Password-Based Authenticated Key Exchange in the Three-Party Setting

International audiencePassword-based authenticated key exchange (PAKE) are protocols which are designed to be secure even when the secret key used for authentication is a human-memorable password. In this paper, we consider PAKE protocols in the three-party scenario, in which the users trying to establish a common secret do not share a password between themselves but only with a trusted server. Towards our goal, we recall some of the existing security notions for PAKE protocols and introduce new ones that are more suitable to the case of generic constructions of three-party pro- tocols. We then present a natural generic construction of a three-party PAKE protocol from any two-party PAKE protocol and prove its security. To the best of our knowledge, the new protocol is the first provably-secure PAKE protocol in the three-party setting