The synergy between integrated sensing and communication (ISAC) and reconfigurable intelligent surfaces (RISs) unlocks novel applications and advanced services for next-generation wireless networks, yet also introduces new security challenges. In this study, a novel dual target-mounted RISs-assisted ISAC scheme is proposed, where a base station with ISAC capability performs sensing of two unmanned aerial vehicle (UAV) targets, one of which is legitimate and the other is eavesdropper, while communicating with the users through an RIS mounted on the legitimate UAV target. The proposed scheme addresses dual security threats posed by a hostile UAV target: eavesdropping on legitimate user communications and random interference attacks launched by a malicious RIS mounted on this eavesdropper UAV target, aiming to disrupt secure transmissions. Moreover, malicious RIS interference is also optimized for a worst-case scenario, in which both the channel state information (CSI) and the transmit beamforming of the base station are assumed to be fully compromised by a malicious RIS-mounted eavesdropper UAV. A non-convex optimization problem maximizing the secrecy rate of the users is formulated, and a semi-definite relaxation (SDR)-based two-stage solution is developed to optimize the transmit beamforming matrix of the base station and the phase shift coefficients of the legitimate RIS. Extensive computer simulations are conducted to evaluate the robustness of the proposed solution under various system configurations. The proposed system's communication performance is assessed using the secrecy rate metric, while the sensing performance is evaluated through the signal-to-interference-plus-noise ratio and the Cramer-Rao bound (CRB) for angle-of-departure (AoD) estimation of the eavesdropper UAV target.

翻译：集成感知与通信（ISAC）与可重构智能表面（RIS）的协同作用为下一代无线网络解锁了新型应用与先进服务，但也带来了新的安全挑战。本研究提出了一种新颖的双目标挂载RIS辅助ISAC方案：具备ISAC能力的基站对两架无人机（UAV）目标进行感知——其中一架为合法目标，另一架为窃听目标——同时通过挂载于合法UAV目标上的RIS与用户进行通信。该方案应对了敌对UAV目标带来的双重安全威胁：窃听合法用户通信，以及由挂载于该窃听UAV目标上的恶意RIS发起的随机干扰攻击（旨在破坏安全传输）。此外，针对最坏场景对恶意RIS干扰进行优化，在该场景中，假设恶意RIS挂载的窃听UAV完全掌握了信道状态信息（CSI）与基站的发射波束成形。本文构建了以最大化用户保密速率为目标的非凸优化问题，并开发了基于半定松弛（SDR）的两阶段求解方法，以优化基站的发射波束成形矩阵与合法RIS的相位偏移系数。通过大量计算机仿真评估了所提方案在不同系统配置下的鲁棒性。系统通信性能采用保密速率指标评估，感知性能则通过信干噪比和针对窃听UAV目标离向角（AoD）估计的克拉美罗界（CRB）进行衡量。