Kami Vaniea

Access Control for Home Data Sharing: Attitudes, Needs and Practices

As digital content becomes more prevalent in the home, non-technical users are increasingly interested in sharing that content with others and accessing it from multiple devices. Not much is known about how these users think about controlling access to this data. To better understand this, we conducted semi-structured, in-situ interviews with 33 users in 15 households. We found that users create ad-hoc access-control mechanisms that do not always work; that their ideal policies are complex and multi-dimensional; that a priori policy specification is often insufficient; and that peoples mental models of access control and security are often misaligned with current systems. We detail these findings and present a set of associated guidelines for designing usable access-control systems for the home environment.As digital content becomes more prevalent in the home, non-technical users are increasingly interested in sharing that content with others and accessing it from multiple devices. Not much is known about how these users think about controlling access to this data. To better understand this, we conducted semi-structured, in-situ interviews with 33 users in 15 households. We found that users create ad-hoc access-control mechanisms that do not always work; that their ideal policies are complex and multi-dimensional; that a priori policy specification is often insufficient; and that peoples mental models of access control and security are often misaligned with current systems. We detail these findings and present a set of associated guidelines for designing usable access-control systems for the home environment.

User-Controllable Security and Privacy for Pervasive Computing

We describe our current work in developing novel mechanisms for managing security and privacy in pervasive computing environments. More specifically, we have developed and evaluated three different applications, including a contextual instant messenger, a people finder application, and a phone-based application for access control. We also draw out some themes we have learned thus far for user-controllable security and privacy.

A user study of policy creation in a flexible access-control system

Significant effort has been invested in developing expressive and flexible access-control languages and systems. However, little has been done to evaluate these systems in practical situations with real users, and few attempts have been made to discover and analyze the access-control policies that users actually want to implement. We report on a user study in which we derive the ideal access policies desired by a group of users for physical security in an office environment. We compare these ideal policies to the policies the users actually implemented with keys and with a smartphone-based distributed access-control system. We develop a methodology that allows us to show quantitatively that the smartphone system allowed our users to implement their ideal policies more accurately and securely than they could with keys, and we describe where each system fell short.

Lessons learned from the deployment of a smartphone-based access-control system

Grey is a smartphone-based system by which a user can exercise her authority to gain access to rooms in our university building, and by which she can delegate that authority to other users. We present findings from a trial of Grey, with emphasis on how common usability principles manifest themselves in a smartphone-based security application. In particular, we demonstrate aspects of the system that gave rise to failures, misunderstandings, misperceptions, and unintended uses; network effects and new flexibility enabled by Grey; and the implications of these for user behavior. We argue that the manner in which usability principles emerged in the context of Grey can inform the design of other such applications.

More than skin deep: measuring effects of the underlying model on access-control system usability

In access-control systems, policy rules conflict when they prescribe different decisions (allow or deny) for the same access. We present the results of a user study that demonstrates the significant impact of conflict-resolution method on policy-authoring usability. In our study of 54 participants, varying the conflict-resolution method yielded statistically significant differences in accuracy in five of the six tasks we tested, including differences in accuracy rates of up to 78%. Our results suggest that a conflict-resolution method favoring rules of smaller scope over rules of larger scope is more usable than the Microsoft Windows operating systems method of favoring deny rules over allow rules. Perhaps more importantly, our results demonstrate that even seemingly small changes to a systems semantics can fundamentally affect the systems usability in ways that are beyond the power of user interfaces to correct.

Tales of Software Updates: The process of updating software

Updates alter the way software functions by fixing bugs, changing features, and modifying the user interface. Sometimes changes are welcome, even anticipated, and sometimes they are unwanted leading to users avoiding potentially unwanted updates. If users delay or do not install updates it can have serious security implications for their computer. Updates are one of the primary mechanisms for correcting discovered vulnerabilities, when a user does not update they remain vulnerable to an increasing number of attacks. In this work we detail the process users go through when updating their software, including both the positive and negative issues they experience. We asked 307 survey respondents to provide two contrasting software update stories. Using content analysis we analysed the stories and found that users go through six stages while updating: awareness, deciding to update, preparation, installation, troubleshooting, and post state. We further detail the issues respondents experienced during each stage and the impact on their willingness to update.

Debunking Security-Usability Tradeoff Myths

Guest editors M. Angela Sasse and Matthew Smith discuss the origins of the security-usability tradeoff myth with leading academic experts Heather Lipford and Kami Vaniea and industry expert Cormac Herley.

Studying access-control usability in the lab: lessons learned from four studies

In a series of studies, we investigated a user interface intended to help users stay aware of their access-control policy even when they are engaged in another activity as their primary task. Methodological issues arose in each study, which impacted the results. We describe the difficulties encountered during each study, and changes to the methodology designed to overcome those difficulties. Through this process, we shed light on the challenges intrinsic to many studies that examine security as a secondary task, and convey a series of lessons that we hope will help other researchers avoid some of the difficulties that we encountered.