trivial_hash.py

def xor_hash(input_bytes: bytes) -> bytes:
    hash_length = 16  # in bytes

    # Get the first 16 bytes
    if len(input_bytes) < hash_length:
        return input_bytes + b"\0" * (hash_length - len(input_bytes))
    hash_value = input_bytes[:hash_length]
    
    # iterate over blocks of the defined length
    remaining = input_bytes[hash_length:]
    while len(remaining) >= hash_length:
        hash_value = xor_bytes(hash_value, remaining[:hash_length])
        remaining = remaining[hash_length:]
        
    # take care of remaining bytes
    if len(remaining) < hash_length:
        hash_value = remaining + b"\0" * (hash_length - len(remaining))
    return hash_value


def xor_bytes(xs: bytes, ys: bytes) -> bytes:
    """Run XOR over two b."""
    assert len(xs) == len(ys)
    return "".join([chr(x ^ y) for x, y in zip(xs, ys)]).encode()


# Try it with an example file
with open("/etc/passwd", "rb") as fp:
    data = fp.read()
print(xor_hash(data))