Research On Key Generation Of Physical Layer Secure Wireless Channel Based On 802.11ax Standard

In recent years,wireless communication technology has become an indispensable part of nations and individuals.Therefore,improving the security of wireless communication has become one of the important research topics.The key generation technology based on characteristics of the physical layer secure channel does not require key distribution and can resist the threat of third-party eavesdropping.In addition,the short-term reciprocity of the wireless channel helps to realize a“one key each time”generation system,which can effectively prevent high-performance computing equipment from cracking.At the same time,Wi-Fi has gradually taken up most of the network traffic.The 802.11 ax protocol which utilizes key technologies,such as OFDMA,MU-MIMO,1024-QAM,and spatial multiplexing,brings high capacity and efficiency to multi-user communication scenarios.Simultaneously,it also provides opportunities for the MIMO wireless channel key generation system in this article.Therefore,this thesis designs pilot signal frames based on 802.11 ax standard and establishes simulation and experimental transceiver models,including single-user MIMO channels,MIMO channels with eavesdroppers,and multi-user MIMO channels.Based on the IEEE 802.11 ax function provided by MATLAB WLAN toolbox,this thesis establishes a transceiver simulation model between AP and STA.Under different antenna distances of AP.The communication parties perform channel estimation after multiple channel detections and then quantize the collected CSI,reconcile information,amplify privacy,and finally generate the consistent key locally.This thesis analyzes the system performance from the CSI correlation,key mismatch rate,key generation rate,key randomness,key uniqueness and information leakage rate.In addition,this article builds SU-MIMO and MU-MIMO experimental systems indoors based on the GNU Radio.The communication parties send and receive Wi-Fi signals many times.After signal timing synchronization and frequency offset correction,they finally generate keys.This thesis studies and analyzes the key generation performance in different environments based on simulations and experiments.The details are as follows:· In order to study the CSI correlation and the initial key mismatch rate of SU-MIMO wireless system,as well as the improvement of the key generation rate and key randomness of SU-MIMO system compared with SISO system,this thesis respectively establishes simulation and experimental models for verification.In SU-MIMO system,simulations and experiments show that the CSI characteristics between adjacent channels are basically irrelevant when the AP antenna distance is greater than 0.5 times of the wavelength and the CSI between uplink and downlink channels always maintains good reciprocity.But compared with the SISO system,the channel reciprocity is slightly reduced.At the same time,the initial KDR of the communication parties is less than 10%,which meets the requirements of key agreement and corresponds to the CSI correlation conclusion.The KDR of the MIMO system is slightly higher than that of the SISO system.In the simulation system,the KGR is increasing with the increase of antenna distance.And compared with the single-antenna key generation system,the KGR of the MIMO system is increased by about 3.5 times.The KGR of the MIMO key generation system in the experiment is about 3.8 times of the SISO experimental KGR.Both in the simulation and experiment,the method for extracting the key from the shared random matrix proposed in this thesis can increase the pass rate of key randomness to more than 70%.The final 256 bits key randomness of SISO system and MIMO system is not much different.· In order to verify the channel characteristics security of both legal parties in MIMO communication when existing an eavesdropper attack,this thesis builds a simulation model system,and compares results with the conclusion of SISO system.When MIMO channel communication exists an eavesdropper,the CSI correlation between eavesdropping channel and legal channel shows a downward trend as the eavesdropping distance increases.And beyond 0.25 times of the wavelength,they are basically irrelevant.So the key generation system is very safe.Similarly,the information leakage rate of the STA decreases as the eavesdropping distance increasing.When the eavesdropping distance is greater than 0.25 times of the wavelength,the information leakage rate decreases to 10%.Comparing the security of SISO system,the CSI correlation and information leakage rate of MIMO system are higher,and the security of the MIMO system is slightly lower.· With the support of 802.11 ax standard,in order to observe the CSI correlation,KDR and the key uniqueness of the MU-MIMO key system,and compare the KGR of SU-MIMO systems in which each user communicates sequentially and the KGR of MU-MIMO system in which each user transmits at the same time,this article also establishes a simulation and experimental system for verification.In the MU-MIMO system,the CSI between adjacent channels of four users is basically irrelevant outside 0.5 times of the wavelength.And the uplink and downlink of each user always maintain good channel reciprocity under different antenna distances.Different from the simulation,due to the insufficient information of multipath fading in the indoor environment,the user channel CSI characteristics of the first and last frequency bands are less.The initial KDR of each user is basically less than 10%,and the key consistency is good.But the overall KDR is higher than that of SU-MIMO simulation system.In the simulation,although the efficiency of SU-MIMO system is a quarter of that of MUMIMO system,the KGR is about 4.8 times that of MU-MIMO system.Overall,the system efficiency is higher.Experiments have verified that when the antenna distance is greater than half a wavelength,the KGR of SUMIMO experimental system is about 4.5 times that of MU-MIMO,and the KGR of users in different frequency bands is different.The method sharing the random matrix to extract key also improves the key randomness in MU-MIMO system,and the key randomness of MU-MIMO experimental system is also not significantly different from that of SU-MIMO experiment.Through Pearson correlation coefficient and key repetition rate,simulations and experiments have proved the key uniqueness between four users.