Research On Enhancing The Security Of Chaotic Optical Communication With Digital Key Modulation Feedback Phase

Due to its characteristics of noise-like,wide spectrum and unpredictability,chaotic signal can be used in secure communication.Ordinary and simple optical feedback leads the semiconductor laser(SL)to introduce a degree of freedom to generate chaotic laser,but there is also a common chaotic delay signature caused by feedback,that is,auto-correlation curve of chaotic laser has a significant peak at the feedback delay,which will seriously affect the security of chaotic secure communication.Meanwhile,using laser internal parameters as communication key is not easy to change,and the key parameter space is limited.Therefore,eliminating chaotic delay signature and increasing key space are very important for the security of chaotic communication system.How to solve these two key problems is current research focus of chaotic secure communication,in the paper,this topic is chosen as the research direction,aiming at optimizing chaotic output and enhancing the security of secure communication.The research contents and results are as follows:(1)Digital sequence is used as the key,by means of digital signal processor(DSP)and arbitrary wave generator(AWG),to control external cavity optical feedback random change,chaotic signal with complex dynamics is output.The scheme can effectively eliminate chaotic delay signature and increase key space,ensuring the security of transmission information.On this basis,unidirectional and bidirectional chaotic secure communication systems are designed.Moreover,chaotic bidirectional secure communication is realized successfully,and the influence of transmission channel signal-noise ratio(SNR)on bit error rate(BER)is studied.(2)A scheme is proposed to output chaotic light by feedback phase modulation of arbitrary wave.Auto-correlation function(ACF)and delay mutual information(DMI)technologies are used to confirm that chaotic delay signature is effectively suppressed.The effects of feedback strength,modulation frequency and modulation depth on time delay characteristics hiding of chaotic signal intensity and phase information are studied numerically.It is shown that chaotic signal source with no time delay and flat spectrum can be output under appropriate parameters.(3)Chaotic secure communication system based on single feedback phase modulation is designed,in which a random square wave is used as communication key to modulate the phase of feedback light,chaotic signal with wide spectrum and no delay is generated.A message is modulated into chaotic carrier and effectively demodulated at the receiving end.Under the condition of different channel SNR,by comparing the synchronization of two chaotic signalsat receiving end and BER of demodulated output message,two encryption methods of chaotic message modulation(CMM)and chaotic message masking(CMS)are studied.