This paper is the first to assess the impact of touchscreen damage on smartphone interaction. We gathered a dataset consisting of 95 closeup images of damaged smartphones and extensive information about a device's usage history, damage severity, and impact on use. 88% of our participants continued to use their damaged smartphone for at least three months; 32% plan to use it for another year or more, mainly due to high repair and replacement costs. From the dataset, we identified three categories of damaged smartphone displays. Reading and text input were most affected. Further interviews (n=11) revealed that users adapt to damage with diverse coping strategies, closely tailored to specific interaction issues. In total, we identified 23 different strategies. Based on our results, we proposed guidelines for interaction design in order to provide a positive user experience when display damage occurs.

The vision of pervasive ambient information displays which show relevant information has not yet come true. One of the main reasons is the limited number of available displays in the environment which is a fundamental requirement of the original vision. We introduce the concept of an Ambient Mobile Pervasive Display AMP-D which is a wearable projector system that constantly projects an ambient information display in front of the user. The floor display provides serendipitous access to public and personal information. The display is combined with a projected display on the user's hand, forming a continuous interaction space that is controlled by hand gestures. The paper introduces this novel device concept, discusses its interaction design, and explores its advantages through various implemented application examples. Furthermore, we present the AMP-D prototype which illustrates the involved challenges concerning hardware, sensing, and visualization.

Handheld displays enable flexible spatial exploration of information spaces -- users can physically navigate through three-dimensional space to access information at specific locations. Having users constantly hold the display, however, has several limitations: (1) inaccuracies due to natural hand tremors; (2) fatigue over time; and (3) limited exploration within arm's reach. We investigate autonomous, self-actuated displays that can freely move and hold their position and orientation in space without users having to hold them at all times. We illustrate various stages of such a display's autonomy ranging from manual to fully autonomous, which -- depending on the tasks -- facilitate the interaction. Further, we discuss possible motion control mechanisms for these displays and present several interaction techniques enabled by such displays. Our Hover Pad toolkit enables exploring five degrees of freedom of self-actuated and autonomous displays and the developed control and interaction techniques. We illustrate the utility of our toolkit with five prototype applications, such as a volumetric medical data explorer.

Current interactive surfaces do not support user identification. Hence, personalized applications that consider user-specific access control are not possible. Diverse approaches for identifying and distinguishing users have been investigated in previous research. Token-based approaches -- e.g., which utilize the user's mobile phone -- are especially promising, as they also allow for consideration of the user's personal digital context (e.g., stored messages, contacts, or media data). However, existing interaction techniques are limited regarding their ability to enable users to manipulate (e.g., select or copy) multiple items at the same time, as they are cumbersome when the number of files exceeds a certain amount. We present MobiZone, a technique that enables users to interact with large numbers of items on an interactive surface while enabling personalized access by using the mobile phone as a token. MobiZone provides a spatial zone that can be positioned, resized and associated with any action according to the user's needs; items enclosed by the zone can be manipulated simultaneously. We present three interaction techniques (FlashLight&Control, Remote&Control, and Place&Control) that enable users to control the zone. Additionally, we report the results of a comparative user study in which we compared the different interaction techniques for MobiZone. The results indicate that users are fastest with Remote&Control, and they also rated Remote&Control slightly higher than the other techniques.

Many interactions naturally extend across smart-phones and devices with larger screens. Indeed, data might be received on the mobile but more conveniently processed with an application on a larger device, or vice versa. Such interactions require spontaneous data transfer from a source location on one screen to a target location on the other device. We introduce a cross-device Drag-and-Drop technique to facilitate these interactions involving multiple touchscreen devices, with minimal effort for the user. The technique is a two-handed gesture, where one hand is used to suitably align the mobile phone with the larger screen, while the other is used to select and drag an object between devices and choose which application should receive the data.

We present the technical framework supporting a cross-device Drag-and-Drop technique designed to facilitate interactions involving multiple touchscreen devices. This technique supports users that need to transfer information received or produced on one device to another device which might be more suited to process it. Furthermore, it does not require any additional instrumentation. The technique is a two-handed gesture where one hand is used to suitably align the mobile phone with the larger screen, while the other is used to select and drag an object from one device to the other where it can be applied directly onto a target application. We describe the implementation of the framework that enables spontaneous data-transfer between a mobile device and a desktop computer.

Natural forms of interaction have evolved for personal devices that we carry with us (mobiles) as well as for shared interactive displays around us (surfaces) but interaction across the two remains cumbersome in practice. We propose a novel cross-device interaction style for mobiles and surfaces that uses the mobile for tangible input on the surface in a stylus-like fashion. Building on the direct manipulation that we can perform on either device, it facilitates fluid and seamless interaction spanning across device boundaries. We provide a characterization of the combined interaction style in terms of input, output, and contextual attributes, and demonstrate its versatility by implementation of a range of novel interaction techniques for mobile devices on interactive surfaces.

Recent mobile phones allow users to perform a multitude of different tasks. Complexity of tasks challenges the design of mobile applications in many ways. For instance, the limited screen space of mobile devices allows only a small number of items to be displayed. Therefore, users often have to change the view or have to resize the displayed content (e.g., images or maps) to view the required information. We present the system MobIES, which allows users to extend the mobile interfaces of their mobiles phones using external screens. Users connect their mobile phone with an external display by holding it on the border of the external display. When the connection is established, the user interface of the currently active mobile application is distributed on the phone and the external screen. This enables users to take advantage of using existing screens in their environments and temporarily benefit from an extended screen space. In this paper, we discuss the concept of MobIES and present a prototype implementation.

Public terminals for service provision provide high convenience to users due to their constant availability. Yet, the interaction with them lacks security and privacy as it takes place in a public setting. Additionally, users have to wait in line until they can interact with the terminal. In comparison to that, personal mobile devices allow for private service execution. Since many services, like with-drawing money from an ATM, require physical presence at the terminal, hybrid approaches have been developed. These move parts of the interaction to a mobile device. In this work we present the results of a four week long real world user study, in which we investigated whether hybrid approaches would actually be used. The results show that users accept the hybrid service as they understood that they could use down downtimes (like bus rides) to prepare the interaction with the public terminal. Our findings give novel insights about security relevant aspects such as where and when users interact with the mobile service before accessing the public terminal. So the preparation of the transaction on the mobile phone was often conducted much further away from the terminal than expected (81.0% with a distance greater than 400m) and earlier than expected (82.1% at least 5 minutes in advance).

Internet users are targets for ever-advancing phishing- and other attacks. The risks are, for example, to disclose credit card information or passwords to unauthorized instances. One approach to help users with insecure situations is provided by MoodyBoard, which uses ambient information to highlight potential risks. In this paper, we present findings from an evaluation of this system. Two user studies were conducted in order to find out whether an ambient security tool can protect users during sensitive tasks. We designed a pilot study to find out whether users understand the warnings and a security study to see if it helps to protect users from phishing attacks. Results show that MoodyBoard users behaved significantly more secure.

Currently, the development of mobile applications heavily relies on using conventional computers as development platform. MobiDev enables people in emerging countries without access to a computer but to a cell phone to develop their own locally relevant applications. The goal of the Mo-biDev project is to simplify development and deployment of applications directly on mobile phones. As a first step, we focus on the design of applications and try to support the computer science curriculum in developing countries to bootstrap the mobile developer culture and community. MobiDev allows the creation of graphical user interfaces (GUI) using various concepts. We present the results of a first system evaluation that show how people perceive the concepts for UI creation of MobiDev.

In this paper we present a context-sensitive security model for privacy protection on mobile phones. We describe the system TreasurePhone which implements this security model. The Privacy Protection is realized by spheres, which represent the user's context specific need for privacy. That is, users can create any number of spheres and define which services and data are accessible in each sphere. TreasurePhone integrates context information for supporting authentication and activation of spheres by locations and actions. A basic hierarchy is used for determining which location should be activated based on the associated sensor value.