Abstract

Reliable communication between parties in a network is a basic requirement for executing any protocol. In this work, we consider the effect on reliable communication when some pairs of parties have common authentication keys. The pairs sharing keys define a natural "authentication graph", which may be quite different from the "communication graph" of the network. We characterize when reliable communication is possible in terms of these two graphs, focusing on the very strong setting of a Byzantine adversary with unlimited computational resources. Key Words: Reliable Communication, Private Communication, Authentication Keys, Graph Connectivity, Byzantine Failures. 1 Introduction Suppose that some processors are connected by a network of reliable channels. All of the processors cooperate to execute some protocol, but some of them are maliciously faulty. Dolev [4] and Dolev et al. [5] proved that if there are t faulty processors, then every pair of processors can communicate reliably if...

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