MIMOCrypt: Multi-User Privacy-Preserving Wi-Fi Sensing via MIMO Encryption

TL;DR

MIMOCrypt introduces a MIMO-based physical encryption framework for Wi-Fi signals, enabling multi-user privacy-preserving human sensing without sacrificing sensing accuracy or communication quality.

Contribution

It is the first to exploit Wi-Fi's MIMO capability for physical encryption in multi-user human sensing scenarios, balancing privacy, sensing, and communication.

Findings

Effective in preventing eavesdropping in multi-user scenarios

Maintains high sensing accuracy for legitimate users

Demonstrates practicality through SDR prototype experiments

Abstract

Wi-Fi signals may help realize low-cost and non-invasive human sensing, yet it can also be exploited by eavesdroppers to capture private information. Very few studies rise to handle this privacy concern so far; they either jam all sensing attempts or rely on sophisticated technologies to support only a single sensing user, rendering them impractical for multi-user scenarios. Moreover, these proposals all fail to exploit Wi-Fi's multiple-in multiple-out (MIMO) capability. To this end, we propose MIMOCrypt, a privacy-preserving Wi-Fi sensing framework to support realistic multi-user scenarios. To thwart unauthorized eavesdropping while retaining the sensing and communication capabilities for legitimate users, MIMOCrypt innovates in exploiting MIMO to physically encrypt Wi-Fi channels, treating the sensed human activities as physical plaintexts. The encryption scheme is further enhanced via an optimization framework, aiming to strike a balance among i) risk of eavesdropping, ii) sensing accuracy, and iii) communication quality, upon securely conveying decryption keys to legitimate users. We implement a prototype of MIMOCrypt on an SDR platform and perform extensive experiments to evaluate its effectiveness in common application scenarios, especially privacy-sensitive human gesture recognition.