*Policy management in secure group communication.

Contemporary group communication systems address the security requirements envisioned by software developers. However, the ability of these systems to address unanticipated requirements arising from their introduction into new environments is limited. This thesis addresses these limitations through the realization of an infrastructure supporting policy determination and enforcement in multiparty communication. The traditional definition of policy is extended to encompass provisioning, authentication, and access control. Hence, all aspects of communication security are explicitly stated through policy. A policy instantiation is constructed at run-time through policy determination. The Ismene policy determination engine reconciles the conditional, abstract, and discretionary policies stated by communication participants to arrive at an instantiation. The resulting instantiation is a concrete specification of the mechanisms, configurations, and access control model to be implemented by the session. The algorithms used to derive policy are formally analyzed. An empirical investigation of Ismene shows that the cost of policy determination is nominal. The semantics of an instantiation are achieved through policy enforcement. The Antigone policy enforcement architecture implements session policies through the composition and configuration of security mechanisms. Each mechanism implements some service for the group. Policy is enforced through the observation of and reaction to relevant events. Antigone, however, is not a subscription-based event architecture. An event-bus is used to broadcast events to all mechanisms. Hence, overheads associated with subscription management and event routing are avoided. Experiments have shown that Antigone can achieve very high throughput and low latencies in a wide range of group environments. A key consideration of any policy infrastructure is its ability to represent the policies appropriate for the target user communities. Policies appropriate for the Antigone-based AMirD filesystems mirroring application in a wide range of application environments are considered and performance evaluated. These results show that Antigone can flexibly represent and efficiently enforce policies appropriate for many applications and environments.PhDApplied SciencesComputer scienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/128200/2/3029392.pd