Research On Physical Layer Key Technology Based On Wireless Channel Characteristics

With the development and application of wireless communication systems,wireless information security has become the focus of scholars at home and abroad.Wireless channels have the characteristics of reciprocity,rapid time variability and spatial variability,and can become a natural random signal source for encryption systems.This thesis conducts simulation analysis from three aspects of key generation rate,key inconsistency rate and randomness.The main research work is as follows:（1）This thesis analyzes eavesdropper channel model for the third-party eavesdropping end Eve,the performance index of the physical layer key and the general process of the physical layer key scheme are expounded,and two classical key generation algorithms are simulated and studied,including the double-gate quantized key generation algorithm and the Level Crossing Algorithm（Level Crossing Algorithm,LCA）.Based on the three performance indicators for evaluating the physical layer key,the two algorithms are analyzed and compared.It can be seen that the two-gate quantization algorithm is better than the common equal-probability quantization algorithm,and can obtain random key bits;LCA encryption The key generation algorithm obtains a lower key inconsistency rate through the design of the negotiation mechanism,but this will undoubtedly have a certain impact on the generation rate of the system.（2）Aiming at the problem that the traditional LCA algorithm filters out a large number of measurement values that can generate key bits,the key generation rate cannot meet the encryption requirements,an improved LCA key generation algorithm is studied.By smoothing the windowing process on the central position index set of both legitimate communication parties,one more channel feature sequence with window length can be retained each time,and range detection and threshold judgment are added to ensure that the inconsistency rate index of the algorithm is hardly affected.At the same time,the larger the window width m,the more sequences that can be matched and retained,and the higher the generation rate of the corresponding algorithm.The simulation results show that compared with the traditional algorithm,when the signal-to-noise ratio is 15d B and m is set to 5,the key bit generation rate of the improved algorithm is increased by more than 2 times.（3）In the static or slowly changing communication environment,the key inconsistency rate is high,and the received signal strength（RSS）cannot change significantly with time,which causes the correlation between key bits at adjacent times.In order to solve the above problems,an adaptive key generation algorithm based on received signal intensity is applied.In order to adapt to the slow change of the channel,the channel sequence is processed in blocks and the negotiation protocol m window screening mechanism is introduced.After screening the block channel feature sequence,the Karhunen-Loève Transform（KLT）is applied.Implement the decorrelation operation.As the block size increases,the corresponding negotiation efficiency increases in the algorithm.It can be seen through simulation experiments that when the signal-to-noise ratio is 25d B,inconsistency rate is about from10^-5has been reduced to10^-7.