Fast and Efficient Physical Layer Secret Key Generation over Static Wireless Channels

Recently, shared secret key generation from wireless channel characteristics has attracted a lot of attention due to its low computational overhead. However, in a static environment, the secret key rate is relatively lower due to the lack of channel time-variation. In this paper, we propose a lightweight and efficient PLKG scheme for static channels. Different from current schemes, in the proposed scheme, the transmitter attaches the information of the secret key into the downlink pilot signals to the legitimate receiver by the proposed secret precoding. At the receiving end, the legitimate receiver can directly observe the correct information of secret key from the public downlink pilot signals, while keeping perfect secrecy of the generated key against eavesdroppers. The key principle lies in that the information of the secret key is coded in the index of the non-activated MIMO (multiple-input-multiple-output) sub-channel. Consequently, only the legitimate receiver can accurately observe the value of the key information. For any other eavesdroppers who suffer an independent channel from the legitimate transmitter and receiver, it is proven that she cannot observe any key information from her received signals. Therefore, the key rate can be improved for the static channels by increasing the symbol rate of the pilot signals. Simulations are conducted to validate the effectiveness of the proposed scheme.