Trusted Reconfigurable Intelligent Surface for Multi-User Quantum Key Distribution

We consider a multi-user quantum key distribution (QKD) system based on free-space optics (FSO) in terrestrial environment. Due to obstacles the signal path, FSO-QKD is heavily affected by decoherence and other harmful effects. In order avoid performance degradation, trusted nodes (TNs) are introduced QKD network. However, absence of alternative routes, classical data relayed same TN, which makes it promising target for an eavesdropping attack. address this issue, we explore use reconfigurable intelligent surface (RIS) that passively reflects signals manipulates them make encryption consistent with distributed keys. The concept supported numerical simulations multiple users eavesdropper. demonstrate level protection very high proposed even case successful attack RIS complete acquisition