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Publication
Information and Computation
Paper
Perfectly Secure Key Distribution for Dynamic Conferences
Abstract
In this paper we analyze perfectly secure key distribution schemes for dynamic conferences. In this setting, any member of a group of t users can compute a common key using only his private initial piece of information and the identities of the other t - 1 users in the group. Keys are secure against coalitions of up to k users; that is, even if k users pool together their pieces they cannot compute anything about a key of any conference comprised of t other users. First we consider a noninteractive model where users compute the common key without any interaction. We prove the tight bound on the size of each user's piece of information of (k + t - 1t - 1) times the size of the common key. Then, we consider the model where interaction is allowed in the common key computation phase and show a gap between the models by exhibiting a one-round interactive scheme in which the user's information is only k + t - 1 times the size of the common key. Finally, we present its adaptation to network topologies with neighbourhood constraints and to asymmetric (e.g., client-server) communication models. © 1998 Academic Press.