The Research Of Chaos Synchronization And Its Applications To Secure Communication

In this thesis, characters of chaos and the main means to identify chaotic system areintroduced, and some methods about synchronization and control of chaos are introducedtoo. We propose some new improved methods to study the phase synchronization ofchaotic systems and the parameter identification of the Ro&&ssler hyperchaotic system, anda new chaos-based secure communication is proposed. This thesis shows my works in thefollowing three parts:(1) In order to find the correct corresponding relation between phase synchronize in manywinding center of chaotic systems and dynamics variety in system, phase synchronizingLorenz system and Duffing system via amplitude coupling is proposed. First , we convertthe original Lorenz system and Duffing system into the dynamics of amplitude and phase,then we add amplitude coupling to it and compute the winding number and the Lyapunovexponent, The simulation result indicate that as the coupling intension increasing, thephase synchronize occur in the system, and the phase synchronize is corresponding to thetransition of the Lyapunov exponent, this show that there is correct corresponding relationbetween phase synchronize in many winding center of chaotic systems and dynamicstopological variety in system..(2)In the parameter identification of the hyperchaotic system, it need too much informationto accurately identify parameters, and the precision is low in the case of the limitinformation, the observations are too complex, in order to avoid these, the followingobservations for the Ro&&ssler hyperchaotic system is proposed. a)& = ?δ1(y2 ? x2)y2 ,b)& = ?δ2(y4 ? x4)y1, d)& = ?δ3(y4 ? x4)y4 。The simulation results indicate that it can identify three unknown parameters of the drivesystem quickly and accurately if two time series of the drive system are known. Even if theparameters of the drive system vary, the unknown parameters can be also identified.(3) There are low resistant decryption, long synchronization's time, narrow key'schoice ,slow encryption speed in many chaos-based secure communication scheme, basingon Ro&&ssler hyperchaotic system, we propose a new high secure communication schemeAbstractwhich using mod technology. In this scheme, firstly we change the driving signal intodigital signal, then we execute shift of the digital signal and bitwise XOR with thekeys ,after this operation we transmit the driving signal in open channel to receiver tosynchronize the decryption by the extracted synchronized signal. After synchronized,keystream produced by encryption is used to secure communication. It is impossible toattack by the method of error function attack(EFA), so this secure communication methodhas advantage of property of high resistant decryption, and it also effectively avoid thesedefects above.