Reconfigurable Intelligent Surface for Physical Layer Key Generation: Constructive or Destructive?

TL;DR

This paper explores how reconfigurable intelligent surfaces (RIS) can both enhance and hinder physical layer key generation (PKG), demonstrating improved key rates and security considerations in various wireless environments.

Contribution

It provides a comprehensive analysis of RIS effects on PKG, including experimental results showing increased entropy and key rates, and discusses potential security threats and countermeasures.

Findings

RIS can increase key entropy and rate in static environments.

RIS improves secret key rate by over 2 dB in multi-user scenarios.

RIS can be exploited for jamming and leakage attacks, requiring countermeasures.

Abstract

Physical layer key generation (PKG) is a promising means to provide on-the-fly shared secret keys by exploiting the intrinsic randomness of the radio channel. However, the performance of PKG is highly dependent on the propagation environments. Due to its feature of controlling the wireless environment, reconfigurable intelligent surface~(RIS) is appealing to be applied in PKG. In this paper, in contrast to the existing literature, we investigate both the constructive and destructive effects of RIS on the PKG scheme. For the constructive aspect, we have identified static and wave-blockage environments as two RIS-empowered-PKG applications in future wireless systems. In particular, our experimental results in a static environment showed that RIS can enhance the entropy of the secret key, achieving a key generation rate (KGR) of 97.39 bit/s with a bit disagreement rate (BDR) of 0.083. In multi-user systems where some remote users are in worse channel conditions, the proposed RIS-assisted PKG algorithm improves the sum secret key rate by more than 2 dB, compared to the literature. Furthermore, we point out that RIS could be utilized by an attacker to perform new jamming and leakage attacks and give countermeasures, respectively. Finally, we outline future research directions for PKG systems in light of the RIS.