Merge pull request #1 from onyb/support-pycryptodome-backend

Add pycryptodome backend to compute keccak256 hash

eth_hash/backends/pycryptodome.py

@@ -1,2 +1,9 @@
-def keccak256(prehash):
-    return b''
+from Crypto.Hash import (
+    keccak,
+)
+
+
+def keccak256(prehash: bytes) -> bytes:
+    hash = keccak.new(digest_bits=256)
+    hash.update(prehash)
+    return hash.digest()

eth_hash/main.py

@@ -1,7 +1,8 @@
 class Keccak256:
     def __init__(self, backend):
         self.hasher = backend.keccak256
-        # TODO run assertion to validate hash once on load, after first backend set up
+
+        assert self.hasher(b'') == b"\xc5\xd2F\x01\x86\xf7#<\x92~}\xb2\xdc\xc7\x03\xc0\xe5\x00\xb6S\xca\x82';{\xfa\xd8\x04]\x85\xa4p"  # noqa: E501
 
     def __call__(self, preimage):
         if not isinstance(preimage, bytes):

setup.py

@@ -45,6 +45,7 @@
     url='https://github.com/ethereum/eth-hash',
     include_package_data=True,
     install_requires=[
+        "pycryptodome>=3.4.6",
     ],
     setup_requires=['setuptools-markdown'],
     extras_require=extras_require,