crypto.py 文件源码

def hash_chain(message: bytes) -> bytes:
    """Mix several hash functions to distribute trust.

    This construction remains secure in case a weakness is discovered
    in one of the hash functions (e.g. insecure algorithm that is not
    unpredictable or that has weak preimage resistance, or if the
    algorithm is badly implemented).

    In case where the implementation is malicious, this construction
    forces stateless implementations  -- that try to compromise mixing
    phase -- to guess it's position in the construction, which will
    eventually lead to key state mismatch and thus detection.
    """
    d1 = sha3_256(blake2s(sha256(message)))
    d2 = sha3_256(sha256(blake2s(message)))

    d3 = blake2s(sha3_256(sha256(message)))
    d4 = blake2s(sha256(sha3_256(message)))

    d5 = sha256(blake2s(sha3_256(message)))
    d6 = sha256(sha3_256(blake2s(message)))

    d7 = sha3_256(message)
    d8 = blake2s(message)
    d9 = sha256(message)

    # Mixing phase
    x1 = xor(d1, d2)
    x2 = xor(x1, d3)
    x3 = xor(x2, d4)
    x4 = xor(x3, d5)
    x5 = xor(x4, d6)
    x6 = xor(x5, d7)
    x7 = xor(x6, d8)
    x8 = xor(x7, d9)

    return x8