As immersive Virtual Reality (VR) applications become increasingly widespread, ensuring secure and usable authentication is critical. Traditional knowledge-based methods (e.g., passwords, PINs) suffer from memorability issues and are highly vulnerable to observation attacks such as Man-in-the-Room (MITR). Meanwhile, biometric and behavioral approaches raise concerns regarding practicality, privacy, and cross-platform deployment. We present SemanticAction, a semantic-driven, behavior-augmented authentication framework that integrates knowledge-based passwords with gesture-based behavioral biometrics. Passwords are encoded as scene-anchored directions executed through intuitive hand gestures, enabling semantic meaning to guide user interactions. To counter observation attacks, SemanticAction employs randomized scene prompts and decoy scenes, while a dual-constraint verification mechanism adapts to both cold-start/few-shot conditions. Two user studies provide initial evidence that SemanticAction can mitigate MITR attacks while alleviating memorability challenges, maintaining favorable usability and security performance even with limited behavioral data. This work offers early insights and practical design considerations for behavior-aware authentication in VR.

Various locomotion techniques, such as teleportation, walking in place, redirected walking, and walking, have been proposed. However, conventional methods overlooked the human ability to coordinate multiple modalities (e.g., eyes and feet) for natural virtual locomotion within a small physical space. Inspired by the natural coordination of the eyes and feet in human walking, as well as insights from prior work, this study investigates how eye-foot coordination can be leveraged more effectively for VR teleportation. We present four novel teleportation techniques based on eye-foot coordination, using users' gaze behavior and 3D foot positions as input modalities. A user study with 20 participants compared our techniques with a state-of-the-art foot-based locomotion method. Results demonstrate the superiority of our approaches: task completion times were significantly reduced, NASA-TLX workload scores and SUS usability scores were markedly improved, and participants expressed a clear preference for our techniques over the baseline. These findings provide a strong foundation for the design and implementation of future eye-foot coordinated teleportation methods in VR.

Behavioral authentication has become increasingly popular as a natural method for authentication in Virtual Reality (VR). However, existing studies often overlook the fact that users may perform behavioral authentication in different postures (i.e., sitting, standing, reclining) during VR use. Therefore, understanding how posture variations affect classification accuracy is crucial for designing posture-robust systems. In this study, we conducted a controlled experiment (N = 30) to investigate the impact of posture on classification accuracy during a target-selection task. We collected behavioral trajectory data and analyzed it using multivariate time series classification algorithms, addressing authentication performance under three different postures. In a within-posture authentication, reclining took longer but achieved the highest classification accuracy, with an interaction effect between posture and target vertical layout. In cross-posture authentication, transfers from sitting to standing/reclining were more effective than direct transfers between standing and reclining, with vertical layout crucial for classification accuracy. In mixed-posture training, the cross-posture classification accuracy increased, particularly when standing and reclining data were combined to help the model indirectly learn features of sitting posture. These findings provide valuable insights for designing tasks and data collection strategies that support the development of robust cross-posture authentication systems.

Teleportation is widely used in Virtual Reality (VR) applications, especially for enabling efficient navigation in large-scale virtual environments. Leveraging foot movements for teleportation frees the hands for parallel tasks and helps maintain spatial orientation, making it particularly suitable for seated and multitasking VR scenarios. This work explores feasible foot actions for teleportation in confined seating conditions, such as traveling on an airplane or train, where users' leg motion is feasible, but its range is constrained. Such scenarios are common but are underexplored. We propose seven metaphor-inspired teleportation techniques based on foot interactions and evaluate their effectiveness through a user study. The findings provide valuable insights for designing effective teleportation techniques in VR scenarios where users are seated in constrained spaces.

Virtual reality (VR) users often encounter interruptions, posing challenges to maintaining real-world awareness during immersive experiences. The Passthrough feature in VR headsets allows users to view their physical surroundings without removing the headset. However, when interruptions come from the rear, users need to turn their heads to see the real world, which can lead to negative experiences in VR. Study 1, conducted through semi-structured interviews involving 13 participants, found that users are less likely to use Passthrough for rear interruptions due to large head-turning movements, which cause inconvenience, increase the risk of motion sickness, and reduce the experience. Building on these findings, we introduced three Passthrough techniques in Study 2 for displaying the rear view in front of the user: Full Rear Passthrough + Pause (FRPP), Rear Passthrough Window (RPW), and Rear Passthrough AR (RPAR). Compared to the Baseline method that requires head-turning, all three systems reduced physical and temporal demands, alleviated disorientation caused by motion sickness, and provided a better user experience for managing rear interruptions. Among these, FRPP and RPAR were the most preferred. These findings provide valuable insights for future VR design, emphasizing the need for solutions that effectively manage rear interruptions while maintaining user comfort and experience.

Foot-based input can serve as a supplementary or alternative approach to text entry in virtual reality (VR). This work explores the feasibility and design of foot-based techniques that are hands-free. We first conducted a preliminary study to assess foot-based text entry in standing and seated positions with tap and swipe input approaches. The findings showed that foot-based text input was feasible, with the possibility for performance and usability improvements. We then developed three foot-based techniques, including two tap-based techniques (FeetSymTap and FeetAsymTap) and one swipe-based technique (FeetGestureTap), and evaluated their performance via another user study. The results show that the two tap-based techniques supported entry rates of 11.12 WPM and 10.80 WPM, while the swipe-based technique led to 9.16 WPM. Our findings provide a solid foundation for the future design and implementation of foot-based text entry in VR and have the potential to be extended to MR and AR.

Virtual reality (VR) not only allows head-mounted display (HMD) users to immerse themselves in virtual worlds but also to share them with others. When designed correctly, this shared experience can be enjoyable. However, in typical scenarios, HMD users are isolated by their devices, and non-HMD observers lack connection with the virtual world. To address this, our research investigates visually representing observers on both HMD and 2D screens to enhance shared experiences. The study, including five representation conditions, reveals that incorporating observer representation positively impacts both HMD users and observers. For how to design and represent them, our work shows that HMD users prefer methods displaying real-world visuals, while observers exhibit diverse preferences regarding being represented with real or virtual images. We provide design guidelines tailored to both displays, offering valuable insights to enhance co-located shared VR experiences for HMD users and non-HMD observers.

With the exponential growth of digital information, ensuring text security, a fundamental component of information security, becomes increasingly paramount. While authentication remains a primary focus for data access control and protection, the rich sensor ecosystem and immersive experiences of virtual reality (VR) environments introduce new privacy risks, particularly with inconspicuous sensors like motion and location sensors. In this context, protecting the security of text entered by users poses a unique challenge. This paper explores the feasibility of enhancing text security by introducing variability in virtual input tools during typing processes. Specifically, we investigate the impact of introducing successive and random intermittent variations to the virtual ray (start point and direction) with controller-based raycasting techniques on text security and typing experience. The results demonstrate that introducing variability in virtual ray effectively protects regular text and passwords. Random intermittent introducing variability balances security and user experience for regular text. These findings provide insights into enhancing text security beyond authentication and defending against the potential risks in VR environments.

Alphanumeric and special characters are essential during text entry. Text entry in virtual reality (VR) is usually performed on a virtual Qwerty keyboard to minimize the need to learn new layouts. As such, entering capitals, symbols, and numbers in VR is often a direct migration from a physical/touchscreen Qwerty keyboard-that is, using the mode-switching keys to switch between different types of characters and symbols. However, there are inherent differences between a keyboard in VR and a physical/touchscreen keyboard, and as such, a direct adaptation of mode-switching via switch keys may not be suitable for VR. The high flexibility afforded by VR opens up more possibilities for entering alphanumeric and special characters using the Qwerty layout. In this work, we designed two controller-based raycasting text entry methods for alphanumeric and special characters input (Layer-ButtonSwitch and Key-ButtonSwitch) and compared them with two other methods (Standard Qwerty Keyboard and Layer-PointSwitch) that were derived from physical and soft Qwerty keyboards. We explored the performance and user preference of these four methods via two user studies (one short-term and one prolonged use), where participants were instructed to input text containing alphanumeric and special characters. Our results show that Layer-ButtonSwitch led to the highest statistically significant performance, followed by Key-ButtonSwitch and Standard Qwerty Keyboard, while Layer-PointSwitch had the slowest speed. With continuous practice, participants' performance using Key-ButtonSwitch reached that of Layer-ButtonSwitch. Further, the results show that the key-level layout used in Key-ButtonSwitch led users to parallel mode switching and character input operations because this layout showed all characters on one layer. We distill three recommendations from the results that can help guide the design of text entry techniques for alphanumeric and special characters in VR.

Authentication in digital security relies heavily on text-based passwords, even with other available methods like biometrics and graphical passwords. While virtual reality (VR) keyboards are typically invisible to onlookers, the presence of inconspicuous sensors, including accelerometers, gyroscopes, and barometers, poses a potential risk of unauthorized observation and recording. Traditional defense shoulder-surfing attack methods typically involve breaking apart the Qwerty layout, which destroys the user's inherent familiarity with the layout. This research addresses the need for secure password entry in VR environments while retaining the Qwerty layout. We explore three keyboard-related position alteration strategies to ensure security while mitigating the decline in user experience. These strategies involve moving the entire keyboard, cursor, and keys. Our theoretical study assesses the effectiveness of these strategies against shoulder-surfing attacks. Two user studies, employing ray-based and position-based text entry methods, respectively, evaluate the practical effectiveness of the three strategies in resisting shoulder-surfing attacks, as well as their impact on typing performance and user experience. Our findings demonstrate that the three strategies achieve shoulder-surfing attack resistance comparable to a random layout keyboard. Moreover, compared to a random layout, the two strategies involving the movement of the entire keyboard and the repositioning of keys support faster entry rates and enhanced user experience.