From 13f108f926a84eec9c0598164f25cedaece567e3 Mon Sep 17 00:00:00 2001
From: Paul Kehrer <paul.l.kehrer@gmail.com>
Date: Mon, 9 Sep 2013 21:41:03 -0500
Subject: Add ECB class + docs + tests

* Slightly refactors test_nist to allow fetching of data that has no IV
* Does not modify create_block_cipher_context (next commit)
---
 cryptography/primitives/block/modes.py   |  7 +++++
 docs/primitives/symmetric-encryption.rst | 12 ++++++++
 tests/primitives/test_nist.py            | 47 ++++++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+)

diff --git a/cryptography/primitives/block/modes.py b/cryptography/primitives/block/modes.py
index de31f086..0bf8010b 100644
--- a/cryptography/primitives/block/modes.py
+++ b/cryptography/primitives/block/modes.py
@@ -20,3 +20,10 @@ class CBC(object):
     def __init__(self, initialization_vector):
         super(CBC, self).__init__()
         self.initialization_vector = initialization_vector
+
+
+class ECB(object):
+    name = "ECB"
+
+    def __init__(self):
+        super(ECB, self).__init__()
diff --git a/docs/primitives/symmetric-encryption.rst b/docs/primitives/symmetric-encryption.rst
index 1b8d1d73..8a9bbbdf 100644
--- a/docs/primitives/symmetric-encryption.rst
+++ b/docs/primitives/symmetric-encryption.rst
@@ -67,3 +67,15 @@ Modes
                                         ``block_size`` of the cipher. Do not
                                         reuse an ``initialization_vector`` with
                                         a given ``key``.
+
+
+Insecure Modes
+--------------
+
+.. class:: cryptography.primitives.block.modes.ECB()
+
+    ECB (Electronic Code Book) is the simplest mode of operation for block
+    ciphers. The data is separated into blocks and each block is encrypted
+    separately. This means identical plaintext blocks will always result in
+    identical encrypted blocks. Due to this property it is not recommended
+    for use. Really, don't use it. Just. Don't.
diff --git a/tests/primitives/test_nist.py b/tests/primitives/test_nist.py
index 8bef118e..3dc8277a 100644
--- a/tests/primitives/test_nist.py
+++ b/tests/primitives/test_nist.py
@@ -86,3 +86,50 @@ class TestAES_CBC(object):
         actual_ciphertext = cipher.encrypt(binascii.unhexlify(plaintext))
         actual_ciphertext += cipher.finalize()
         assert binascii.hexlify(actual_ciphertext) == ciphertext
+
+
+class TestAES_ECB(object):
+    @parameterize_encrypt_test(
+        "AES", "KAT",
+        ("key", "plaintext", "ciphertext"),
+        [
+            "ECBGFSbox128.rsp",
+            "ECBGFSbox192.rsp",
+            "ECBGFSbox256.rsp",
+            "ECBKeySbox128.rsp",
+            "ECBKeySbox192.rsp",
+            "ECBKeySbox256.rsp",
+            "ECBVarKey128.rsp",
+            "ECBVarKey192.rsp",
+            "ECBVarKey256.rsp",
+            "ECBVarTxt128.rsp",
+            "ECBVarTxt192.rsp",
+            "ECBVarTxt256.rsp",
+        ]
+    )
+    def test_KAT(self, key, plaintext, ciphertext):
+        cipher = BlockCipher(
+            ciphers.AES(binascii.unhexlify(key)),
+            modes.ECB()
+        )
+        actual_ciphertext = cipher.encrypt(binascii.unhexlify(plaintext))
+        actual_ciphertext += cipher.finalize()
+        assert binascii.hexlify(actual_ciphertext) == ciphertext
+
+    @parameterize_encrypt_test(
+        "AES", "MMT",
+        ("key", "plaintext", "ciphertext"),
+        [
+            "ECBMMT128.rsp",
+            "ECBMMT192.rsp",
+            "ECBMMT256.rsp",
+        ]
+    )
+    def test_MMT(self, key, plaintext, ciphertext):
+        cipher = BlockCipher(
+            ciphers.AES(binascii.unhexlify(key)),
+            modes.ECB()
+        )
+        actual_ciphertext = cipher.encrypt(binascii.unhexlify(plaintext))
+        actual_ciphertext += cipher.finalize()
+        assert binascii.hexlify(actual_ciphertext) == ciphertext
-- 
cgit v1.2.3


From fe9b82d1526113f6f08e5de9b8d5e75ab1527bbd Mon Sep 17 00:00:00 2001
From: Paul Kehrer <paul.l.kehrer@gmail.com>
Date: Mon, 9 Sep 2013 22:09:21 -0500
Subject: add ECB support to create_block_cipher_context

* This is a basic refactor to support ECB and CBC mode in this method.
  We can use this as a starting point to discuss a better solution.
---
 cryptography/bindings/openssl/api.py | 14 +++++++++++++-
 tests/bindings/test_openssl.py       |  6 ++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/cryptography/bindings/openssl/api.py b/cryptography/bindings/openssl/api.py
index 54a74d03..17823786 100644
--- a/cryptography/bindings/openssl/api.py
+++ b/cryptography/bindings/openssl/api.py
@@ -74,9 +74,11 @@ class API(object):
         assert evp_cipher != self._ffi.NULL
         # TODO: only use the key and initialization_vector as needed. Sometimes
         # this needs to be a DecryptInit, when?
+        iv = self._get_iv(mode)
+
         res = self._lib.EVP_EncryptInit_ex(
             ctx, evp_cipher, self._ffi.NULL, cipher.key,
-            mode.initialization_vector
+            iv
         )
         assert res != 0
 
@@ -85,6 +87,16 @@ class API(object):
         self._lib.EVP_CIPHER_CTX_set_padding(ctx, 0)
         return ctx
 
+    def _get_iv(self, mode):
+        # TODO: refactor this to visitor pattern
+        klass_name = mode.__class__.__name__
+        if klass_name == 'CBC':
+            return mode.initialization_vector
+        elif klass_name == 'ECB':
+            return self._ffi.NULL
+        else:
+            raise NotImplementedError
+
     def update_encrypt_context(self, ctx, plaintext):
         buf = self._ffi.new("unsigned char[]", len(plaintext))
         outlen = self._ffi.new("int *")
diff --git a/tests/bindings/test_openssl.py b/tests/bindings/test_openssl.py
index 1579f002..e4b73460 100644
--- a/tests/bindings/test_openssl.py
+++ b/tests/bindings/test_openssl.py
@@ -11,6 +11,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import pytest
+
 from cryptography.bindings.openssl import api
 
 
@@ -28,3 +30,7 @@ class TestOpenSSL(object):
         for every OpenSSL.
         """
         assert api.openssl_version_text().startswith("OpenSSL")
+
+    def test_get_iv_invalid_mode(self):
+        with pytest.raises(NotImplementedError):
+            api._get_iv(None)
-- 
cgit v1.2.3


From 09980a55fe5a3e4f586425a11b20ba89e84d0452 Mon Sep 17 00:00:00 2001
From: Paul Kehrer <paul.l.kehrer@gmail.com>
Date: Tue, 10 Sep 2013 08:24:30 -0500
Subject: remove unneeded init in ECB class, add warning to docs for ECB mode

---
 cryptography/primitives/block/modes.py   | 3 ---
 docs/primitives/symmetric-encryption.rst | 1 +
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/cryptography/primitives/block/modes.py b/cryptography/primitives/block/modes.py
index 0bf8010b..ac3392c5 100644
--- a/cryptography/primitives/block/modes.py
+++ b/cryptography/primitives/block/modes.py
@@ -24,6 +24,3 @@ class CBC(object):
 
 class ECB(object):
     name = "ECB"
-
-    def __init__(self):
-        super(ECB, self).__init__()
diff --git a/docs/primitives/symmetric-encryption.rst b/docs/primitives/symmetric-encryption.rst
index 8a9bbbdf..d0429d4b 100644
--- a/docs/primitives/symmetric-encryption.rst
+++ b/docs/primitives/symmetric-encryption.rst
@@ -72,6 +72,7 @@ Modes
 Insecure Modes
 --------------
 
+.. warning:: Do not use. This is an insecure mode.
 .. class:: cryptography.primitives.block.modes.ECB()
 
     ECB (Electronic Code Book) is the simplest mode of operation for block
-- 
cgit v1.2.3


From 29cfa6989bfbc9545c2b40e9e3b316e89c0c14ca Mon Sep 17 00:00:00 2001
From: Paul Kehrer <paul.l.kehrer@gmail.com>
Date: Tue, 10 Sep 2013 10:01:50 -0500
Subject: add get_iv_or_nonce() methods to replace _get_iv() on api

---
 cryptography/bindings/openssl/api.py   | 18 +++++-------------
 cryptography/primitives/block/modes.py |  6 ++++++
 tests/bindings/test_openssl.py         |  7 ++-----
 3 files changed, 13 insertions(+), 18 deletions(-)

diff --git a/cryptography/bindings/openssl/api.py b/cryptography/bindings/openssl/api.py
index 17823786..02957d74 100644
--- a/cryptography/bindings/openssl/api.py
+++ b/cryptography/bindings/openssl/api.py
@@ -72,13 +72,12 @@ class API(object):
         )
         evp_cipher = self._lib.EVP_get_cipherbyname(ciphername.encode("ascii"))
         assert evp_cipher != self._ffi.NULL
-        # TODO: only use the key and initialization_vector as needed. Sometimes
-        # this needs to be a DecryptInit, when?
-        iv = self._get_iv(mode)
+        iv_nonce = mode.get_iv_or_nonce(self)
 
+        # TODO: Sometimes this needs to be a DecryptInit, when?
         res = self._lib.EVP_EncryptInit_ex(
             ctx, evp_cipher, self._ffi.NULL, cipher.key,
-            iv
+            iv_nonce
         )
         assert res != 0
 
@@ -87,15 +86,8 @@ class API(object):
         self._lib.EVP_CIPHER_CTX_set_padding(ctx, 0)
         return ctx
 
-    def _get_iv(self, mode):
-        # TODO: refactor this to visitor pattern
-        klass_name = mode.__class__.__name__
-        if klass_name == 'CBC':
-            return mode.initialization_vector
-        elif klass_name == 'ECB':
-            return self._ffi.NULL
-        else:
-            raise NotImplementedError
+    def get_null_for_ecb(self):
+        return self._ffi.NULL
 
     def update_encrypt_context(self, ctx, plaintext):
         buf = self._ffi.new("unsigned char[]", len(plaintext))
diff --git a/cryptography/primitives/block/modes.py b/cryptography/primitives/block/modes.py
index ac3392c5..82141437 100644
--- a/cryptography/primitives/block/modes.py
+++ b/cryptography/primitives/block/modes.py
@@ -21,6 +21,12 @@ class CBC(object):
         super(CBC, self).__init__()
         self.initialization_vector = initialization_vector
 
+    def get_iv_or_nonce(self, api):
+        return self.initialization_vector
+
 
 class ECB(object):
     name = "ECB"
+
+    def get_iv_or_nonce(self, api):
+        return api.get_null_for_ecb()
diff --git a/tests/bindings/test_openssl.py b/tests/bindings/test_openssl.py
index e4b73460..c5927b76 100644
--- a/tests/bindings/test_openssl.py
+++ b/tests/bindings/test_openssl.py
@@ -11,8 +11,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import pytest
-
 from cryptography.bindings.openssl import api
 
 
@@ -31,6 +29,5 @@ class TestOpenSSL(object):
         """
         assert api.openssl_version_text().startswith("OpenSSL")
 
-    def test_get_iv_invalid_mode(self):
-        with pytest.raises(NotImplementedError):
-            api._get_iv(None)
+    def test_get_null_for_ecb(self):
+        assert api.get_null_for_ecb() == api._ffi.NULL
-- 
cgit v1.2.3


From dc689293704e9181af452aaef495e4c417160e40 Mon Sep 17 00:00:00 2001
From: Paul Kehrer <paul.l.kehrer@gmail.com>
Date: Tue, 10 Sep 2013 10:50:06 -0500
Subject: rename get_null_for_ecb to get_iv_for_ecb per alex's comments

---
 cryptography/bindings/openssl/api.py   | 2 +-
 cryptography/primitives/block/modes.py | 2 +-
 tests/bindings/test_openssl.py         | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/cryptography/bindings/openssl/api.py b/cryptography/bindings/openssl/api.py
index 02957d74..fd54a8ff 100644
--- a/cryptography/bindings/openssl/api.py
+++ b/cryptography/bindings/openssl/api.py
@@ -86,7 +86,7 @@ class API(object):
         self._lib.EVP_CIPHER_CTX_set_padding(ctx, 0)
         return ctx
 
-    def get_null_for_ecb(self):
+    def get_iv_for_ecb(self):
         return self._ffi.NULL
 
     def update_encrypt_context(self, ctx, plaintext):
diff --git a/cryptography/primitives/block/modes.py b/cryptography/primitives/block/modes.py
index 82141437..e4fc886e 100644
--- a/cryptography/primitives/block/modes.py
+++ b/cryptography/primitives/block/modes.py
@@ -29,4 +29,4 @@ class ECB(object):
     name = "ECB"
 
     def get_iv_or_nonce(self, api):
-        return api.get_null_for_ecb()
+        return api.get_iv_for_ecb()
diff --git a/tests/bindings/test_openssl.py b/tests/bindings/test_openssl.py
index c5927b76..f25236cc 100644
--- a/tests/bindings/test_openssl.py
+++ b/tests/bindings/test_openssl.py
@@ -29,5 +29,5 @@ class TestOpenSSL(object):
         """
         assert api.openssl_version_text().startswith("OpenSSL")
 
-    def test_get_null_for_ecb(self):
-        assert api.get_null_for_ecb() == api._ffi.NULL
+    def test_get_iv_for_ecb(self):
+        assert api.get_iv_for_ecb() == api._ffi.NULL
-- 
cgit v1.2.3


From 5266752c9e462ac988af3d222470a68b2950d2d6 Mon Sep 17 00:00:00 2001
From: Paul Kehrer <paul.l.kehrer@gmail.com>
Date: Tue, 10 Sep 2013 15:41:37 -0500
Subject: modify modes to use abc so api can determine what attribute to call

* Due to a circular dependency issue I had to put the abcs in
  cryptography.primitives.abc.block.modes
* The ABCs look like they do because that is the form that is compatible
  with 2.x and 3.x
---
 cryptography/bindings/openssl/api.py          | 13 ++++++++++---
 cryptography/primitives/abc/__init__.py       |  0
 cryptography/primitives/abc/block/__init__.py |  0
 cryptography/primitives/abc/block/modes.py    | 21 +++++++++++++++++++++
 cryptography/primitives/block/modes.py        |  9 ++++-----
 tests/bindings/test_openssl.py                |  5 +----
 6 files changed, 36 insertions(+), 12 deletions(-)
 create mode 100644 cryptography/primitives/abc/__init__.py
 create mode 100644 cryptography/primitives/abc/block/__init__.py
 create mode 100644 cryptography/primitives/abc/block/modes.py

diff --git a/cryptography/bindings/openssl/api.py b/cryptography/bindings/openssl/api.py
index fd54a8ff..f95e4d62 100644
--- a/cryptography/bindings/openssl/api.py
+++ b/cryptography/bindings/openssl/api.py
@@ -13,6 +13,8 @@
 
 from __future__ import absolute_import, division, print_function
 
+from cryptography.primitives.abc.block import modes
+
 import cffi
 
 
@@ -72,7 +74,7 @@ class API(object):
         )
         evp_cipher = self._lib.EVP_get_cipherbyname(ciphername.encode("ascii"))
         assert evp_cipher != self._ffi.NULL
-        iv_nonce = mode.get_iv_or_nonce(self)
+        iv_nonce = self._introspect(mode)
 
         # TODO: Sometimes this needs to be a DecryptInit, when?
         res = self._lib.EVP_EncryptInit_ex(
@@ -86,8 +88,13 @@ class API(object):
         self._lib.EVP_CIPHER_CTX_set_padding(ctx, 0)
         return ctx
 
-    def get_iv_for_ecb(self):
-        return self._ffi.NULL
+    def _introspect(self, mode):
+        if isinstance(mode, modes.ModeWithInitializationVector):
+            return mode.initialization_vector
+        elif isinstance(mode, modes.ModeWithNonce):
+            return mode.nonce
+        else:
+            return self._ffi.NULL
 
     def update_encrypt_context(self, ctx, plaintext):
         buf = self._ffi.new("unsigned char[]", len(plaintext))
diff --git a/cryptography/primitives/abc/__init__.py b/cryptography/primitives/abc/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/cryptography/primitives/abc/block/__init__.py b/cryptography/primitives/abc/block/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/cryptography/primitives/abc/block/modes.py b/cryptography/primitives/abc/block/modes.py
new file mode 100644
index 00000000..609a2ae3
--- /dev/null
+++ b/cryptography/primitives/abc/block/modes.py
@@ -0,0 +1,21 @@
+# 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.
+
+from __future__ import absolute_import, division, print_function
+
+import abc
+
+
+ModeWithInitializationVector = abc.ABCMeta('ModeWithInitializationVector',
+                                           (object, ), {})
+ModeWithNonce = abc.ABCMeta('ModeWithNonce', (object, ), {})
diff --git a/cryptography/primitives/block/modes.py b/cryptography/primitives/block/modes.py
index e4fc886e..1e9b14b7 100644
--- a/cryptography/primitives/block/modes.py
+++ b/cryptography/primitives/block/modes.py
@@ -13,6 +13,8 @@
 
 from __future__ import absolute_import, division, print_function
 
+from cryptography.primitives.abc.block import modes
+
 
 class CBC(object):
     name = "CBC"
@@ -21,12 +23,9 @@ class CBC(object):
         super(CBC, self).__init__()
         self.initialization_vector = initialization_vector
 
-    def get_iv_or_nonce(self, api):
-        return self.initialization_vector
-
 
 class ECB(object):
     name = "ECB"
 
-    def get_iv_or_nonce(self, api):
-        return api.get_iv_for_ecb()
+
+modes.ModeWithInitializationVector.register(CBC)
diff --git a/tests/bindings/test_openssl.py b/tests/bindings/test_openssl.py
index f25236cc..b23c4ccc 100644
--- a/tests/bindings/test_openssl.py
+++ b/tests/bindings/test_openssl.py
@@ -11,7 +11,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from cryptography.bindings.openssl import api
+from cryptography.bindings.openssl.api import api
 
 
 class TestOpenSSL(object):
@@ -28,6 +28,3 @@ class TestOpenSSL(object):
         for every OpenSSL.
         """
         assert api.openssl_version_text().startswith("OpenSSL")
-
-    def test_get_iv_for_ecb(self):
-        assert api.get_iv_for_ecb() == api._ffi.NULL
-- 
cgit v1.2.3


From c024255dda87decd65bd05bd767feda0b43f80c7 Mon Sep 17 00:00:00 2001
From: Paul Kehrer <paul.l.kehrer@gmail.com>
Date: Tue, 10 Sep 2013 18:54:13 -0500
Subject: move abc, inline introspect method, use six for abcs

* abc moved to cryptography.primitive.interfaces
* six added to dependencies
* six used to have py2x/py3x compatible abc
* nonce abc removed for now
---
 cryptography/bindings/openssl/api.py          | 18 ++++++------------
 cryptography/primitives/abc/__init__.py       |  0
 cryptography/primitives/abc/block/__init__.py |  0
 cryptography/primitives/abc/block/modes.py    | 21 ---------------------
 cryptography/primitives/block/modes.py        |  4 ++--
 cryptography/primitives/interfaces.py         | 21 +++++++++++++++++++++
 setup.py                                      |  2 ++
 tox.ini                                       |  1 +
 8 files changed, 32 insertions(+), 35 deletions(-)
 delete mode 100644 cryptography/primitives/abc/__init__.py
 delete mode 100644 cryptography/primitives/abc/block/__init__.py
 delete mode 100644 cryptography/primitives/abc/block/modes.py
 create mode 100644 cryptography/primitives/interfaces.py

diff --git a/cryptography/bindings/openssl/api.py b/cryptography/bindings/openssl/api.py
index f95e4d62..917c1846 100644
--- a/cryptography/bindings/openssl/api.py
+++ b/cryptography/bindings/openssl/api.py
@@ -13,7 +13,7 @@
 
 from __future__ import absolute_import, division, print_function
 
-from cryptography.primitives.abc.block import modes
+from cryptography.primitives import interfaces
 
 import cffi
 
@@ -74,12 +74,14 @@ class API(object):
         )
         evp_cipher = self._lib.EVP_get_cipherbyname(ciphername.encode("ascii"))
         assert evp_cipher != self._ffi.NULL
-        iv_nonce = self._introspect(mode)
+        if isinstance(mode, interfaces.ModeWithInitializationVector):
+            iv_nonce = mode.initialization_vector
+        else:
+            iv_nonce = self._ffi.NULL
 
         # TODO: Sometimes this needs to be a DecryptInit, when?
         res = self._lib.EVP_EncryptInit_ex(
-            ctx, evp_cipher, self._ffi.NULL, cipher.key,
-            iv_nonce
+            ctx, evp_cipher, self._ffi.NULL, cipher.key, iv_nonce
         )
         assert res != 0
 
@@ -88,14 +90,6 @@ class API(object):
         self._lib.EVP_CIPHER_CTX_set_padding(ctx, 0)
         return ctx
 
-    def _introspect(self, mode):
-        if isinstance(mode, modes.ModeWithInitializationVector):
-            return mode.initialization_vector
-        elif isinstance(mode, modes.ModeWithNonce):
-            return mode.nonce
-        else:
-            return self._ffi.NULL
-
     def update_encrypt_context(self, ctx, plaintext):
         buf = self._ffi.new("unsigned char[]", len(plaintext))
         outlen = self._ffi.new("int *")
diff --git a/cryptography/primitives/abc/__init__.py b/cryptography/primitives/abc/__init__.py
deleted file mode 100644
index e69de29b..00000000
diff --git a/cryptography/primitives/abc/block/__init__.py b/cryptography/primitives/abc/block/__init__.py
deleted file mode 100644
index e69de29b..00000000
diff --git a/cryptography/primitives/abc/block/modes.py b/cryptography/primitives/abc/block/modes.py
deleted file mode 100644
index 609a2ae3..00000000
--- a/cryptography/primitives/abc/block/modes.py
+++ /dev/null
@@ -1,21 +0,0 @@
-# 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.
-
-from __future__ import absolute_import, division, print_function
-
-import abc
-
-
-ModeWithInitializationVector = abc.ABCMeta('ModeWithInitializationVector',
-                                           (object, ), {})
-ModeWithNonce = abc.ABCMeta('ModeWithNonce', (object, ), {})
diff --git a/cryptography/primitives/block/modes.py b/cryptography/primitives/block/modes.py
index 1e9b14b7..c722e739 100644
--- a/cryptography/primitives/block/modes.py
+++ b/cryptography/primitives/block/modes.py
@@ -13,7 +13,7 @@
 
 from __future__ import absolute_import, division, print_function
 
-from cryptography.primitives.abc.block import modes
+from cryptography.primitives import interfaces
 
 
 class CBC(object):
@@ -28,4 +28,4 @@ class ECB(object):
     name = "ECB"
 
 
-modes.ModeWithInitializationVector.register(CBC)
+interfaces.ModeWithInitializationVector.register(CBC)
diff --git a/cryptography/primitives/interfaces.py b/cryptography/primitives/interfaces.py
new file mode 100644
index 00000000..a2b091df
--- /dev/null
+++ b/cryptography/primitives/interfaces.py
@@ -0,0 +1,21 @@
+# 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.
+
+from __future__ import absolute_import, division, print_function
+
+import abc
+import six
+
+
+class ModeWithInitializationVector(six.with_metaclass(abc.ABCMeta)):
+    pass
diff --git a/setup.py b/setup.py
index 1044c979..cbbf100a 100644
--- a/setup.py
+++ b/setup.py
@@ -21,9 +21,11 @@ with open("cryptography/__about__.py") as fp:
 
 
 CFFI_DEPENDENCY = "cffi>=0.6"
+SIX_DEPENDENCY = "six>=1.4.1"
 
 install_requires = [
     CFFI_DEPENDENCY,
+    SIX_DEPENDENCY
 ]
 
 setup_requires = [
diff --git a/tox.ini b/tox.ini
index 4d17ebe8..02d521b1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,6 +5,7 @@ envlist = py26,py27,pypy,py32,py33,docs,pep8
 deps =
     pytest-cov
     pretend
+    six
 commands = py.test --cov=cryptography/ --cov=tests/
 
 [testenv:docs]
-- 
cgit v1.2.3


From 7d9e0d9af5343aea7b4b949c20635ed414238927 Mon Sep 17 00:00:00 2001
From: Paul Kehrer <paul.l.kehrer@gmail.com>
Date: Tue, 10 Sep 2013 19:10:33 -0500
Subject: address style on import + remove a tox dependency (in setup.py
 already)

---
 cryptography/primitives/interfaces.py | 1 +
 tox.ini                               | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/cryptography/primitives/interfaces.py b/cryptography/primitives/interfaces.py
index a2b091df..6f74ccf7 100644
--- a/cryptography/primitives/interfaces.py
+++ b/cryptography/primitives/interfaces.py
@@ -14,6 +14,7 @@
 from __future__ import absolute_import, division, print_function
 
 import abc
+
 import six
 
 
diff --git a/tox.ini b/tox.ini
index 02d521b1..4d17ebe8 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,7 +5,6 @@ envlist = py26,py27,pypy,py32,py33,docs,pep8
 deps =
     pytest-cov
     pretend
-    six
 commands = py.test --cov=cryptography/ --cov=tests/
 
 [testenv:docs]
-- 
cgit v1.2.3