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+.. hazmat::
+
+Interfaces
+==========
+
+
+``cryptography`` uses `Abstract Base Classes`_ as interfaces to describe the
+properties and methods of most primitive constructs.  Backends may also use
+this information to influence their operation.  Interfaces should also be used
+to document argument and return types.
+
+.. _`Abstract Base Classes`: http://www.python.org/dev/peps/pep-3119/
+
+
+Cipher Modes
+~~~~~~~~~~~~
+
+.. currentmodule:: cryptography.hazmat.primitives.interfaces
+
+Interfaces used by the symmetric cipher modes described in
+:ref:`Symmetric Encryption Modes <symmetric-encryption-modes>`.
+
+.. class:: Mode
+
+    A named cipher mode.
+
+    .. attribute:: name
+
+        :type: str
+
+        This should be the standard shorthand name for the mode, for example
+        Cipher-Block Chaining mode is "CBC".
+
+        The name may be used by a backend to influence the operation of a
+        cipher in conjunction with the algorithm's name.
+
+
+.. class:: ModeWithInitializationVector
+
+    A cipher mode with an initialization vector.
+
+    .. attribute:: initialization_vector
+
+        :type: bytes
+
+        Exact requirements of the initialization are described by the
+        documentation of individual modes.
+
+
+.. class:: ModeWithNonce
+
+    A cipher mode with a nonce.
+
+    .. attribute:: nonce
+
+        :type: bytes
+
+        Exact requirements of the nonce are described by the documentation of
+        individual modes.