Research On Security Enhancement Of Electro-optic Feedback Laser Chaotic Communication System

Due to the chaotic laser sources can generate the high-dimensional chaotic signal with high complexity,unpredictable,and noise-like dynamics,it has been a hot spot in the secure communication field.Chaotic laser sources can be divided into two categories:all-optical chaotic system based on internal nonlinear effect of laser and electro-optic chaotic system based on external nonlinear feedback loop.Electro-optic feedback laser chaotic system has great practicability because of its strong robustness and wide output signal bandwidth.However,the security of the system is flawed.Since the dynamic equation of electro-optic feedback laser chaotic system is a kind of delay differential equation,the time delay signature caused by the periodic components are introduced.By statistical analysis,the eavesdropper can easily steal the time delay parameter which is the most important key of electro-optic feedback chaotic system.After the eavesdropper obtains the time delay parameters,he can crack the whole system by means of artificial intelligence.In this paper,the security enhancement of electro-optic feedback laser chaotic communication system is studied,and two innovative time delay signature concealing electro-optic chaotic systems are designed from two perspectives:(1)An attempt is made to introduce noise signal into electro-optic chaotic system.The results show that the time delay signature of electro-optic chaotic system will be suppressed when noise signal is introduced.According to its noise-like characteristics,chaotic signal is used to replace the noise signal,and the effect of time delay signature suppressing is also obvious.An innovative theory is proposed.Basing this theory,a time-delay signature concealing electro-optic chaotic system with multiply feedback nonlinear loops(MFNL)is proposed.The modeling process of the system is analyzed in detail.The bifurcation diagram and permutation entropy of MFNL is analyzed,and the results show the nonlinear dynamic behavior of the system becomes more complex due to the nonlinear loops is introduced.The autocorrelation function and delayed mutual information is employed to analyze the statistical characteristics of the system.The results show that the time delay signature of the system is concealed when the feedback gain is relative low.The performance of communication system is evaluated from the perspective of synchronization quality.The results show that the synchronization quality of the system is very sensitive to the mismatching of time delay parameters and is more robust to the mismatching of other parameters such as the feedback gain coefficient.The time-delay parameter of the system is suitable as a key parameter,and the key space of the system is greatly increased by introducing more tunable delay parameters.(2)The complexity and statistical property of electro-optic chaotic system depend on the driving voltage of Mach-Zehnder modulator in the feedback loop.Some systems conceal the time-delay signature by handling the drive voltage of the Mach-Zehnder modulator.In order to solve the problem that the feedback gain coefficient is difficult to realize and the system delay parameter will be exposed in the cross-correlation function of the multi-channel transmission signal,a novel time-delay signature concealing electro-optic chaotic system is designed.The dynamic behavior of the system is similar to that of the traditional electro-optic chaotic system.By analyzing the time sequence waveform of the system under different feedback gain coefficients,the process of the system from stable state to chaos can be reflected intuitively.When the feedback gain coefficient is low,the timing waveform of the system has obvious periodicity.With the increase of the feedback coefficient,the periodicity of the system gradually disappears.The permutation entropy is employed to analyze the complexity of the system.Due to the more times of nonlinear transformation are introduced,the complexity of the system has been greatly increased.The autocorrelation function and delayed mutual information is employed to analyze the statistical characteristics of the system.The results show that the time delay signature of the system is concealed when the feedback gain is relative low.Based on this model,a chaotic synchronous communication system is designed.The performance of communication system is evaluated from the perspective of synchronization quality.The sensitivity of the synchronous quality to the parameter mismatch of the receiver and the initiator is analyzed.The synchronization quality is very sensitive to the mismatching of delay parameters.The delay parameters are suitable for the key parameters of the system.By introducing more tunable delay parameters,the key space of the system is greatly increased.To sum up,two time-delay signature concealing electro-optic chaotic systems are proposed in this paper.The dynamic behavior characteristics,complexity,security and synchronization performance of the two systems are deeply analyzed,and the relevant results have been recognized by peer review.This paper is a further exploration and innovation in the direction of security enhancement of electro-optic feedback chaotic communication system.This paper is wished to contribute to the field of laser chaotic communication.