Reconciling privacy and security in pervasive computing: the case for pseudonymous group membership

In this paper, we outline an approach to the identification of entities for access control that is based on the membership of groups, rather than individuals. By using group membership as a level of indirection between the individual and the system, we can increase privacy and provide incentives for better behaviour. Privacy comes from the use of pseudonyms generated within the group and which can be authenticated as belonging to the group. The incentives for better behaviour come from the continuous nature of groups - members may come and go, but the group lives on, and groups are organised so as to ensure group-longevity, and prevent actions which may harm the group's reputation. We present a novel pseudonym generation mechanism suitable for use in groups without a centralised administration. Finally, we argue that the use of group membership as the basis for formulating policies on interaction is more efficient for disconnected operation, facilitating proxies and the efficient storage of revoked membership and distrusted organisations within bloom filters for small memory footprints.