1 files changed, 55 insertions, 0 deletions
diff --git a/cryptography/primitives/block/base.py b/cryptography/primitives/block/base.py
new file mode 100644
index 00000000..207c83d9
--- /dev/null
+++ b/cryptography/primitives/block/base.py
@@ -0,0 +1,55 @@
+# 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.
+
+# TODO: which binding is used should be an option somewhere
+from cryptography.bindings.openssl import api
+
+
+class BlockCipher(object):
+    def __init__(self, cipher, mode):
+        super(BlockCipher, self).__init__()
+        self.cipher = cipher
+        self.mode = mode
+        self._ctx = api.create_block_cipher_context(cipher, mode)
+        self._operation = None
+
+    @property
+    def name(self):
+        return "{0}-{1}-{2}".format(
+            self.cipher.name, self.cipher.key_size, self.mode.name,
+        )
+
+    def encrypt(self, plaintext):
+        if self._ctx is None:
+            raise ValueError("BlockCipher was already finalized")
+
+        if self._operation is None:
+            self._operation = "encrypt"
+        elif self._operation != "encrypt":
+            raise ValueError("BlockCipher cannot encrypt when the operation is"
+                             " set to %s" % self._operation)
+
+        return api.update_encrypt_context(self._ctx, plaintext)
+
+    def finalize(self):
+        if self._ctx is None:
+            raise ValueError("BlockCipher was already finalized")
+
+        if self._operation == "encrypt":
+            result = api.finalize_encrypt_context(self._ctx)
+        else:
+            raise ValueError("BlockCipher cannot finalize the unknown "
+                             "operation %s" % self._operation)
+
+        self._ctx = None
+        return result