Wireless Communication in the Presence of Illegal Reconfigurable Intelligent Surface: Signal Leakage and Interference Attack

Reconfigurable intelligent surface (RIS) is a promising technology in realizing a smart wireless communication system. RIS is a man-made surface consisting of massive passive reflecting elements, where each element can reflect the incident signal with tunable phase shifts. To protect wireless communication from security breaches, physical layer security (PLS), which exploits the characteristics of wireless channels, has been widely studied to ensure secure transmission. Due to the reconfigurability of RIS, it has great potential to enhance PLS in wireless systems by enhancing the channel condition of a legitimate user (LU) and impairing that of an eavesdropper (EAV). However, low hardware cost and reconfigurability lead to non-negligible risk as the EAV and attacker can also apply RIS to promote the data rate at EAV or strengthen the interference signal transmitted to jam a LU. In this article, we introduce a new concept, illegal reconfigurable intelligent surface (IRIS), which represents the illegal deployment and utilization of RIS. Two main security concerns in the presence of IRIS, namely, signal leakage and interference attack, are inves-tigated. The signal leakage means that IRIS can collect the information signal, which could not be received before. The interference attack means the information signal can deploy IRIS to enhance the interference signal power. We discuss several key challenges brought by IRIS, and an artificial noise (AN)-aided joint optimization-based solution to enhance PLS in the wireless communication system with both RIS and IRIS. Simulation results demonstrate the significant impact of IRIS on PLS and verify the effectiveness of the proposed AN-aided joint optimization-based solution.