Joint Beamforming Optimization for RIS-Aided ISAC Security Systems

In Integrated Sensing and Communication (ISAC) systems, there is a significant risk of information leakage to eavesdroppers when ISAC waveforms are used for communication. In this paper, we address the physical layer security (PLS) issue in ISAC systems by deploying reconfigurable intelligent surfaces (RIS). Specifically, under the scenario where the base station employs dual-functional radar-communication (DFRC) waveforms, we formulate a complex multi-objective optimization problem. This problem involves jointly optimizing the passive beamforming of the RIS and the active beamforming of the base station, aiming to maximize the secrecy capacity of the communication system while enhancing target detection power. Given the inherently multi-objective and non-convex nature of this optimization problem, we propose to use an improved multi-objective evolutionary algorithm based on adaptive geometric estimation (IAGEMOEA) to find a solution. Through extensive numerical simulations, we validate the effectiveness of the RIS deployment and the proposed algorithm in improving the secrecy capacity and target tracking performance of ISAC systems.