Design Of Nonlinear Dynamic Filter And Its Application In Information Security

This thesis mainly focuses on the research of secure chaotic systems and their application in information security, which involves the following three aspects: firstly, propose the secure criterions for chaotic system oriented to cryptographic design and the corresponding secure chaotic models satisfying these criterions; secondly, investigate the applications of these secure chaotic models in digital chaotic cryptography; thirdly, study the secure chaotic model in the applications of chaotic secure communication. The main contributions of this thesis are given as follows:In chapter 1, the up-to-date research on chaotic cryptography is systematically classfied and analyzed, and herein three common problems are pointed out. To solve the second common problem, secure criterions of chaotic model oriented to crypgraphic design are given.Based on the analysis of nonlinear digital filter, in chapter 2, a specific secure chaotic system, namely nonlinear dynamical filter (NDF) is proposed to fulfill above secure chaotic model criterions. Furthermore, two other secure chaotic systems are also built on the basic NDF, which are named feedforward-feedback NDF (FFNDF) and NDF-based coupled map lattice (NDF-CML) respectively. Since the three chaotic models have different security level and structure complexity, they can be employed in various chaotic ciphers.In chapter 3, sevearl typical chaotic Hash functions are cryptanalyzed and some problems are pointed out. After that, a keyed Hash function based on M-D iteration structure and FFNDF is proposed (FFNDF-KHF). The analysis results show that FFNDF-KHF avoids all known security pitfalls of chaotic Hash function, and has high security and acceptable hashing speed.To overcome the dilemma between low information reduandancy and high bit speed in most chaotic keystream generators, a novel NDF based keystream generator (NDF-CKG) is proposed in chapter 4, which is designed with metric entropy princple and parallelity of NDF. Since the structure of NDF-CKG partly merges nonlinear feedback, nonlinear feedforward and clocked control approaches together, it has very high security. To evaluate its performance, software version with C language and FPGA hardware synthesis using symplify are further performed. The experimental results show that NDF-CKG has low cost and high speed, and can be used instead of LFSR in conventional stream ciphers.Based on the two-dimenional feature of NDF-CML and the product cipher feature of Feistel structure, in chapter 5 a digital image encryption scheme is given. The highlights of this scheme are the Poker shuffling scrambling and the SPN. By using substitution-permutation-diffusion operations alternately in Feistel round transformation, this scheme can resist several attacks, especially the attacks in literatures [199-121].In chapter 6, the application of NDF in chaotic secure communication is investigated. Herein a digital secure spread-spectrum communication scheme (NDF-CSK) is proposed and its security and anti-jamming capability are analyzed.To evaluate its practicability under strong jamming, furthermore, four FRFT-based jamming cancellations vs three kinds of frequency-modulated interferences are discussed and simulated. The theoretical and experimental results show that the jamming cancellations are valid for improving the bit-error-rate of NDF-CSK under jamming environment. This work has important reference value for the robustness of digital chaotic communication in practice.