replaces cryptography.hazmat.primitives.BLAKE2b with hashlib.Blake2b from Python standardlib

Pipfile

@@ -9,6 +9,7 @@ setuptools = "*"
 cryptography = ">=2.3"
 pynacl = "*"
 pysha3 = "*"
+hkdf = "*"
 # NuCypher
 bytestring-splitter = "*"
 constant-sorrow = ">=0.1.0a7"
@@ -36,6 +37,7 @@ sphinx-autobuild = "*"
 sphinx_rtd_theme = "*"
 # Overrides vulnerable versions allowed by codecov and sphinx:
 requests = ">=2.20.0"
+umbral = {editable = true, path = "."}
 
 [pipenv]
 allow_prereleases = true

setup.py

@@ -63,6 +63,7 @@ INSTALL_REQUIRES = [
     'pysha3',
     'constant-sorrow>=0.1.0a7',
     'bytestring-splitter',
+    'hkdf'
 ]
 
 DEV_INSTALL_REQUIRES = [

tests/unit/test_serialization_property_based.py

@@ -104,12 +104,12 @@ def test_pubkey_roundtrip(p):
     k = UmbralPublicKey(p, params)
     assert(k == UmbralPublicKey.from_bytes(k.to_bytes(), params=params))
 
-# @given(binary(min_size=1))
-# #@settings(max_examples=20, suppress_health_check=[HealthCheck.hung_test])
-# def test_privkey_roundtrip(p):
-#     insecure_scrypt_cost = 5   # This is deliberately insecure, just to make it faster
-#     k = UmbralPrivateKey.gen_key()
-#     rt = UmbralPrivateKey.from_bytes(k.to_bytes(password=p, _scrypt_cost=insecure_scrypt_cost),
-#                                      password=p,
-#                                      _scrypt_cost=insecure_scrypt_cost)
-#     assert(k.get_pubkey() == rt.get_pubkey())
+@given(binary(min_size=1))
+@settings(max_examples=20)
+def test_privkey_roundtrip(p):
+    insecure_scrypt_cost = 5   # This is deliberately insecure, just to make it faster
+    k = UmbralPrivateKey.gen_key()
+    rt = UmbralPrivateKey.from_bytes(k.to_bytes(password=p, _scrypt_cost=insecure_scrypt_cost),
+                                     password=p,
+                                     _scrypt_cost=insecure_scrypt_cost)
+    assert(k.get_pubkey() == rt.get_pubkey())

umbral/keys.py

@@ -21,8 +21,6 @@ from typing import Callable, Optional, Any
 from cryptography.hazmat.backends import default_backend
 from cryptography.hazmat.backends.openssl.ec import _EllipticCurvePrivateKey, _EllipticCurvePublicKey
 from cryptography.exceptions import InternalError
-from cryptography.hazmat.primitives import hashes
-from cryptography.hazmat.primitives.kdf.hkdf import HKDF
 from cryptography.hazmat.primitives.kdf.scrypt import Scrypt as CryptographyScrypt
 from nacl.secret import SecretBox
 
@@ -34,6 +32,8 @@ from umbral.point import Point
 from umbral.curve import Curve
 from umbral.random_oracles import hash_to_curvebn
 
+from hkdf import Hkdf
+from hashlib import blake2b
 
 __SALT_SIZE = 32
 
@@ -407,13 +407,11 @@ class UmbralKeyingMaterial:
         """
         params = params if params is not None else default_params()
 
-        key_material = HKDF(
-            algorithm=hashes.BLAKE2b(64),
-            length=64,
-            salt=salt,
-            info=b"NuCypher/KeyDerivation/"+label,
-            backend=default_backend()
-        ).derive(self.__keying_material)
+        key_material = Hkdf(
+            salt,
+            self.__keying_material,
+            hash=blake2b,
+        ).expand(info=b"NuCypher/KeyDerivation/"+label, length=64)
 
         bn_key = hash_to_curvebn(key_material, params=params)
         return UmbralPrivateKey(bn_key, params)

umbral/random_oracles.py

@@ -18,9 +18,6 @@ from abc import abstractmethod, ABC
 from typing import Optional, Type
 
 from cryptography.hazmat.backends.openssl import backend
-from cryptography.hazmat.backends import default_backend
-from cryptography.hazmat.primitives import hashes
-from cryptography.hazmat.primitives.kdf.hkdf import HKDF
 from cryptography.exceptions import InternalError
 
 import sha3
@@ -31,6 +28,8 @@ from umbral.point import Point
 from umbral.params import UmbralParameters
 from umbral.config import default_params
 
+from hkdf import Hkdf
+from hashlib import blake2b
 
 class Hash(ABC):
 
@@ -66,7 +65,7 @@ class Hash(ABC):
 class Blake2b(Hash):
     def __init__(self, customization_string: bytes = b''):
         # TODO: use a Blake2b implementation that supports personalization (see #155)
-        self._blake2b = hashes.Hash(hashes.BLAKE2b(64), backend=backend)
+        self._blake2b = blake2b(digest_size=64)
         super().__init__(customization_string)
 
     def update(self, data: bytes) -> None:
@@ -78,7 +77,7 @@ class Blake2b(Hash):
         return replica
 
     def finalize(self) -> bytes:
-        return self._blake2b.finalize()
+        return self._blake2b.digest()
 
 
 class ExtendedKeccak(Hash):
@@ -116,12 +115,14 @@ def kdf(ecpoint: Point,
         ) -> bytes:
 
     data = ecpoint.to_bytes(is_compressed=True)
-    hkdf = HKDF(algorithm=hashes.BLAKE2b(64),
-                length=key_length,
-                salt=salt,
-                info=info,
-                backend=default_backend())
-    return hkdf.derive(data)
+
+    salt = salt or b''
+    info = info or b''
+    return Hkdf(
+            salt,
+            data,
+            hash=blake2b,
+        ).expand(info=info, length=key_length)
 
 
 # TODO: Common API for all hash_to_curvebn functions.