RIS-Based Physical Layer Security: Realistic Evaluation and Challenges Ahead

Physical layer security (PLS) deals with implementing security mechanisms directly at the physical layer, potentially at the signal level. The recent advances on reconfigurable intelligent surfaces (RISs) make it possible to exploit their manipulation capabilities to make a signal decodable at specific locations and unintelligible at other ones, adding additional security and privacy mechanisms on top of existing ones. In previous work, we devised a mathematical framework to achieve multi-receiver PLS in the presence of multiple RISs, showing its effectiveness by means of spatial bit error rate (BER) maps. Our analyses, however, modeled each reception point in the BER map as affected by an independent Rice fading realization on top of path loss, making it impossible to study the size of the secured area around intended receivers. In this work, we extend our analyses by exploiting the Sionna ray tracing (RT) software which, by considering 3D scenarios, can properly estimate the effects of fading by considering realistic reflections and multi-path propagation. The results confirm the applicability of the methodology, but raise several interesting points regarding spatial correlation and undesired signal attenuation effects.