Verifier-Based Three-Party Password Authenticated Key Exchange Protocol

Three-party password authenticated key exchange (3PAKE) protocols enable two parties to establish a common session key where each party only shares one password with a trusted server. In the situation of large-scale peer-to-peer communication, a user in two-party PAKE protocols has to remember n passwords if the user has n communication parties. The main advantage of 3PAKE protocols is that each user needs only to store a single password when he wants to communicate any party in the peer-to-peer circumstance. However, the security of the existing 3PAKE protocols is generally provided in the random oracle model, and in these protocols, passwords are stored in cleartext on the server. Only a few of protocols are proven secure in the standard model and do not require a server’s public key. We generally assumed that servers are secure. But once the password file in the server is compromised, the damage will be huge. In this paper, we propose a verifier-based three-party password authenticated key exchange protocol constructed by smooth projective Hash functions(SPHFs). The protocol is proven secure in the standard model. Our protocol satisfies the secure properties such as resilient to server corruption, undetectable on-line dictionary attack and key privacy.