Using AVL Trees for Fault Tolerant Group Key Management

Abstract

In this paper we describe an efficient algorithm for the management of group-keys for Group Communication Systems. Our algorithm is based on the notion of key-graphs, previously used for managing keys in large IP-multicast groups. The standard protocol requires a centralized key-server that has knowledge of the full key-graph. Our protocol does not delegate this role to any one process. Rather, members enlist in a collaborative effort to create the group key-graph. The key-graph contains n keys, of which each member learns log_2n. We show how to balance the key-graph, a result that is applicable to the centralized protocol. We also show how to optimize our distributed protocol and provide a performance study of its capabilities.