpr_free(error_message);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+/* --- Integrity-only and privacy-integrity mixed. --- */
+
+static void record_protocol_wrong_mode(
+    alts_iovec_record_protocol* integrity_only_protect_rp,
+    alts_iovec_record_protocol* integrity_only_unprotect_rp,
+    alts_iovec_record_protocol* privacy_integrity_protect_rp,
+    alts_iovec_record_protocol* privacy_integrity_unprotect_rp) {
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  grpc_status_code status;
+  char* error_message = nullptr;
+  /* Call integrity-only protect on privacy-integrity record protocol.  */
+  status = alts_iovec_record_protocol_integrity_only_protect(
+      privacy_integrity_protect_rp, var->data_iovec, var->data_iovec_length,
+      var->header_iovec, var->tag_iovec, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+      "Integrity-only operations are not allowed for this object."));
+  gpr_free(error_message);
+  /* Call integrity-only unprotect on privacy-integrity record protocol.  */
+  status = alts_iovec_record_protocol_integrity_only_unprotect(
+      privacy_integrity_unprotect_rp, var->data_iovec, var->data_iovec_length,
+      var->header_iovec, var->tag_iovec, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+      "Integrity-only operations are not allowed for this object."));
+  gpr_free(error_message);
+  /* Call privacy-integrity protect on integrity-only record protocol.  */
+  status = alts_iovec_record_protocol_privacy_integrity_protect(
+      integrity_only_protect_rp, var->data_iovec, var->data_iovec_length,
+      var->protected_iovec, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+      "Privacy-integrity operations are not allowed for this object."));
+  gpr_free(error_message);
+  /* Call privacy-integrity unprotect on integrity-only record protocol.  */
+  status = alts_iovec_record_protocol_privacy_integrity_unprotect(
+      integrity_only_unprotect_rp, var->header_iovec, var->data_iovec,
+      var->data_iovec_length, var->unprotected_iovec, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_FAILED_PRECONDITION, error_message,
+      "Privacy-integrity operations are not allowed for this object."));
+  gpr_free(error_message);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+static void integrity_seal_privacy_unseal(
+    alts_iovec_record_protocol* integrity_only_sender,
+    alts_iovec_record_protocol* privacy_integrity_receiver) {
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  grpc_status_code status;
+  char* error_message = nullptr;
+  /* Seals with integrity-only protect.  */
+  status = alts_iovec_record_protocol_integrity_only_protect(
+      integrity_only_sender, var->data_iovec, var->data_iovec_length,
+      var->header_iovec, var->tag_iovec, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  /* Unseal with privacy-integrity unprotect.  */
+  memcpy(var->protected_buf, var->data_buf, var->data_length);
+  memcpy(var->protected_buf + var->data_length, var->tag_buf, var->tag_length);
+  iovec_t protected_iovec = {var->protected_buf,
+                             var->data_length + var->tag_length};
+  status = alts_iovec_record_protocol_privacy_integrity_unprotect(
+      privacy_integrity_receiver, var->header_iovec, &protected_iovec, 1,
+      var->unprotected_iovec, &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INTERNAL, error_message, "Frame decryption failed."));
+  gpr_free(error_message);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+static void privacy_seal_integrity_unseal(
+    alts_iovec_record_protocol* privacy_integrity_sender,
+    alts_iovec_record_protocol* integrity_only_receiver) {
+  alts_iovec_record_protocol_test_var* var =
+      alts_iovec_record_protocol_test_var_create();
+  grpc_status_code status;
+  char* error_message = nullptr;
+  /* Seals with privacy-integrity protect.  */
+  status = alts_iovec_record_protocol_privacy_integrity_protect(
+      privacy_integrity_sender, var->data_iovec, var->data_iovec_length,
+      var->protected_iovec, nullptr);
+  GPR_ASSERT(status == GRPC_STATUS_OK);
+  /* Unseal with integrity-only unprotect.  */
+  iovec_t header_iovec = {var->protected_buf, var->header_length};
+  iovec_t data_iovec = {var->protected_buf + var->header_length,
+                        var->data_length};
+  iovec_t tag_iovec = {
+      var->protected_buf + var->header_length + var->data_length,
+      var->tag_length};
+  status = alts_iovec_record_protocol_integrity_only_unprotect(
+      integrity_only_receiver, &data_iovec, 1, header_iovec, tag_iovec,
+      &error_message);
+  GPR_ASSERT(gsec_test_expect_compare_code_and_substr(
+      status, GRPC_STATUS_INTERNAL, error_message,
+      "Frame tag verification failed."));
+  gpr_free(error_message);
+  alts_iovec_record_protocol_test_var_destroy(var);
+}
+
+/* --- Test cases. --- */
+
+static void alts_iovec_record_protocol_random_seal_unseal_tests() {
+  alts_iovec_record_protocol_test_fixture* fixture =
+      alts_iovec_record_protocol_test_fixture_create(
+          /*rekey=*/false, /*integrity_only=*/true);
+  integrity_only_random_seal_unseal(fixture->client_protect,
+                                    fixture->server_unprotect);
+  integrity_only_random_seal_unseal(fixture->server_protect,
+                                    fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/true);
+  integrity_only_random_seal_unseal(fixture->client_protect,
+                                    fixture->server_unprotect);
+  integrity_only_random_seal_unseal(fixture->server_protect,
+                                    fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/false, /*integrity_only=*/false);
+  privacy_integrity_random_seal_unseal(fixture->client_protect,
+                                       fixture->server_unprotect);
+  privacy_integrity_random_seal_unseal(fixture->server_protect,
+                                       fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/false);
+  privacy_integrity_random_seal_unseal(fixture->client_protect,
+                                       fixture->server_unprotect);
+  privacy_integrity_random_seal_unseal(fixture->server_protect,
+                                       fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+}
+
+static void alts_iovec_record_protocol_empty_seal_unseal_tests() {
+  alts_iovec_record_protocol_test_fixture* fixture =
+      alts_iovec_record_protocol_test_fixture_create(
+          /*rekey=*/false, /*integrity_only=*/true);
+  integrity_only_empty_seal_unseal(fixture->client_protect,
+                                   fixture->server_unprotect);
+  integrity_only_empty_seal_unseal(fixture->server_protect,
+                                   fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/true);
+  integrity_only_empty_seal_unseal(fixture->client_protect,
+                                   fixture->server_unprotect);
+  integrity_only_empty_seal_unseal(fixture->server_protect,
+                                   fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/false, /*integrity_only=*/false);
+  privacy_integrity_empty_seal_unseal(fixture->client_protect,
+                                      fixture->server_unprotect);
+  privacy_integrity_empty_seal_unseal(fixture->server_protect,
+                                      fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/false);
+  privacy_integrity_empty_seal_unseal(fixture->client_protect,
+                                      fixture->server_unprotect);
+  privacy_integrity_empty_seal_unseal(fixture->server_protect,
+                                      fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+}
+
+static void alts_iovec_record_protocol_unsync_seal_unseal_tests() {
+  alts_iovec_record_protocol_test_fixture* fixture =
+      alts_iovec_record_protocol_test_fixture_create(
+          /*rekey=*/false, /*integrity_only=*/true);
+  integrity_only_unsync_seal_unseal(fixture->client_protect,
+                                    fixture->server_unprotect);
+  integrity_only_unsync_seal_unseal(fixture->server_protect,
+                                    fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/true);
+  integrity_only_unsync_seal_unseal(fixture->client_protect,
+                                    fixture->server_unprotect);
+  integrity_only_unsync_seal_unseal(fixture->server_protect,
+                                    fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/false, /*integrity_only=*/false);
+  privacy_integrity_unsync_seal_unseal(fixture->client_protect,
+                                       fixture->server_unprotect);
+  privacy_integrity_unsync_seal_unseal(fixture->server_protect,
+                                       fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/false);
+  privacy_integrity_unsync_seal_unseal(fixture->client_protect,
+                                       fixture->server_unprotect);
+  privacy_integrity_unsync_seal_unseal(fixture->server_protect,
+                                       fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+}
+
+static void alts_iovec_record_protocol_corrupted_data_tests() {
+  alts_iovec_record_protocol_test_fixture* fixture =
+      alts_iovec_record_protocol_test_fixture_create(
+          /*rekey=*/false, /*integrity_only=*/true);
+  integrity_only_corrupted_data(fixture->client_protect,
+                                fixture->server_unprotect);
+  integrity_only_corrupted_data(fixture->server_protect,
+                                fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/true);
+  integrity_only_corrupted_data(fixture->client_protect,
+                                fixture->server_unprotect);
+  integrity_only_corrupted_data(fixture->server_protect,
+                                fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/false, /*integrity_only=*/false);
+  privacy_integrity_corrupted_data(fixture->client_protect,
+                                   fixture->server_unprotect);
+  privacy_integrity_corrupted_data(fixture->server_protect,
+                                   fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/false);
+  privacy_integrity_corrupted_data(fixture->client_protect,
+                                   fixture->server_unprotect);
+  privacy_integrity_corrupted_data(fixture->server_protect,
+                                   fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+}
+
+static void alts_iovec_record_protocol_input_check_tests() {
+  alts_iovec_record_protocol_test_fixture* fixture =
+      alts_iovec_record_protocol_test_fixture_create(
+          /*rekey=*/false, /*integrity_only=*/true);
+  integrity_only_protect_input_check(fixture->client_protect);
+  integrity_only_unprotect_input_check(fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/true);
+  integrity_only_protect_input_check(fixture->client_protect);
+  integrity_only_unprotect_input_check(fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/false, /*integrity_only=*/false);
+  privacy_integrity_protect_input_check(fixture->client_protect);
+  privacy_integrity_unprotect_input_check(fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+
+  fixture = alts_iovec_record_protocol_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/false);
+  privacy_integrity_protect_input_check(fixture->client_protect);
+  privacy_integrity_unprotect_input_check(fixture->client_unprotect);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture);
+}
+
+static void alts_iovec_record_protocol_mix_operations_tests() {
+  alts_iovec_record_protocol_test_fixture* fixture_1 =
+      alts_iovec_record_protocol_test_fixture_create(
+          /*rekey=*/false, /*integrity_only=*/true);
+  alts_iovec_record_protocol_test_fixture* fixture_2 =
+      alts_iovec_record_protocol_test_fixture_create(
+          /*rekey=*/false, /*integrity_only=*/false);
+
+  record_protocol_wrong_mode(
+      fixture_1->client_protect, fixture_1->client_unprotect,
+      fixture_2->client_protect, fixture_2->client_unprotect);
+  integrity_seal_privacy_unseal(fixture_1->client_protect,
+                                fixture_2->server_unprotect);
+  privacy_seal_integrity_unseal(fixture_2->client_protect,
+                                fixture_1->server_unprotect);
+
+  alts_iovec_record_protocol_test_fixture_destroy(fixture_1);
+  alts_iovec_record_protocol_test_fixture_destroy(fixture_2);
+}
+
+int main(int argc, char** argv) {
+  alts_iovec_record_protocol_random_seal_unseal_tests();
+  alts_iovec_record_protocol_empty_seal_unseal_tests();
+  alts_iovec_record_protocol_unsync_seal_unseal_tests();
+  alts_iovec_record_protocol_corrupted_data_tests();
+  alts_iovec_record_protocol_input_check_tests();
+  alts_iovec_record_protocol_mix_operations_tests();
+  return 0;
+}
diff --git a/test/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector_test.cc b/test/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector_test.cc
new file mode 100644
index 0000000..2388be9
--- /dev/null
+++ b/test/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector_test.cc
@@ -0,0 +1,289 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <grpc/slice_buffer.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/slice/slice_internal.h"
+#include "src/core/tsi/alts/crypt/gsec.h"
+#include "src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h"
+#include "src/core/tsi/transport_security_grpc.h"
+#include "test/core/tsi/alts/crypt/gsec_test_util.h"
+
+/* TODO: tests zero_copy_grpc_protector under TSI test library, which
+ * has more comprehensive tests.  */
+
+constexpr size_t kSealRepeatTimes = 50;
+constexpr size_t kSmallBufferSize = 16;
+constexpr size_t kLargeBufferSize = 16384;
+constexpr size_t kChannelMaxSize = 2048;
+constexpr size_t kChannelMinSize = 128;
+
+/* Test fixtures for each test cases.  */
+struct alts_zero_copy_grpc_protector_test_fixture {
+  tsi_zero_copy_grpc_protector* client;
+  tsi_zero_copy_grpc_protector* server;
+};
+
+/* Test input variables for protect/unprotect operations.  */
+struct alts_zero_copy_grpc_protector_test_var {
+  grpc_slice_buffer original_sb;
+  grpc_slice_buffer duplicate_sb;
+  grpc_slice_buffer staging_sb;
+  grpc_slice_buffer protected_sb;
+  grpc_slice_buffer unprotected_sb;
+};
+
+/* --- Test utility functions. --- */
+
+static void create_random_slice_buffer(grpc_slice_buffer* sb,
+                                       grpc_slice_buffer* dup_sb,
+                                       size_t length) {
+  GPR_ASSERT(sb != nullptr);
+  GPR_ASSERT(dup_sb != nullptr);
+  GPR_ASSERT(length > 0);
+  grpc_slice slice = GRPC_SLICE_MALLOC(length);
+  gsec_test_random_bytes(GRPC_SLICE_START_PTR(slice), length);
+  grpc_slice_buffer_add(sb, grpc_slice_ref(slice));
+  grpc_slice_buffer_add(dup_sb, slice);
+}
+
+static uint8_t* pointer_to_nth_byte(grpc_slice_buffer* sb, size_t index) {
+  GPR_ASSERT(sb != nullptr);
+  GPR_ASSERT(index < sb->length);
+  for (size_t i = 0; i < sb->count; i++) {
+    if (index < GRPC_SLICE_LENGTH(sb->slices[i])) {
+      return GRPC_SLICE_START_PTR(sb->slices[i]) + index;
+    } else {
+      index -= GRPC_SLICE_LENGTH(sb->slices[i]);
+    }
+  }
+  return nullptr;
+}
+
+/* Checks if two slice buffer contents are the same. It is not super efficient,
+ * but OK for testing.  */
+static bool are_slice_buffers_equal(grpc_slice_buffer* first,
+                                    grpc_slice_buffer* second) {
+  GPR_ASSERT(first != nullptr);
+  GPR_ASSERT(second != nullptr);
+  if (first->length != second->length) {
+    return false;
+  }
+  for (size_t i = 0; i < first->length; i++) {
+    uint8_t* first_ptr = pointer_to_nth_byte(first, i);
+    uint8_t* second_ptr = pointer_to_nth_byte(second, i);
+    GPR_ASSERT(first_ptr != nullptr && second_ptr != nullptr);
+    if ((*first_ptr) != (*second_ptr)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+static alts_zero_copy_grpc_protector_test_fixture*
+alts_zero_copy_grpc_protector_test_fixture_create(bool rekey,
+                                                  bool integrity_only) {
+  alts_zero_copy_grpc_protector_test_fixture* fixture =
+      static_cast<alts_zero_copy_grpc_protector_test_fixture*>(
+          gpr_zalloc(sizeof(alts_zero_copy_grpc_protector_test_fixture)));
+  grpc_core::ExecCtx exec_ctx;
+  size_t key_length = rekey ? kAes128GcmRekeyKeyLength : kAes128GcmKeyLength;
+  uint8_t* key;
+  size_t max_protected_frame_size = 1024;
+  gsec_test_random_array(&key, key_length);
+  GPR_ASSERT(alts_zero_copy_grpc_protector_create(
+                 key, key_length, rekey, /*is_client=*/true, integrity_only,
+                 &max_protected_frame_size, &fixture->client) == TSI_OK);
+  GPR_ASSERT(alts_zero_copy_grpc_protector_create(
+                 key, key_length, rekey, /*is_client=*/false, integrity_only,
+                 &max_protected_frame_size, &fixture->server) == TSI_OK);
+  gpr_free(key);
+  grpc_core::ExecCtx::Get()->Flush();
+  return fixture;
+}
+
+static void alts_zero_copy_grpc_protector_test_fixture_destroy(
+    alts_zero_copy_grpc_protector_test_fixture* fixture) {
+  if (fixture == nullptr) {
+    return;
+  }
+  grpc_core::ExecCtx exec_ctx;
+  tsi_zero_copy_grpc_protector_destroy(fixture->client);
+  tsi_zero_copy_grpc_protector_destroy(fixture->server);
+  grpc_core::ExecCtx::Get()->Flush();
+  gpr_free(fixture);
+}
+
+static alts_zero_copy_grpc_protector_test_var*
+alts_zero_copy_grpc_protector_test_var_create() {
+  alts_zero_copy_grpc_protector_test_var* var =
+      static_cast<alts_zero_copy_grpc_protector_test_var*>(
+          gpr_zalloc(sizeof(alts_zero_copy_grpc_protector_test_var)));
+  grpc_slice_buffer_init(&var->original_sb);
+  grpc_slice_buffer_init(&var->duplicate_sb);
+  grpc_slice_buffer_init(&var->staging_sb);
+  grpc_slice_buffer_init(&var->protected_sb);
+  grpc_slice_buffer_init(&var->unprotected_sb);
+  return var;
+}
+
+static void alts_zero_copy_grpc_protector_test_var_destroy(
+    alts_zero_copy_grpc_protector_test_var* var) {
+  if (var == nullptr) {
+    return;
+  }
+  grpc_slice_buffer_destroy_internal(&var->original_sb);
+  grpc_slice_buffer_destroy_internal(&var->duplicate_sb);
+  grpc_slice_buffer_destroy_internal(&var->staging_sb);
+  grpc_slice_buffer_destroy_internal(&var->protected_sb);
+  grpc_slice_buffer_destroy_internal(&var->unprotected_sb);
+  gpr_free(var);
+}
+
+/* --- ALTS zero-copy protector tests. --- */
+
+static void seal_unseal_small_buffer(tsi_zero_copy_grpc_protector* sender,
+                                     tsi_zero_copy_grpc_protector* receiver) {
+  grpc_core::ExecCtx exec_ctx;
+  for (size_t i = 0; i < kSealRepeatTimes; i++) {
+    alts_zero_copy_grpc_protector_test_var* var =
+        alts_zero_copy_grpc_protector_test_var_create();
+    /* Creates a random small slice buffer and calls protect().  */
+    create_random_slice_buffer(&var->original_sb, &var->duplicate_sb,
+                               kSmallBufferSize);
+    GPR_ASSERT(tsi_zero_copy_grpc_protector_protect(
+                   sender, &var->original_sb, &var->protected_sb) == TSI_OK);
+    /* Splits protected slice buffer into two: first one is staging_sb, and
+     * second one is is protected_sb.  */
+    uint32_t staging_sb_size =
+        gsec_test_bias_random_uint32(
+            static_cast<uint32_t>(var->protected_sb.length - 1)) +
+        1;
+    grpc_slice_buffer_move_first(&var->protected_sb, staging_sb_size,
+                                 &var->staging_sb);
+    /* Unprotects one by one.  */
+    GPR_ASSERT(tsi_zero_copy_grpc_protector_unprotect(
+                   receiver, &var->staging_sb, &var->unprotected_sb) == TSI_OK);
+    GPR_ASSERT(var->unprotected_sb.length == 0);
+    GPR_ASSERT(tsi_zero_copy_grpc_protector_unprotect(
+                   receiver, &var->protected_sb, &var->unprotected_sb) ==
+               TSI_OK);
+    GPR_ASSERT(
+        are_slice_buffers_equal(&var->unprotected_sb, &var->duplicate_sb));
+    alts_zero_copy_grpc_protector_test_var_destroy(var);
+  }
+  grpc_core::ExecCtx::Get()->Flush();
+}
+
+static void seal_unseal_large_buffer(tsi_zero_copy_grpc_protector* sender,
+                                     tsi_zero_copy_grpc_protector* receiver) {
+  grpc_core::ExecCtx exec_ctx;
+  for (size_t i = 0; i < kSealRepeatTimes; i++) {
+    alts_zero_copy_grpc_protector_test_var* var =
+        alts_zero_copy_grpc_protector_test_var_create();
+    /* Creates a random large slice buffer and calls protect().  */
+    create_random_slice_buffer(&var->original_sb, &var->duplicate_sb,
+                               kLargeBufferSize);
+    GPR_ASSERT(tsi_zero_copy_grpc_protector_protect(
+                   sender, &var->original_sb, &var->protected_sb) == TSI_OK);
+    /* Splits protected slice buffer into multiple pieces. Receiver unprotects
+     * each slice buffer one by one.  */
+    uint32_t channel_size = gsec_test_bias_random_uint32(static_cast<uint32_t>(
+                                kChannelMaxSize + 1 - kChannelMinSize)) +
+                            static_cast<uint32_t>(kChannelMinSize);
+    while (var->protected_sb.length > channel_size) {
+      grpc_slice_buffer_reset_and_unref_internal(&var->staging_sb);
+      grpc_slice_buffer_move_first(&var->protected_sb, channel_size,
+                                   &var->staging_sb);
+      GPR_ASSERT(tsi_zero_copy_grpc_protector_unprotect(
+                     receiver, &var->staging_sb, &var->unprotected_sb) ==
+                 TSI_OK);
+    }
+    GPR_ASSERT(tsi_zero_copy_grpc_protector_unprotect(
+                   receiver, &var->protected_sb, &var->unprotected_sb) ==
+               TSI_OK);
+    GPR_ASSERT(
+        are_slice_buffers_equal(&var->unprotected_sb, &var->duplicate_sb));
+    alts_zero_copy_grpc_protector_test_var_destroy(var);
+  }
+  grpc_core::ExecCtx::Get()->Flush();
+}
+
+/* --- Test cases. --- */
+
+static void alts_zero_copy_protector_seal_unseal_small_buffer_tests() {
+  alts_zero_copy_grpc_protector_test_fixture* fixture =
+      alts_zero_copy_grpc_protector_test_fixture_create(
+          /*rekey=*/false, /*integrity_only=*/true);
+  seal_unseal_small_buffer(fixture->client, fixture->server);
+  seal_unseal_small_buffer(fixture->server, fixture->client);
+  alts_zero_copy_grpc_protector_test_fixture_destroy(fixture);
+
+  fixture = alts_zero_copy_grpc_protector_test_fixture_create(
+      /*rekey=*/false, /*integrity_only=*/false);
+  seal_unseal_small_buffer(fixture->client, fixture->server);
+  seal_unseal_small_buffer(fixture->server, fixture->client);
+  alts_zero_copy_grpc_protector_test_fixture_destroy(fixture);
+
+  fixture = alts_zero_copy_grpc_protector_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/true);
+  seal_unseal_small_buffer(fixture->client, fixture->server);
+  seal_unseal_small_buffer(fixture->server, fixture->client);
+  alts_zero_copy_grpc_protector_test_fixture_destroy(fixture);
+
+  fixture = alts_zero_copy_grpc_protector_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/false);
+  seal_unseal_small_buffer(fixture->client, fixture->server);
+  seal_unseal_small_buffer(fixture->server, fixture->client);
+  alts_zero_copy_grpc_protector_test_fixture_destroy(fixture);
+}
+
+static void alts_zero_copy_protector_seal_unseal_large_buffer_tests() {
+  alts_zero_copy_grpc_protector_test_fixture* fixture =
+      alts_zero_copy_grpc_protector_test_fixture_create(
+          /*rekey=*/false, /*integrity_only=*/true);
+  seal_unseal_large_buffer(fixture->client, fixture->server);
+  seal_unseal_large_buffer(fixture->server, fixture->client);
+  alts_zero_copy_grpc_protector_test_fixture_destroy(fixture);
+
+  fixture = alts_zero_copy_grpc_protector_test_fixture_create(
+      /*rekey=*/false, /*integrity_only=*/false);
+  seal_unseal_large_buffer(fixture->client, fixture->server);
+  seal_unseal_large_buffer(fixture->server, fixture->client);
+  alts_zero_copy_grpc_protector_test_fixture_destroy(fixture);
+
+  fixture = alts_zero_copy_grpc_protector_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/true);
+  seal_unseal_large_buffer(fixture->client, fixture->server);
+  seal_unseal_large_buffer(fixture->server, fixture->client);
+  alts_zero_copy_grpc_protector_test_fixture_destroy(fixture);
+
+  fixture = alts_zero_copy_grpc_protector_test_fixture_create(
+      /*rekey=*/true, /*integrity_only=*/false);
+  seal_unseal_large_buffer(fixture->client, fixture->server);
+  seal_unseal_large_buffer(fixture->server, fixture->client);
+  alts_zero_copy_grpc_protector_test_fixture_destroy(fixture);
+}
+
+int main(int argc, char** argv) {
+  alts_zero_copy_protector_seal_unseal_small_buffer_tests();
+  alts_zero_copy_protector_seal_unseal_large_buffer_tests();
+  return 0;
+}
diff --git a/test/core/tsi/fake_transport_security_test.cc b/test/core/tsi/fake_transport_security_test.cc
index bec81ed..5e66719 100644
--- a/test/core/tsi/fake_transport_security_test.cc
+++ b/test/core/tsi/fake_transport_security_test.cc
@@ -107,7 +107,7 @@
     tsi_test_frame_protector_config_destroy(fake_fixture->base.config);
     fake_fixture->base.config = tsi_test_frame_protector_config_create(
         bit_array[0], bit_array[1], bit_array[2], bit_array[3], bit_array[4],
-        bit_array[5], bit_array[6], bit_array[7]);
+        bit_array[5], bit_array[6]);
     tsi_test_do_round_trip(&fake_fixture->base);
     tsi_test_fixture_destroy(fixture);
   }
diff --git a/test/core/tsi/ssl_transport_security_test.cc b/test/core/tsi/ssl_transport_security_test.cc
index 8f255a3..d9eb747 100644
--- a/test/core/tsi/ssl_transport_security_test.cc
+++ b/test/core/tsi/ssl_transport_security_test.cc
@@ -528,7 +528,7 @@
     tsi_test_frame_protector_config_destroy(ssl_fixture->base.config);
     ssl_fixture->base.config = tsi_test_frame_protector_config_create(
         bit_array[0], bit_array[1], bit_array[2], bit_array[3], bit_array[4],
-        bit_array[5], bit_array[6], bit_array[7]);
+        bit_array[5], bit_array[6]);
     tsi_test_do_round_trip(&ssl_fixture->base);
     tsi_test_fixture_destroy(fixture);
   }
diff --git a/test/core/tsi/transport_security_test_lib.cc b/test/core/tsi/transport_security_test_lib.cc
index 8ea83f7..26349db 100644
--- a/test/core/tsi/transport_security_test_lib.cc
+++ b/test/core/tsi/transport_security_test_lib.cc
@@ -110,27 +110,29 @@
   fixture->vtable->check_handshaker_peers(fixture);
   /* Check unused bytes. */
   if (fixture->test_unused_bytes) {
+    tsi_test_channel* channel = fixture->channel;
     if (fixture->server_result != nullptr &&
         fixture->client_result != nullptr) {
       check_unused_bytes(fixture);
     }
-    fixture->bytes_written_to_server_channel = 0;
-    fixture->bytes_written_to_client_channel = 0;
-    fixture->bytes_read_from_client_channel = 0;
-    fixture->bytes_read_from_server_channel = 0;
+    channel->bytes_written_to_server_channel = 0;
+    channel->bytes_written_to_client_channel = 0;
+    channel->bytes_read_from_client_channel = 0;
+    channel->bytes_read_from_server_channel = 0;
   }
 }
 
-static void send_bytes_to_peer(tsi_test_fixture* fixture,
+static void send_bytes_to_peer(tsi_test_channel* test_channel,
                                const unsigned char* buf, size_t buf_size,
                                bool is_client) {
-  GPR_ASSERT(fixture != nullptr);
+  GPR_ASSERT(test_channel != nullptr);
   GPR_ASSERT(buf != nullptr);
   uint8_t* channel =
-      is_client ? fixture->server_channel : fixture->client_channel;
+      is_client ? test_channel->server_channel : test_channel->client_channel;
   GPR_ASSERT(channel != nullptr);
-  size_t* bytes_written = is_client ? &fixture->bytes_written_to_server_channel
-                                    : &fixture->bytes_written_to_client_channel;
+  size_t* bytes_written = is_client
+                              ? &test_channel->bytes_written_to_server_channel
+                              : &test_channel->bytes_written_to_client_channel;
   GPR_ASSERT(bytes_written != nullptr);
   GPR_ASSERT(*bytes_written + buf_size <= TSI_TEST_DEFAULT_CHANNEL_SIZE);
   /* Write data to channel. */
@@ -145,7 +147,8 @@
   if (fixture->test_unused_bytes && !args->appended_unused_bytes) {
     args->appended_unused_bytes = true;
     send_bytes_to_peer(
-        fixture, reinterpret_cast<const unsigned char*>(TSI_TEST_UNUSED_BYTES),
+        fixture->channel,
+        reinterpret_cast<const unsigned char*>(TSI_TEST_UNUSED_BYTES),
         strlen(TSI_TEST_UNUSED_BYTES), args->is_client);
     if (fixture->client_result != nullptr &&
         fixture->server_result == nullptr) {
@@ -154,19 +157,21 @@
   }
 }
 
-static void receive_bytes_from_peer(tsi_test_fixture* fixture,
+static void receive_bytes_from_peer(tsi_test_channel* test_channel,
                                     unsigned char** buf, size_t* buf_size,
                                     bool is_client) {
-  GPR_ASSERT(fixture != nullptr);
+  GPR_ASSERT(test_channel != nullptr);
   GPR_ASSERT(*buf != nullptr);
   GPR_ASSERT(buf_size != nullptr);
   uint8_t* channel =
-      is_client ? fixture->client_channel : fixture->server_channel;
+      is_client ? test_channel->client_channel : test_channel->server_channel;
   GPR_ASSERT(channel != nullptr);
-  size_t* bytes_read = is_client ? &fixture->bytes_read_from_client_channel
-                                 : &fixture->bytes_read_from_server_channel;
-  size_t* bytes_written = is_client ? &fixture->bytes_written_to_client_channel
-                                    : &fixture->bytes_written_to_server_channel;
+  size_t* bytes_read = is_client
+                           ? &test_channel->bytes_read_from_client_channel
+                           : &test_channel->bytes_read_from_server_channel;
+  size_t* bytes_written = is_client
+                              ? &test_channel->bytes_written_to_client_channel
+                              : &test_channel->bytes_written_to_server_channel;
   GPR_ASSERT(bytes_read != nullptr);
   GPR_ASSERT(bytes_written != nullptr);
   size_t to_read = *buf_size < *bytes_written - *bytes_read
@@ -178,14 +183,13 @@
   *bytes_read += to_read;
 }
 
-static void send_message_to_peer(tsi_test_fixture* fixture,
-                                 tsi_frame_protector* protector,
-                                 bool is_client) {
+void tsi_test_frame_protector_send_message_to_peer(
+    tsi_test_frame_protector_config* config, tsi_test_channel* channel,
+    tsi_frame_protector* protector, bool is_client) {
   /* Initialization. */
-  GPR_ASSERT(fixture != nullptr);
-  GPR_ASSERT(fixture->config != nullptr);
+  GPR_ASSERT(config != nullptr);
+  GPR_ASSERT(channel != nullptr);
   GPR_ASSERT(protector != nullptr);
-  tsi_test_frame_protector_config* config = fixture->config;
   unsigned char* protected_buffer =
       static_cast<unsigned char*>(gpr_zalloc(config->protected_buffer_size));
   size_t message_size =
@@ -205,7 +209,7 @@
         &protected_buffer_size_to_send);
     GPR_ASSERT(result == TSI_OK);
     /* Send protected data to peer. */
-    send_bytes_to_peer(fixture, protected_buffer, protected_buffer_size_to_send,
+    send_bytes_to_peer(channel, protected_buffer, protected_buffer_size_to_send,
                        is_client);
     message_bytes += processed_message_size;
     message_size -= processed_message_size;
@@ -218,7 +222,7 @@
             protector, protected_buffer, &protected_buffer_size_to_send,
             &still_pending_size);
         GPR_ASSERT(result == TSI_OK);
-        send_bytes_to_peer(fixture, protected_buffer,
+        send_bytes_to_peer(channel, protected_buffer,
                            protected_buffer_size_to_send, is_client);
       } while (still_pending_size > 0 && result == TSI_OK);
       GPR_ASSERT(result == TSI_OK);
@@ -228,17 +232,16 @@
   gpr_free(protected_buffer);
 }
 
-static void receive_message_from_peer(tsi_test_fixture* fixture,
-                                      tsi_frame_protector* protector,
-                                      unsigned char* message,
-                                      size_t* bytes_received, bool is_client) {
+void tsi_test_frame_protector_receive_message_from_peer(
+    tsi_test_frame_protector_config* config, tsi_test_channel* channel,
+    tsi_frame_protector* protector, unsigned char* message,
+    size_t* bytes_received, bool is_client) {
   /* Initialization. */
-  GPR_ASSERT(fixture != nullptr);
+  GPR_ASSERT(config != nullptr);
+  GPR_ASSERT(channel != nullptr);
   GPR_ASSERT(protector != nullptr);
   GPR_ASSERT(message != nullptr);
   GPR_ASSERT(bytes_received != nullptr);
-  GPR_ASSERT(fixture->config != nullptr);
-  tsi_test_frame_protector_config* config = fixture->config;
   size_t read_offset = 0;
   size_t message_offset = 0;
   size_t read_from_peer_size = 0;
@@ -253,7 +256,7 @@
     /* Receive data from peer. */
     if (read_from_peer_size == 0) {
       read_from_peer_size = config->read_buffer_allocated_size;
-      receive_bytes_from_peer(fixture, &read_buffer, &read_from_peer_size,
+      receive_bytes_from_peer(channel, &read_buffer, &read_from_peer_size,
                               is_client);
       read_offset = 0;
     }
@@ -314,7 +317,7 @@
   }
   /* Send data to peer, if needed. */
   if (bytes_to_send_size > 0) {
-    send_bytes_to_peer(args->fixture, bytes_to_send, bytes_to_send_size,
+    send_bytes_to_peer(fixture->channel, bytes_to_send, bytes_to_send_size,
                        args->is_client);
     args->transferred_data = true;
   }
@@ -361,8 +364,8 @@
   /* Receive data from peer, if available. */
   do {
     size_t buf_size = args->handshake_buffer_size;
-    receive_bytes_from_peer(args->fixture, &args->handshake_buffer, &buf_size,
-                            args->is_client);
+    receive_bytes_from_peer(fixture->channel, &args->handshake_buffer,
+                            &buf_size, args->is_client);
     if (buf_size > 0) {
       args->transferred_data = true;
     }
@@ -411,6 +414,50 @@
   handshaker_args_destroy(server_args);
 }
 
+static void tsi_test_do_ping_pong(tsi_test_frame_protector_config* config,
+                                  tsi_test_channel* channel,
+                                  tsi_frame_protector* client_frame_protector,
+                                  tsi_frame_protector* server_frame_protector) {
+  GPR_ASSERT(config != nullptr);
+  GPR_ASSERT(channel != nullptr);
+  GPR_ASSERT(client_frame_protector != nullptr);
+  GPR_ASSERT(server_frame_protector != nullptr);
+  /* Client sends a message to server. */
+  tsi_test_frame_protector_send_message_to_peer(
+      config, channel, client_frame_protector, true /* is_client */);
+  unsigned char* server_received_message =
+      static_cast<unsigned char*>(gpr_zalloc(TSI_TEST_DEFAULT_CHANNEL_SIZE));
+  size_t server_received_message_size = 0;
+  tsi_test_frame_protector_receive_message_from_peer(
+      config, channel, server_frame_protector, server_received_message,
+      &server_received_message_size, false /* is_client */);
+  GPR_ASSERT(config->client_message_size == server_received_message_size);
+  GPR_ASSERT(memcmp(config->client_message, server_received_message,
+                    server_received_message_size) == 0);
+  /* Server sends a message to client. */
+  tsi_test_frame_protector_send_message_to_peer(
+      config, channel, server_frame_protector, false /* is_client */);
+  unsigned char* client_received_message =
+      static_cast<unsigned char*>(gpr_zalloc(TSI_TEST_DEFAULT_CHANNEL_SIZE));
+  size_t client_received_message_size = 0;
+  tsi_test_frame_protector_receive_message_from_peer(
+      config, channel, client_frame_protector, client_received_message,
+      &client_received_message_size, true /* is_client */);
+  GPR_ASSERT(config->server_message_size == client_received_message_size);
+  GPR_ASSERT(memcmp(config->server_message, client_received_message,
+                    client_received_message_size) == 0);
+  gpr_free(server_received_message);
+  gpr_free(client_received_message);
+}
+
+void tsi_test_frame_protector_do_round_trip_no_handshake(
+    tsi_test_frame_protector_fixture* fixture) {
+  GPR_ASSERT(fixture != nullptr);
+  tsi_test_do_ping_pong(fixture->config, fixture->channel,
+                        fixture->client_frame_protector,
+                        fixture->server_frame_protector);
+}
+
 void tsi_test_do_round_trip(tsi_test_fixture* fixture) {
   /* Initialization. */
   GPR_ASSERT(fixture != nullptr);
@@ -437,33 +484,11 @@
                      ? nullptr
                      : &server_max_output_protected_frame_size,
                  &server_frame_protector) == TSI_OK);
-  /* Client sends a message to server. */
-  send_message_to_peer(fixture, client_frame_protector, true /* is_client */);
-  unsigned char* server_received_message =
-      static_cast<unsigned char*>(gpr_zalloc(TSI_TEST_DEFAULT_CHANNEL_SIZE));
-  size_t server_received_message_size = 0;
-  receive_message_from_peer(
-      fixture, server_frame_protector, server_received_message,
-      &server_received_message_size, false /* is_client */);
-  GPR_ASSERT(config->client_message_size == server_received_message_size);
-  GPR_ASSERT(memcmp(config->client_message, server_received_message,
-                    server_received_message_size) == 0);
-  /* Server sends a message to client. */
-  send_message_to_peer(fixture, server_frame_protector, false /* is_client */);
-  unsigned char* client_received_message =
-      static_cast<unsigned char*>(gpr_zalloc(TSI_TEST_DEFAULT_CHANNEL_SIZE));
-  size_t client_received_message_size = 0;
-  receive_message_from_peer(
-      fixture, client_frame_protector, client_received_message,
-      &client_received_message_size, true /* is_client */);
-  GPR_ASSERT(config->server_message_size == client_received_message_size);
-  GPR_ASSERT(memcmp(config->server_message, client_received_message,
-                    client_received_message_size) == 0);
+  tsi_test_do_ping_pong(config, fixture->channel, client_frame_protector,
+                        server_frame_protector);
   /* Destroy server and client frame protectors. */
   tsi_frame_protector_destroy(client_frame_protector);
   tsi_frame_protector_destroy(server_frame_protector);
-  gpr_free(server_received_message);
-  gpr_free(client_received_message);
 }
 
 static unsigned char* generate_random_message(size_t size) {
@@ -483,8 +508,7 @@
     bool use_default_protected_buffer_size, bool use_default_client_message,
     bool use_default_server_message,
     bool use_default_client_max_output_protected_frame_size,
-    bool use_default_server_max_output_protected_frame_size,
-    bool use_default_handshake_buffer_size) {
+    bool use_default_server_max_output_protected_frame_size) {
   tsi_test_frame_protector_config* config =
       static_cast<tsi_test_frame_protector_config*>(
           gpr_zalloc(sizeof(*config)));
@@ -552,24 +576,42 @@
 
 void tsi_test_frame_protector_config_destroy(
     tsi_test_frame_protector_config* config) {
-  GPR_ASSERT(config != nullptr);
+  if (config == nullptr) {
+    return;
+  }
   gpr_free(config->client_message);
   gpr_free(config->server_message);
   gpr_free(config);
 }
 
+static tsi_test_channel* tsi_test_channel_create() {
+  tsi_test_channel* channel =
+      static_cast<tsi_test_channel*>(gpr_zalloc(sizeof(*channel)));
+  channel->client_channel =
+      static_cast<uint8_t*>(gpr_zalloc(TSI_TEST_DEFAULT_CHANNEL_SIZE));
+  channel->server_channel =
+      static_cast<uint8_t*>(gpr_zalloc(TSI_TEST_DEFAULT_CHANNEL_SIZE));
+  channel->bytes_written_to_client_channel = 0;
+  channel->bytes_written_to_server_channel = 0;
+  channel->bytes_read_from_client_channel = 0;
+  channel->bytes_read_from_server_channel = 0;
+  return channel;
+}
+
+static void tsi_test_channel_destroy(tsi_test_channel* channel) {
+  if (channel == nullptr) {
+    return;
+  }
+  gpr_free(channel->client_channel);
+  gpr_free(channel->server_channel);
+  gpr_free(channel);
+}
+
 void tsi_test_fixture_init(tsi_test_fixture* fixture) {
   fixture->config = tsi_test_frame_protector_config_create(
-      true, true, true, true, true, true, true, true);
+      true, true, true, true, true, true, true);
   fixture->handshake_buffer_size = TSI_TEST_DEFAULT_BUFFER_SIZE;
-  fixture->client_channel =
-      static_cast<uint8_t*>(gpr_zalloc(TSI_TEST_DEFAULT_CHANNEL_SIZE));
-  fixture->server_channel =
-      static_cast<uint8_t*>(gpr_zalloc(TSI_TEST_DEFAULT_CHANNEL_SIZE));
-  fixture->bytes_written_to_client_channel = 0;
-  fixture->bytes_written_to_server_channel = 0;
-  fixture->bytes_read_from_client_channel = 0;
-  fixture->bytes_read_from_server_channel = 0;
+  fixture->channel = tsi_test_channel_create();
   fixture->test_unused_bytes = true;
   fixture->has_client_finished_first = false;
   gpr_mu_init(&fixture->mu);
@@ -578,14 +620,15 @@
 }
 
 void tsi_test_fixture_destroy(tsi_test_fixture* fixture) {
-  GPR_ASSERT(fixture != nullptr);
+  if (fixture == nullptr) {
+    return;
+  }
   tsi_test_frame_protector_config_destroy(fixture->config);
   tsi_handshaker_destroy(fixture->client_handshaker);
   tsi_handshaker_destroy(fixture->server_handshaker);
   tsi_handshaker_result_destroy(fixture->client_result);
   tsi_handshaker_result_destroy(fixture->server_result);
-  gpr_free(fixture->client_channel);
-  gpr_free(fixture->server_channel);
+  tsi_test_channel_destroy(fixture->channel);
   GPR_ASSERT(fixture->vtable != nullptr);
   GPR_ASSERT(fixture->vtable->destruct != nullptr);
   fixture->vtable->destruct(fixture);
@@ -593,3 +636,34 @@
   gpr_cv_destroy(&fixture->cv);
   gpr_free(fixture);
 }
+
+tsi_test_frame_protector_fixture* tsi_test_frame_protector_fixture_create() {
+  tsi_test_frame_protector_fixture* fixture =
+      static_cast<tsi_test_frame_protector_fixture*>(
+          gpr_zalloc(sizeof(*fixture)));
+  fixture->config = tsi_test_frame_protector_config_create(
+      true, true, true, true, true, true, true);
+  fixture->channel = tsi_test_channel_create();
+  return fixture;
+}
+
+void tsi_test_frame_protector_fixture_init(
+    tsi_test_frame_protector_fixture* fixture,
+    tsi_frame_protector* client_frame_protector,
+    tsi_frame_protector* server_frame_protector) {
+  GPR_ASSERT(fixture != nullptr);
+  fixture->client_frame_protector = client_frame_protector;
+  fixture->server_frame_protector = server_frame_protector;
+}
+
+void tsi_test_frame_protector_fixture_destroy(
+    tsi_test_frame_protector_fixture* fixture) {
+  if (fixture == nullptr) {
+    return;
+  }
+  tsi_test_frame_protector_config_destroy(fixture->config);
+  tsi_test_channel_destroy(fixture->channel);
+  tsi_frame_protector_destroy(fixture->client_frame_protector);
+  tsi_frame_protector_destroy(fixture->server_frame_protector);
+  gpr_free(fixture);
+}
diff --git a/test/core/tsi/transport_security_test_lib.h b/test/core/tsi/transport_security_test_lib.h
index 9b07448..b6a431f 100644
--- a/test/core/tsi/transport_security_test_lib.h
+++ b/test/core/tsi/transport_security_test_lib.h
@@ -35,8 +35,8 @@
 #define TSI_TEST_DEFAULT_CHANNEL_SIZE 32768
 #define TSI_TEST_BIG_MESSAGE_SIZE 17000
 #define TSI_TEST_SMALL_MESSAGE_SIZE 10
-#define TSI_TEST_NUM_OF_ARGUMENTS 8
-#define TSI_TEST_NUM_OF_COMBINATIONS 256
+#define TSI_TEST_NUM_OF_ARGUMENTS 7
+#define TSI_TEST_NUM_OF_COMBINATIONS 128
 #define TSI_TEST_UNUSED_BYTES "HELLO GOOGLE"
 
 /* ---  tsi_test_fixture object ---
@@ -46,12 +46,22 @@
   protect/unprotect operations with respect to TSI implementations. */
 typedef struct tsi_test_fixture tsi_test_fixture;
 
-/* ---  tsi_test_frame_protector_config object ---
+/* ---  tsi_test_frame_protector_fixture object ---
+  The object wraps all necessary information used to test correctness of TSI
+  frame protector implementations. */
+typedef struct tsi_test_frame_protector_fixture
+    tsi_test_frame_protector_fixture;
 
+/* ---  tsi_test_frame_protector_config object ---
   This object is used to configure different parameters of TSI frame protector
   APIs. */
 typedef struct tsi_test_frame_protector_config tsi_test_frame_protector_config;
 
+/* ---  tsi_test_channel object ---
+  This object represents simulated channels between the client and server
+  from/to which they could read/write the exchanged information. */
+typedef struct tsi_test_channel tsi_test_channel;
+
 /* V-table for tsi_test_fixture operations that are implemented differently in
    different TSI implementations. */
 typedef struct tsi_test_fixture_vtable {
@@ -73,17 +83,8 @@
   tsi_handshaker_result* server_result;
   /* size of buffer used to store data received from the peer. */
   size_t handshake_buffer_size;
-  /* simulated channels between client and server. If the server (client)
-     wants to send data to the client (server), he will write data to
-     client_channel (server_channel), which will be read by client (server). */
-  uint8_t* client_channel;
-  uint8_t* server_channel;
-  /* size of data written to the client/server channel. */
-  size_t bytes_written_to_client_channel;
-  size_t bytes_written_to_server_channel;
-  /* size of data read from the client/server channel */
-  size_t bytes_read_from_client_channel;
-  size_t bytes_read_from_server_channel;
+  /* tsi_test_channel instance. */
+  tsi_test_channel* channel;
   /* tsi_test_frame_protector_config instance */
   tsi_test_frame_protector_config* config;
   /* a flag indicating if client has finished TSI handshake first (i.e., before
@@ -106,6 +107,30 @@
   bool notified;
 };
 
+struct tsi_test_frame_protector_fixture {
+  /* client/server TSI frame protectors whose ownership are transferred. */
+  tsi_frame_protector* client_frame_protector;
+  tsi_frame_protector* server_frame_protector;
+  /* tsi_test_channel instance. */
+  tsi_test_channel* channel;
+  /* tsi_test_frame_protector_config instance */
+  tsi_test_frame_protector_config* config;
+};
+
+struct tsi_test_channel {
+  /* simulated channels between client and server. If the server (client)
+     wants to send data to the client (server), he will write data to
+     client_channel (server_channel), which will be read by client (server). */
+  uint8_t* client_channel;
+  uint8_t* server_channel;
+  /* size of data written to the client/server channel. */
+  size_t bytes_written_to_client_channel;
+  size_t bytes_written_to_server_channel;
+  /* size of data read from the client/server channel */
+  size_t bytes_read_from_client_channel;
+  size_t bytes_read_from_server_channel;
+};
+
 struct tsi_test_frame_protector_config {
   /* size of buffer used to store protected frames to be unprotected. */
   size_t read_buffer_allocated_size;
@@ -135,8 +160,7 @@
     bool use_default_protected_buffer_size, bool use_default_client_message,
     bool use_default_server_message,
     bool use_default_client_max_output_protected_frame_size,
-    bool use_default_server_max_output_protected_frame_size,
-    bool use_default_handshake_buffer_size);
+    bool use_default_server_max_output_protected_frame_size);
 
 /* This method sets different buffer and frame sizes of a
    tsi_test_frame_protector_config instance with user provided values. */
@@ -160,6 +184,35 @@
    this function. */
 void tsi_test_fixture_destroy(tsi_test_fixture* fixture);
 
+/* This method creates a tsi_test_frame_protector_fixture instance. */
+tsi_test_frame_protector_fixture* tsi_test_frame_protector_fixture_create();
+
+/* This method initializes members of tsi_test_frame_protector_fixture instance.
+   Note that the struct instance should be allocated before making
+   this call. */
+void tsi_test_frame_protector_fixture_init(
+    tsi_test_frame_protector_fixture* fixture,
+    tsi_frame_protector* client_frame_protector,
+    tsi_frame_protector* server_frame_protector);
+
+/* This method destroys a tsi_test_frame_protector_fixture instance. Note that
+   the fixture intance must be dynamically allocated and will be freed by this
+   function. */
+void tsi_test_frame_protector_fixture_destroy(
+    tsi_test_frame_protector_fixture* fixture);
+
+/* This method performs a protect opeation on raw data and sends the result to
+   peer. */
+void tsi_test_frame_protector_send_message_to_peer(
+    tsi_test_frame_protector_config* config, tsi_test_channel* channel,
+    tsi_frame_protector* protector, bool is_client);
+
+/* This method receives message from peer and unprotects it. */
+void tsi_test_frame_protector_receive_message_from_peer(
+    tsi_test_frame_protector_config* config, tsi_test_channel* channel,
+    tsi_frame_protector* protector, unsigned char* message,
+    size_t* bytes_received, bool is_client);
+
 /* This method performs a full TSI handshake between a client and a server.
    Note that the test library will implement the new TSI handshaker API to
    perform handshakes. */
@@ -171,4 +224,8 @@
    the client and server switching its role. */
 void tsi_test_do_round_trip(tsi_test_fixture* fixture);
 
+/* This method performs the above round trip test without doing handshakes. */
+void tsi_test_frame_protector_do_round_trip_no_handshake(
+    tsi_test_frame_protector_fixture* fixture);
+
 #endif  // GRPC_TEST_CORE_TSI_TRANSPORT_SECURITY_TEST_LIB_H_
diff --git a/third_party/nanopb/pb.h b/third_party/nanopb/pb.h
index 4576f79..62dca73 100644
--- a/third_party/nanopb/pb.h
+++ b/third_party/nanopb/pb.h
@@ -25,7 +25,7 @@
 /* #define PB_FIELD_16BIT 1 */
 
 /* Add support for tag numbers > 65536 and fields larger than 65536 bytes. */
-/* #define PB_FIELD_32BIT 1 */
+/* #define PB_FIELD_32BIT 1 */ 
 
 /* Disable support for error messages in order to save some code space. */
 /* #define PB_NO_ERRMSG 1 */
diff --git a/tools/codegen/core/gen_nano_proto.sh b/tools/codegen/core/gen_nano_proto.sh
index 4246840..6ce1517 100755
--- a/tools/codegen/core/gen_nano_proto.sh
+++ b/tools/codegen/core/gen_nano_proto.sh
@@ -43,9 +43,9 @@
   echo "Input proto file '$INPUT_PROTO' doesn't exist."
   exit 2
 fi
+
 if [[ ! -f "${EXPECTED_OPTIONS_FILE_PATH}" ]]; then
-  echo "Expected nanopb options file '${EXPECTED_OPTIONS_FILE_PATH}' missing"
-  exit 3
+  echo "Input proto file may need .options file to be correctly compiled."
 fi
 
 if [[ "${OUTPUT_DIR:0:1}" != '/' ]]; then
@@ -81,6 +81,11 @@
 sed -i "s:$PROTO_BASENAME.pb.h:${GRPC_OUTPUT_DIR}/$PROTO_BASENAME.pb.h:g" \
   "$OUTPUT_DIR/$PROTO_BASENAME.pb.c"
 
+if [ $PROTO_BASENAME == "handshaker" ] || [ $PROTO_BASENAME == "altscontext" ]; then
+  sed -i "s:transport_security_common.pb.h:${GRPC_OUTPUT_DIR}/transport_security_common.pb.h:g" \
+    "$OUTPUT_DIR/$PROTO_BASENAME.pb.h"
+fi
+
 # Fix up the include guards such that they pass the check_include_guards.py
 # test. Assumes that the generated files are being placed in gRPC src dir.
 readonly INCLUDE_GUARD_BASE=`echo $GRPC_OUTPUT_DIR | tr [a-z/] [A-Z_] | sed s:^.*SRC_::`
diff --git a/tools/distrib/check_copyright.py b/tools/distrib/check_copyright.py
index 6e1a303..e7893a1 100755
--- a/tools/distrib/check_copyright.py
+++ b/tools/distrib/check_copyright.py
@@ -77,6 +77,12 @@
     'examples/python/route_guide/route_guide_pb2_grpc.py',
     'src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h',
     'src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c',
+    'src/core/tsi/alts/handshaker/altscontext.pb.h',
+    'src/core/tsi/alts/handshaker/altscontext.pb.c',
+    'src/core/tsi/alts/handshaker/handshaker.pb.h',
+    'src/core/tsi/alts/handshaker/handshaker.pb.c',
+    'src/core/tsi/alts/handshaker/transport_security_common.pb.h',
+    'src/core/tsi/alts/handshaker/transport_security_common.pb.c',
     'src/cpp/server/health/health.pb.h',
     'src/cpp/server/health/health.pb.c',
 
diff --git a/tools/distrib/check_include_guards.py b/tools/distrib/check_include_guards.py
index 05d34c2..b356a74 100755
--- a/tools/distrib/check_include_guards.py
+++ b/tools/distrib/check_include_guards.py
@@ -157,6 +157,9 @@
 
 KNOWN_BAD = set([
     'src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h',
+    'src/core/tsi/alts/handshaker/altscontext.pb.h',
+    'src/core/tsi/alts/handshaker/handshaker.pb.h',
+    'src/core/tsi/alts/handshaker/transport_security_common.pb.h',
     'include/grpc++/ext/reflection.grpc.pb.h',
     'include/grpc++/ext/reflection.pb.h',
 ])
diff --git a/tools/distrib/check_nanopb_output.sh b/tools/distrib/check_nanopb_output.sh
index a30b73f..8b5823b 100755
--- a/tools/distrib/check_nanopb_output.sh
+++ b/tools/distrib/check_nanopb_output.sh
@@ -15,6 +15,7 @@
 
 set -ex
 
+readonly NANOPB_ALTS_TMP_OUTPUT="$(mktemp -d)"
 readonly NANOPB_TMP_OUTPUT="$(mktemp -d)"
 readonly PROTOBUF_INSTALL_PREFIX="$(mktemp -d)"
 
@@ -55,3 +56,29 @@
   echo "Outputs differ: $NANOPB_TMP_OUTPUT vs $LOAD_BALANCER_GRPC_OUTPUT_PATH"
   exit 2
 fi
+
+#
+# Checks for handshaker.proto and transport_security_common.proto
+#
+readonly HANDSHAKER_GRPC_OUTPUT_PATH='src/core/tsi/alts/handshaker'
+# nanopb-compile the proto to a temp location
+./tools/codegen/core/gen_nano_proto.sh \
+  src/core/tsi/alts/handshaker/proto/handshaker.proto \
+  "$NANOPB_ALTS_TMP_OUTPUT" \
+  "$HANDSHAKER_GRPC_OUTPUT_PATH"
+./tools/codegen/core/gen_nano_proto.sh \
+  src/core/tsi/alts/handshaker/proto/transport_security_common.proto \
+  "$NANOPB_ALTS_TMP_OUTPUT" \
+  "$HANDSHAKER_GRPC_OUTPUT_PATH"
+./tools/codegen/core/gen_nano_proto.sh \
+  src/core/tsi/alts/handshaker/proto/altscontext.proto \
+  "$NANOPB_ALTS_TMP_OUTPUT" \
+  "$HANDSHAKER_GRPC_OUTPUT_PATH"
+
+# compare outputs to checked compiled code
+for NANOPB_OUTPUT_FILE in $NANOPB_ALTS_TMP_OUTPUT/*.pb.*; do
+  if ! diff "$NANOPB_OUTPUT_FILE" "src/core/tsi/alts/handshaker/$(basename $NANOPB_OUTPUT_FILE)"; then
+    echo "Outputs differ: $NANOPB_ALTS_TMP_OUTPUT vs $HANDSHAKER_GRPC_OUTPUT_PATH"
+    exit 2
+  fi
+done
diff --git a/tools/doxygen/Doxyfile.core.internal b/tools/doxygen/Doxyfile.core.internal
index 57f9147..e7e9e04 100644
--- a/tools/doxygen/Doxyfile.core.internal
+++ b/tools/doxygen/Doxyfile.core.internal
@@ -1284,6 +1284,17 @@
 src/core/lib/profiling/timers.h \
 src/core/lib/security/context/security_context.cc \
 src/core/lib/security/context/security_context.h \
+src/core/lib/security/credentials/alts/alts_credentials.cc \
+src/core/lib/security/credentials/alts/alts_credentials.h \
+src/core/lib/security/credentials/alts/check_gcp_environment.cc \
+src/core/lib/security/credentials/alts/check_gcp_environment.h \
+src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc \
+src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc \
+src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc \
+src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc \
+src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc \
+src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h \
+src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc \
 src/core/lib/security/credentials/composite/composite_credentials.cc \
 src/core/lib/security/credentials/composite/composite_credentials.h \
 src/core/lib/security/credentials/credentials.cc \
@@ -1308,6 +1319,8 @@
 src/core/lib/security/credentials/plugin/plugin_credentials.h \
 src/core/lib/security/credentials/ssl/ssl_credentials.cc \
 src/core/lib/security/credentials/ssl/ssl_credentials.h \
+src/core/lib/security/security_connector/alts_security_connector.cc \
+src/core/lib/security/security_connector/alts_security_connector.h \
 src/core/lib/security/security_connector/security_connector.cc \
 src/core/lib/security/security_connector/security_connector.h \
 src/core/lib/security/transport/auth_filters.h \
@@ -1401,6 +1414,53 @@
 src/core/lib/transport/transport_op_string.cc \
 src/core/plugin_registry/grpc_plugin_registry.cc \
 src/core/tsi/README.md \
+src/core/tsi/alts/crypt/aes_gcm.cc \
+src/core/tsi/alts/crypt/gsec.cc \
+src/core/tsi/alts/crypt/gsec.h \
+src/core/tsi/alts/frame_protector/alts_counter.cc \
+src/core/tsi/alts/frame_protector/alts_counter.h \
+src/core/tsi/alts/frame_protector/alts_crypter.cc \
+src/core/tsi/alts/frame_protector/alts_crypter.h \
+src/core/tsi/alts/frame_protector/alts_frame_protector.cc \
+src/core/tsi/alts/frame_protector/alts_frame_protector.h \
+src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc \
+src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h \
+src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc \
+src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc \
+src/core/tsi/alts/frame_protector/frame_handler.cc \
+src/core/tsi/alts/frame_protector/frame_handler.h \
+src/core/tsi/alts/handshaker/alts_handshaker_client.cc \
+src/core/tsi/alts/handshaker/alts_handshaker_client.h \
+src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc \
+src/core/tsi/alts/handshaker/alts_handshaker_service_api.h \
+src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc \
+src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h \
+src/core/tsi/alts/handshaker/alts_tsi_event.cc \
+src/core/tsi/alts/handshaker/alts_tsi_event.h \
+src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc \
+src/core/tsi/alts/handshaker/alts_tsi_handshaker.h \
+src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h \
+src/core/tsi/alts/handshaker/alts_tsi_utils.cc \
+src/core/tsi/alts/handshaker/alts_tsi_utils.h \
+src/core/tsi/alts/handshaker/altscontext.pb.c \
+src/core/tsi/alts/handshaker/altscontext.pb.h \
+src/core/tsi/alts/handshaker/handshaker.pb.c \
+src/core/tsi/alts/handshaker/handshaker.pb.h \
+src/core/tsi/alts/handshaker/transport_security_common.pb.c \
+src/core/tsi/alts/handshaker/transport_security_common.pb.h \
+src/core/tsi/alts/handshaker/transport_security_common_api.cc \
+src/core/tsi/alts/handshaker/transport_security_common_api.h \
+src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc \
+src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h \
+src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc \
+src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h \
+src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h \
+src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc \
+src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h \
+src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc \
+src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h \
+src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc \
+src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h \
 src/core/tsi/alts_transport_security.cc \
 src/core/tsi/alts_transport_security.h \
 src/core/tsi/fake_transport_security.cc \
diff --git a/tools/run_tests/generated/sources_and_headers.json b/tools/run_tests/generated/sources_and_headers.json
index 6b8b26f..7249671 100644
--- a/tools/run_tests/generated/sources_and_headers.json
+++ b/tools/run_tests/generated/sources_and_headers.json
@@ -2417,6 +2417,215 @@
   }, 
   {
     "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_counter_test", 
+    "src": [
+      "test/core/tsi/alts/frame_protector/alts_counter_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "gpr_test_util", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_crypt_test", 
+    "src": [
+      "test/core/tsi/alts/crypt/aes_gcm_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_crypter_test", 
+    "src": [
+      "test/core/tsi/alts/frame_protector/alts_crypter_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_frame_handler_test", 
+    "src": [
+      "test/core/tsi/alts/frame_protector/frame_handler_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc", 
+      "transport_security_test_lib"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_frame_protector_test", 
+    "src": [
+      "test/core/tsi/alts/frame_protector/alts_frame_protector_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_grpc_record_protocol_test", 
+    "src": [
+      "test/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_handshaker_client_test", 
+    "src": [
+      "test/core/tsi/alts/handshaker/alts_handshaker_client_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_handshaker_service_api_test", 
+    "src": [
+      "test/core/tsi/alts/handshaker/alts_handshaker_service_api_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_iovec_record_protocol_test", 
+    "src": [
+      "test/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_security_connector_test", 
+    "src": [
+      "test/core/security/alts_security_connector_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_tsi_handshaker_test", 
+    "src": [
+      "test/core/tsi/alts/handshaker/alts_tsi_handshaker_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_tsi_utils_test", 
+    "src": [
+      "test/core/tsi/alts/handshaker/alts_tsi_utils_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "alts_zero_copy_grpc_protector_test", 
+    "src": [
+      "test/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
       "gpr", 
       "gpr_test_util", 
       "grpc", 
@@ -2828,6 +3037,36 @@
   {
     "deps": [
       "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "check_gcp_environment_linux_test", 
+    "src": [
+      "test/core/security/check_gcp_environment_linux_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "check_gcp_environment_windows_test", 
+    "src": [
+      "test/core/security/check_gcp_environment_windows_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "gpr", 
       "gpr_test_util", 
       "grpc", 
       "grpc_test_util"
@@ -3213,6 +3452,21 @@
   {
     "deps": [
       "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "grpc_alts_credentials_options_test", 
+    "src": [
+      "test/core/security/grpc_alts_credentials_options_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "gpr", 
       "grpc", 
       "grpc++", 
       "grpc++_proto_reflection_desc_db", 
@@ -4373,6 +4627,22 @@
   }, 
   {
     "deps": [
+      "alts_test_util", 
+      "gpr", 
+      "grpc"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c++", 
+    "name": "transport_security_common_api_test", 
+    "src": [
+      "test/core/tsi/alts/handshaker/transport_security_common_api_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
       "gpr", 
       "gpr_test_util", 
       "grpc", 
@@ -6291,6 +6561,26 @@
   }, 
   {
     "deps": [
+      "grpc"
+    ], 
+    "headers": [
+      "test/core/tsi/alts/crypt/gsec_test_util.h", 
+      "test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.h"
+    ], 
+    "is_filegroup": false, 
+    "language": "c", 
+    "name": "alts_test_util", 
+    "src": [
+      "test/core/tsi/alts/crypt/gsec_test_util.cc", 
+      "test/core/tsi/alts/crypt/gsec_test_util.h", 
+      "test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.cc", 
+      "test/core/tsi/alts/handshaker/alts_handshaker_service_api_test_lib.h"
+    ], 
+    "third_party": false, 
+    "type": "lib"
+  }, 
+  {
+    "deps": [
       "gpr_base"
     ], 
     "headers": [], 
@@ -8289,6 +8579,138 @@
   }, 
   {
     "deps": [
+      "nanopb"
+    ], 
+    "headers": [
+      "src/core/tsi/alts/handshaker/altscontext.pb.h", 
+      "src/core/tsi/alts/handshaker/handshaker.pb.h", 
+      "src/core/tsi/alts/handshaker/transport_security_common.pb.h"
+    ], 
+    "is_filegroup": true, 
+    "language": "c", 
+    "name": "alts_proto", 
+    "src": [
+      "src/core/tsi/alts/handshaker/altscontext.pb.c", 
+      "src/core/tsi/alts/handshaker/altscontext.pb.h", 
+      "src/core/tsi/alts/handshaker/handshaker.pb.c", 
+      "src/core/tsi/alts/handshaker/handshaker.pb.h", 
+      "src/core/tsi/alts/handshaker/transport_security_common.pb.c", 
+      "src/core/tsi/alts/handshaker/transport_security_common.pb.h"
+    ], 
+    "third_party": false, 
+    "type": "filegroup"
+  }, 
+  {
+    "deps": [
+      "alts_util", 
+      "gpr", 
+      "grpc_base", 
+      "grpc_transport_chttp2_client_insecure", 
+      "tsi", 
+      "tsi_interface"
+    ], 
+    "headers": [
+      "src/core/tsi/alts/crypt/gsec.h", 
+      "src/core/tsi/alts/frame_protector/alts_counter.h", 
+      "src/core/tsi/alts/frame_protector/alts_crypter.h", 
+      "src/core/tsi/alts/frame_protector/alts_frame_protector.h", 
+      "src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h", 
+      "src/core/tsi/alts/frame_protector/frame_handler.h", 
+      "src/core/tsi/alts/handshaker/alts_handshaker_client.h", 
+      "src/core/tsi/alts/handshaker/alts_tsi_event.h", 
+      "src/core/tsi/alts/handshaker/alts_tsi_handshaker.h", 
+      "src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h"
+    ], 
+    "is_filegroup": true, 
+    "language": "c", 
+    "name": "alts_tsi", 
+    "src": [
+      "src/core/tsi/alts/crypt/aes_gcm.cc", 
+      "src/core/tsi/alts/crypt/gsec.cc", 
+      "src/core/tsi/alts/crypt/gsec.h", 
+      "src/core/tsi/alts/frame_protector/alts_counter.cc", 
+      "src/core/tsi/alts/frame_protector/alts_counter.h", 
+      "src/core/tsi/alts/frame_protector/alts_crypter.cc", 
+      "src/core/tsi/alts/frame_protector/alts_crypter.h", 
+      "src/core/tsi/alts/frame_protector/alts_frame_protector.cc", 
+      "src/core/tsi/alts/frame_protector/alts_frame_protector.h", 
+      "src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc", 
+      "src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h", 
+      "src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc", 
+      "src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc", 
+      "src/core/tsi/alts/frame_protector/frame_handler.cc", 
+      "src/core/tsi/alts/frame_protector/frame_handler.h", 
+      "src/core/tsi/alts/handshaker/alts_handshaker_client.cc", 
+      "src/core/tsi/alts/handshaker/alts_handshaker_client.h", 
+      "src/core/tsi/alts/handshaker/alts_tsi_event.cc", 
+      "src/core/tsi/alts/handshaker/alts_tsi_event.h", 
+      "src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc", 
+      "src/core/tsi/alts/handshaker/alts_tsi_handshaker.h", 
+      "src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc", 
+      "src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h"
+    ], 
+    "third_party": false, 
+    "type": "filegroup"
+  }, 
+  {
+    "deps": [
+      "alts_proto", 
+      "gpr", 
+      "grpc_base", 
+      "nanopb", 
+      "tsi_interface"
+    ], 
+    "headers": [
+      "src/core/lib/security/credentials/alts/check_gcp_environment.h", 
+      "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h", 
+      "src/core/tsi/alts/handshaker/alts_handshaker_service_api.h", 
+      "src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h", 
+      "src/core/tsi/alts/handshaker/alts_tsi_utils.h", 
+      "src/core/tsi/alts/handshaker/transport_security_common_api.h"
+    ], 
+    "is_filegroup": true, 
+    "language": "c", 
+    "name": "alts_util", 
+    "src": [
+      "src/core/lib/security/credentials/alts/check_gcp_environment.cc", 
+      "src/core/lib/security/credentials/alts/check_gcp_environment.h", 
+      "src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc", 
+      "src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc", 
+      "src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc", 
+      "src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc", 
+      "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc", 
+      "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h", 
+      "src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc", 
+      "src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc", 
+      "src/core/tsi/alts/handshaker/alts_handshaker_service_api.h", 
+      "src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc", 
+      "src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h", 
+      "src/core/tsi/alts/handshaker/alts_tsi_utils.cc", 
+      "src/core/tsi/alts/handshaker/alts_tsi_utils.h", 
+      "src/core/tsi/alts/handshaker/transport_security_common_api.cc", 
+      "src/core/tsi/alts/handshaker/transport_security_common_api.h"
+    ], 
+    "third_party": false, 
+    "type": "filegroup"
+  }, 
+  {
+    "deps": [
       "gpr", 
       "grpc_base", 
       "nanopb"
@@ -9371,6 +9793,7 @@
   }, 
   {
     "deps": [
+      "alts_tsi", 
       "gpr", 
       "grpc_base", 
       "grpc_transport_chttp2_alpn", 
@@ -9379,6 +9802,7 @@
     "headers": [
       "include/grpc/grpc_security.h", 
       "src/core/lib/security/context/security_context.h", 
+      "src/core/lib/security/credentials/alts/alts_credentials.h", 
       "src/core/lib/security/credentials/composite/composite_credentials.h", 
       "src/core/lib/security/credentials/credentials.h", 
       "src/core/lib/security/credentials/fake/fake_credentials.h", 
@@ -9390,6 +9814,7 @@
       "src/core/lib/security/credentials/oauth2/oauth2_credentials.h", 
       "src/core/lib/security/credentials/plugin/plugin_credentials.h", 
       "src/core/lib/security/credentials/ssl/ssl_credentials.h", 
+      "src/core/lib/security/security_connector/alts_security_connector.h", 
       "src/core/lib/security/security_connector/security_connector.h", 
       "src/core/lib/security/transport/auth_filters.h", 
       "src/core/lib/security/transport/secure_endpoint.h", 
@@ -9406,6 +9831,8 @@
       "src/core/lib/http/httpcli_security_connector.cc", 
       "src/core/lib/security/context/security_context.cc", 
       "src/core/lib/security/context/security_context.h", 
+      "src/core/lib/security/credentials/alts/alts_credentials.cc", 
+      "src/core/lib/security/credentials/alts/alts_credentials.h", 
       "src/core/lib/security/credentials/composite/composite_credentials.cc", 
       "src/core/lib/security/credentials/composite/composite_credentials.h", 
       "src/core/lib/security/credentials/credentials.cc", 
@@ -9430,6 +9857,8 @@
       "src/core/lib/security/credentials/plugin/plugin_credentials.h", 
       "src/core/lib/security/credentials/ssl/ssl_credentials.cc", 
       "src/core/lib/security/credentials/ssl/ssl_credentials.h", 
+      "src/core/lib/security/security_connector/alts_security_connector.cc", 
+      "src/core/lib/security/security_connector/alts_security_connector.h", 
       "src/core/lib/security/security_connector/security_connector.cc", 
       "src/core/lib/security/security_connector/security_connector.h", 
       "src/core/lib/security/transport/auth_filters.h", 
diff --git a/tools/run_tests/generated/tests.json b/tools/run_tests/generated/tests.json
index 6ce7ec2..b7fdb6f 100644
--- a/tools/run_tests/generated/tests.json
+++ b/tools/run_tests/generated/tests.json
@@ -2876,6 +2876,318 @@
     "exclude_configs": [], 
     "exclude_iomgrs": [], 
     "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_counter_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_crypt_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_crypter_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_frame_handler_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_frame_protector_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_grpc_record_protocol_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_handshaker_client_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_handshaker_service_api_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_iovec_record_protocol_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_security_connector_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_tsi_handshaker_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_tsi_utils_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "alts_zero_copy_grpc_protector_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
     "gtest": true, 
     "language": "c++", 
     "name": "async_end2end_test", 
@@ -3350,6 +3662,54 @@
     "exclude_configs": [], 
     "exclude_iomgrs": [], 
     "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "check_gcp_environment_linux_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "check_gcp_environment_windows_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
     "gtest": true, 
     "language": "c++", 
     "name": "chttp2_settings_timeout_test", 
@@ -3782,6 +4142,30 @@
     "exclude_configs": [], 
     "exclude_iomgrs": [], 
     "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "grpc_alts_credentials_options_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
     "gtest": true, 
     "language": "c++", 
     "name": "grpc_tool_test", 
@@ -4678,6 +5062,30 @@
     "ci_platforms": [
       "linux", 
       "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c++", 
+    "name": "transport_security_common_api_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "uses_polling": true
+  }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
       "posix"
     ], 
     "cpu_cost": 0.5,