Secrecy Rate Analysis of RIS-Aided Massive Mimo with Active Adversaries

An adversarial reconfigurable intelligent surface (ARIS) poses a severe threat to the physical layer security provisions of massive multiple-input-multiple-output (MIMO) systems. When active eavesdroppers aided by an ARIS transmit identical pilot sequences to those of the legitimate users, the achievable secrecy rate can be degraded. This paper hence presents a secrecy rate analysis for a legitimate RIS (LRIS)aided massive MIMO systems under ARIS-aided active pilot attacks. We consider practical impairments including imperfect channel state information (CSI) and spatially correlated Rayleigh fading. Artificial noise is transmitted with the users' confidential signals to counter eavesdropping. Closed-form expressions for the achievable user rate and information leakage rate are derived for conjugate precoding designed when ARIS-aided contaminated CSI is available at the base-station. A statistical CSI-based optimization procedure is adopted for optimizing the phase-shifts at the LRIS. Through our analytical and numerical results, it is unveiled that the achievable secrecy sum rate can be boosted by the proposed optimization procedures.