memo.py 文件源码

def init_aes(shared_secret, nonce):
    """ Initialize AES instance

        :param hex shared_secret: Shared Secret to use as encryption key
        :param int nonce: Random nonce
        :return: AES instance and checksum of the encryption key
        :rtype: length 2 tuple

    """
    " Seed "
    ss = unhexlify(shared_secret)
    n = struct.pack("<Q", int(nonce))
    encryption_key = hashlib.sha512(n + ss).hexdigest()
    " Check'sum' "
    check = hashlib.sha256(unhexlify(encryption_key)).digest()
    check = struct.unpack_from("<I", check[:4])[0]
    " AES "
    key = unhexlify(encryption_key[0:64])
    iv = unhexlify(encryption_key[64:96])
    return AES.new(key, AES.MODE_CBC, iv), check