Policy Groups

This paper contributes to the current discussion on multipolicy systems: Systems that support a multitude of independent security domains in which an individual security policy is enforced on the applications. In multipolicy systems, the interoperability between diierent security domains constitutes a major problem. While security policies are capable of controlling the applications within their domains, interactions between diierent security domains create security loopholes and cause connicts between the involved security policies. This paper introduces policy groups as an approach to secure domain interactions. A policy group combines a set of security policies with a set of policies that control interdomain actions. It composes a multipolicy system's security policies into a single structure and provides a single point of reference for the discussion of a system's security properties. In order to provide a precise foundation for this discussion, the paper introduces a formal model of policy groups based on Harrison, Ruzzo and Ullman's access control calculus. The paper concludes with statements about the decidability of the safety problem for policy groups.