Chaotic Synchronization And Its Application In Secure Communication

Chaos is a product of the combination of modern science and modern technology. In recent decades, the new developing subject which develops rapidly in theoretical concept and practical application has penetrated into every subject and field. Along with computer technology, information technology and communication swift and violent development, the traditional secure communication method already could not satisfy the people to the communication security performance request. In this kind of situation, people are urgent to need to seek the new secure communication method to guarantee the network the security. Because the chaos secure communication has merit of strong character in real time, higher security performance, demonstrates it has the formidable vitality in secure communication domain. Simply saying, chaotic theory is an important branch of non-linear theory and also an important component of modern non-linear theory. Chaotic system can produce instable, pseudo-random, uncertainly but boundary behaviors and it is sensitive to its initial conditions. Chaos is a quasi-stochastic phenomenon appearing possibly in definite nonlinear dynamic systems. Chaotic motion is a complex nonlinear motion and the chaotic phenomenon has been observed in a lot of real systems. The dynamic properties of chaos signal such as ergodicity, aperiodic, uncorrelated, broadband and noise-like have been proved to be useful for secure communication. The chaotic synchronization is the theory basis of secure communication. The research of the chaotic synchronization and its application becomes a new research focus in nonlinear science fields.The key reason why the chaos synchronization research becomes one hotspot nowadays is that this research is the sticking point of the hyper chaotic communication. Chaotic synchronization is the foundation of chaotic communication, and with every new method putting forward, we are able to get original revelations in our research. Here has also given some definitions for analyzing and describing some characters of chaotic mapping and mathematical tools in the letterpress.It also analyzed the synchronization design method of low-dimensional chaotic system, and the application and analysis of secure communication of hi-dimensional hyperchaotic synchronization. Hyperchaotic synchronization plays an important part in research of non-linear theory for its better secrecy and stronger robust. The application of secure communication of hyperchaotic synchronization will be the direction of developing in future.Then work content:Chapter one has introduced the non-linear theory. Also, several kinds of research are summarized in the non-linear theory, those are: analytic method, method of phasic plane, and method of numerical value. Meanwhile, the purpose and importance in research of chaos and expectation of application of chaotic synchronization is introduced.Chapter two has put forward two basic concepts in relation to this article, Lyapunov exponent and attractor, and summarized representative chaos models which consist of disperse system of chaos models and continuous ones. Disperse ones include Logistic mapping, Henon mapping, Lozi mapping. The ones continuous include Lorenz system, Lu&& system, Chen system, Rossler system, Duffing equation, and Chua circuit.Chapter three has introduced the development, definition, and stability of chaotic synchronization, put forward synchronization methods existing and their traits, and analyzed the synchronization designing methods. In a broad sense, chaotic synchronization is part of chaotic control which is making use of chaos signal to control chaotic system and then follow the complete reconstruction of the two systems. This designing aims at classical synchronization method, coupling synchronization, to simulate the test. Mutual coupling non-linear systems have very complex dynamics motions, which have no universal theories till now. But these systems exist everywhere in nature. So theories and researches in this kind of synchronization are of importance.Design the unilateralism coupling synchronization system according to autonomy chaotic system and conclude error system in operation to drive system and respond system therefore receive the gradual stability based on the Lyapunov function.Chapter four has researched the tissue of secure communication of hyperchaotic synchronization. Most of the researches of chaotic synchronization at present aim at three-dimensional chaotic system, which is a low dimensional chaotic system with an up-zero Lyapunov index. It is proved that in use of hyperchaotic system, there is better secrecy, greater storage and capacity of information dealing, and stronger robust. Firstly, because of the properties of quasi-stochastic and continuum broadband frequency spectrum, chaos signal counts great value in research of secure communication. Introduce a few synchronous schemes in common use, such as chaos masking, chaos shift keying, and chaos parameter modulation. Communication capabilities of kinds of schemes have been analyzed so that we can design a communication system with better secrecy. Because of hyperchaotic synchronization with better secrecy, apply it to design a hyperchaotic secure communication system based on a state observer and multistage time-delayed hyperchaotic secure communication system. In the two schemes, it induct both encrypt module and decrypt module. From the simulation, hyperchaotic secure communication system based on a state observer has strong robust in condition of existing inner noise disturb. But in case of parameters not agreed, robust is bad. As for famous Markey-Glass time-delayed system, even if snoopers get the signals and system structure, the scheme has ideal robust still if parameters unknown.Finally, it has made conclusions for completed work, main contributions of this research work, and prospect for directions of future research.