Chaos Synchronization Secure Communication System

In the first part of this thesis, after discovering that the low-dimension chaos sequence cipher is low in security, a scheme of chaos sequence cipher based improved Lorenz system is proposed. The chaos sequence cipher is tested, and results manifest the scheme established using this sequence cipher is high in security. Then the synchronization characteristics of several chaotic synchronization methods are analyzed by the way of computer simulation, such as the theory of drive-response synchronization, the theory of active-passive synchronization, the theory of synchronization by feedback and the theory of synchronization based observer. After considering the practicability and synchronization precision, we allege the theory of active-passive synchronization is the best one for building chaotic synchronized secure communication system. And then, the synchronization of unified systems with different parameters is achieved, which is practical. Finally we discuss three typical attacking methods against chaotic synchronized secure communication system, such as attacking method based phase space reconstructing, attacking method based return map and attacking method based chaotic synchronization, at the same time we also study the security of several current schemes of chaotic synchronized secure communication system. According to the above research, a new two-grade chaotic synchronized secure communication system scheme is proposed. The first grade of this scheme adopts one-dimension spatio-temporal chaotic cryptography, the improved Lorenz system adopting parameter perturbation is introduced in the second grade of this scheme. The results of computer simulation show that the scheme is good in applicability and high in security.