S-盒特性与DES强度

介绍了差分密码分析，讨论了数据加密标准（ＤＥＳ）的Ｓ－盒的结构与差分特性，然后通过Ｆ－函数将Ｓ－盒的局部特性扩展到整个密码结构。为考察Ｓ－盒顺序对ＤＥＳ强度的影响，进行了大量的测试工作，指出了改变Ｓ－盒的顺序不会影响密文对明文和密钥的敏感性，并揭示了Ｓ－盒顺序的改变对密文影响的正态分布特性。以最佳概率讨论了Ｓ－盒顺序有利于抗差分密码分析，证明了Ｓ－盒顺序对抗差分密码分析是一个良好的方法。最后给出了重排Ｓ－盒的随机化算法。

Properties of S boxes and the strength of DES

The differential cryptanalysis is introduced. The properties of construction and difference on the S boxes of the date encryption standard (DES) are discussed. The local property of S boxes is extended to the entire cipher structure through F function. In order to observe that how the order of S boxes affects the strength of DES, the tests for a number on the order of S boxes are made. The testing results indicade that the change of order of S boxes can't affect the ciphertext sensitivity to the plaintext and the key. The normal distribution of the order of S boxes affecting to the ciphertext is revealed. It is proved that the order of S boxes is a good method for differential cryptanalysis. The randomized algorithm on rearranging the order of S boxes is given.