The appearance of sixth-generation networks has resulted in the proposal of several solutions to tackle signal loss. One of these solutions is the utilization of reconfigurable intelligent surfaces (RIS), which can reflect or refract signals as required. This integration offers significant potential to improve the coverage area from the sender to the receiver. In this paper, we present a comprehensive framework for analyzing the secrecy performance of a RIS-aided mixed radio frequency (RF)-free space optics (FSO) system, for the first time. Our study assumes that a secure message is transmitted from a RF transmitter to a FSO receiver through an intermediate relay. The RF link experiences Rician fading while the FSO link experiences M\'alaga distributed turbulence with pointing errors. We examine three scenarios: 1) RF-link eavesdropping, 2) FSO-link eavesdropping, and 3) a simultaneous eavesdropping attack on both RF and FSO links. We evaluate the secrecy performance using analytical expressions to compute secrecy metrics such as the average secrecy capacity, secrecy outage probability, strictly positive secrecy capacity, effective secrecy throughput, and intercept probability. Our results are confirmed via Monte-Carlo simulations and demonstrate that fading parameters, atmospheric turbulence conditions, pointing errors, and detection techniques play a crucial role in enhancing secrecy performance.

翻译：第六代网络的出现催生了多种应对信号损失的解决方案。其中一种方案是利用可重构智能表面（RIS），它能够根据需要反射或折射信号。这种集成技术为扩大从发送端到接收端的覆盖区域提供了显著潜力。本文首次提出了一个用于分析RIS辅助混合射频（RF）-自由空间光（FSO）系统安全性能的综合框架。我们的研究假设一条安全消息通过中间中继从RF发送端传输至FSO接收端。RF链路经历莱斯衰落，而FSO链路经历带有指向误差的Málaga分布湍流。我们考察了三种场景：1) RF链路窃听，2) FSO链路窃听，以及3) 对RF和FSO链路的同时窃听攻击。我们利用解析表达式评估安全性能，计算平均安全容量、安全中断概率、严格正安全容量、有效安全吞吐量和截获概率等安全指标。结果通过蒙特卡洛模拟得到验证，并表明衰落参数、大气湍流条件、指向误差和检测技术在提升安全性能中发挥着关键作用。