In this paper we show how reading text on large display can be used to enable gaze interaction in public space. Our research is motivated by the fact that much of the content on public displays includes text. Hence, researchers and practitioners could greatly benefit from users being able to spontaneously interact as well as to implicitly calibrate an eye tracker while simply reading this text. In particular, we adapt Pursuits, a technique that correlates users' eye movements with moving on-screen targets. While prior work used abstract objects or dots as targets, we explore the use of Pursuits with text (read-and-pursue). Thereby we address the challenge that eye movements performed while reading interfere with the pursuit movements. Results from two user studies (N=37) show that Pursuits with text is feasible and can achieve similar accuracy as non text-based pursuit approaches. While calibration is less accurate, it integrates smoothly with reading and allows areas of the display the user is looking at to be identified.

In this paper, we present the design and evaluation of dynamic security questions for fallback authentication. In case users lose access to their device, the system asks questions about their usage behavior (e.g. calls, text messages or app usage). We performed two consecutive user studies with real users and real adversaries to identify questions that work well in the sense that they are easy to answer for the genuine user, but hard to guess for an adversary. The results show that app installations and communication are the most promising categories of questions. Using three questions from the evaluated categories was sufficient to get an accuracy of 95.5% - 100%.

We present the results of an MTurk survey (n=383) on the reasons for using and not using biometric authentication systems on smartphones. We focused on Apple's Touch ID as well as Android's Face Unlock as they are the most prevalent systems on the market. For both systems, we categorized the participants as a) current users, b) former users that deactivated it at some point and c) nonusers. The results show that usability is one of the main factors that influences the decision on whether or not to use biometric verification on the smartphone. To our surprise and as opposed to previous research on biometric authentication, privacy and trust issues were not among the most important decision factors.

We describe three scenarios in which fallback authentication on smartphones can occur and evaluate their real-life occurrences in an online survey (n=244) and complementing interviews (n=12). The results provide first insights into frequencies, reasons, countermeasures taken and problems of lockout experiences. Overall, study participants were satisfied with current fallback schemes, but at the same time, fallback authentication was aggravated when special circumstances applied and thus, leave room for improvements. Based on this, we propose an alternative concept for fallback authentication that quizzes users about installed and not installed apps on their device. Authentication succeeds, when users identify a certain number of apps correctly. Our evaluation showed that the concept yields an overall accuracy of 95%.

In this paper, we present the results of a four-week real world study on app launches on smartphones. The results show that smartphone users are confident in the way they navigate on their devices, but that there are many opportunities for refinements. Users in our study tended to sort apps based on frequency of use, putting the most frequently used apps in places that they considered fastest to reach. Interestingly, users start most apps from within other apps, followed by the use of the homescreen.

Password patterns, as used on current Android phones, and other shape-based authentication schemes are highly usable and memorable. In terms of security, they are rather weak since the shapes are easy to steal and reproduce. In this work, we introduce an implicit authentication approach that enhances password patterns with an additional security layer, transparent to the user. In short, users are not only authenticated by the shape they input but also by the way they perform the input. We conducted two consecutive studies, a lab and a long-term study, using Android applications to collect and log data from user input on a touch screen of standard commercial smartphones. Analyses using dynamic time warping (DTW) provided first proof that it is actually possible to distinguish different users and use this information to increase security of the input while keeping the convenience for the user high.

Near Field Communication (NFC) can facilitate mobile interaction with everyday objects, associated digital information and ubiquitous services. Despite the simplicity of the touch-like interaction between mobile devices and tagged physical objects, most people are still unfamiliar with this physical interaction, resulting in various usability problems. In order to improve mobile interaction with NFC-tagged objects, that serve as physical user interfaces (UI), we examine various aspects of their visual design. We identify different phases of mobile interaction with tagged objects and apply a user centered design process to create and evaluate different symbols for these phases. We report on the iterative design of NFC-symbols and physical UIs using low- and high-fidelity prototyping and present the results of a user study which was carried out with an experience prototype for an advertising scenario.

It is expected that projector phones (mobile phones with built-in pico projectors) will hit the market by 2010. Such phones provide a completely new way to display information and interaction techniques. The system presented in this paper allows the simulation of these projector phones as the real devices are not yet available. Through this, we demonstrate that it is currently possible to design, develop and evaluate applications for projector phones. The system supports three different modalities in order to compare when which display (phone display, projection) should be used. This prototype system was used for the implementation of two applications in order to test the advantages and disadvantages of projector phones for two common scenarios, picture browsing and map interaction. This demonstration paper describes the hardware used for the simulation of projector phones and the two developed prototypes. These prototypes were used for two different studies discussed in [1] and [2].

First working prototypes of mobile phones with integrated pico projectors have already been demonstrated and it is expected that such projector phones will be sold within the next three years. Applications that require interaction with large amounts of information will benefit from the large projection and its high resolution. This paper analyses the advantages and disadvantages of an integrated projector when interacting with maps, and discusses findings useful for the development of mobile applications for projector phones. We report in particular the implementation of an application that uses either the screen of the mobile phone, the projection or a combination of both. These three options were compared in a user study in which the participants had to perform three different tasks with each option. The results provide clear evidence for the positive aspects of using a built-in projector, but also show some negative aspects related to text input.