A Provably-Secure Password-Authenticated Group Key Agreement in the Standard Model

Abstract

Password-authenticated group key exchange protocols (PAGKE) refer to the protocols that with low entropy human-memorable passwords users of a group can agree on a session key which is used to communication secretly through an insecure channel. Because password is easy to memorize, do not need hard devices to store and password-authenticated group key exchange protocols do not need support of the public key infrastructure, this kinds of protocols are widely used to realize key exchange in the setting which is hard to fix public key infrastructure. Up to now, in most password-authenticated group key exchange protocols the users of the group share one common password. It is not suitable to some network where different user holding different password. In this paper, we present a new provable-secure password-authenticated group key exchange protocol based on the scheme of Burmester and Desmedt. Outbalancing existing protocols in which every user of the group holds different password, the protocol proposed in this paper satisfies the security property of key privacy with respect to server. The proof of security is in the standard model and based Bellare, Pointcheval and Rogaway’s model, under the Decisional Diffie-Hellman assumption. In the last, we also consider the dynamic scenario of our protocol, including new members joining and members leaving.