Researches On The Application Of Intelligent Algorithms In Some Key Issues Of Cryptography And Information Security

Morden Cryptography theory and technology are the important basis of information security. With the rapid development of network and communication, the security and protection of information transmitted in the Internet becomes more important. It is very hard that many problems are resolved by mathmetics methods in cryptography and information security. Recent years, intelligent algorithms are good at the resolement and application of NP-C problems. In this dissertation, the theory and application of intelligent algorithms are researched, and the models of four key problems in information security, which are block cipher, stream cipher, Boolean fuctions and intrusion detection, are constructed. We research and analyze the theory basis, application and astringency deeply. Through the emulation, we analyze, validate and compare the effect and perforement of these models. All innovations in detail as followed:1. Two algorithms based on intelligent algorithms are proposed to construct S-boxes. Firstly, S-boxes are optimized by genetic algorithm. The guarantee of orthogonality is become effective by coding type. Crossover and mutation probabilities are adaptive in iterative process. Based on this construction method, the flow chart of constructing S-boxes is given and the group of S-boxes with high nonlinearity and low difference uniformity are generated. And then, S-boxes are optimized by, which combines the mechanism of feedback organically with the thinking of evolution, accordingly develops enough advantages of the two algorithms. Based on this construction method, the flow chart of constructing S-boxes is given and the group of S-boxes with high nonlinearity and low difference uniformity are generated. The simulation results show that this kind of construction method is better at reducing a large redundancy calculation and quickening the speed of convergence, compared with the one based on genetic algorithm.2. It is researched that genetic algorithm and cellular automata design stream cipher. The problem of generation by cellular automata of high quality pseudorandom sequences useful in cryptography is considered in the paper. For this purpose one dimensional nonuniform cellular automata is considered. The quality of pseudorandom sequences generated by cellular automata depends on collective behavior of rules assigned to cellular automata cells. Genetic algorithm is used to find suitable rules from predefined earlier set of rules. It has been shown that genetic algorithm eliminates bad subsets of rules and founds subsets of rules, which provide high quality pseudorandom sequences. These sequences are suitable for symmetric key cryptography and can be used in different cryptographic modules.3. To analyze Walsh-Hadamard transformation and autocorrelation of Boolean functions, two rules to optimize Boolean functions are deduced. One plus one climbing hill algorithm based on the two rules is able to design Boolean functions with high nonlinearity and low autocorrelation. To combine the above algorithm with genetic, genetic and climbing hill algorithm is proposed. Experiment data show that the latter can further find Boolean function to be good at nonlinearity and autocorrelation.4. To overcome some shortcomings of previous clustering algorithm to be applied in intrusion prevention system in face of unknown attack type, an algorithm based on genetic algorithms and fuzzy connectedness clustering is presented in order to measure the similarity. The near optimal cluster centers are chosen by genetic algorithm. This algorithm is applied in intrusion prevention and Computer simulations show that this algorithm is effective.Finally, the work of this dissertation is summarized and the prospective of future research is discussed.