Study On Chaotic Secure Communication System

The advance of the digital signal processing technology and the prevalence of the network communication have brought about a crisis of multimedia security, which triggered an avalanche of attentions either paid by the government or by the general public. Since the multimedia data like image, video and audio have certain intrinsic properties such as high redundancy and bulk capacities, special concerns on speed, computational construction payload and many other security issues have operation to be made in of the encryption algorithms that would not be taken the into account in that of text encryption. In this regards, currently existing cryptological methods are not appropriate for the applications of nowadays multimedia encryption.As a phenomenon found in non-linear dynamic system, chaos is deterministic and random-like. Because chaotic systems have the characteristics of sensitive dependence on their initial conditions, a large number of non-periodic, continuous broadband frequency spectrum, noise-like, and this characteristics are fit of demands of cryptology, so chaos have become of a new resource of cryptology. This dissertation studies chaotic technology and its application in secure communication system, the primary endeavor.First, combine with the research actuality and development tide of chaos theory, makes a systematic exposition for the development of the chaos theory, the definition and characteristic of chaos. Through the analysis and simulation research of typical chaotic systems and chaos analysis technology, we complete the computation of Lyapunov exponent of typical chaotic systems. We also summarize the research of chaos control and chaos synchronization, and its potential applications. The computer experiments for secure communication of digital voice messages and digital image are implemented and the results are satisfactory.In this foundation, this article has made the improvement to the traditional encryption algorithm and proposed Multi-Chaos image encryption, and had proven through the simulation experiment this kind of image encryption technology expanded the key space, further sharpened ability which the cryptographic system anti-breaks a code. At the same time, in the P-C synchronization foundation, this article proposed one introduction composite signal feedback chaos pronunciation encryption, Through to the actual pronunciation signal simulation experiment, had proven the introduction composite signal feedback to the chaos actuation end, causes the pronunciation signal to melt truly to the chaos signal in, thus further enhanced the signal in the realization synchronization encryption foundation anti-to break a code ability, simultaneously anti-noise ability also was improved, and enhanced this privacy system usability.This article in view of the chaos privacy communication system main flaw, namely quite is sensitive to the noise and the channel distortion, establishes the effective synchronization with difficulty, has analyzed the CPPM(Chaotic pulse position modulation)privacy communication technology and the CPWM (Chaotic pulse width modulation)privacy communication technology. This article proposed passes through using the phase space path from the definition phase space took the chaos pulse sequence the method, enable the chaos pulse sequence to be more complex, to have the pseudo-random, has the simple dynamic change control characteristic, thus used in the encryption chaos pulse sequence is difficult to track, is explained, enhanced the encryption security. Applied this chaos arteries sequence in the CPPM privacy communication system, discovered through the simulation, obtained the pulse control sequence with the phase space law greatly to promote the chaos localization pulse pseudo-random, further has increased the time delay signal the difficulty which tracked, explained, increased the privacy system security.The characteristics of chaos in it self decide its wide application prospects. Especially in recent years, the progress about chaotic synchronization and chaotic control makes its potential application prospects in the secure communication field with its particular charm. At present, the research of chaotic synchronization technology and its application is still developing. The problem that how to combine it with the need of every field is still being explored in order to provide new technology and methods for every applied subject.