RIS Enabled Secure Communication with Covert Constraint

Reconfigurable intelligent surface (RIS)-empowered communication is an emerging technology that is able to effectively reshape the wireless environment into the desired form. This promising technology appears as a remedy for a wide range of wireless applications including physical layer (PHY) security. In this paper, we consider the use of RISs for a challenging PHY security scenario with two kinds of adversaries, where a warden aims to detect and an eavesdropper aims to sniff the legitimate communication. Our objective is to maximize the secrecy rate under a covert constraint. For this purpose, a sub-optimal optimization algorithm is proposed where transmit beamforming and the RIS phase shift vectors are alternately optimized. The secrecy rate performance of the proposed algorithm is investigated with computer simulations for Rician fading channels. Our results indicate that the use of RISs significantly improves the secure communication rate of a wireless system without waking the warden.