Performance Analysis And Application Of Chaotic Key Sequence Generator

At present, science and technology of the world is changing rapidly. Meanwhile, with the quick increasing of scicence and technology, people move forward in their lives continuously. All conrners of the world are linked together due to information networks and economic globalization, so that there will be some kinds of direct or indirect contacts and interaction effects between two points even though they are far away from each other. However, each coin has two sides. Due to the existence of such an intrinsic link between them, it leads to a serious threat to information security issues of the whole society. Therefore, people have paid more and more attention to how to solve and protect the security of information with the society developing.After the proposal of chaos theory, many researchers embark on the journey of exploring the combination of chaos and secure communication gradually. Chaotic system is a complex and nonlinear system with a lot of good characteristics, such as the extreme sensitivity to initial conditions, the long-term unpredictability, the overall stability and internal randomicity, etc. Moreover, because of these characteristics, the complexity, randomness and relevance of the sequences generated by chaotic systems are very good and difficult to be predicted. Therefore, it indicates that chaos theory is very suitable for privacy policies. According to chaotic mathematical equations, chaotic key stream generators can be designed and the sequences generated can be used as the key streams for encryption and decryption. It is a quite meaningful and significant research subject.In this thesis, the related basic knowledge of chaos theory is studied firstly. For the requirements of application, this research focuses on the discrete chaotic systems, especially on comprehensively analyzing the characteristics of three typical systems, namely Logistic system, Tent system and Henon system. In order to choose a more suitable system which can be used as the key sequence generator, three chaotic key sequence generators are built by DSP Builder tool according to the equations. At the same time, the performances of these generators are analyzed and compared through several common methods of chaotic characteristics and statistical properties. The final results show that the x output sequence of Henon sequence generator designed in this paper is the most advantageous. Due to the output sequences of Logistic and Tent sequence generators are short-period, a new key sequence generator is designed by cascading multiple chaotic systems. The test results indicate that the sequences generated by this new generator are not periodic in a large sequence length. These studies make this paper achieve substantive results in the researches and applications of using discrete chaotic system as key sequence generators. Meanwhile, these results also provide the foudations for comparing them with the generators desinged by continuous chaotic systems in order to design an optimal generator. Finally, a chaotic encryption system based on FPGA is designed. It applies Henon sequence generator proved to be the best to provide the key sequence.