Advancements in IoT system security: a reconfigurable intelligent surfaces and backscatter communication approach

In 6 G wireless networks, secure communication is crucial due to the inherent susceptibility of electromagnetic waves to eavesdropping. Reconfigurable intelligent surfaces (RIS) and backscatter communication technologies offer promising solutions by securely directing signals to authorized users, even in the presence of multiple passive eavesdroppers equipped with multi-antenna setups. This paper proposes a novel RIS-enhanced backscatter communication system that utilizes radio frequency (RF) signals from a power beacon (PB) to transmit confidential information to multiple authorized users, each equipped with a single antenna. To optimize system performance, the deep deterministic policy gradient (DDPG) algorithm is employed to dynamically control RIS beamforming and mitigate eavesdropping attempts by adversaries using linear decoding techniques. Simulation results demonstrate that the proposed DDPG-based strategy significantly improves multicast secrecy rates while satisfying transmit power and unit modulus constraints. Compared to conventional optimization methods, the DDPG algorithm enhances the alignment of RIS reflections toward intended users and minimizes signal leakage to eavesdroppers. This research highlights how RIS and backscatter communication technologies can enhance security and energy efficiency in 6 G networks, providing a scalable solution to reduce eavesdropping threats in future wireless systems.