Secure Design for RIS-Assisted Multi-Target ISAC Systems

This paper investigates a multi-target secure integrated sensing and communication (ISAC) system based on a reconfigurable intelligent surface (RIS). In this system, a multi-antenna dual-functional radar and communication base station serves a multi-antenna communication user while si-multaneously detecting malicious eavesdropping targets. The paper first establishes the system model, including the signal models for communication and radar target detection. Next, an optimization problem is proposed to maximize the secrecy rate, involving the joint optimization of the transmission matrix and the phase matrix of the RIS. To address the non-convex constraint problem, an approximation approach is employed, transforming the problem into an alternating optimization problem. Specifically, auxiliary variables are introduced, and a block coordinate descent algorithm is used to optimize the variables in each block. Simulation results demonstrate that the proposed algorithm effectively improves the secrecy rate of the system and achieves excellent target detection performance.