Research On Chaotic Pseudorandom Sequence And Its Applications

With the fast development of computer and Internet technology, Information security has become the common focus of both academia and enterprises. Cryptology is the core of information security and the random sequence has played a very important role in it. The key generation, digital signature, authentication and many kinds of communication protocol all need random sequence. Just as the famous expert of cryptology Bruce Schneier had pointed out that the random sequence is the problem which is discussed very less in cryptology, but it is the most important one in cryptology. In some case, the security of the random sequence decides the security of the system. So, how can we get high quality random sequence generator has become a very vital problem. In this thesis, we will study how to design high quality, fast, convenient random sequence generator. Currently, it is one of the hot promising reseachfields on the combination of nonlinear science and information science to apply chaos theory to pseudorandom sequence. In this dissertation, the design and implementation of chaotic pseudorandom sequence generator have been carefully studied and applied successfully to protect the security of information.The following tasks have been accomplished in this dissertation:①Chaos theory is introduced in detail from different aspects and views, the definition of chaos is presented, the characteristics of chaotic dynamics are described, and the criterion and rule of chaos are given.②The relevant theory of random sequence is introduced, and theusual random sequence generators used in information security have been summarized, these generators' disadvantages, such as short period, predictability, bad quality, lower pace, inconvenience, are given.③The piecewise linear chaotic map with a segment number parameter (SNP-PLCM) is analyzed in detail. Based on SNP-PLCM, a chaotic pseudorandom sequence generator is presented. The generator employs perturbation strategy of controls parameter and output sequences to avoid dynamical degradation of digital chaotic systems. Theoretical analysis and computer simulation results show that the chaotic pseudorandom sequence generator can get high quality sequences.④A measurable dynamic S-box algorithm is proposed by use of chaotic pseudo- random sequences, and the performance of these S-boxes is analyzed mathematically. Theoretical analysis and computer test results show that this scheme has good security and performance.⑤Based on chaotic pseudorandom sequence generator and non-linear feedback shift register (NLFSR), a fast streamer cipher is proposed. The approach is that chaotic pseudorandom sequence initializes NLFSR and constructs the update function of NLFSR, and chaotic dynamic S-boxes. The update function which is called once per round, manipulates the internal state to generate 64 bits of pseudorandom key stream. The chaotic dynamic S-box of the update function should be reconstructed at lease once for every 21 6 bit of key stream generated, that is, iteration 1024 times of chaotic system can produces 21 6 bits of pseudo-random key stream. The theoretical and numerical analyses show that the scheme can not only produce the independently and uniformly distributed key stream, but also can improve largely the period of chaotic sequence under the finite-precision circumstances and increase in efficiency.⑥By combining the traditional iteration structure of Hash function with the dynamic S-boxes, a novel keyed Hash function is presented. The proposed approach can give a chaotic Hash value by means of the lookup table of functions and chaotic dynamic S-box. Compared with the existing chaotic Hash functions, this method improves computational performance of Hash system by using the chaotic S-box substitution. Theoretical and experimental results show that the proposed method has not only strong one way property, sensitivity to initial conditions and chaotic system's parameters, but also high speed.Finally, the research work of this dissertation is summarized, and the future reseach direction is indicated.