Secret Key Generation Assisted by Reconfigurable Intelligent Surfaces for Quasi-static Channel

To address the problem of low secret key rate (SKR) for quasi-static environments, a secret key generation protocol assisted by Reconfigurable Intelligent Surface (RIS) and artificial noise is proposed. On the one hand, RIS is used to construct the fast-changing channel, and on the other hand, artificial noise is designed to disturb the eavesdropper, both of which boost the SKR. Then, the closed-form expressions for the lower and upper bounds of the secret key capacity of the protocol are derived. Based on this expression, the impact of pilot and artificial noise power allocation on the key capacity is analyzed and the pilot power ratio is optimized. In addition, the influences of RIS elements number, channel correlation coefficient and pilot length on the SKR are further analyzed. Finally, the simulation analysis shows that compared to existing works, the proposed protocol reduces information leakage and further increases the SKR.