Channel Reciprocity Attacks Using Intelligent Surfaces with Non-Diagonal Phase Shifts

TL;DR

This paper introduces a passive RIS-based attack using non-diagonal phase shifts to disrupt channel reciprocity in wireless systems, significantly reducing downlink throughput and highlighting security vulnerabilities.

Contribution

It presents the first analysis of ND-RIS channel reciprocity attacks, including theoretical degradation analysis and an optimization method for malicious ND-RIS design.

Findings

ND-RIS can substantially decrease downlink throughput.

Theoretical analysis confirms significant performance degradation.

Genetic algorithm effectively optimizes ND-RIS structure for attack.

Abstract

While reconfigurable intelligent surface (RIS) technology has been shown to provide numerous benefits to wireless systems, in the hands of an adversary such technology can also be used to disrupt communication links. This paper describes and analyzes an RIS-based attack on multi-antenna wireless systems that operate in time-division duplex mode under the assumption of channel reciprocity. In particular, we show how an RIS with a non-diagonal (ND) phase shift matrix (referred to here as an ND-RIS) can be deployed to maliciously break the channel reciprocity and hence degrade the downlink network performance. Such an attack is entirely passive and difficult to detect and counteract. We provide a theoretical analysis of the degradation in the sum ergodic rate that results when an arbitrary malicious ND-RIS is deployed and design an approach based on the genetic algorithm for optimizing the ND structure under partial knowledge of the available channel state information. Our simulation results validate the analysis and demonstrate that an ND-RIS channel reciprocity attack can dramatically reduce the downlink throughput.