A novel three-party encrypted key exchange protocol

The passwords people can remember are usually simple or meaningful. In three-party key exchange protocols with password authentication, clients are allowed to share an easy-to-remernber password with a trusted server such that two clients can communicate with each other through a common secret key without the existence of redundant keys. Such protocols are quite suitable for application when light-weight clients need secure communications. Steiner, Tsudik, and Waidner proposed a three-party protocol based on the encrypted key exchange (EKE) protocols in 1995; however, the proposed protocol suffered from off-line and undetectable on-line guessing attacks. In 2000, Lin, Sun, and Hwang proposed a secure three-party protocol with server's public keys. Because certificates are needed to verify the server's public keys to avoid impersonation attacks, this protocol is not practical for some environments. In 2001, Lin, Sun, Steiner and Hwang proposed a brand-new three-party protocol without servers' public keys. Nevertheless, more rounds are needed by using this protocol. In this paper, we propose a secure three-party EKE protocol with round efficiency. (C) 2004 Elsevier B.V. All rights reserved.