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Abstract: We present and analyze a new algorithm for establishing shared cryptographic keys in large, dynamically changing groups. Our algorithm is based on a novel application of one-way function trees. In comparison with previously published methods, our algorithm reduces by approximately half the number of bits that need to be broadcast to members in order to re-key after a member is added or evicted. The number of keys stored by group members, the number of keys broadcast to the group when new members are added or evicted, and the computational effort of group members, are logarithmic in the number of group members. Our algorithm provides complete forward and backwards security: newly admitted group members cannot read previous messages, and evicted members cannot read future messages, even with collusion by arbitrarily many evicted members.
This algorithm offers a new scalable method for establishing group session keys for secure large-group applications such as electronic conferences, multicast sessions, and military command and control. A paper based on this work can be found on Sherman's homepage.
sherman@umbc.edu, www.csee.umbc.edu/~sherman
About the Speaker
Dr. Alan T. Sherman is associate professor of computer science in the Department of Computer Science and Electrical Engineering at the University of Maryland, Baltimore County (UMBC). He is an editor of Cryptologia and the leader of the UMBC Security Technology Research Group.