| Information security affects the national security,the economic stability and the people’s privacy.Chaotic communication has a high degree of security and provide better protection for information security based on the characteristics of physical layer encryption,so it has achieved rapid development in the past decades.Chaos synchronization secure communication is an important branch in the field of chaotic communication,and the realization of high-quality synchronization requires the completely matched parameters between the sender and the receiver,which not only makes the traditional chaotic synchronization communication face the problem of lower synchronization coefficient,but also increase the difficulty of hardware implementation.As a new type of neural network,the reservoir computing（RC）with good nonlinear fitting ability has become a hot topic,and it has been proved that RC can be used to predict chaotic time series.Based on this,this thesis proposes a research on chaos synchronization secure communication based on RC.The sender uses the chaotic signal generated by chaotic circuit or chaotic semiconductor laser as the carrier,and the encrypted signal is obtained by the method of chaos masking.At the same time,the RC is used as the receiver in chaotic synchronization communication,which trains itself by using the encrypted signal and the chaotic carrier,so that the RC can predict the unknown chaotic carrier according to the known encrypted signal,and then realize the chaotic synchronization and communication with the sender.The synchronization performance and the communication performance of the system are studied through numerical simulation and experimental verification,and the results show that the RC can achieve high-quality chaotic synchronization and communication.This method avoids the problem that the parameters of the transmitter and the receiver are difficult to match completely and provides a new idea for chaos synchronization secure communication.The process and results of the research in this thesis are as follows:（1）The chaos synchronization secure communication method based on RC is proposed,in which the RC is trained by using the encrypted signal and a part of the chaotic carrier signal to synchronize with the sender that means the prediction of the chaotic carrier is realized and then the secure communication can also be achieved through direct subtractive demodulation of the encrypted signal and the synchronous chaotic carrier.Further,the cross-prediction algorithm reduces the prediction error of the RC and eliminates the accumulation effect of the carrier synchronization error so that the long-term prediction synchronization and communication can be achieved.（2）The Lorenz chaotic synchronization communication system based on RC is designed,and the influence of the internal and the external parameters on the synchronization performance and the communication performance of the proposed system is explored by simulation.Firstly,the influence of the external parameters（the mask coefficient and the signal-to-noise ratio）on the normalized mean-square error（NMSE）of carrier prediction and the communication bit error rate（BER）is explored,and the external parameter range is determined that the system can achieve the communication standard of the hard decision threshold of forward error correlation.Secondly,on this basis,the influence of the internal parameters（the number of reservoir nodes and the leakage rate）on the NMSE and the BER is further explored.Finally,the optimal operation point of the system is determined under the combined effect of the internal and the external parameters.At the same time,the direct linear filtering attack of the attacker is simulated to verify the security of the system.In addition,the simulation of image communication is also carried out to prove the feasibility of the method proposed in this thesis.The research results show that the NMSE of the proposed system can reach the order of 10-6and the BER can reach 10-8 orders of magnitude,besides,the BER of the direct linear filtering attack is about 0.5,which proves that the synchronization quality,the communication quality and the security of the proposed system can be guaranteed at the same time.（3）The laser chaotic synchronization communication system based on RC is designed,and the influence of the internal and the external parameters on the synchronization performance and the communication performance of the proposed system is explored by simulation.Firstly,the influence of the external parameters（the mask coefficient and the signal-to-noise ratio）on the NMSE and the BER is explored,and the external parameter range is determined that the system can achieve the communication standard of the hard decision threshold of forward error correlation.Secondly,on this basis,the influence of the internal parameters（the number of reservoir nodes and the spectral radius）on the NMSE and the BER is further explored.Finally,the optimal operation point of the system is determined under the combined effect of the internal and the external parameters.At the same time,the direct linear filtering attack of the attacker is simulated to verify the security of the system.In addition,the simulation of image communication is also carried out to prove the feasibility of the method proposed in this thesis.The research results show that the NMSE of the proposed system can reach the order of 10-4and the BER can reach 10-9 orders of magnitude,besides,the BER of the direct linear filtering attack is above 0.28,which proves that the synchronization quality,the communication quality and the security of the proposed system can be guaranteed at the same time.（4）Various schemes of the chaos synchronization secure communication based on RC are comparatively studied,including the comparison between the cross-prediction scheme and the model-free prediction scheme,the comparison between the activation function tanh scheme and the activation function sigmoid scheme.The research results show that the synchronization holding time and the prediction accuracy of the cross-prediction scheme are more superior than those of the model-free prediction scheme,besides,the prediction accuracy and the communication quality of the activation function tanh scheme are higher than those of the activation function sigmoid scheme.The above results prove the superiority of the chaos synchronization secure communication method based on RC and the cross-prediction algorithm proposed in this thesis.In addition,the Lorenz chaotic synchronization communication experiment with a distance of 200m is also carried out,among them,the pseudo-random code and the image are used as the useful message respectively.And the experimental results are highly consistent with the simulation results,which verifies the practicability of the method proposed in this thesis. |
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