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（RIS）辅助的集成感知与通信（ISAC）系统的物理层安全问题。系统中存在一个主动窃听者（AE）和一个被动窃听者（PE），且二者相互协作。通过联合设计基站波束成形与RIS反射，我们的目标是在保证感知性能的前提下实现最优的安全数据通信。在数学上，考虑感知性能与发射功率约束，建立了关于发射波束成形、RIS反射及接收波束成形的系统保密速率最大化问题。该问题是非凸的，通过应用交替优化（AO）方法将其分解为三个子问题。针对分解后的子问题，我们采用二次惩罚法与逐次凸逼近（SCA）技术进行求解。随后，提出了一种称为联合波束成形与反射设计（JBRD）算法的迭代数值算法。最后，数值结果验证了所提算法的有效性与优越性。