Secrecy Rate Maximization for Coupled Phase-Shift STAR-RIS-Assisted ISAC Networks Under Dual Eavesdropping Attacks

This paper investigates a secure coupled phase-shift simultaneous transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) assisted integrated sensing and communication (ISAC) network, where a base station (BS) utilizes the STAR-RIS to enable simultaneous communication with a user and target detection on opposite sides, while the transmitted signals are exposed to interception by communication and sensing eavesdroppers. We aim to maximize the secrecy rate of the communication user by jointly optimizing the BS beamforming and the STAR-RIS transmission and reflection coefficients, while ensuring the constraints on BS power, coupled STAR-RIS transmission and reflection coefficients, sensing performance, and sensing security. To tackle the non-convex problem, we propose an optimization algorithm that combines successive convex approximation (SCA) and penalty dual decomposition (PDD). Simulation results demonstrate that the proposed scheme achieves superior performance compared to the benchmarks.