说明：  des算法简单实现。它以64位的明文和56位的密钥作为输入，通过DES加密运算产生64位密文输出。其解密过程利用同以密钥和算法将密文还原成明文。因为java语言的安全性＆网络处理能力强，所以就利用了java语言编写
(des simple algorithm to achieve. It's expressly 64 and 56 as the key input, through DES encryption algorithms have 64 ciphertext output. Its use decryption process with a key and cipher algorithm reduced explicitly. Java language because of the security & network processing capability, on the use of the Java language)