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 transmitting beamforming, RIS reflection, and receiving beamforming. The formulated problem is non-convex and is decomposed to three subproblem by applying the alternating optimization scheme. 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），且两者相互协作。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，综合考虑感知性能与发射功率约束，我们针对发射波束成形、RIS反射及接收波束成形，构建了系统保密速率最大化问题。该问题为非凸问题，通过采用交替优化方案，可分解为三个子问题。对于分解后的子问题，我们利用二次惩罚法与逐次凸逼近（SCA）技术进行求解推导。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。