Based On The Theory Of Chaos Encryption Algorithm

Chaotic systems have many properties which can be connect with cryptography, such as pseudo-random, unpredictability of evolution of its orbits, properties of mixing and sensitivity to initial conditions and system parameters. Chaos is becoming a new rich source of cryptography.This thesis focuses on the information encryption and puts emphasis on the design of chaotic sequence cipher. The main research contents and originality of this paper can be summarized as following:This paper has summarized the current situation of application research on information encryption by using chaos, and pointed out that several existing problems should be solved at present.The applications of discrete chaos theory in chaotic cryptography are studies. Our research showed that discrete chaos theory contribute greatly to the problems that how to choose better chaotic maps, how to estimate the maximum differential probability of a bijective mapping according to its discrete lyapunov expontents, how to estimate the diffusion degree of nonlinear transformation and how to choose the better S box.This paper analysis the security of three classes of chaotic pseudo-random number generators, that is prime number based generators, trigonometric function based generators and truncation function based generators, and pointed out that these three kinds of generators were not cryptological secure. For the He’s pseudo-random bit generator, given a piece of sequence produced by such kind of generator, we can completely recover the whole secret keys. For the Wang’s pseudo-random bit generator, research showed that algorithm exist weak keys, and output function is not distribution preserving mapping, the keystreams is not uniformly distributing. J. A. Gonzalez had study the problems that explicit function forms of logistic map can produce completely unpredictable random sequences, but our conclusion is that this kind of sequence is weak in cryptological view. For Kocarev’s two kinds of pseudo-random bit generators, they are also not cryptological secure.Based on theoretical results on discrete chaos theory and cryptanalyses of several recently-proposed chaotic ciphers, we propose a discrete skew tent map stream cipher based on coupled lattice model. With the incorporation of the counter assisted technique and the couple of multiple lattices, the period of the keystreams comparative large, and cipher has the capability to resist all kinds of attacks ever known.