Research On The Design Of Chaotic S-box And Its Application In Block Cryptography

The development of science and technology and the Internet has not only brought unexpected convenience and improved people's quality of life,but also unnecessary troubles.For example,the disclosure of personal privacy,company plans and even state secret information.For these important information data,encryption methods are usually used to ensure security,so it is of practical significance to propose a safe and effective password scheme.The emergence of chaotic systems has led to the rapid development of cryptography.This is because the characteristics of chaos and cryptography have many similar characteristics,which can provide new impetus and direction for research in the field of cryptography.This article mainly takes chaotic S-box and block cipher as the research object,and designs a block cipher algorithm with higher security and efficiency.The work content mainly includes: designing an S-box with excellent characteristics by using a chaotic system;proposing a block cipher algorithm with higher performance,and using the S-box obtained from the previous step algorithm in the block cipher;optimizing the overall cipher algorithm and safety analysis.The details are as follows:(1)An algorithm is proposed to expand the number of lattices of spatiotemporal chaos coupled map models to construct S-boxes.With the help of the excellent characteristics of spatiotemporal chaos,this paper first takes the improved chaotic system as the local mapping of the model,and then expands the model horizontally,that is,expands the number of grids to multiples of the integer number of S-boxes,and uses chaotic mapping to randomly select values for some parameters,and there is some improvement in the scrambling effect.Based on changes to the initial values,control parameters,and iteration times of the model and mapping,the algorithm also has the advantage of generating S-boxes in batches.Finally,the cryptographic performance of the S-box is tested according to the existing evaluation criteria,and compared with other S-boxes.The results show that the S-box generated by the algorithm in this paper has excellent data in multiple tests,which shows that it has good cryptographic characteristics.That can prepare for the next step of block cipher design.(2)An improved block cipher algorithm based on the substitution-permutation structure of AES is proposed.After studying and understanding the design principles and common structures of block ciphers.This paper first selects the S-boxes that meet the conditions and the number of iterations according to the designed new S-box algorithm,and designs it as an S-function;then proposes an improved key expansion algorithm using the S-function,and then the obtained rounds key is cyclically shifted with different digits to enhance the confusion effect.Afterwards,a safety analysis is carried out.The results show that the scheme can improve the security strength of the algorithm to a certain extent.(3)An optimized scheme for the decryption function is proposed.After studying and analyzing the encryption and decryption operations of the cryptographic algorithm,first,the principle that the decryption part takes up a large amount of time is explained,and then the relevant mathematical characteristics in the column mixing transformation are further derived to draw a conclusion,which is applied to the decryption algorithm.And from a theoretical point of view,it is proved that the computational complexity of the optimized algorithm in this paper is lower.Finally,the safety analysis and performance test of the whole algorithm are carried out.Through the test and comparison,it can be concluded that the optimization scheme is feasible,and the efficiency of the algorithm is improved several times.Therefore,it shows that the new S-box algorithm generated by the chaotic system and the use of it to design an improved block cipher has certain advantages,and it can be put into practical applications.