Physical-Layer Security with Benign and Malicious RISs

The reconfigurable intelligent surface (RIS) is an innovative smart surface composed of massive low-cost passive reflecting elements, each capable of dynamically adjusting its electromagnetic response, enabling adaptive control of signal reflections. This technology has found numerous applications in wireless systems, including the improvement of physical-layer technology. This chapter first investigates the potential of a malicious RIS, belonging to an unauthorized system, to disrupt the received signal power and degrade secrecy rate through passive jamming attacks. To guarantee system robustness against these passive jamming attacks, robust beamforming and benign RIS’s phase shifting strategies are presented, considering different optimization priority levels between legitimate and eavesdropping systems in multiple-antenna point-to-point and wiretap channels. Extensive numerical results are provided to evaluate the disruptive capabilities of the malicious RISs under diverse channel conditions. The results showcase the susceptibilities of systems to passive jamming attacks, offering valuable insights into strategies to minimize their impact on the performance of wireless communications.