Research On Chaotic Security Communication Based On Delayed Concealment

Chaotic signal has the performance such as great bandwidth,indeterminism and noise-like,it combines the optic-fiber's low attenuation,and as a result,the chaos can be used to chaotic carrier to realize unidirectional and bidirectional secure communication.The research has attracted the attention of scholars.Chaotic communication has developed rapidly in recent decades.As a very important application of nonlinear dynamics theory about the field of communication,its theory has gradually improved.The implementation of chaotic communication lies in the chaotic synchronization between the receiver and the transmitter,as well as the robustness against external perturbance.This fact indicates that once the dynamics of the receiver is synchronized to that of the transmitter,the chaotic dynamics of the receiver is not affected by the perturbance of the transmitter.Under external discrete perturbations,the chaotic dynamics of the receiver jump between synchronization and desynchronization relative to the transmitter,so that the transmitted information can be recovered by detecting their synchronization errors.For optical chaotic communication,the security of chaotic communication mainly depends on the match of external and internal parameters between two transceiver lasers.The internal parameters(such as carrier lifetime and line width enhancement factor)have small variation range so that eavesdroppers easily guess them.For external parameters such as feedback time delay signature(TDS),if the TDS can't be extracted by using autocorrelation coefficient,it can be well hidden.Thus the eavesdropper can't recover the chaotic dynamics of the transmitter,and the security of the system is ensured.Motivate by this,basing on the forerunner's researches on chaotic communication and laser chaos theory,and starting from the ideal of the privacy of secure communication,this paper uses different methods to conceal the TDS information on the system to achieve unidirectional and bidirectional secure communication.The main work and achievements are as follows:(1)Firstly,this paper numerically studies an improved electro-optical phase chaotic system,which can hide the delay and allow one-way transmission of information.The structure includes two cascaded delay loops.In one of two loops a parallel coupled microresonator(PCMR)is introduced to generate the frequency dependent group delay.By using the maximum Lyapunov exponent(LLE),L-Z complexity(LZC)and permutation entropy(PE)to analyze the chaotic behavior and complexity of time series,the autocorrelation function(ACF)and delay mutual information(DMI)are drawn to extract TDS.The results indicate that:The results show that: phase chaos with positive LLE,and highly complex LZC,PE can be generated within a certain range of feedback strength;the TDS is well hidden as the number of PCMR increases;the delay chaotic system has good synchronization performance and the synchronization is robust;in addition,it can successfully recover the transmitted message of the transmitting end by monitoring the synchronization errors of two chaotic sequences which correspond to the outputs of transmitting and receiving lasers.In this scheme,the feedback TDS are concealed,eavesdropping is impeded,and the security of the chaotic communication system is ensured.(2)Then,this paper proposes and theoretically studies a new architecture that combines the all optical intensity chaos and optoelectronic phase chaotic generator to realize bi-directional secure communication.The structure comprises three all-optical chaotic semiconductor lasers and two identical phase chaotic optoelectronic delay oscillators.A laser and an optoelectronic phase delay oscillator comprising a cascade system.The complexity of the chaotic time trajectory generated by the system has been studied by using LLE,LZC,PE and fractal box-counting dimension(FBCD).The system's TDS concealment performance is analyzed by calculating ACF and DMI.At the same time,we also studied the impact on synchronization performance by the mismatch of parameters such as TDS,bias current,and linewidth enhancement factor.Finally,we study the effect of the Q factor of the system communication performance when the information bit rate and modulation index change.The results indicate that:The results of calculating LLE,LZC,PE and FBCD point out that: when the bias current of the laser is increased to a certain range,the cascade system can generate chaotic signals with relatively high complexity.Moreover,by calculating ACF and DMI,one can find that when the laser output is fed into the phase modulator,the TDS information in the photoelectric phase oscillator can be well concealed,thus the security of the communication system is ensured.One notices that when the parameters are matched,the delayed chaotic dynamics can be completely synchronized,and the synchronization of the system has good robustness;at the same time,the change of bit rate and modulation index has a certain influence on the Q factor of the system,namely,an increase in the modulation index leads to an increase in the Q factor,but an increase in the bit rate causes a decrease in the Q factor.In summary,this paper proposes two lasers chaotic communication systems based on delay concealment of the model of laser chaotic communication system.And these investigations include theoretical and numerical analysis which correspond to delay concealment performance,complexity analysis,synchronization performance and robustness analysis,information transmission and so on.The main conclusions obtained are as follows: In one of two loops a parallel coupled microresonator(PCMR)the frequency dependent group delay is introduced,and the system can conceal the TDS well,and unidirectional chaotic communication with good synchronization robustness is realized;in a cascade system comprising a semiconductor laser and a photoelectric phase oscillating ring,the chaotic signal with high complexity and fractal dimension can generate,and the TDS is hidden well,and its good synchronization robustness and high Q factor ensure the achievement of high-speed bidirectional information communication.This paper is a further innovation and development of laser chaotic communication.It can enrich and improve the theory and put forward application of laser chaotic communication.And it is of great practical and long-term significance to promote the early realization of laser chaotic communication.