Efficient and secure conference-key distribution

Abstract

Key distribution is a major cryptographic component for secure communication. For privacy data must be encrypted with keys which are distributed securely. In this paper we focus on conference key distribution. Our approach is to use a two-party key distribution system as an underlying cryptographic primitive and extend it to a conference system. We consider three different models: an unconditionally secure model, a provably secure model, and a model whose security is based on the difficulty of breaking the Diffie-Hellman problem. For each of these we present a conference key distribution system which is as secure as the primitive. These extend and generalize our conference scheme presented at Eurocrypt '94. In particular, (i) we are not restricted to any specific network or primitive and, (ii) our system based on the Diffie-Hellman key exchange is more efficient.