Biometric authentication has become increasingly popular due to its security and convenience; however, traditional biometrics are becoming less desirable in scenarios such as new mobile devices, Virtual Reality, and Smart Vehicles. For example, while face authentication is widely used, it suffers from significant privacy concerns. The collection of complete facial data makes it less desirable for privacy-sensitive applications. Lip authentication, on the other hand, has emerged as a promising biometrics method. However, existing lip-based authentication methods heavily depend on static lip shape when the mouth is closed, which can be less robust due to lip shape dynamic motion and can barely work when the user is speaking. In this paper, we revisit the nature of lip biometrics and extract shape-independent features from the lips. We study the dynamic characteristics of lip biometrics based on articulator motion. Building on the knowledge, we propose a system for shape-independent continuous authentication via lip articulator dynamics. This system enables robust, shape-independent, and continuous authentication, making it particularly suitable for scenarios with high security and privacy requirements. We conducted comprehensive experiments in different environments and attack scenarios and collected a dataset of 50 subjects. The results indicate that our system achieves an overall accuracy of 99.06% and demonstrates robustness under advanced replay attacks and AI deepfake attacks, making it a viable solution for continuous biometric authentication in various applications.

As earables gain popularity, there emerges a need for intuitive user interfaces that adapt to diverse daily scenarios. Traditional methods like touchscreens and voice control often fall short in environments like movie theatres, where silence and darkness are required, or on busy streets where visual distraction introduces extra risk. We propose an innovative earable-based system utilizing unique acoustic friction generated by fingers for alphanumeric input. Our approach digs into the acoustic friction theory, applying this knowledge to better understand the transformation from 2D handwriting into a 1D acoustic time series. This theoretical foundation guides our system design and feature extraction. Specifically, we have redesigned certain characters to enhance their acoustic distinctiveness without compromising the natural handwriting style of users, ensuring the system userfriendly. Our system combines DenseNet and GRU architectures in a multimodal model, refined through transfer learning to adapt to diverse user behaviors. Tested in real-world scenarios with 10 participants, our system achieves a 95% accuracy in recognizing both letters and numbers.

Ear wearables (earables) have become an emerging and wide acceptable platform for various applications. Because of the limited input interface of earables, traditional authentication methods become less desired. However, the feature-rich sensing abilities of earables and the unique human face-ear channel bring us new sensing opportunities to reutilize fingerprints. In this work, we proposed SlidePass, a secure earables authentication system that leverages the finger-face acoustic friction produced by sliding finger gestures on the face. In particular, our system leverages the inward-facing microphone of the earables to reliably capture the acoustic of finger-face frictions. The core insight of our system is to utilize the face as a natural scanner for finger-face friction and earables to capture and reconstruct the fingerprint features. SlidePass is specially designed for earables. Due to the finger-face friction captured and encrypted by the face channel that is unique and hidden in the human skull, SlidePass is more resistant to various spoofing attacks. Our preliminary evaluation included ten different fingerprints showing that SlidePass achieves an average accuracy of 94%.

Sensing the liquid level in a container is critical to building many smart home and mobile healthcare applications. This paper presents a liquid level sensing system that is low-cost, high accuracy, widely applicable to different daily liquids and containers, and can be easily integrated with existing smart home networks. Our system uses an existing home WiFi network and a low-cost transducer that is attached to the container to sense the resonance of the container for liquid level detection. We evaluate our system in home environments with various containers and liquids. Preliminary results show that our system achieves an accuracy of 97% for continuous prediction and an F-score of 0.968 for discrete prediction.

Earables (ear wearable) are rapidly emerging as a new platform to enable a variety of personal applications. The traditional authentication methods thus become less applicable and inconvenient for earables due to their limited input interface. Earables, however, often feature rich around the head sensing capability that can be leveraged to capture new types of biometrics. In this work, we propose ToothSonic that leverages the toothprint-induced sonic effect produced by a user performing teeth gestures for user authentication. In particular, we design several representative teeth gestures that can produce effective sonic waves carrying the information of the toothprint. To reliably capture the acoustic toothprint, it leverages the occlusion effect of the ear canal and the inward-facing microphone of the earables. It then extracts multi-level acoustic features to represent the intrinsic acoustic toothprint for authentication. The key advantages of ToothSonic are that it is suitable for earables and is resistant to various spoofing attacks as the acoustic toothprint is captured via the private teeth-ear channel of the user that is unknown to others. Our preliminary studies with 20 participants show that ToothSonic achieves 97% accuracy with only three teeth gestures.

WiFi human sensing has become increasingly attractive in enabling emerging human-computer interaction applications. The corresponding technique has gradually evolved from the classification of multiple activity types to more fine-grained tracking of 3D human poses. However, existing WiFi-based 3D human pose tracking is limited to a set of predefined activities. In this work, we present Winect, a 3D human pose tracking system for free-form activity using commodity WiFi devices. Our system tracks free-form activity by estimating a 3D skeleton pose that consists of a set of joints of the human body. In particular, Winect first identifies the moving limbs by leveraging the signals reflected off the human body and separates the entangled signals for each limb. Then, our system tracks each limb and constructs a 3D skeleton of the body by modeling the inherent relationship between the movements of the limb and the corresponding joints. Our evaluation results show that Winect achieves centimeter-level accuracy for free-form activity tracking under various environments.

Biometric-based authentication is gaining increasing attention for wearables and mobile applications. Meanwhile, the growing adoption of sensors in wearables also provides opportunities to capture novel wearable biometrics. In this work, we propose EarDynamic, an ear canal deformation based user authentication using ear wearables (earables). EarDynamic provides continuous and passive user authentication and is transparent to users. It leverages ear canal deformation that combines the unique static geometry and dynamic motions of the ear canal when the user is speaking for authentication. It utilizes an acoustic sensing approach to capture the ear canal deformation with the built-in microphone and speaker of the earables. Specifically, it first emits well-designed inaudible beep signals and records the reflected signals from the ear canal. It then analyzes the reflected signals and extracts fine-grained acoustic features that correspond to the ear canal deformation for user authentication. Our experimental evaluation shows that EarDynamic can achieve a recall of 97.38% and an F1 score of 96.84%.

This paper presents GoPose, a 3D skeleton-based human pose estimation system that uses commodity WiFi devices at home. Our system leverages the WiFi signals reflected off the human body for 3D pose estimation. In contrast to prior systems that need dedicated sensors, our system does not require a user to wear any sensors and can reuse the WiFi devices that already exist in a home environment for mass adoption. To realize such a system, we leverage the 2D AoA estimation of the signals reflected from the human body and the deep learning techniques. Preliminary results show GoPose achieves a high accuracy of 4.5cm in various scenarios.

The voice user interface (VUI) has been progressively used to authenticate users to numerous devices and applications. Such massive adoption of VUIs in IoT environments like individual homes and businesses arises extensive privacy and security concerns. Latest VUIs adopting traditional voice authentication methods are vulnerable to spoofing attacks, where a malicious party spoofs the VUIs with pre-recorded or synthesized voice commands of the genuine user. In this paper, we design VibLive, a continuous liveness detection system for secure VUIs in IoT environments. The underlying principle of VibLive is to catch the dissimilarities between bone-conducted vibrations and air-conducted voices when human speaks for liveness detection. VibLive is a text-independent system that verifies live users and detects spoofing attacks without requiring users to enroll specific passphrases. Moreover, VibLive is practical and transparent as it requires neither additional operations nor extra hardwares, other than a loudspeaker and a microphone that are commonly equipped on VUIs. Our evaluation with 25 participants under different IoT intended experiment settings shows that VibLive is highly effective with over 97% detection accuracy. Results also show that VibLive is robust to various use scenarios.

This paper presents MultiTrack, a commodity WiFi based human sensing system that can track multiple users and recognize activities of multiple users performing them simultaneously. Such a system can enable easy and large-scale deployment for multi-user tracking and sensing without the need for additional sensors through the use of existing WiFi devices (e.g., desktops, laptops and smart appliances). The basic idea is to identify and extract the signal reflection corresponding to each individual user with the help of multiple WiFi links and all the available WiFi channels at 5GHz. Given the extracted signal reflection of each user, MultiTrack examines the path of the reflected signals at multiple links to simultaneously track multiple users. It further reconstructs the signal profile of each user as if only a single user has performed activity in the environment to facilitate multi-user activity recognition. We evaluate MultiTrack in different multipath environments with up to 4 users for multi-user tracking and up to 3 users for activity recognition. Experimental results show that our system can achieve decimeter localization accuracy and over 92% activity recognition accuracy under multi-user scenarios.