Merge branch 'master' into arc4-support

* master:
  Typo
  Be really explicit about what's good and bad
  Mention return types.
  Consistently use e.g.
  Module documentation.
  Single space.
  Add a new Mode interface to document mode.name and start on some prose docs for interfaces.
  Proper name for the iv thing.
  Actually note the properties for cipher modes types on their ABCs.

Conflicts:
	docs/hazmat/primitives/symmetric-encryption.rst

2 files changed, 24 insertions, 3 deletions

diff --git a/cryptography/hazmat/primitives/ciphers/modes.py b/cryptography/hazmat/primitives/ciphers/modes.py
index a60e8a34..e54872a6 100644
--- a/cryptography/hazmat/primitives/ciphers/modes.py
+++ b/cryptography/hazmat/primitives/ciphers/modes.py
@@ -16,6 +16,7 @@ from __future__ import absolute_import, division, print_function
 from cryptography.hazmat.primitives import interfaces
 
 
+@interfaces.register(interfaces.Mode)
 @interfaces.register(interfaces.ModeWithInitializationVector)
 class CBC(object):
     name = "CBC"
@@ -25,10 +26,12 @@ class CBC(object):
         self.initialization_vector = initialization_vector
 
 
+@interfaces.register(interfaces.Mode)
 class ECB(object):
     name = "ECB"
 
 
+@interfaces.register(interfaces.Mode)
 @interfaces.register(interfaces.ModeWithInitializationVector)
 class OFB(object):
     name = "OFB"
@@ -38,6 +41,7 @@ class OFB(object):
         self.initialization_vector = initialization_vector
 
 
+@interfaces.register(interfaces.Mode)
 @interfaces.register(interfaces.ModeWithInitializationVector)
 class CFB(object):
     name = "CFB"
@@ -47,6 +51,7 @@ class CFB(object):
         self.initialization_vector = initialization_vector
 
 
+@interfaces.register(interfaces.Mode)
 @interfaces.register(interfaces.ModeWithNonce)
 class CTR(object):
     name = "CTR"
diff --git a/cryptography/hazmat/primitives/interfaces.py b/cryptography/hazmat/primitives/interfaces.py
index ebf5e31e..67dbe6fa 100644
--- a/cryptography/hazmat/primitives/interfaces.py
+++ b/cryptography/hazmat/primitives/interfaces.py
@@ -25,12 +25,28 @@ def register(iface):
     return register_decorator
 
 
+class Mode(six.with_metaclass(abc.ABCMeta)):
+    @abc.abstractproperty
+    def name(self):
+        """
+        A string naming this mode.  (e.g. ECB, CBC)
+        """
+
+
 class ModeWithInitializationVector(six.with_metaclass(abc.ABCMeta)):
-    pass
+    @abc.abstractproperty
+    def initialization_vector(self):
+        """
+        The value of the initialization vector for this mode as bytes.
+        """
 
 
 class ModeWithNonce(six.with_metaclass(abc.ABCMeta)):
-    pass
+    @abc.abstractproperty
+    def nonce(self):
+        """
+        The value of the nonce for this mode as bytes.
+        """
 
 
 class CipherContext(six.with_metaclass(abc.ABCMeta)):
@@ -65,7 +81,7 @@ class HashAlgorithm(six.with_metaclass(abc.ABCMeta)):
     @abc.abstractproperty
     def name(self):
         """
-        A string naming this algorithm. (ex. sha256, md5)
+        A string naming this algorithm. (e.g. sha256, md5)
         """
 
     @abc.abstractproperty