Investigation On Bidirectional Closed-loop Chaotic Laser For Private Communication

Facing informatization of people’s daily lives and networking of the society increasingly, how to ensure the security of the information becomes a key issue, what related to the national security, enterprise economic benefits and people’s life stability. Chaotic secure communication, what is concerned with applying chaos to information security aspect, will have a good development prospect in the21st century. According to the latest domestic and international research status, a new bidirectional closed-loop chaotic laser system with three-laser for private message transmission is proposed. Comprehensive numerical analysis about the feasibility and privacy of this scheme has been presented in this paper.In this paper, appropriate theoretical model of bidirectional open-loop chaotic secret communication system is built. The Matlab software is used for theoretical investigation. With the changes of feedback level and injection current, SLs go through steady state, period and chaos. The research shows that the twin responses achieve synchronization without any time delay, however, the cross correlation coefficients between driver and responses is very small; system shows different alignment tolerances for different parameters mismatch; when the common driver suddenly is damaged or can’t work, the information on channel cannot effectively be hidden.In view of the problem in open-loop system, the system is improved. The closed-loop secret communication system about bidirectional communication has been designed. We get related mathematical model by revising the rate equation of open-loop system. The simulation results show that, the emission and receiver achieves chaos by self-optical feedback, so there is no information hidden failure problem. Optical injection by the driving laser forces two response lasers to achieve completely synchronization. What’s more, some comparisons with open-loop system have been done. The results show that the closed-loop has a wider and flatter band; system become more sensitive to parameter mismatch in closed-loop system; when multi-parameter mismatch appear, the system will become more complicated. So it’s more difficult to achieve synchronous demodulation for eavesdroppers, and gets a better privacy level in closed-loop scheme.Finally, we present chaotic masking(CM) and chaos keying(CK) two kinds of encryption based on the closed-loop bidirectional transmission mode, the processes information transmission are numerical simulated, the security of message is also analyzed. Study results prove that CM and CK all can hide information very well. The idea of masking method is simpler and easier to implement compared with keying method, but the secrecy is relatively lower; because keying method modulates two different chaotic outputs with different initial conditions, so it requires a more accurate trimming.