Secret Key Generation with Signal-like Noise in Polar Coded Wireless MIMO Systems

Physical-layer secret key generation is a meaningful approach to enhance the security of wireless links by taking advantages of wireless channels. However eavesdroppers may obtain the secret key bits if their channels become correlated to the legitimate channels. In this paper, to increase the mismatch rate at the eavesdroppers, we propose a new secret key generation scheme for polar coded multiple-input multiple-output (MIMO) systems by applying MIMO precoding and adding signal-like noise on the transmitted signals. Furthermore, considering the channel polarization phenomenon of polar codes, we propose to adaptively send messages that are used for secret key generation over the less reliable channel-bits of eavesdroppers. In addition, we propose to add randomness to messages to ensure that eavesdroppers are unable to generate the secret key bits even when their channels are highly correlated to the legitimate channels. Simulation results demonstrate that our proposed scheme prevents eavesdroppers to generate the secret key with an extremely high probability.