Research On Physical Layer Secret Key Generation Technology Under Correlated Eavesdropping Channels Conditions

With the rapid development of wireless communication technology,higher requirements have been put on the protection of information.The physical layer secret key generation technology uses the intrinsic security attributes of the wireless channel — randomness,time-varying,and reciprocity to generate a consistent physical layer secret key on both sides of the legitimate users,which provides a new idea for solving wireless communication security problems.After more than 10 years of development,the theoretical study of this technology has gradually improved,but the following problems still need to be solved:(1)when the eavesdropping channel is related to the legitimate channel,the eavesdropper can obtain some information of legitimate channels,and existing researches do not fully analyze the influence of eavesdropper on the physical layer secret key capacity;(2)When the eavesdropper approaches to the legitimate users,he can obtain relevant Received Signal Strength Indication because of the same large-scale fading,so that the secret key generated by the legitimate communication parties using the received signal strength has the risk of eavesdropper prediction;(3)Existing key agreement methods are expensive and difficult to implement in resource constrained communication nodes;(4)How to implement and verify the secret key generation technology in resource-constrained physical network nodes remains to be studied.In view of the above problems,aiming at the scenario where the eavesdropper's channel and legitimate users' channel are correlated,this paper comprehensively analyzes the influencing factors of the physical layer secret key capacity,proposes solutions to resist passive eavesdroppers,and finally carries out experimental verification and test analysis in engineering.Specific research content includes:1.This article researches the secret key capacity under the effects of eavesdropper position,channel estimation time difference,channel coherence time and noise where the eavesdropper's channel and legitimate users' channel are correlated Firstly,the channel response is modeled as a generalized stationary stochastic process under Rayleigh channel conditions,then the problem of calculating the secret key capacity is transformed into the problem of solving the conditional mutual information between related random variables,and the covariance matrix between random variables is used.The correctness of the derivation results was verified by Monte Carlo simulation in Rayleigh channel environment.The effects on secret key capacity were analyzed.This content provides theoretical guidance about solving the problem of secret key generation schemes under channel related conditions for subsequent chapters.2.A physical layer secret key generation scheme based on wireless signal fading characteristics is proposed.When the eavesdropper is close to the legitimate users and the eavesdropping channel has a correlated,the legitimate users' secret key which generated by traditional secret key generation schemes based on received signal strength is easily acquired by the eavesdropper.The solution first estimates the large scale fading of the RSSI,and extracts small scale parameters of RSSI under the influence of multipath effect to generate the secret key,and finally use the BCH code to correct error bits.Simulation shows that this method can improve the eavesdroppers' secret key bit error rate and protect the legitimate users' secret key from being stolen,and only by once key agreement interaction can reduce the bit error rate of the legitimate users to almost 0.3.Based on the research and scheme of the first three chapters,we designed and implemented a physical layer secret key generation system for the Internet of Things,which tested and verified in the actual environment.In the experiment,a malicious eavesdropping node was also set up to eavesdrop on the legitimate nodes.The results show that the scheme proposed in this paper can increase the eavesdropper's secret key bid error rate close to 0.5 under the condition that the eavesdropper has obtained the relevant RSSI,and the legal users' secret key bit error rate is lower than 10E-3,which can realize secure and reliable encrypted communication.