# -*- coding: UTF-8 -*-
import string
import random
from Crypto.Cipher import AES
def keyGenerater(length):
  '''''生成指定長度的秘鑰'''
  if length not in (16, 24, 32):
    return None
  x = string.ascii_letters+string.digits
  return ''.join([random.choice(x) for i in range(length)])
def encryptor_decryptor(key, mode):
  return AES.new(key, mode, b'0000000000000000')
#使用指定密鑰和模式對給定信息進行加密
def AESencrypt(key, mode, text):
  encryptor = encryptor_decryptor(key, mode)
  return encryptor.encrypt(text)
#使用指定密鑰和模式對給定信息進行解密
def AESdecrypt(key, mode, text):
  decryptor = encryptor_decryptor(key, mode)
  return decryptor.decrypt(text)
if __name__ == '__main__':
  text = 'Python3.5 is excellent.'
  key = keyGenerater(16)
  #隨機選擇AES的模式
  mode = random.choice((AES.MODE_CBC, AES.MODE_CFB, AES.MODE_ECB, AES.MODE_OFB))
  if not key:
    print('Something is wrong.')
  else:
    print('key:', key)
    print('mode:', mode)
    print('Before encryption:', text)
    #明文必須以字節串形式，且長度為16的倍數
    text_encoded = text.encode()
    text_length = len(text_encoded)
    padding_length = 16 - text_length%16
    text_encoded = text_encoded + b'0'*padding_length
    text_encrypted = AESencrypt(key, mode, text_encoded)
    print('After encryption:', text_encrypted)
    text_decrypted =AESdecrypt(key, mode, text_encrypted)
    print('After decryption:', text_decrypted.decode()[:-padding_length])