Apparatus and method having a function of client-to-clinet authenticattion

PURPOSE: An Apparatus and method having a function of client-to-client authentication are provided to decrease a system load on a server by minimizing an operation of the server during a session key generation among users. CONSTITUTION: An apparatus and method having a function of client-to-client authentication includes receivers(325,345), transmitters(326,346), secret key generators(322,342), and session key generators(323,343). The receivers receive a ticket encoded with a symmetry key shared with an authentication server(310) and a server(330) of a connection target terminal, and it receives a first encoded message coded with a hash key generated from the ticket from the target terminal. The transmitters transmit the encoded ticket to the target terminal. The secret key generators generate a secret key shared with the target terminal based on the first encoded message and a password. The session key generators decode an encode random variable received from the target terminal using the secret key to generate a session key.