PPG as a Bridge: Cross-Device Authentication for Smart Wearables with Photoplethysmography

2026-02-09

AI Summary

This work addresses the challenges of local authentication and repeated verification burdens on interaction-constrained wearable devices—such as rings, earbuds, and smart glasses—by proposing PPGTransID, the first cross-device, seamless authentication scheme leveraging the physiological consistency of photoplethysmography (PPG) signals across body sites. The method enables secure, interaction-free transfer of authentication status by comparing remote PPG (rPPG) signals extracted from a smartphone camera with locally acquired PPG signals from wearables. Evaluated with 33 participants, the system achieves a balanced accuracy of 95.5%, supports diverse wearable form factors, and demonstrates robustness under varying lighting conditions, camera positions, and user behaviors—significantly reducing user interaction overhead while maintaining high reliability.

Technology Category

• Humans and AI: Interaction Techniques and Devices
• Computer Vision: Biometrics, Face, Gesture & Pose
• Intelligent Robots: Multimodal Perception & Sensor Fusion

Application Category

• Security and Privacy: Large-scale security measurements
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments

Abstract

As smart wearable devices become increasingly powerful and pervasive, protecting user privacy on these devices has emerged as a critical challenge. While existing authentication mechanisms are available for interaction-rich devices such as smartwatches, enabling on-device authentication (ODA) on interaction-limited wearables including rings, earphones, glasses, and wristbands remains difficult. Moreover, as users increasingly own multiple smart devices, relying on device-specific authentication methods becomes redundant and burdensome. To address these challenges, we present PPGTransID, a ubiquitous and unobtrusive cross-device authentication (CDA) approach that leverages the real-time physiological consistency of photoplethysmography (PPG) signals across the human body. PPGTransID utilizes widely available PPG sensors on wearable devices to capture users'physiological signals and compares them with remote PPG (rPPG) signals extracted from a smartphone camera, where robust face-based authentication is already established. In doing so, PPGTransID securely transfers the reliable authentication status of the smartphone to nearby wearable devices without requiring additional user interaction. An evaluation with 33 participants shows that PPGTransID achieves a balanced accuracy of 95.5 percent and generalizes across multiple wearable form factors. Robustness experiments with 10 participants demonstrate resilience to variations in lighting, camera placement, and user behavior, while a real-time usability study with 14 participants confirms reliable performance with minimal interaction burden.

Problem

• cross-device authentication
• smart wearables
• on-device authentication
• photoplethysmography
• user privacy

Innovation

• Photoplethysmography
• Cross-device authentication
• Remote PPG
• Wearable security
• Physiological consistency