DES算法把64位的明文输入块变为64位的密文输出块，它所使用的密钥也是64位，首先，DES把输入的64位数据块按位重新组合，并把输出分为L0、 R0两部分，每部分各长32位，并进行前后置换（输入的第58位换到第一位，第50位换到第2位，依此类推，最后一位是原来的第7位），最终由L0输出左 32位，R0输出右32位，根据这个法则经过16次迭代运算后，得到L16、R16，将此作为输入，进行与初始置换相反的逆置换，即得到密文输出。-DES algorithm combines the 64 expressly to block the importation of 64 of the ciphertext output block, it is also the key 64, first of all, DES importation of 64 data blocks per caput regrouped and the output is divided into L0, R0 two parts, each of the 32 long, and pre- and post exchange (the importation of 58 account for one, 50 for the first of two, and so forth. the final one is the original clause 7), and ultimately by the L0 32 left output, the output right R0 32, Under this rule after 16 iterations operator, was L16, R16 and as input, with the initial replacement for the opposite inverse replacement, which is the output ciphertext.