Invisible Walls: Privacy-Preserving ISAC Empowered by Reconfigurable Intelligent Surfaces

TL;DR

This paper introduces PrivISAC, a low-cost RIS-based method that enhances privacy in ISAC systems by randomizing configurations to mask sensitive information from eavesdroppers while maintaining legitimate communication and sensing performance.

Contribution

The paper proposes a novel RIS configuration strategy with randomized activation and a masking method, enabling privacy-preserving ISAC without high hardware complexity.

Findings

PrivISAC effectively masks sensing information from eavesdroppers.

It maintains high communication throughput and sensing accuracy.

Experimental results validate strong privacy protection with commodity devices.

Abstract

The environmental and target-related information inherently carried in wireless signals, such as channel state information (CSI), has brought increasing attention to integrated sensing and communication (ISAC). However, it also raises pressing concerns about privacy leakage through eavesdropping. While existing efforts have attempted to mitigate this issue, they either fail to account for the needs of legitimate communication and sensing users or rely on hardware with high complexity and cost. To overcome these limitations, we propose PrivISAC, a plug-and-play, low-cost solution that leverages RIS to protect user privacy while preserving ISAC performance. At the core of PrivISAC is a novel strategy in which each RIS row is assigned two distinct beamforming vectors, from which we deliberately construct a limited set of RIS configurations. During operation, exactly one configuration is randomly activated at each time slot to introduce additional perturbations, effectively masking sensitive sensing information from unauthorized eavesdroppers. To jointly ensure privacy protection and communication performance, we design the two vectors such that their responses remain nearly identical in the communication direction, thereby preserving stable, high-throughput transmission, while exhibiting pronounced differences in the sensing direction, which introduces sufficient perturbations to thwart eavesdroppers. Additionally, to enable legitimate sensing under such randomized configurations, we introduce a time-domain masking and demasking method that allows the authorized receiver to associate each CSI sample with its underlying configuration and eliminate configuration-induced discrepancies, thereby recovering valid CSI. We implement PrivISAC on commodity wireless devices and experiment results show that PrivISAC provides strong privacy protection while preserving high-quality legitimate ISAC.