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Due to the channel estimation error, most of the physical layer secret key generation schemes need information reconciliation to correct error key bits, resulting in reduced efficiency. To solve the problem, this work proposes a novel secure communication scheme based on a equivalent interference channel. Different keys generated from imperfect channel state information are directly applied to signal scrambling and descrambling, which is equivalent to the process of a signal passing through an interference channel. Legitimate communication parties can reduce interference with the help of similar keys and channel coding without sending additional signals, while the eavesdropper channel is deteriorated due to the spatial decorrelation. For this kind of schemes, we first establish a discrete memoryless broadcast channel model to derive the expressions of bit error rate (BER), channel capacity, and security capacity for performance analysis. Simulation results verify the derivations that the proposed scheme achieves secure communication with a correlated eavesdropping channel and has a higher upper bound of transmission rate. Furthermore, we design a new metric to evaluate the efficiency and the result shows that the proposed scheme has superior performance on error reconciliation efficiency, despite its slight increase in BER.

A multiple relays aided secret key generation algorithm is proposed to improve the generated secret key rate for Internet of things when the wireless channels change slowly. First, the two legitimate users and relays send training sequences in turn to estimate the channels. Then, the relays employ secure network coding technique to help the two legitimate users exploit the randomness of relay channels. Finally, the two legitimate users agree on a secret key without the help of relays. In addition, the optimal relays selection with optimal power allocation algorithm is present to further improve the secret key rate when relay selection is needed. The performances of the proposed algorithms are verified by Monte Carlo simulation results.

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When the eavesdropping channel has a certain correlation with the legitimate channel, the physical layer key is susceptible to eavesdroppers. To ensure the security of the secret key, we propose a two-layer secure (TLS) quantization algorithm in this paper. First, we model the correlation between the distance and the channel correlation and derive the joint probability density function of channel phase and the key capacity. Then, we describe the detail of the TLS algorithm and prove the validity of our algorithm. Finally, we evaluate the performances of the TLS quantization algorithm using two parameters-key rate and bit disagreement rate. The Simulation results verify the effectiveness of the algorithm.