crypto.py 文件源码

def crypt_create(key_bytes,
                 is_encrypt_flag=None,
                 iv_bytes=None,
                 algorithm=ciphers_algorithms.AES,
                 mode=ciphers_modes.CTR):
    '''
    Create and return a crypto context for symmetric key encryption using the
    key key_bytes.

    Uses algorithm in mode with an IV of iv_bytes.
    If iv_bytes is None, an all-zero IV is used.

    AES CTR mode uses the same operations for encryption and decyption.
    '''
    #print "Key: " + binascii.hexlify(bytes(key_bytes))
    algo = algorithm(bytes(key_bytes))
    # The block_size is in bits
    if iv_bytes is None:
        iv_bytes = get_zero_pad(algo.block_size/BITS_IN_BYTE)
    cipher = ciphers.Cipher(algo, mode(bytes(iv_bytes)),
                            backend=backends.default_backend()) 
    if is_encrypt_flag:
        return cipher.encryptor()
    else:
        return cipher.decryptor()