add output feedback mode support + test vectors (aes)
diff --git a/cryptography/primitives/block/modes.py b/cryptography/primitives/block/modes.py
index c722e73..70ef817 100644
--- a/cryptography/primitives/block/modes.py
+++ b/cryptography/primitives/block/modes.py
@@ -28,4 +28,13 @@
name = "ECB"
+class OFB(object):
+ name = "OFB"
+
+ def __init__(self, initialization_vector):
+ super(OFB, self).__init__()
+ self.initialization_vector = initialization_vector
+
+
interfaces.ModeWithInitializationVector.register(CBC)
+interfaces.ModeWithInitializationVector.register(OFB)
diff --git a/docs/primitives/symmetric-encryption.rst b/docs/primitives/symmetric-encryption.rst
index d0429d4..7ec42a3 100644
--- a/docs/primitives/symmetric-encryption.rst
+++ b/docs/primitives/symmetric-encryption.rst
@@ -68,6 +68,19 @@
reuse an ``initialization_vector`` with
a given ``key``.
+.. class:: cryptography.primitives.block.modes.OFB(initialization_vector)
+
+ OFB (Output Feedback) is a mode of operation for block ciphers. It
+ transforms a block cipher into a stream cipher.
+
+ :param bytes initialization_vector: Must be random bytes. They do not need
+ to be kept secret (they can be included
+ in a transmitted message). Must be the
+ same number of bytes as the
+ ``block_size`` of the cipher. Do not
+ reuse an ``initialization_vector`` with
+ a given ``key``.
+
Insecure Modes
--------------
diff --git a/tests/primitives/test_nist.py b/tests/primitives/test_nist.py
index 3dc8277..0e16cc9 100644
--- a/tests/primitives/test_nist.py
+++ b/tests/primitives/test_nist.py
@@ -133,3 +133,50 @@
actual_ciphertext = cipher.encrypt(binascii.unhexlify(plaintext))
actual_ciphertext += cipher.finalize()
assert binascii.hexlify(actual_ciphertext) == ciphertext
+
+
+class TestAES_OFB(object):
+ @parameterize_encrypt_test(
+ "AES", "KAT",
+ ("key", "iv", "plaintext", "ciphertext"),
+ [
+ "OFBGFSbox128.rsp",
+ "OFBGFSbox192.rsp",
+ "OFBGFSbox256.rsp",
+ "OFBKeySbox128.rsp",
+ "OFBKeySbox192.rsp",
+ "OFBKeySbox256.rsp",
+ "OFBVarKey128.rsp",
+ "OFBVarKey192.rsp",
+ "OFBVarKey256.rsp",
+ "OFBVarTxt128.rsp",
+ "OFBVarTxt192.rsp",
+ "OFBVarTxt256.rsp",
+ ]
+ )
+ def test_KAT(self, key, iv, plaintext, ciphertext):
+ cipher = BlockCipher(
+ ciphers.AES(binascii.unhexlify(key)),
+ modes.OFB(binascii.unhexlify(iv))
+ )
+ actual_ciphertext = cipher.encrypt(binascii.unhexlify(plaintext))
+ actual_ciphertext += cipher.finalize()
+ assert binascii.hexlify(actual_ciphertext) == ciphertext
+
+ @parameterize_encrypt_test(
+ "AES", "MMT",
+ ("key", "iv", "plaintext", "ciphertext"),
+ [
+ "OFBMMT128.rsp",
+ "OFBMMT192.rsp",
+ "OFBMMT256.rsp",
+ ]
+ )
+ def test_MMT(self, key, iv, plaintext, ciphertext):
+ cipher = BlockCipher(
+ ciphers.AES(binascii.unhexlify(key)),
+ modes.OFB(binascii.unhexlify(iv))
+ )
+ actual_ciphertext = cipher.encrypt(binascii.unhexlify(plaintext))
+ actual_ciphertext += cipher.finalize()
+ assert binascii.hexlify(actual_ciphertext) == ciphertext