Research On Implementation Technologies Of Physical Layer Security Based On Channel Difference

Due to the openness of wireless media,there are many security loopholes in wireless communication.With the rapid development of cryptographic analysis algorithms,the traditional cryptographic-based security mechanisms are gradually limited.Physical layer security makes use of the unique characteristics and has the advantages of low complexity and lightweight,which is an important supplement to the upper-layer security mechanism.This thesis examines physical layer security technology,including key generation,identity authentication,and secure transmission,based on the differences between wireless channels.For key generation technology,this thesis focuses on the key generation process,investigates and compares the traditional algorithms of channel sounding,pretreatment,quantization and information consultation successively.Following that,it conducts a rounded evaluation in several aspects,such as key performance,information interaction times,operation complexity and security.Finally,the two-way detection based on frequency division duplex mode,improved wavelet transform preprocessing,equal probability quantization and repeated code negotiation are selected to form the final key generation scheme.Based on the binary hypothesis model,the thesis compares the similarity of channel features between data frames for identity identification.This thesis investigates two statistical calculation methods: normalized likelihood ratio test（LRT）and sequential probability ratio test（SPRT）.The authentication performance and complexity of different statistics under LRT and SPRT are simulated and analyzed.SPRT scheme has high complexity and requires strong correlation of multi-frame data,but its performance is only slightly improved compared with LRT scheme.Therefore,this paper finally chooses to use LRT statistics combined with amplitude and phase for identity authentication.For the secure transmission technology,the thesis studies the symmetric encryption scheme and the data interlocking scheme based on the feedback fountain code security transmission model under the condition that the quality of the eavesdropping channel is better than that of the legitimate channel.Symmetric encryption scheme only encrypts the source data and synchronizes the encoded information directly.The operation is simple but the security is low.The interlocking encryption scheme uses random seeds to generate pseudo-random sequence disturbance coding information,which forms an interlocking structure with fountain coding package,with more interactions but improved security performance.In the interlock scheme,the feedback packet index set is encrypted with the key generated based on the channel characteristics,which further enhances the anti-eavesdropping performance of the system.On the basis of the above scheme confirmation,the thesis uses Laboratory Virtual Instrument Engineering Workbench drives Universal Software Radio Peripheral（USRP）to implement a complete set of physical layer security transmission system.According to the system needs,a multi-device synchronization scheme is designed,and the link design of the modules corresponding to the three key contents of the above research is carried out.Finally,function demonstration and performance test of each module are completed based on channel simulation platform.The test findings reveal that when the SNR of the eavesdropping channel has a certain gain compared with that of the legitimate channel,the system can still prevent the information from being eavesdropped effectively.