PHY-Layer Security in RIS-based Systems: A Jamming Recycling Approach Against Active Attacks

Abstract

This study investigates a RIS-assisted secure communication system in the presence of an active eavesdropper, where both the legitimate receiver and the eavesdropper are equipped with energy-harvesting capabilities. In such a setting, adversarial jamming not only degrades communication reliability but also serves as a potential energy source for both parties. To address this challenge, a jamming-recycling strategy is proposed, enabling the legitimate receiver to exploit the received signals, including interference, to support cooperative jamming. A powersplitting architecture is considered to jointly perform information decoding and energy harvesting. To capture the interplay between security and reliability, we develop a unified analytical framework based on the security–reliability trade-off (SRT), characterized by the connection outage probability (COP) and secrecy outage probability (SOP). Closed-form expressions for these metrics are derived, along with asymptotic analyses that reveal key system behaviors under different operating regimes. Numerical results demonstrate that the proposed scheme significantly improves secrecy performance while maintaining reliable communication, especially in the presence of active eavesdropper.