Securing RIS-Aided Wireless Networks Against Full Duplex Active Eavesdropping

Abstract: This paper investigates the physical layer security of a Reconfigurable Intelligent Surface (RIS)-aided wireless network in the presence of full-duplex active eavesdropping. In this scenario, the RIS cooperates with the Base Station (BS) to transfer information to the intended user while an active attacker attempts to intercept the information through a wiretap channel. In addition, the attacker sends jamming signals to interfere with the legitimate user's reception of the signal and increase the eavesdropping rate. Our objective is to maximize the secrecy rate by jointly optimizing the active and passive beamformers at the BS and RIS, respectively. To solve the resulting non-convex optimization problem, we propose a solution that decomposes it into two disjoint beamforming design sub-problems solved iteratively using Alternating Optimization (AO) techniques. Numerical analysis is conducted to evaluate the impacts of varying the number of active attacking antennas and elements of the RIS on the secrecy performance of the considered systems under the presence of jamming signals sent by the attacker. The results demonstrate the importance of considering the impact of jamming signals on physical layer security in RIS-aided wireless networks. Overall, our work contributes to the growing body of literature on RIS-aided wireless networks and highlights the need to address the effects of jamming and active eavesdropping signals in such systems.