Martina Angela Sasse

Users are not the enemy

Many system security departments treat users as a security risk to be controlled. The general consensus is that most users are careless and unmotivated when it comes to system security. In a recent study, we found that users may indeed compromise computer security mechanisms, such as password authentication, both knowing and unknowingly. A closer analysis, however, revealed that such behavior is often caused by the way in which security mechanisms are implemented, and users’ lack of knowledge. We argue that to change this state of affairs, security departments need to communicate more with users, and adopt a usercentered design approach.

The impact of eye gaze on communication using humanoid avatars

In this paper we describe an experiment designed to investigate the importance of eye gaze in humanoid avatars representing people engaged in conversation. We compare responses to dyadic conversations in four mediated conditions: video, audio-only, and two avatar conditions. The avatar conditions differed only in their treatment of eye gaze. In the random-gaze condition the avatars head and eye animations were unrelated to conversational flow. In the informed-gaze condition, they were related to turn-taking during the conversation. The head animations were tracked and the eye animations were inferred from the audio stream. Our comparative analysis of 100 post-experiment questionnaires showed that the random-gaze avatar did not improve on audio-only communication. The informed-gaze avatar significantly outperformed the random-gaze model and also outperformed audio-only on several response measures. We conclude that an avatar whose gaze behaviour is related to the conversation provides a marked improvement on an avatar that merely exhibits liveliness.

Making Passwords Secure and Usable

To date, system research has focused on designing security mechanisms to protect systems access although their usability has rarely been investigated. This paper reports a study in which users’ perceptions of password mechanisms were investigated through questionnaires and interviews. Analysis of the questionnaires shows that many users report problems, linked to the number of passwords and frequency of password use. In-depth analysis of the interview data revealed that the degree to which users conform to security mechanisms depends on their perception of security levels, information sensitivity and compatibility with work practices. Security mechanisms incompatible with these perceptions may be circumvented by users and thereby undermine system security overall.

Privacy in multimedia communications: protecting users not just data

As the use of ubiquitous multimedia communication increases so do the privacy risks associated with widespread accessibility and utilisation of data generated by such applications. Most invasions of privacy are not intentional but due to designers inability to anticipate how this data could be used, by whom, and how this might affect users. This paper addresses the problem by providing a model of user perceptions of privacy in multimedia environments. The model has been derived from an analysis of empirical studies conducted by the authors and other researchers and aids designers to determine which information users regard as private, and in which context It also identifies trade-offs that users are willing to make rendering some privacy risks acceptable. To demonstrate how this model can be used to assess the privacy implications of multimedia communications in a specific context, an example of the models application for a specific usage scenario is provided.

Successful multiparty audio communication over the Internet

The Internet was once perceived as a computer network used by researchers to transfer files and send text messages. Today, more users are becoming aware of its potential as a general communication network. Multicast conferencing over the Internet has the potential to offer low-cost real-time multimedia solutions to a wide range of user groups, provided that sufficient audio quality can be sustained. C ommercial interest in Internet audio has focused primarily on point-to-point applications such as Internet telephony, which provides roughly the same functionality as Public Switched Telephone Networks (PSTNs) over a computer network. The second focus of Internet audio developers has been download-ing audio files—typically from a WorldWide Web server—for playout on a remote users workstation [9]. Multicast conferencing [1], on the other hand, allows real-time multiway audio and video communication over the Internet and is now moving from the pilot stage [7] to a usable service in countries like the U.K. and the U.S. Multicast audio allows groups of users to participate in real-time, simultaneous audio conferences, supporting communication that goes beyond the possibilities of telephony or broadcast technology. Since the multicast backbone (Mbone—an overlay over the Internet [7]) can also support video and shared workspace, collaboration environments can be tailored to support the requirements of many distributed user groups. Another important benefit, particularly for applications such as distance education, is that multicast conferencing costs a fraction of the cost of other solutions. While video and shared data are essential to many distributed tasks, audio of sufficient quality is a necessary condition for almost any successful real-time interaction. Therefore, ensuring sufficient audio quality is a major stepping stone for realizing the potential of multicast conferencing.

Evaluating audio and video quality in low-cost multimedia conferencing systems

Abstract Real-time audio and video transmission over shared packet networks, such as the Internet, has become possible thanks to efficient data compression schemes and the provision of high-speed networks. Low-cost multimedia conferencing technology could benefit many users in different areas, such as remote collaboration, distance education and health-care. It is likely that diverse tasks performed by users in different application domains will require different levels of audio and video quality. Established methods of rating audio and video quality in the broadcast and telephony world cannot be applied to digital, lower quality images and sound. The providers of networks and services are looking to HCI to provide a means of assessing audio and video quality. The paper describes two different approaches to assessing audio and video of desktop conferencing systems — a controlled experimental study and an informal field trial. The advantages and disadvantages of both approaches for providing task-specific quality assessment are discussed, and future work to integrate lab-based and field trials into a valid and reliable assessment approach is outlined.

Of packets and people: a user-centered approach to quality of service

Multimedia communication has gained increasing attention, both from the application side and the network provider side. While resource provisioning for QoS support in packet switched networks has led to the design and development of sophisticated QoS architectures, notably ATM, IntServ or DiffServ, research has not exactly been user or application-context centered. In the cause of the evolution of QoS architectures, the integrated service network approach has lost momentum, and with it, the notion of QoS guarantees. Differentiation of QoS classes within the DiffServ framework is based on the definition of various per-hop behaviors. What is currently missing is a technique for specification and mapping of application and user QoS preferences onto evolving service profiles. In addition, adaptation of applications (and users) is becoming increasingly important in the face of dominating weak QoS-assurance paradigms, both in wireline and wireless environments. As a prerequisite, this paper investigates cognitive and perceptive conditioning of users and applications in a situated setting. The contribution of this paper is twofold: first, essential empirical results on user QoS preferences and QoS graduations are presented, and second, methodological foundations are laid for investigating user-centered QoS.

The big picture on small screens delivering acceptable video quality in mobile TV

Mobile TV viewers can change the viewing distance and (on some devices) scale the picture to their preferred viewing ratio, trading off size for angular resolution. We investigated optimal trade-offs between size and resolution through a series of studies. Participants selected their preferred size and rated the acceptability of the visual experience on a 200ppi device at a 4:3 aspect ratio. They preferred viewing ratios similar to living room TV setups regardless of the much lower resolution: at a minimum 14 pixels per degree. While traveling on trains people required videos with a height larger than 35mm.

Support for collaborative authoring via Email: the MESSIE environment

MESSIE is a collaborative authoring environment to support the production of large-scale document by teams of geographically distributed groups of authors working with heterogenous systems. The environment allows authors to submit text at various stages of gestation (e.g. list of topics, first draft) to a shared filestore via email. All authors collaborating on a document can read each others contributions, and add suggestions, comments and additional material directly to the document. The system integrates automatically answered electronic mail, shared file store administration, and a version control tool in a UNIX environment. The paper describes design and implementation strategy, and reports observations and a number of changes which were made during a 4-month trial period with three collaborative authoring teams.

Too close for comfort: a study of the effectiveness and acceptability of rich-media personalized advertising

Online display advertising is predicted to make