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.

翻译：随着智能可穿戴设备功能日益强大且普及，保护这些设备上的用户隐私已成为一项关键挑战。尽管现有认证机制已适用于智能手表等交互丰富的设备，但在戒指、耳机、眼镜和腕带等交互受限的可穿戴设备上实现设备端认证（ODA）仍然困难。此外，随着用户拥有的智能设备数量不断增加，依赖设备特定的认证方法显得冗余且繁琐。为应对这些挑战，我们提出了PPGTransID，一种普遍存在且无干扰的跨设备认证（CDA）方法，该方法利用光电容积描记法（PPG）信号在人体内的实时生理一致性。PPGTransID利用可穿戴设备上广泛配备的PPG传感器采集用户的生理信号，并将其与智能手机摄像头提取的远程PPG（rPPG）信号进行比对——智能手机上已建立基于面部的稳健认证机制。通过这种方式，PPGTransID可在无需额外用户交互的情况下，将智能手机的可靠认证状态安全地转移至附近的穿戴设备。对33名参与者的评估表明，PPGTransID实现了95.5%的平衡准确率，并能泛化至多种可穿戴设备形态。针对10名参与者的鲁棒性实验证明，该方法对光照条件、摄像头位置和用户行为的变化具有适应性；而对14名参与者的实时可用性研究则证实，该系统在最小交互负担下仍能保持可靠性能。