Secure Beamforming Design for RIS-Assisted Integrated Sensing and Communication Systems

The communication messages carried by the detected waveforms in integrated sensing and communication (ISAC) will be at risk of being eavesdropped by the detected targets, which leads to wireless security challenges. In this letter, the physical layer security (PLS) of reconfigurable intelligent surface (RIS)-assisted ISAC systems is investigated. Specifically, after introducing artificial noise, we formulate a joint active and passive beamforming optimization problem that maximizes the multi-user sum secrecy rate. Given that the nonconvex nature of the optimization problem exists, it becomes necessary to convert it into two convex sub-problems utilizing successive convex approximation and alternating optimization. This transformation incorporates the utilization of Taylor expansion and semidefinite relaxation. Numerical simulations verify the validity of the proposed algorithm for guaranteeing security.