Defensive Reconfigurable Intelligent Surface (D-RIS) Based on Non-Reciprocal Channel Links

TL;DR

This paper introduces a novel defensive RIS (D-RIS) that creates a non-reciprocal channel to counteract RIS-based attacks, enhancing security in wireless systems by preventing eavesdropping and false data injection.

Contribution

It proposes a new D-RIS design with precoding, combining, and channel estimation techniques to defend against RIS-In-The-Middle attacks, maintaining RIS benefits while improving security.

Findings

The D-RIS effectively increases the secrecy rate.

The system can detect fake data with high probability.

Robustness against attacks is demonstrated through analysis.

Abstract

A reconfigurable intelligent surface (RIS) is commonly made of low-cost passive and reflective meta-materials with excellent beam steering capabilities. It is applied to enhance wireless communication systems as a customizable signal reflector. However, RIS can also be adversely employed to disrupt the existing communication systems by introducing new types of vulnerability to the physical layer. We consider the \emph{RIS-In-The-Middle (RITM) attack}, in which an adversary uses RIS to jeopardize the direct channel between two transceivers by providing an alternative one with higher signal quality. This adversary can eavesdrop on all exchanged data by the legitimate users, but also perform a false data injection to the receiver. This work devises anti-attack techniques based on a non-reciprocal channel produced by a defensive RIS (D-RIS). The proposed precoding and combining methods and the channel estimation procedure for a non-reciprocal link are effective against potential adversaries while keeping the existing advantages of the RIS. We analyse the robustness of the system against attacks in terms of achievable secrecy rate and probability of detecting fake data. We believe that this defensive role of RIS can be a basis for new protocols and algorithms in the area.