move KDF interface

3 files changed, 28 insertions, 5 deletions

diff --git a/src/cryptography/hazmat/primitives/kdf/__init__.py b/src/cryptography/hazmat/primitives/kdf/__init__.py
index 4b540884..2d0724e5 100644
--- a/src/cryptography/hazmat/primitives/kdf/__init__.py
+++ b/src/cryptography/hazmat/primitives/kdf/__init__.py
@@ -3,3 +3,24 @@
 # for complete details.
 
 from __future__ import absolute_import, division, print_function
+
+import abc
+
+import six
+
+
+@six.add_metaclass(abc.ABCMeta)
+class KeyDerivationFunction(object):
+    @abc.abstractmethod
+    def derive(self, key_material):
+        """
+        Deterministically generates and returns a new key based on the existing
+        key material.
+        """
+
+    @abc.abstractmethod
+    def verify(self, key_material, expected_key):
+        """
+        Checks whether the key generated by the key material matches the
+        expected derived key. Raises an exception if they do not match.
+        """
diff --git a/src/cryptography/hazmat/primitives/kdf/hkdf.py b/src/cryptography/hazmat/primitives/kdf/hkdf.py
index 3d4c9fb1..65b7091a 100644
--- a/src/cryptography/hazmat/primitives/kdf/hkdf.py
+++ b/src/cryptography/hazmat/primitives/kdf/hkdf.py
@@ -11,10 +11,11 @@ from cryptography.exceptions import (
     AlreadyFinalized, InvalidKey, UnsupportedAlgorithm, _Reasons
 )
 from cryptography.hazmat.backends.interfaces import HMACBackend
-from cryptography.hazmat.primitives import constant_time, hmac, interfaces
+from cryptography.hazmat.primitives import constant_time, hmac
+from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
 
 
-@utils.register_interface(interfaces.KeyDerivationFunction)
+@utils.register_interface(KeyDerivationFunction)
 class HKDF(object):
     def __init__(self, algorithm, length, salt, info, backend):
         if not isinstance(backend, HMACBackend):
@@ -53,7 +54,7 @@ class HKDF(object):
             raise InvalidKey
 
 
-@utils.register_interface(interfaces.KeyDerivationFunction)
+@utils.register_interface(KeyDerivationFunction)
 class HKDFExpand(object):
     def __init__(self, algorithm, length, info, backend):
         if not isinstance(backend, HMACBackend):
diff --git a/src/cryptography/hazmat/primitives/kdf/pbkdf2.py b/src/cryptography/hazmat/primitives/kdf/pbkdf2.py
index 3d565be2..f8ce7a3b 100644
--- a/src/cryptography/hazmat/primitives/kdf/pbkdf2.py
+++ b/src/cryptography/hazmat/primitives/kdf/pbkdf2.py
@@ -9,10 +9,11 @@ from cryptography.exceptions import (
     AlreadyFinalized, InvalidKey, UnsupportedAlgorithm, _Reasons
 )
 from cryptography.hazmat.backends.interfaces import PBKDF2HMACBackend
-from cryptography.hazmat.primitives import constant_time, interfaces
+from cryptography.hazmat.primitives import constant_time
+from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
 
 
-@utils.register_interface(interfaces.KeyDerivationFunction)
+@utils.register_interface(KeyDerivationFunction)
 class PBKDF2HMAC(object):
     def __init__(self, algorithm, length, salt, iterations, backend):
         if not isinstance(backend, PBKDF2HMACBackend):