Improvement Of The AES Encryption Algorithm And The Realization With MATLAB

With the application of computer and the development of information industry, more attention is paid to information security. Information security is composed of security protocol and cryptographic algorithm, the latter is the base and core. Therefor, it is very important to study and analyze the popular cryptographic algorithm for the sake of nation's information security. The block cipher is one of the two aspects of the modern applied cryptography systems. It has some characteristics—the fast speed, the easy standardization, convenient implement by software and hardware, and so on. So it is used in wide range in the security area of the computer communication or in the security area of the information systems. On October 2, 2000, National Institute of Standards and Technology claimed to adopt Rijndael algorithm as Advance Encryption Standard, and come into force formally on May 26, 2002. By way of the new American data encryption standard, Rijndael algorithm is an international standard, furthermore, Rijndael algorithm is free and open, so that the Rijndael crypto product will gained more applocations.This paper has detailly analysised and researched the AES algorithm, including algebraic proper. Thecentral contribution is as follows:1. A detail introdution of AES is prisented, including the base of mathematics design principle of AES algorithm and the structure.2. It details the currently more popular method of sub-encryption algorithm of the attack methods.strong attack, differential attack, linear attack and Square attack. This paper analysises the algorithm's ability which resistes the existing attacks.3. The period of affine transformation pair is 4, the period of iterative-output is less than 88 and algebraic expression is only 9 items. Based on these defects, an improved S-box is designed in the paper, with period of affine transformation pair as 16, period of iterative-output as 256 and algebraic expression of improved S-box as 252 items and inverse S-box unchanged. The improved S-box is compared with the S-box of rijndael algorithm, for example, the balance, strict avalanche criterion, nonlinear degree and so on. The results indicate that the improved S-box has better algebraic characteristics and stronger resistance against algebraic attack. The improved AES encryption algorithm is verified by Matlab language. Finally, The paper gives an example, in order to better understand the AES encryption algorithm. Then According to the actual situation, the paper gives the specific encryption solution.