Flying Reconfigurable Intelligent Surfaces for 6G: Enhancing Physical Layer Security in Low-Altitude Wireless Networks
Low-altitude wireless networks (LAWNs) are expected to play a pivotal role in sixth-generation (6G) systems by enabling flexible, on-demand, and infrastructure-light connectivity for communication, sensing, and security-critical applications. However, the highly dynamic propagation conditions, frequent blockages, and evolving security threats inherent to LAWNs pose fundamental challenges to conventional static network architectures. In this article, we investigate flying reconfigurable intelligent surfaces (FRIS) as a transformative enabler for cell-free integrated sensing and communication (CF-ISAC) in LAWNs. By jointly exploiting aerial mobility and programmable electromagnetic reflections, FRIS introduces a new degree of freedom for three-dimensional and environment-aware control of wireless propagation. We present a comprehensive overview of enabling technologies, highlight physical layer security benefits, and provide a representative case study demonstrating the performance gains and sensing-communication trade-offs of FRIS-assisted CF-ISAC systems. Finally, we discuss key research challenges and future directions toward practical and secure 6G low-altitude deployments.