In the paper, the physical-layer security for reconfigurable intelligent surface (RIS) aided integrated sensing and communication (ISAC) system is studied. There is an active eavesdropper (AE) as well as a passive eavesdropper (PE), and they cooperate each other. By joint base station beamforming and RIS reflection design, we aim to achieve the best secure data communications with guaranteed sensing performance. Mathematically, taking the constraints on sensing performance and transmission power in consideration, the system secrecy rate maximization problem is formulated with respect to transmit beamforming, RIS reflection, and receive beamforming. The formulated problem is non-convex and is decomposed to three subproblems by applying the alternating optimization (AO). For the decomposed subproblem, we utilize the quadratic penalty method and successive convex approximation (SCA) for the solution derivation. Thereafter, an iterative numerical algorithm, referred to as the joint beamforming and reflection design (JBRD) algorithm, is proposed. Finally, numerical results demonstrate the effectiveness and superiority of the proposed algorithm.

翻译：本文研究了可重构智能表面辅助的通感一体化系统中的物理层安全问题。系统中同时存在主动窃听者和被动窃听者，两者相互协作。通过联合基站波束赋形与RIS反射面设计，我们旨在在保证感知性能的前提下实现最优的安全数据通信。数学上，考虑感知性能与发射功率约束，以发射波束赋形、RIS反射面和接收波束赋形为变量，建立了系统保密速率最大化问题。该问题非凸，通过交替优化方法将其分解为三个子问题。针对分解后的子问题，采用二次罚函数法和逐次凸近似求解。进而提出一种迭代数值算法——联合波束赋形与反射面设计算法。最后，数值结果验证了所提算法的有效性与优越性。