System and method for generating reproducible session keys

In a radio communications system, it is the system and method for generating a refreshable session key. A session key is generated based on hash of the message itself, and is alternatively connected with additional information. Since local servers save the message, each MORE request can be answered and regeneration of the same session key can be carried out easily. The method of the present invention may be enforced with the message of the origin saved, a public key, and the algorithm for generating a session key based on hash of a message.