Add nacl.hash, a module for secure message digests

* Supports sha256 and sha512

nacl/__init__.py

+from . import hash

nacl/hash.py

+import binascii
+
+from . import nacl
+from .exceptions import CryptoError
+
+
+def sha256(message, binary=False):
+    digest = nacl.ffi.new("unsigned char[]", nacl.lib.crypto_hash_sha256_BYTES)
+    if not nacl.lib.crypto_hash_sha256(digest, message, len(message)):
+        raise CryptoError("Hashing failed")
+    digest = nacl.ffi.string(digest)
+
+    if binary:
+        return digest
+    return binascii.hexlify(digest).decode("ascii")
+
+
+def sha512(message, binary=False):
+    digest = nacl.ffi.new("unsigned char[]", nacl.lib.crypto_hash_sha512_BYTES)
+    if not nacl.lib.crypto_hash_sha512(digest, message, len(message)):
+        raise CryptoError("Hashing failed")
+    digest = nacl.ffi.string(digest)
+
+    if binary:
+        return digest
+    return binascii.hexlify(digest).decode("ascii")