A simple three party password based key exchange protocol

The three-party password-based key exchange protocol (3PAKE) is the protocol in which two communications entities can authenticate each other and establish a session key through the assistance of an authentication server. All exsisting 3PAKE need certain encrypion system which are not suitable to some certain application such as low devices. In this paper, we propose a simple three-party password-based key exchange protocol(S3PAKE) without encrypton based on augmented password by this way that every client only shares a common password with a trusted server and any two clients can authenticate each other and negotiate a session key relying on the help of the trusted server. Compared to previous protocols, our proposed protocols are more efficient and convenient since the protocol need not encrypt passwords..