Research On The Theory And Technology Of Wireless Physical Layer Key Generation

With the rapid development of wireless communication technology,the rise of Internet of Things,autonomous driving,mobile payment and other services has put forward more stringent requirements for wireless communication security.The wireless physical layer key generation technology uses the inherent characteristics of wireless channels to establish a security mechanism,which has become a hot issue in academia and industry in recent years.The wireless physical layer key generation technology is lightweight and does not require a third-party organization for key management and distribution,which can effectively make up for the shortcomings of traditional encryption mechanisms and jointly enhance the security of wireless communication systems.Although the wireless physical layer key generation technology has many advantages mentioned above,there are still some challenges that need to be solved urgently.For example,the key generation performance is poor in a low signal-to-noise-ratio(SNR),the channel detection is difficult in the large antenna array system,and the key update is difficult in the static environment,etc.In view of the above problems,this paper will seek solutions from the aspects of improving the key generation rate,equivalent dimensionality reduction channel,and introducing reconfigurable intelligent surface(RIS),and study the wireless physical layer key generation technology.Firstly,the basic theory of wireless physical layer key generation technology and wireless channel characteristics are mainly studied.Starting from the development history of wireless physical layer security,the related literature is investigated,combined with the common fading of wireless channels,including large-scale fading and small-scale fading,the characteristics of wireless channels that key generation depends on are described,including the short-term reciprocity of wireless channels,spatial uniqueness and time-varying.At the same time,from the overall control of key generation technology,the basic process of key generation is introduced in detail,including channel detection,bit quantization,information coordination and privacy amplification.On this basis,three commonly used key evaluation indicators such as key inconsistency rate,key generation rate and key randomness are analyzed.Secondly,in order to solve the problem of low key generation performance under low SNR,a wireless physical layer key generation method based on amplitude-phase joint partitioning is proposed.Considering orthogonal frequency division multiplexing(OFDM)broadband mobile communication system,starting from the key length problem,using the advantages of OFDM multi-carrier and channel reciprocity to extract the channel frequency response(CFR)characteristics,and obtain the phase information and amplitude information of CFR respectively.Combined with the problem of key inconsistency rate,phase partition and amplitude partition methods are proposed to quantize phase and amplitude by region,and obtain highly consistent quantization keys.On this basis,a cross-merging of the phase-based key and the amplitudebased key is considered to enhance the randomness of the key.The experimental simulation results show that this scheme can effectively improve the key generation rate.Afterwards,aiming at the problem of excessive channel sounding overhead in wideband large-scale antenna array systems,a low-overhead key generation method combining slowlyvarying channel state information(CSI)and fast-varying CSI is proposed.Considering the scenario where the base station is configured with a large-scale antenna array to serve singleantenna users,starting from enhancing the accuracy of channel estimation,consider using the extended newton orthogonal matching pursuit(NOMP)algorithm.This algorithm can detect the channel slow-varying CSI with high accuracy,including the direction angle and delay of the path.At the same time,the slow-varying CSI is used to generate a long-term key that is highly consistent between the two parties.Combined with the problem of excessive channel probing pilot overhead,the channel dimension reduction method is considered,and the maximum ratio combining(MRC)reception and maximum ratio transmission(MRT)precoding are used on the base station side to reduce the equivalent channel dimension.Thus,the downlink pilot training overhead is greatly reduced,at the same time,the fast-varying CSI of the equivalent low-dimensional channel is estimated to generate a short-term key.On this basis,the long-term key and the short-term key are used jointly to enhance the key performance.The experimental results show that the scheme has good performance even in the low SNR environment,and the combined use of long-term and short-term keys can improve the security of the keys.Finally,in view of the difficulty of key update in static environment,a RIS-assisted wireless physical layer key generation method is proposed.Considering static scenarios,starting from the channel time variability and randomness that the physical layer key generation technology relies on,considering that RIS can adjust the propagation direction of reflected electromagnetic waves in real time,it can improve the problem of weakened channel time variability and reduced key update rate in static scenarios.Therefore,the RIS is introduced into the wireless channel as a public random source,adding randomness and time-varying to the static channel,and solving the problems of weakening the randomness of the key and reducing the update rate.On this basis,the influence on key generation when RIS is controlled by illegal party is studied.The experiment uses hardware equipment to build a communication system.Through the analysis of the measured data,it is verified that when the RIS is controlled by the legitimate party,it can enhance the key generation,but when the RIS is controlled by the illegal party,it will hinder the key generation.