| In the era of big data,high-speed information security transmission has put forward new requirements for secure communication,and various encryption technologies have been proposed in succession.As an important technology to ensure information security,encryption based on the physical layer can effectively alleviate the security risks brought by algorithm encryption.The most representative physical layer encryption is quantum secure communication,which provides an absolutely secure communication.However,it is limited by the communication distance and the strict requirements for quantum devices.Therefore,it is urgent to seek breakthroughs in communication speed and compatibility with current communication systems.Chaos secure communication is widely concerned because of its advantages of hardware encryption,suitable for high-speed and long-distance transmission,and compatibility with the current communication systems.In addition,high-speed key distribution based on chaos synchronization and chaos key extraction has also been thoroughly studied.Chaos shift keying is an important keying method in chaos secure communication and key distribution.During the shift keying process,the chaos synchronization state is randomly switched.Only when the keying state is the same,legal users can demodulate the transmission information from the synchronized chaos waveform or extract the consistent random key.As a result,chaos shift keying further improves the security of key distribution beyond the security of laser parameter matching.However,it should be pointed out that the synchronization state will be switched randomly during shift keying,while the desynchronization and synchronization switching process needs a certain recovery time.The chaos resynchronization time limits the rate of chaos shifting keying which determines the rate of chaos communication and key distribution based on shift keying.Focusing on the problem of chaos resynchronization time,this paper mainly carried out the following work:1.Based on the spin flip model of the vertical cavity surface emitting laser,the chaos resynchronization time of VCSEL under unidirectional open-loop injection-locking synchronization configuration is investigated numerically.The influence of system injection parameters and laser parameters on the recovery time is proved.The key parameters that have significant influence on the resynchronization time are obtained,mainly including injection rate and frequency detuning,as well as the laser's parameters including bias current,carrier decay rate,field decay rate,gain coefficient and linewidth enhancement factor.2.By injecting continuous light into VCSEL,We analyze the changes of the relaxation oscillation period and locking time to obtain the internal relationship between the relaxation oscillation period,locking time and resynchronization time,and explain the physical mechanism of chaos resynchronization time from the perspective of relaxation oscillation period and locking time.It is initially clear that there are three ways to shorten the resynchronization time:increasing the lasers' bias current and differential gain coefficient,or reducing the photon lifetime and carrier lifetime to shorten the relaxation oscillation period;reducing the linewidth enhancement factor;increasing injection intensity and reducing frequency detuning to achieve strong injection locking.3.The theoretical model of key distribution system for VCSEL is based on random phase feedback.Randomly switching the chaos synchronization state is achieved by randomly modulating the feedback phase of the response laser,using short-term cross-correlation to calculate the chaos resynchronization time,it is theoretically confirmed that VCSEL can achieve a shorter resynchronization time than the edge emitting semiconductor laser.Thereby,VCSEL can be used to improve the rate of key distribution. |
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