Cryptanalysis Of Chaotic Sequence And Applied Research

With the rapid development of extensive applications of computer, communication and internet technologies in information time, the security problem about information has become a hot focus in every way of our life. As the most basic method, cryptograph also receives abroad attention. Chaos theory deals with nonlinear dynamical systems with special properties. Its security properties make a natural relationship with cryptography, such as determinacy, sensitive dependence on initial conditions, unpredictable result for long, etc. The main purpose of this dissertation is to investigate analysis of chaotic stream ciphers and application of chaotic cryptography. The main achievements and originality are as follows:1. Chaos theory is introduced in detail from different aspects, taking the definition of chaos, the characteristics of chaotic dynamics, Lyapunov exponent and chaotic attractors for example. Moreover, the research status of chaotic stream ciphers has been summarized.2. The analysis on the cipher is carried in two parts. In security analysis, it contains key space analysis, information entropy analysis and correlation analysis. In the part of attack the cryptograph, it analysis the structure of LFSR by divide and conquer attack.3. The dissertation has emphasized to analyze the Lyapunov exponent characteristic of Logistic system, and has analyzed the chaotic sequences generated by Logistic map. Under the fixed parameter and precision, it estimates period, which is the key problem of chaotic cryptograph applications.4. This dissertation discusses that application of the chaotic cryptosystem should combine with standard cryptograph arithmetic. A new chaotic cryptosystem, which is mainly constitute Logistic system and A5/1 arithmetic is proposed. The result indicates that the output sequences satisfy requests of the stream cipher. And the scheme can be performed by the hardware and be used in the application by FPGA.