Research On Chaotic Dynamic S-box Based Cryptography And Its Applications

The research of digital chaotic ciphers has attracted more and more attention after British mathematician Matthews first definitely put forward the conception of chaotic encryption algorithm in 1989, especially MD5 and SHA-1 have been cracked. In addition, a lot of modern cipher construction techniques and components are excellent, so it is suggested combining with modern ciphers to construct secure chaotic cryptosystems.This dissertation focuses on the design and application of chaotic ciphers based on chaotic dynamic S-Box, which involves the following aspects. First of all, this paper investigates the main problems of the chaotic ciphers faced. Secondly, it proposes some new chaotic cryptographic primitives, including a chaotic Hash function, a variable length block cipher and an image encryption scheme. Finally, it studies the proposed primitives in the application of security protocols. Specifically, the main achievements and originalities contained in this dissertation are as follows:(1) Detailed analysis of the state-of-the-art techniques in chaotic cryptography is carried out. Chaos-based S-boxes are proposed to cut down floating-point calculations in the existing chaotic ciphers.(2) Combined with the excellent thinking of traditional Hash function, a novel keyed one-way Hash function based on the designed chaotic dynamic S-Box is proposed. The new Hash function can give a chaotic Hash value by means of the look up table of functions and chaotic dynamic S-Box. Compared with the existing chaotic Hash functions, the new method improves computational performance of Hash system by using the chaotic dynamical S-Box substitution in place of iterating the original message directly in chaos system. Theoretical and experimental results show that the proposed Hash function has strong one way property, large key space, sensitivity to initial conditions and chaotic parameters.(3) To overcome the dilemma between performance and security, a variable length block cipher (VLBC) based on piecewise linear chaotic map and Tent map is proposed. The new cryptosystem gains confusion by dynamic S-Box substitution and avalanche property by modular and cycle shift arithmetic. In addition, the plaintext determined block length can effectively resist chosen plaintext attack and chosen ciphertext attack. The security analysis demonstrates that the chaotic S-Box based VLBC not only has large key space but also can withstand the existing attacks.(4) The diffusion and efficiency of the spatial chaotic based image cryptosystem are investigated. And then shows that the diffusion property of the spatial chaotic cryptosystem is too weak to withstand chosen plaintext attack. To improve the security, a novel image encryption scheme based a group of S-Boxes is proposed. The new scheme employs one spatial chaotic to shuffle the position of image pixels and build 4 S-Boxes dynamically, and then confuses the relationship between the cipher-image and the plain-image by utilizing a look-up table of S-Boxes, thereby significantly increasing the resistance to statistical and differential attacks. Theoretical and experimental results demonstrate that at the similar performance level, the proposed cryptosystem provides a secure way for image encryption and transmission.(5) Based on careful security analysis of the chaotic key agreements, pointes out that none of these schemes can satisfy the contributory nature of key agreement. To fill the gaps, a secure contributory key agreement protocol based on chaotic Hash is proposed. The proposed scheme utilizes the chaotic Hash function to achieve the contributory nature and enhance its security. Cryptanalysis demonstrates that the proposed chaotic-Hash-based scheme can overcome all the current deficiencies.(6) By analyzing current multi-secret sharing schemes, it pointes out that they are not adaptive the mobile condition. And then presents an improved chaotic Hash-based verifiable multi-secret sharing scheme on mobile devices e.g. cell phone and PDA. Compare with the existing verifiable multi-secret sharing schemes, the proposed scheme has the following strong points:a) more efficiency; b) the theory is simple and pellucid; c) fewer publishing data; d) the long-term secret si is reusable.