Constructing a Conversation Key in Three-Party Communications Environment

This paper proposes an efficient, less communication rounds, three-party encrypted key exchange protocol to achieve the authentication requirement. The protocol is provided with no asymmetric encryption algorithm which is adopted to reduce the costs (such as any public-key infrastructure), using pre-shared key to prevent adversaries that masquerade as legal users after guessing attacks, avoiding the variant man-in-the-middle attacks on Diffie-Hellman based protocols, achieving mutual authentication. With these four features, the proposed protocol is suitable for being applied for establishing secure channels between two clients, which are supported with the same trusted server.