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 people's 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.

A large number of papers have proposed cryptographic protocols for establishing secure group communication. These protocols allow a set of group members to exchange or establish keys to encrypt and authenticate messages within the group. At the same time, individuals outside of the group cannot eavesdrop on group communication or inject messages. There have even been usability studies, demonstrating an average user can successfully complete some of these protocols. However, group protocols are rarely used in the real world. In this work, we conduct a survey to help uncover why the general population ignores such mechanisms for group communication. We also try to determine what protocols would best match respondents' current expectations for group protocols and methods for establishing trust. Survey results indicate that a group protocol that leverages location-limited channels, PKI, or Web-of-Trust authenticated public keys and allows addition and deletion of members fulfills the majority of users' expectations.