S－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。

加密算法包括5个函数：初始置换（IP）；复杂函数fk，它包含有置换和代换运算，并且依赖于输入的密钥；用以转换数据两个部分的简单置换函数（SW）；再一次运用函数fk；最后的一个置换函数是IP的逆。解密过程是加密的逆过程。

-S-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 Algorithm including five functions : initial exchange (IP); Fk complex functions, which include replacement and substitution operations and reliance on imported key; Data conversion for the simple two-part replacement function (SW); again use function FKP; Finally a replacement IP function is the inverse. Encryption and decryption is the inverse process.