This paper examines how Reconfigurable Intelligent Surfaces (RIS) can be used to strengthen wireless challenge–response physical-layer authentication (CR-PLA). In CR-PLA, the receiver verifies a transmitter by sending a challenge and checking whether the resulting channel response matches the expected physical characteristics. The RIS introduces new degrees of freedom in this process by dynamically shaping the wireless environment. The study analyzes a system where the legitimate transmitter and a potential attacker are located randomly, while the receiver controls an RIS panel to generate different channel responses. For each challenge, the RIS applies a new phase configuration, creating a unique signature that an attacker—who does not know the RIS state—cannot easily mimic.
A key focus of the paper is on missed-detection and false-alarm probabilities, which quantify the reliability of authentication. The authors derive expressions for these probabilities under various RIS configurations and signal conditions, showing how parameters such as RIS size, geometry, and proximity influence authentication performance. An important insight is that RIS behavior introduces a trade-off between channel diversity and path loss. Large RIS surfaces can create stronger and more distinguishable responses, improving authentication accuracy, but their impact depends heavily on placement and the relative positions of legitimate and adversarial transmitters. Through a combination of theoretical analysis and numerical evaluation, the paper demonstrates that RIS-assisted CR-PLA can significantly enhance physical-layer security by making channel responses more controllable and unpredictable to attackers. The work provides a system-level framework for understanding how RIS design choices affect authentication reliability in future wireless networks.
Analysis_of_Challenge-Response_Authentication_With_Reconfigurable_Intelligent_Surfaces