Playfair

代码说明：

  本代码实现了playfair加密方法的变种，手动输入一个密钥和一串需要加密的字符串，解密的时候，则输入密钥和已加密的字符串，即加密解密是一个程序。详细请看代码。(This code implements a variant of the playfair encryption method to manually enter a key and a string of encrypted string decryption, enter the key and the encrypted string, that is, encryption decryption is a program. Look at the code in detail.)