Add a new Mode interface to document mode.name and start on some prose docs for interfaces.
diff --git a/docs/hazmat/primitives/index.rst b/docs/hazmat/primitives/index.rst
index c81018a..614c414 100644
--- a/docs/hazmat/primitives/index.rst
+++ b/docs/hazmat/primitives/index.rst
@@ -10,3 +10,4 @@
hmac
symmetric-encryption
padding
+ interfaces
diff --git a/docs/hazmat/primitives/interfaces.rst b/docs/hazmat/primitives/interfaces.rst
new file mode 100644
index 0000000..b526158
--- /dev/null
+++ b/docs/hazmat/primitives/interfaces.rst
@@ -0,0 +1,59 @@
+.. 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.
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index 7d3b072..4b37d39 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -149,6 +149,9 @@
:param bytes key: The secret key, 32-448 bits in length (in increments of
8). This must be kept secret.
+
+.. _symmetric-encryption-modes:
+
Modes
~~~~~