Security Of Block Cipher And Its Improvement

With rapid development in technology of computer and communication, demands of secure storage, safe handling and secure transmission of information increases urgently. As it's fast, easy to be standardized and easy to be implemented on both hardware and software, block cipher is the core component in data encryption, digital signature, authentication and key management. Study of block cipher includes three aspects: designing principle, cryptanalysis and statistical test.In this paper, we survey researches and results on block cipher, mainly on the designing principle, cryptanalysis and statistical test.Firstly, this paper presentsthe state of arts of block cipher, and then give a brief discussion of working model of block cipher, followed by a more detailed discussion in design technical and guidelines used in block cipher.Secondly, we summarize the technology of the differential cryptanalysis, linear cryptanalysis, birthday attack, energy attack in block cipher.Third, with regard to the statistical test, we summarize the technology of frequency test, poker test, run test and autocorrelation test and their basic mathematical foundation.Finally, We do a study in DES in detail, summarize the research on it and its variants as its improved program as well as the advantages and disadvantages of these programs are discussed. Then propose our own algorithm, DESM, that based on DES. With the technology summarized above, we then analyse the security, the randomness and the efficiency of DESM.Furthermore, we take useful discussion in the development of cipher block with regard to developing a new cipher or improving the security, using pattern of a existing cipher, which has been proved practically secure.