一类特殊的比特变换的研究

 在S-P网络中,P变换的设计直接影响着分组密码的整体扩散性能.基于此,提出了一类特殊的比特变换的概念,证明了该类比特变换是对合变换且其分支数为4,并给出了输入和输出重量之和等于4的输入输出对的个数.进一步的分析表明,尽管该类比特变换的分支数没有达到最大值,但仍然具有较好的扩散性能.

Researches on A Class of Special Bit Transformation

In the S-P networks,the design of P-transformation is very important,and is related to integral diffusion performance of block cipher.Based on the importance of P transformation,we propose the concept of a class of special bit transformation.We prove that the special bit transformation is involutory transformation and it’s branch number is 4.We also give the number of input-output correspondences whose weight sum equals to 4.By further analyzing,it is shown that the special bit transformation has good diffusion performance though it’s branch number does not obtain maximum.