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Passive RFID is ubiquitous for key use-cases that include authentication, contactless payment, and location track- ing. Yet, RFID chips can be read without users’ knowledge and consent, causing security and privacy concerns that reduce trust. To improve trust, we employed physically-intuitive design prin- ciples to create On-demand RFID (ORFID). ORFID’s antenna, disconnected by default, can only be re-connected by a user pressing and holding the tag. When the user lets go, the antenna automatically disconnects. ORFID helps users visibly examine the antenna’s connection: by pressing a liquid well, users can observe themselves pushing out a dyed, conductive liquid to fill the void between the antenna’s two bisected ends; by releasing their hold, they can see the liquid recede. A controlled evaluation with 17 participants showed that users trusted ORFID significantly more than a commodity RFID tag, both with and without an RFID- blocking wallet. Users attributed this increased trust to visible state inspection and intentional activation. 

Users make hundreds of transactional permission decisions for smartphone applications, but these decisions persist beyond the context in which they were made. We hypothesized that user concern over permissions varies by context, e.g., that users might be more concerned about location permissions at home than work. To test our hypothesis, we ran a 44-participant, 4-week experience sampling study, asking users about their concern over specific application-permission pairs, plus their physical environment and context. We found distinguishable differences in participants’ concern about permissions across locations and activities, suggesting that users might benefit from more dynamic and contextually-aware approaches to permission decision-making. However, attempts to assist users in configuring these more complex permissions should be made with the aim to reduce concern and affective discomfort—not to normalize and perpetuate this discomfort by replicating prior decisions alone. 

Laptop webcams can be covertly activated by malware and law enforcement agencies. Consequently, 59% percent of Americans manually cover their webcams to avoid being surveilled. However, manual covers are prone to human error---through a survey with 200 users, we found that 61.5% occasionally forget to re-attach their cover after using their webcam. To address this problem, we developed Smart Webcam Cover (SWC): a thin film that covers the webcam (PDLC-overlay) by default until a user manually uncovers the webcam, and automatically covers the webcam when not in use. Through a two-phased design iteration process, we evaluated SWC with 20 webcam cover users through a remote study with a video prototype of SWC, compared to manual operation, and discussed factors that influence users' trust in the effectiveness of SWC and their perceptions of its utility.