Study On Speech Secure Communication Technology Based On Chaotic Synchronization

With the rapid development of electronic information technology,information security is beginning to face more and more challenges.Chaotic secure communication technology as a new branch of secure communication field has been developing rapidly under the continuous efforts of scholars.On the basis of chaotic synchronization,this thesis mainly studies the problems of the identification of unknown parameters in the chaotic communication system,chaotic signals and the technology of chaotic modulation.The main contents of the thesis are as follows:First of all,in order to solve the problem of the identification of unknown parameters in chaotic communication system,a new method of parameter identification of chaotic system based on pattern search method is designed.This method turns the problem of parameter identification into the identification of the product of parameters and use pattern search method to estimate the product of parameters.The identification of unknown parameters is realized by using the amplitude ratio of the state variables in the drive and response system and the estimated value of the product of the parameters.The experimental simulation shows the effectiveness and feasibility of the method,the convergence rate of parameters is fast and identification precision is high.Secondly,since the structure of the existing M-ary digital chaotic communication systems are complex,on the basis of the method of parameter identification of chaotic system mentioned above,a new method of multilevel digital chaotic communication is presented by combining chaotic parameter modulation with chaotic keying modulation.The simulation shows that the method can not only transmit the multilevel digital signal effectively,but also improve the security of the communication system.Finally,aiming at the problem of high DC component and low frequency component in the traditional chaotic signal,after analyzing the characteristics of many chaotic systems,we find a way to improve the power spectrum distribution of chaotic signals and transform a new chaotic system based on Lü system.The experimental simulation shows that the chaotic system effectively inhibits the DC and low frequency components.By the way,a new chaos shift keying modulation method based on dual synchronization structure is proposed by usingthe chaotic system mentioned above.In this method,the signal multiplied by the digital pulse signal and the chaotic signal is sent to the receiving end,the demodulation of the signal is realized by comparing the error signals' value of the dual synchronous response system.Theoretical and experimental results show that the system can not only effectively realize the transmission of voice signals,but also eliminate the bifurcation of the attractors in return maps,and improve the implementation and secrecy of the chaotic shift keying communication system.