Exploiting RIS for Limiting Information Leakage to Active Eavesdropper in Cell-Free Massive MIMO

This letter analyzes the potential of reconfigurable intelligent surfaces (RIS)s in boosting the secrecy capacities of cell-free (CF) massive multiple-input multiple-output (mMIMO) systems under pilot spoofing attacks. A novel RIS-based downlink (DL) transmission scheme is proposed in which the DL power coefficients at access points as well as the RIS phase shifts are jointly optimized to minimize the information leakage to eavesdropper while maintaining certain quality-of-service for legitimate users. Simulation results show the great potential of RISs in boosting the robustness of CF mMIMO systems against pilot spoofing attacks. Besides, various insights are drawn towards high-secure RIS-based CF mMIMO systems.