Design Of Cryptographic Hash Function Based On Chaotic System

With the rapid development of the Internet-based e-commerce technology, public key cryptography and digital signatures as the representative of encryption technology has become the research hotspot. One-way Hash function is a key of digital signature, can greatly shorten the signature time, and has a wide range of applications in the message integrity testing and message authentication. Common Hash functions include SHA and MD series, but in the past few years, cryptanalysis on these Hash function have discovered many serious flaws. After the traditional Hash function was successively proved to be unsafe, the researches of hash function based on chaos system have become a hot spot in the field of information security.The following tasks have been accomplished in this thesis:(1) The basic knowledge of cryptography hash function and chaos theroy is introduced. First, the definition of Hash function, properties, application, classification, and common iterative structure and evaluation method are introduced. Meanwhile, in order to give a description of the practical application value of hash function based on chaos theory, this paper lists several basic models for chaos theory, analyzes the advantages and disadvantages of chaotic mapping which is used to construct the one way hash function, and combines several hash functions based on chaos theory.(2) For the defects of an existing Hash function based on spatiotemporal chaos, draw on traditional Hash function for message processing method, adding a message length in the original algorithm filling process and conducted a message extension, while increasing the iteration the number of rounds to improve security of the algorithm. Finally, the confusion and diffusion properties, collision resistance, hash speed of the algorithm are tested by simulation experiments. Theoretical analysis and experimental results show that the algorithm while ensuring the efficiency of the algorithm, to overcome the inherent security flaws, with high security.(3) A hash function based on security chaotic system is proposed. The basic components of the hash function is digital dynamical filters, using an integer of chaotic model, complex chaotic operation can be replace by simply shift, or operation, which reduces the chaotic operation time. Meanwhile, due to scalability of digital dynamical filters, making the proposed Hash functions can produce different length of hash value. In the mode operation of the configuration, the algorithm also has flexibility, there are two operation modes can be selected in the proposed hash function which are parallel operation mode and serial operation mode. Theoretical and simulation results show that the proposed hash algorithm has strong diffusion and confusion capability. Through the FPGA software simulation, parallel operation mode of the Hash function has higher efficiency.Finally, the research work of this dissertation is summarized, and the futuredeveloping direction is indicated.