Multi-Party Key Agreement in Password-Based Setting

In this work, we study the problem of designing efficient password-based encrypted key agreement protocol in multi-party scenario. Recently, Dutta-Barua proposed a constant round group key agreement DB, which is a simple variant of Burmester-Desmedt protocol BD. In this paper, we present a simple and elegant contributory group key agreement in password-based setting, derived from the protocol DB. We have made several modifications in the protocol DB and then enhance it to password-based setting. The security of the proposed scheme against dictionary attacks is in the ideal cipher model under decision Diffie-Hellman (DDH) assumption. We analyze our protocol in the security framework formalized by Bellare et al. Our proposed scheme achieves efficiency over the work of Bresson et al. in terms of both computation and communication power