Authentication method of ad hoc network and wireless communication terminal thereof

On ad hoc networks in which connection relationships among communication terminals constantly change, the processing load increases when authentication is performed each time a connection relationship changes. According to this invention, when communication terminals possess the same common key, mutual authentication is conducted with that common key, and when communication terminals do not possess the same common key, mutual authentication is conducted with a public key. Communication terminals that conducted mutual authentication exchange and retain a common key that they selected and common keys received from other communication terminals. When neither communication terminal possesses a common key at authentication, one terminal creates a common key and distributes it to the other terminal, and when one terminal has a common key it creates that common key and distributes it to the other terminal. Further, a common key possessed by a communication terminal corresponding to a relay node is broadcast periodically.