Secret Key Generation from CFR for OFDM TDD System Over Fading Channels

One of the basic problems in cryptography is the generation of a common secret key between two legitimate parties in order to prevent eavesdropping. In this paper, we develop an information-theoretic secret key generation method that exploits the physical layer properties of the multipath channel in orthogonal frequency division multiplexing (OFDM) systems with time division duplexing (TDD), and in particular the amplitude and phase of the estimated channel frequency response (CFR). Both the fast space decorrelation and the independency of the amplitude and phase of the multipath fading channel are used to generate the secret key, leading to increased secrecy bit rate and negligible secrecy leakage. The effect of the channel estimation error, delay and mobility are investigated for the presented method. Simulation results corroborate the increased performance of the proposed method over existing ones.