S－DES加密算法输入为一个8位的明文组和一个10位的密钥，输出为8位的密文组，解密算法的输入则是一个8位的密文组和一个10位的密钥，输出位8位的明文组。解密过程是加密的逆。程序使用：读入一个文档文件，对其内容加密，输入密钥和选定存放生成密文的目录，点加密；解密操作与加密相似。-S-DES encryption algorithm for the importation of an eight expressly group and a 10 Key, Output for the eight-man group of close, decryption algorithm input is a secret eight-man group and one of the ten key, Output-8 group of expressly. Encryption and decryption is the inverse. Procedure : Reading into a document file, its content encryption, and the importation of selected key storage generating ciphertext directory, point encryption; Encryption and decryption operations similar.