Sensing-Assisted Secure Beamforming Design in the Presence of Illegal Reconfigurable Intelligent Surface

Illegal Intelligent Reconfigurable Surfaces (IRIS) is an emerging concept derived from Reconfigurable Intelligent Surfaces (RIS), and their deployment introduces several potential security risks. To address this, we investigate a secure transmission approach based on the integrated sensing and communication (ISAC) system, which leverages sensing to assist secure communication and mitigate the security threats posed by IRIS. Specifically, the ISAC base station (BS) first transmits an omnidirectional beam to the surroundings, and then analyzes the received echo signals using Capon and approximate maximum likelihood (AML) techniques to estimate the positional parameters of the potential targets. Based on the estimated information, we formulate a weighted optimization problem that simultaneously minimizes the normalized Cramér-Rao Bound (CRB) of the target’s Angle of Departure (AoD) and maximizes the normalized secrecy rate, while satisfying power and beam pattern constraints. Simulation results confirm the effectiveness of the proposed design in mitigating eavesdropping threats posed by IRIS.