DES是一个分组加密算法，他以64位为分组对数据加密。同时DES也是一个对称算法：加密和解密用的是同一个算法。它的密匙长度是56位（因为每个第8位都用作奇偶校验），密匙可以是任意的56位的数，而且可以任意时候改变。-DES is a block cipher algorithm, his 64-bit data encryption for the packet. At the same time, DES is a symmetric algorithm: encryption and decryption using the same algorithm. Its key length is 56 (since each section are used as 8-bit parity), keys can be arbitrary number of 56, but the time can change.