diff --git a/google/auth/crypt/__init__.py b/google/auth/crypt/__init__.py
new file mode 100644
index 0000000..fa59662
--- /dev/null
+++ b/google/auth/crypt/__init__.py
@@ -0,0 +1,79 @@
+# Copyright 2016 Google Inc.
+#
+# 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.
+
+"""Cryptography helpers for verifying and signing messages.
+
+The simplest way to verify signatures is using :func:`verify_signature`::
+
+    cert = open('certs.pem').read()
+    valid = crypt.verify_signature(message, signature, cert)
+
+If you're going to verify many messages with the same certificate, you can use
+:class:`RSAVerifier`::
+
+    cert = open('certs.pem').read()
+    verifier = crypt.RSAVerifier.from_string(cert)
+    valid = verifier.verify(message, signature)
+
+To sign messages use :class:`RSASigner` with a private key::
+
+    private_key = open('private_key.pem').read()
+    signer = crypt.RSASigner(private_key)
+    signature = signer.sign(message)
+"""
+
+import six
+
+from google.auth.crypt import base
+from google.auth.crypt import rsa
+
+
+__all__ = [
+    'RSASigner',
+    'RSAVerifier',
+    'Signer',
+    'Verifier',
+]
+
+# Aliases to maintain the v1.0.0 interface, as the crypt module was split
+# into submodules.
+Signer = base.Signer
+Verifier = base.Verifier
+RSASigner = rsa.RSASigner
+RSAVerifier = rsa.RSAVerifier
+
+
+def verify_signature(message, signature, certs):
+    """Verify an RSA cryptographic signature.
+
+    Checks that the provided ``signature`` was generated from ``bytes`` using
+    the private key associated with the ``cert``.
+
+    Args:
+        message (Union[str, bytes]): The plaintext message.
+        signature (Union[str, bytes]): The cryptographic signature to check.
+        certs (Union[Sequence, str, bytes]): The certificate or certificates
+            to use to check the signature.
+
+    Returns:
+        bool: True if the signature is valid, otherwise False.
+    """
+    if isinstance(certs, (six.text_type, six.binary_type)):
+        certs = [certs]
+
+    for cert in certs:
+        verifier = rsa.RSAVerifier.from_string(cert)
+        if verifier.verify(message, signature):
+            return True
+    return False
diff --git a/google/auth/crypt.py b/google/auth/crypt/_python_rsa.py
similarity index 68%
rename from google/auth/crypt.py
rename to google/auth/crypt/_python_rsa.py
index 65bf37f..1f6384d 100644
--- a/google/auth/crypt.py
+++ b/google/auth/crypt/_python_rsa.py
@@ -12,33 +12,15 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""Cryptography helpers for verifying and signing messages.
+"""Pure-Python RSA cryptography implementation.
 
 Uses the ``rsa``, ``pyasn1`` and ``pyasn1_modules`` packages
 to parse PEM files storing PKCS#1 or PKCS#8 keys as well as
 certificates. There is no support for p12 files.
-
-The simplest way to verify signatures is using :func:`verify_signature`::
-
-    cert = open('certs.pem').read()
-    valid = crypt.verify_signature(message, signature, cert)
-
-If you're going to verify many messages with the same certificate, you can use
-:class:`RSAVerifier`::
-
-    cert = open('certs.pem').read()
-    verifier = crypt.RSAVerifier.from_string(cert)
-    valid = verifier.verify(message, signature)
-
-
-To sign messages use :class:`RSASigner` with a private key::
-
-    private_key = open('private_key.pem').read()
-    signer = crypt.RSASigner(private_key)
-    signature = signer.sign(message)
-
 """
-import abc
+
+from __future__ import absolute_import
+
 import io
 import json
 
@@ -50,6 +32,7 @@
 import six
 
 from google.auth import _helpers
+from google.auth.crypt import base
 
 _POW2 = (128, 64, 32, 16, 8, 4, 2, 1)
 _CERTIFICATE_MARKER = b'-----BEGIN CERTIFICATE-----'
@@ -84,28 +67,7 @@
     return bytes(byte_vals)
 
 
-@six.add_metaclass(abc.ABCMeta)
-class Verifier(object):
-    """Abstract base class for crytographic signature verifiers."""
-
-    @abc.abstractmethod
-    def verify(self, message, signature):
-        """Verifies a message against a cryptographic signature.
-
-        Args:
-            message (Union[str, bytes]): The message to verify.
-            signature (Union[str, bytes]): The cryptography signature to check.
-
-        Returns:
-            bool: True if message was signed by the private key associated
-            with the public key that this object was constructed with.
-        """
-        # pylint: disable=missing-raises-doc,redundant-returns-doc
-        # (pylint doesn't recognize that this is abstract)
-        raise NotImplementedError('Verify must be implemented')
-
-
-class RSAVerifier(Verifier):
+class RSAVerifier(base.Verifier):
     """Verifies RSA cryptographic signatures using public keys.
 
     Args:
@@ -116,7 +78,7 @@
     def __init__(self, public_key):
         self._pubkey = public_key
 
-    @_helpers.copy_docstring(Verifier)
+    @_helpers.copy_docstring(base.Verifier)
     def verify(self, message, signature):
         message = _helpers.to_bytes(message)
         try:
@@ -157,56 +119,7 @@
         return cls(pubkey)
 
 
-def verify_signature(message, signature, certs):
-    """Verify an RSA cryptographic signature.
-
-    Checks that the provided ``signature`` was generated from ``bytes`` using
-    the private key associated with the ``cert``.
-
-    Args:
-        message (Union[str, bytes]): The plaintext message.
-        signature (Union[str, bytes]): The cryptographic signature to check.
-        certs (Union[Sequence, str, bytes]): The certificate or certificates
-            to use to check the signature.
-
-    Returns:
-        bool: True if the signature is valid, otherwise False.
-    """
-    if isinstance(certs, (six.text_type, six.binary_type)):
-        certs = [certs]
-
-    for cert in certs:
-        verifier = RSAVerifier.from_string(cert)
-        if verifier.verify(message, signature):
-            return True
-    return False
-
-
-@six.add_metaclass(abc.ABCMeta)
-class Signer(object):
-    """Abstract base class for cryptographic signers."""
-
-    @abc.abstractproperty
-    def key_id(self):
-        """Optional[str]: The key ID used to identify this private key."""
-        raise NotImplementedError('Key id must be implemented')
-
-    @abc.abstractmethod
-    def sign(self, message):
-        """Signs a message.
-
-        Args:
-            message (Union[str, bytes]): The message to be signed.
-
-        Returns:
-            bytes: The signature of the message.
-        """
-        # pylint: disable=missing-raises-doc,redundant-returns-doc
-        # (pylint doesn't recognize that this is abstract)
-        raise NotImplementedError('Sign must be implemented')
-
-
-class RSASigner(Signer):
+class RSASigner(base.Signer):
     """Signs messages with an RSA private key.
 
     Args:
@@ -221,11 +134,11 @@
         self._key_id = key_id
 
     @property
-    @_helpers.copy_docstring(Signer)
+    @_helpers.copy_docstring(base.Signer)
     def key_id(self):
         return self._key_id
 
-    @_helpers.copy_docstring(Signer)
+    @_helpers.copy_docstring(base.Signer)
     def sign(self, message):
         message = _helpers.to_bytes(message)
         return rsa.pkcs1.sign(message, self._key, 'SHA-256')
diff --git a/google/auth/crypt/base.py b/google/auth/crypt/base.py
new file mode 100644
index 0000000..05c5a2b
--- /dev/null
+++ b/google/auth/crypt/base.py
@@ -0,0 +1,64 @@
+# Copyright 2016 Google Inc.
+#
+# 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.
+
+"""Base classes for cryptographic signers and verifiers."""
+
+import abc
+
+import six
+
+
+@six.add_metaclass(abc.ABCMeta)
+class Verifier(object):
+    """Abstract base class for crytographic signature verifiers."""
+
+    @abc.abstractmethod
+    def verify(self, message, signature):
+        """Verifies a message against a cryptographic signature.
+
+        Args:
+            message (Union[str, bytes]): The message to verify.
+            signature (Union[str, bytes]): The cryptography signature to check.
+
+        Returns:
+            bool: True if message was signed by the private key associated
+            with the public key that this object was constructed with.
+        """
+        # pylint: disable=missing-raises-doc,redundant-returns-doc
+        # (pylint doesn't recognize that this is abstract)
+        raise NotImplementedError('Verify must be implemented')
+
+
+@six.add_metaclass(abc.ABCMeta)
+class Signer(object):
+    """Abstract base class for cryptographic signers."""
+
+    @abc.abstractproperty
+    def key_id(self):
+        """Optional[str]: The key ID used to identify this private key."""
+        raise NotImplementedError('Key id must be implemented')
+
+    @abc.abstractmethod
+    def sign(self, message):
+        """Signs a message.
+
+        Args:
+            message (Union[str, bytes]): The message to be signed.
+
+        Returns:
+            bytes: The signature of the message.
+        """
+        # pylint: disable=missing-raises-doc,redundant-returns-doc
+        # (pylint doesn't recognize that this is abstract)
+        raise NotImplementedError('Sign must be implemented')
diff --git a/google/auth/crypt/rsa.py b/google/auth/crypt/rsa.py
new file mode 100644
index 0000000..d0bf2a0
--- /dev/null
+++ b/google/auth/crypt/rsa.py
@@ -0,0 +1,20 @@
+# Copyright 2017 Google Inc.
+#
+# 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.
+
+"""RSA cryptography signer and verifier."""
+
+from google.auth.crypt import _python_rsa
+
+RSASigner = _python_rsa.RSASigner
+RSAVerifier = _python_rsa.RSAVerifier
diff --git a/tests/crypt/__init__.py b/tests/crypt/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tests/crypt/__init__.py
diff --git a/tests/test_crypt.py b/tests/crypt/test__python_rsa.py
similarity index 65%
rename from tests/test_crypt.py
rename to tests/crypt/test__python_rsa.py
index 56612da..cff1034 100644
--- a/tests/test_crypt.py
+++ b/tests/crypt/test__python_rsa.py
@@ -22,10 +22,10 @@
 import six
 
 from google.auth import _helpers
-from google.auth import crypt
+from google.auth.crypt import _python_rsa
 
 
-DATA_DIR = os.path.join(os.path.dirname(__file__), 'data')
+DATA_DIR = os.path.join(os.path.dirname(__file__), '..', 'data')
 
 # To generate privatekey.pem, privatekey.pub, and public_cert.pem:
 #   $ openssl req -new -newkey rsa:1024 -x509 -nodes -out public_cert.pem \
@@ -42,12 +42,6 @@
 with open(os.path.join(DATA_DIR, 'public_cert.pem'), 'rb') as fh:
     PUBLIC_CERT_BYTES = fh.read()
 
-# To generate other_cert.pem:
-#   $ openssl req -new -newkey rsa:1024 -x509 -nodes -out other_cert.pem
-
-with open(os.path.join(DATA_DIR, 'other_cert.pem'), 'rb') as fh:
-    OTHER_CERT_BYTES = fh.read()
-
 # To generate pem_from_pkcs12.pem and privatekey.p12:
 #   $ openssl pkcs12 -export -out privatekey.p12 -inkey privatekey.pem \
 #   >    -in public_cert.pem
@@ -67,72 +61,50 @@
     SERVICE_ACCOUNT_INFO = json.load(fh)
 
 
-def test_verify_signature():
-    to_sign = b'foo'
-    signer = crypt.RSASigner.from_string(PRIVATE_KEY_BYTES)
-    signature = signer.sign(to_sign)
-
-    assert crypt.verify_signature(
-        to_sign, signature, PUBLIC_CERT_BYTES)
-
-    # List of certs
-    assert crypt.verify_signature(
-        to_sign, signature, [OTHER_CERT_BYTES, PUBLIC_CERT_BYTES])
-
-
-def test_verify_signature_failure():
-    to_sign = b'foo'
-    signer = crypt.RSASigner.from_string(PRIVATE_KEY_BYTES)
-    signature = signer.sign(to_sign)
-
-    assert not crypt.verify_signature(
-        to_sign, signature, OTHER_CERT_BYTES)
-
-
 class TestRSAVerifier(object):
     def test_verify_success(self):
         to_sign = b'foo'
-        signer = crypt.RSASigner.from_string(PRIVATE_KEY_BYTES)
+        signer = _python_rsa.RSASigner.from_string(PRIVATE_KEY_BYTES)
         actual_signature = signer.sign(to_sign)
 
-        verifier = crypt.RSAVerifier.from_string(PUBLIC_KEY_BYTES)
+        verifier = _python_rsa.RSAVerifier.from_string(PUBLIC_KEY_BYTES)
         assert verifier.verify(to_sign, actual_signature)
 
     def test_verify_unicode_success(self):
         to_sign = u'foo'
-        signer = crypt.RSASigner.from_string(PRIVATE_KEY_BYTES)
+        signer = _python_rsa.RSASigner.from_string(PRIVATE_KEY_BYTES)
         actual_signature = signer.sign(to_sign)
 
-        verifier = crypt.RSAVerifier.from_string(PUBLIC_KEY_BYTES)
+        verifier = _python_rsa.RSAVerifier.from_string(PUBLIC_KEY_BYTES)
         assert verifier.verify(to_sign, actual_signature)
 
     def test_verify_failure(self):
-        verifier = crypt.RSAVerifier.from_string(PUBLIC_KEY_BYTES)
+        verifier = _python_rsa.RSAVerifier.from_string(PUBLIC_KEY_BYTES)
         bad_signature1 = b''
         assert not verifier.verify(b'foo', bad_signature1)
         bad_signature2 = b'a'
         assert not verifier.verify(b'foo', bad_signature2)
 
     def test_from_string_pub_key(self):
-        verifier = crypt.RSAVerifier.from_string(PUBLIC_KEY_BYTES)
-        assert isinstance(verifier, crypt.RSAVerifier)
+        verifier = _python_rsa.RSAVerifier.from_string(PUBLIC_KEY_BYTES)
+        assert isinstance(verifier, _python_rsa.RSAVerifier)
         assert isinstance(verifier._pubkey, rsa.key.PublicKey)
 
     def test_from_string_pub_key_unicode(self):
         public_key = _helpers.from_bytes(PUBLIC_KEY_BYTES)
-        verifier = crypt.RSAVerifier.from_string(public_key)
-        assert isinstance(verifier, crypt.RSAVerifier)
+        verifier = _python_rsa.RSAVerifier.from_string(public_key)
+        assert isinstance(verifier, _python_rsa.RSAVerifier)
         assert isinstance(verifier._pubkey, rsa.key.PublicKey)
 
     def test_from_string_pub_cert(self):
-        verifier = crypt.RSAVerifier.from_string(PUBLIC_CERT_BYTES)
-        assert isinstance(verifier, crypt.RSAVerifier)
+        verifier = _python_rsa.RSAVerifier.from_string(PUBLIC_CERT_BYTES)
+        assert isinstance(verifier, _python_rsa.RSAVerifier)
         assert isinstance(verifier._pubkey, rsa.key.PublicKey)
 
     def test_from_string_pub_cert_unicode(self):
         public_cert = _helpers.from_bytes(PUBLIC_CERT_BYTES)
-        verifier = crypt.RSAVerifier.from_string(public_cert)
-        assert isinstance(verifier, crypt.RSAVerifier)
+        verifier = _python_rsa.RSAVerifier.from_string(public_cert)
+        assert isinstance(verifier, _python_rsa.RSAVerifier)
         assert isinstance(verifier._pubkey, rsa.key.PublicKey)
 
     def test_from_string_pub_cert_failure(self):
@@ -144,32 +116,32 @@
 
         with load_pem_patch as load_pem:
             with pytest.raises(ValueError):
-                crypt.RSAVerifier.from_string(cert_bytes)
+                _python_rsa.RSAVerifier.from_string(cert_bytes)
             load_pem.assert_called_once_with(cert_bytes, 'CERTIFICATE')
 
 
 class TestRSASigner(object):
     def test_from_string_pkcs1(self):
-        signer = crypt.RSASigner.from_string(PKCS1_KEY_BYTES)
-        assert isinstance(signer, crypt.RSASigner)
+        signer = _python_rsa.RSASigner.from_string(PKCS1_KEY_BYTES)
+        assert isinstance(signer, _python_rsa.RSASigner)
         assert isinstance(signer._key, rsa.key.PrivateKey)
 
     def test_from_string_pkcs1_unicode(self):
         key_bytes = _helpers.from_bytes(PKCS1_KEY_BYTES)
-        signer = crypt.RSASigner.from_string(key_bytes)
-        assert isinstance(signer, crypt.RSASigner)
+        signer = _python_rsa.RSASigner.from_string(key_bytes)
+        assert isinstance(signer, _python_rsa.RSASigner)
         assert isinstance(signer._key, rsa.key.PrivateKey)
 
     def test_from_string_pkcs8(self):
-        signer = crypt.RSASigner.from_string(PKCS8_KEY_BYTES)
-        assert isinstance(signer, crypt.RSASigner)
+        signer = _python_rsa.RSASigner.from_string(PKCS8_KEY_BYTES)
+        assert isinstance(signer, _python_rsa.RSASigner)
         assert isinstance(signer._key, rsa.key.PrivateKey)
 
     def test_from_string_pkcs8_extra_bytes(self):
         key_bytes = PKCS8_KEY_BYTES
         _, pem_bytes = pem.readPemBlocksFromFile(
             six.StringIO(_helpers.from_bytes(key_bytes)),
-            crypt._PKCS8_MARKER)
+            _python_rsa._PKCS8_MARKER)
 
         key_info, remaining = None, 'extra'
         decode_patch = mock.patch(
@@ -179,44 +151,44 @@
 
         with decode_patch as decode:
             with pytest.raises(ValueError):
-                crypt.RSASigner.from_string(key_bytes)
+                _python_rsa.RSASigner.from_string(key_bytes)
             # Verify mock was called.
             decode.assert_called_once_with(
-                pem_bytes, asn1Spec=crypt._PKCS8_SPEC)
+                pem_bytes, asn1Spec=_python_rsa._PKCS8_SPEC)
 
     def test_from_string_pkcs8_unicode(self):
         key_bytes = _helpers.from_bytes(PKCS8_KEY_BYTES)
-        signer = crypt.RSASigner.from_string(key_bytes)
-        assert isinstance(signer, crypt.RSASigner)
+        signer = _python_rsa.RSASigner.from_string(key_bytes)
+        assert isinstance(signer, _python_rsa.RSASigner)
         assert isinstance(signer._key, rsa.key.PrivateKey)
 
     def test_from_string_pkcs12(self):
         with pytest.raises(ValueError):
-            crypt.RSASigner.from_string(PKCS12_KEY_BYTES)
+            _python_rsa.RSASigner.from_string(PKCS12_KEY_BYTES)
 
     def test_from_string_bogus_key(self):
         key_bytes = 'bogus-key'
         with pytest.raises(ValueError):
-            crypt.RSASigner.from_string(key_bytes)
+            _python_rsa.RSASigner.from_string(key_bytes)
 
     def test_from_service_account_info(self):
-        signer = crypt.RSASigner.from_service_account_info(
+        signer = _python_rsa.RSASigner.from_service_account_info(
             SERVICE_ACCOUNT_INFO)
 
         assert signer.key_id == SERVICE_ACCOUNT_INFO[
-            crypt._JSON_FILE_PRIVATE_KEY_ID]
+            _python_rsa._JSON_FILE_PRIVATE_KEY_ID]
         assert isinstance(signer._key, rsa.key.PrivateKey)
 
     def test_from_service_account_info_missing_key(self):
         with pytest.raises(ValueError) as excinfo:
-            crypt.RSASigner.from_service_account_info({})
+            _python_rsa.RSASigner.from_service_account_info({})
 
-        assert excinfo.match(crypt._JSON_FILE_PRIVATE_KEY)
+        assert excinfo.match(_python_rsa._JSON_FILE_PRIVATE_KEY)
 
     def test_from_service_account_file(self):
-        signer = crypt.RSASigner.from_service_account_file(
+        signer = _python_rsa.RSASigner.from_service_account_file(
             SERVICE_ACCOUNT_JSON_FILE)
 
         assert signer.key_id == SERVICE_ACCOUNT_INFO[
-            crypt._JSON_FILE_PRIVATE_KEY_ID]
+            _python_rsa._JSON_FILE_PRIVATE_KEY_ID]
         assert isinstance(signer._key, rsa.key.PrivateKey)
diff --git a/tests/crypt/test_crypt.py b/tests/crypt/test_crypt.py
new file mode 100644
index 0000000..d8b1d00
--- /dev/null
+++ b/tests/crypt/test_crypt.py
@@ -0,0 +1,59 @@
+# Copyright 2016 Google Inc.
+#
+# 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.
+
+import os
+
+from google.auth import crypt
+
+
+DATA_DIR = os.path.join(os.path.dirname(__file__), '..', 'data')
+
+# To generate privatekey.pem, privatekey.pub, and public_cert.pem:
+#   $ openssl req -new -newkey rsa:1024 -x509 -nodes -out public_cert.pem \
+#   >    -keyout privatekey.pem
+#   $ openssl rsa -in privatekey.pem -pubout -out privatekey.pub
+
+with open(os.path.join(DATA_DIR, 'privatekey.pem'), 'rb') as fh:
+    PRIVATE_KEY_BYTES = fh.read()
+
+with open(os.path.join(DATA_DIR, 'public_cert.pem'), 'rb') as fh:
+    PUBLIC_CERT_BYTES = fh.read()
+
+# To generate other_cert.pem:
+#   $ openssl req -new -newkey rsa:1024 -x509 -nodes -out other_cert.pem
+
+with open(os.path.join(DATA_DIR, 'other_cert.pem'), 'rb') as fh:
+    OTHER_CERT_BYTES = fh.read()
+
+
+def test_verify_signature():
+    to_sign = b'foo'
+    signer = crypt.RSASigner.from_string(PRIVATE_KEY_BYTES)
+    signature = signer.sign(to_sign)
+
+    assert crypt.verify_signature(
+        to_sign, signature, PUBLIC_CERT_BYTES)
+
+    # List of certs
+    assert crypt.verify_signature(
+        to_sign, signature, [OTHER_CERT_BYTES, PUBLIC_CERT_BYTES])
+
+
+def test_verify_signature_failure():
+    to_sign = b'foo'
+    signer = crypt.RSASigner.from_string(PRIVATE_KEY_BYTES)
+    signature = signer.sign(to_sign)
+
+    assert not crypt.verify_signature(
+        to_sign, signature, OTHER_CERT_BYTES)