Research And Analysis Of Diffusion Layer And Confusion Layer Of Block Cipher

In recent years,with the rapid development of computer and Internet technology,people pay more and more attentions to information security.Block cipher has shown great advantages in encryption speed,the amount of encrypted data,design standards and hardware and software implementation,etc.,and has been widely used in the field of information security,becoming a research hotspot in cryptography.Generally,the design of block cipher follows confusion principle and diffusion principle.Generally,nonlinear S-box is used to perform confusion and linear transformation is used to perform diffusion.Therefore,diffusion layer and confusion layer of block cipher play an important role in the security of cipher algorithm.This paper mainly focuses on the linear diffusion layer and nonlinear confusion layer of block cipher in the following aspects:(1)According to the definition of the number of branches,the exhaustive search of the 4-order invertible matrices in the binary finite field is carried out,and twenty-four almost MDS matrices are found.Research and analysis on the searched almost MDS matrix,it is found that almost MDS matrix not only has a low implementation cost,but also provides provable security.(2)The S-box is a vital component of the symmetric cryptographic algorithm.The hardware implementation of many cryptographic algorithms is vulnerable to side channel attacks,threshold implementation is an anti-side channel attack strategy based on secret sharing and multi-party secure computing.This paper constructs safe lightweight 4×4 S-box with optimal cryptographic properties by simply cyclically shifting the variables in the Boolean functions with degree 3.And the threshold implementation is designed for the constructed S-boxes to resist side channel attacks,which is provably secure.The implementation of the four component functions of the S-boxes constructed by this method is the same,greatly reducing the complexity of the hardware implementation.Given a component of the S-box,the remaining three components can be obtained by cyclic shifting of the component,which greatly reduces the hardware implementation cost and is easy to implement in a fast software.