Research On Technology Of Differential Cryptanalysis In Cipher System

Modern cryptographical theory and technology are important basises of information security. Block cipher is an important branch of cryptography. Research on security of block cipher is an important direction. Differential cryptanalysis is a kind of chosen-plaintext attack, which could restore some bits of the key by analyzing the effect of the particular differences in plaintext pairs on the differences in the resultant cipher pairs. Although the differential cryptanalysis is proposed for analyzing DES, it is also an effective cryptanalysis method for other similar ciphers which have fixed-s-box, and it is one of the most effective ways to attack iteration block cipher system so far.Through in depth researching on the relevant theories of differential cryptanalysis technology and the structure of DES, the searching algorithm which was proposed by Mitsuru Matsui to search the biggest differential characteristic of block cipher which has Feistel structure and fixed-s-box was improved. Using the improved algorithm, the biggest differential characteristic and its probability of the high round of DES were got in a little time, differential cryptanalysis for the high round of DES could be carried through and Data complexity could be given by using the biggest differential characteristic and its probability.The structure and s-box of RIJNDAEL have been researched, and the differential distribution table of s-box has been got by computer. The ceiling of the probability of differential characteristic of each round have been given by analyzing the differential distribution table, differential activity box and the distribution of input differential activity box of differential characteristic, and this confirmed that RIJNDAEL has a strong characteristic of anti-differential cryptanalysis.