Enhancing Security in Near-Field RIS Communications Assisted by UAV

Securing the communications link in reconfigurable intelligent surfaces (RISs) near-field (NF) wireless communications presents challenges, especially when uncrewed aerial vehicles (UAVs) provide the wireless communication links. NF communications have emerged as a pivotal area in next-generation wireless systems due to their focus on the spherical nature of waves and enhancing energy efficiency. They considered the best solution for consumer electronics, as the associated NF waves necessitate less energy for transmission in contrast to the planar waves employed in far-field communications. In the context of RIS, NF is critical since, in the far-field, a considerable portion of planar waves passes through the surface elements. Consequently, with UAV assistance, employing RIS in the NF effectively addresses the dynamic characteristics and reliability of communication links. However, the complexity of UAV and RIS models poses significant challenges for secure communication. This paper proposes two secret key generation (SKG) methods to address these challenges and secure RIS-connected users. The convergence of NF and RIS with physical layer-based SKG methods supported by UAV feed links has been analyzed in detail. An information reconciliation method to minimize key mismatch probability (KMP) has been further studied. The simulation results of the proposed methods demonstrate substantial improvements in securing NF-RIS communications within the UAV ecosystem.