Secure key agreement protocols for three-party against guessing attacks

Key exchange protocol is important for sending secret messages using the session key between two parties. In order to reach the objective, the premise is to generate a session key securely. Encryption key exchange was first proposed to generate a session key with a weak authenticated password against guessing attacks. Next, another authenticated key exchange protocols for three-party, two clients who request the session key and one server who authenticates the user's identity and assist in generating a session key, were proposed. In this paper, we focus on the three-party authenticated key exchange protocol. In addition to analyzing and improving a password-based authenticated key exchange protocol, a new verified-based protocol is also proposed.