DDH-based Group Key Agreement in a Mobile Environment.

A group key agreement protocol is designed to efficiently implement secure multicast channels for a group of parties communicating over an untrusted, open network by allowing them to agree on a common secret key. In the past decade many problems related to group key agreement have been tackled and solved (diminished if not solved), and recently some constant-round protocols have been proven secure in concrete, realistic setting. However, all forward-secure protocols so far are still too expensive for small mobile devices. In this paper we propose a new constant-round protocol well suited for a mobile environment and prove its security under the Decisional Diffie-Hellman assumption. The protocol meets simplicity, efficiency, and all the desired security properties.