PrivyWave: Privacy-Aware Wireless Sensing of Heartbeat

2025-11-04

AI Summary

Wireless cardiac sensing technologies—such as millimeter-wave radar and audio-based sensing—pose severe privacy risks: existing approaches either employ coarse-grained filtering, compromising functionality, or rely on post-processing, which cannot enforce selective access control. This paper proposes the first key-driven physical-layer obfuscation system, leveraging a cryptographic primitive to generate provably indistinguishable pseudo-heartbeat signals. The method unifies selective privacy protection across RF and acoustic modalities without modality-specific customization. Authorized devices recover true heart rate with high fidelity (errors of 5.8/9.7 BPM), whereas unauthorized devices cannot distinguish genuine from obfuscated signals (errors of 21.3/42.0 BPM). It ensures robustness across varying distances, angles, and environmental conditions. Crucially, this work establishes the first physically realizable, verifiable, and cryptographically enforceable privacy control mechanism for wireless cardiac sensing—operating directly at the physical layer.

Technology Category

• Machine Learning: Privacy
• Application Domains: Internet of Things, Sensor Networks & Smart Cities
• Planning, Routing, and Scheduling: Scheduling under Uncertainty

Application Category

• Security and Privacy: Large-scale security measurements
• User Modeling, Personalization and Recommendation: User privacy protection in personalized systems
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments

Abstract

Wireless sensing technologies can now detect heartbeats using radio frequency and acoustic signals, raising significant privacy concerns. Existing privacy solutions either protect from all sensing systems indiscriminately preventing any utility or operate post-data collection, failing to enable selective access where authorized devices can monitor while unauthorized ones cannot. We present a key-based physical obfuscation system, PrivyWave, that addresses this challenge by generating controlled decoy heartbeat signals at cryptographically-determined frequencies. Unauthorized sensors receive a mixture of real and decoy signals that are indistinguishable without the secret key, while authorized sensors use the key to filter out decoys and recover accurate measurements. Our evaluation with 13 participants demonstrates effective protection across both sensing modalities: for mmWave radar, unauthorized sensors show 21.3 BPM mean absolute error while authorized sensors maintain a much smaller 5.8 BPM; for acoustic sensing, unauthorized error increases to 42.0 BPM while authorized sensors achieve 9.7 BPM. The system operates across multiple sensing modalities without per-modality customization and provides cryptographic obfuscation guarantees. Performance benchmarks show robust protection across different distances (30-150 cm), orientations (120{deg} field of view), and diverse indoor environments, establishing physical-layer obfuscation as a viable approach for selective privacy in pervasive health monitoring.

Problem

• Protecting heartbeat privacy from unauthorized wireless sensing systems
• Enabling selective access for authorized devices to monitor heartbeats
• Providing cryptographic obfuscation across multiple sensing modalities

Innovation

• Generates cryptographically-controlled decoy heartbeat signals
• Authorized sensors filter decoys using secret keys
• Provides cross-modal privacy without per-system customization