Secure beam control improves wireless group messaging with smart surfaces
Secure RIS-Aided Multicasting: Globally Optimal Beam Management and Discrete-Phase RIS Configuration
Information TheoryNetworking and Internet Architecture
Summary
Wireless signals can be tricky to send securely, especially when many people receive the same message. The authors study special surfaces called reconfigurable intelligent surfaces (RIS) that can control signals better to reach many users. They focus on making sure that people trying to listen secretly (eavesdroppers) get a very weak signal. The authors create a new way to adjust both the base station and the RIS to block eavesdroppers more effectively, even when RIS elements have limited settings. Their method finds the best solution globally and cuts signal leaks a lot compared to older methods.
What this means in practice
- •For wireless network engineers: Design multicasting systems that adjust beam signals and RIS phases jointly to reduce eavesdropping risk in obstructed environments.
- •For telecommunications security teams: Enhance the security of wireless broadcast services by implementing optimal RIS configurations that lower signal leakage to colluding eavesdroppers.
Authors
Luis F. Abanto-Leon, Setareh Maghsudi
Abstract
Reconfigurable intelligent surfaces (RISs) are poised to revolutionize wireless multicasting by enabling extended coverage and reliable operation in obstructed environments. These benefits, however, can be undermined by security vulnerabilities arising from practical deployment factors. This work addresses three such critical factors, (i) the discrete nature of RIS phase shifts, (ii) the presence of colluding eavesdroppers, and (iii) the inefficiency of static illumination beams, each threatening security if not properly accounted for in system design. To mitigate these issues, we formulate a joint resource allocation problem that minimizes the wiretap signal-to-noise ratio (SNR) across all eavesdroppers by co-optimizing the RIS configuration and the base station (BS) beam management. This yields a complex, nonconvex mixed-integer nonlinear program (MINLP), which we equivalently reformulate into a tractable mixed-integer quadratically constrained program (MIQCP) solvable to global optimality. Numerical results confirm that the proposed scheme significantly bolsters security, suppressing the wiretap SNR by up to 58% compared to existing baselines.