Trustworthy digital communication requires the secure exchange of contact information, but current approaches lack usability and scalability for larger groups of users. We evaluate the usability of two secure contact exchange systems: the current state of the art, SafeSlinger, and our newly designed protocol, PairSonic, which extends trust from physical encounters to spontaneous online communication. Our lab study (N=45) demonstrates PairSonic's superior usability, automating the tedious verification tasks from previous approaches via an acoustic out-of-band channel. Although participants significantly preferred our system, minimizing user effort surprisingly decreased the perceived security for some users, who associated security with complexity. We discuss user perceptions of the different protocol components and identify remaining usability barriers for CSCW application scenarios.

About half a billion households are expected to use smart home systems by 2025. Although many IoT sensors, such as smoke detectors or security cameras, are available and governmental crisis warning systems are in place, little is known about how to warn appropriately in smart home environments. We created a Raspberry Pi based prototype with a speaker, a display, and a connected smart light bulb. Together with a focus group, we developed a taxonomy for warning messages in smart home environments, dividing them into five classes with different stimuli. We evaluated the taxonomy using the Experience Sampling Method (ESM) in a field study at participants’ (N = 13) homes testing 331 warnings. The results show that taxonomy-based warning stimuli are perceived to be appropriate and participants could imagine using such a warning system. We propose a deeper integration of warning capabilities into smart home environments to enhance the safety of citizens.

Modern smartphones support FIDO2 passwordless authentication using either external security keys or internal biometric authentication, but it is unclear whether users appreciate and accept these new forms of web authentication for their own accounts. We present the first lab study (N=87) comparing platform and roaming authentication on smartphones, determining the practical strengths and weaknesses of FIDO2 as perceived by users in a mobile scenario. Most participants were willing to adopt passwordless authentication during our in-person user study, but closer analysis shows that participants prioritize usability, security, and availability differently depending on the account type. We identify remaining adoption barriers that prevent FIDO2 from succeeding password authentication, such as missing support for contemporary usage patterns, including account delegation and usage on multiple clients.

During crises such as the COVID-19 pandemic, people spontaneously initiate support groups, while established organizations like soccer clubs set non-regular goals, both offering help. Interested in the coordination of such help and potential challenges of collaboration, we conducted a virtual ethnography of a multi-level network located in Germany. We focused on aims, activities, and technological mediation, with Activity Theory as theoretical framework. Our findings show that the organizational aim of coordinating help was successfully achieved by connecting heterogeneous actors through digitization and institutionalization. Enabled by the context of the COVID-19 pandemic crisis, the network acted virtually, but was also able to integrate analog spaces of help. We identified six crucial implications regarding the use of technology and collaboration for building a successful volunteering network.

Virtual Reality can impose cognitive demands on users and influence their task performance. These cognitive demands, however, have been difficult to measure precisely without inducing breaks of presence. Based on findings in psychological science on how motion trajectories reflect underlying cognitive processes, we investigated entropy (i.e. the degree of movement irregularity) as an unobtrusive measure of mental workload. Entropy values were obtained from a time-series history of controller movement data. Mental workload is considered high over a given time interval, when the measured entropy is high as well. By manipulating the difficulty of a simple rhythm game we could show that the results are comparable to the results of the NASA-TLX questionnaire, which is currently used as the gold standard in VR for measuring mental workload. Thus, our results pave the way for further investigating the entropy of controller movements as a precise measurement of mental workload in VR.

Intelligent Virtual Agents (IVAs) are becoming part of our everyday life, thanks to artificial intelligence technology and Internet of Things devices. For example, users can control their connected home appliances through natural voice commands to the IVA. However, most current-state commercial IVAs, such as Amazon Alexa, mainly focus on voice commands and voice feedback, and lack the ability to provide non-verbal cues which are an important part of social interaction. Augmented Reality (AR) has the potential to overcome this challenge by providing a visual embodiment of the IVA. In this paper we investigate how visual embodiment and social behaviors influence the perception of the IVA. We hypothesize that a user's confidence in an IVA's ability to perform tasks is improved when imbuing the agent with a human body and social behaviors compared to the agent solely depending on voice feedback. In other words, an agent's embodied gesture and locomotion behavior exhibiting awareness of the surrounding real world or exerting influence over the environment can improve the perceived social presence with and confidence in the agent. We present a human-subject study, in which we evaluated the hypothesis and compared different forms of IVAs with speech, gesturing, and locomotion behaviors in an interactive AR scenario. The results show support for the hypothesis with measures of confidence, trust, and social presence. We discuss implications for future developments in the field of IVAs.