Research On Physical Layer Secret Key In Time-Varying Channel Scenario

Nowadays,wireless communication is the fastest developing and most widely used communication technology.However,the open and broadcasting characteristics of wireless channel make it face serious security problems.The traditional encryption mechanism is no longer absolutely secure under the condition that the computing power of the computer is greatly improved.Based on the wireless channel,physical-layer secret key scheme is a new way to solve the security problem of wireless communication.It can generate real-time secret key dynamically,and achieve"one-time pad" by utilizing the characteristics of reciprocity,time-varying and uniqueness of wireless channel.This paper studies the physical layer key scheme in time-varying channel scenario.The main research contents are as follows:(1)The secret key generation schemes of physical-layer based on wireless channel characteristics are summarized,and the key generation process is studied from three aspects:channel feature estimation,initial key generation and key agreement.Then the fading characteristics of time-varying channel are analyzed and the commonly used mathematical models are introduced,the difficulties of the key generation technique under time-varying channels are also pointed out.(2)The impacts of multipath effect and Doppler shift in time-varying channels are elaborated,and the shortcomings of traditional channel estimation methods are analyzed.In this context,the channel estimation methods based on basis expansion model are studied,then the discrete Karhuen-loeve basis expansion model is improved,the improved model can adjust its order as the speed of terminal changes,thus more accurate channel estimation is achieved and more reliable source for key generation is provided.(3)The secret key generation scheme based on the isolation band is studied,and the key generation scheme of the fixed phase isolation band is improved.The imroved scheme can reasonably adjust the phase isolation band area according to the magnitude of channel impulse response,thereby retaining more reliable channel estimation values.The simulation results show that the key generated by this scheme can not only have high key generation rate and more key bit number,but also overcome the influence of Doppler shift.