To prevent the software usage by an illegal user and to prevent the convenience of a user from burring by providing a function for generating second keys existing at every user from the previously registered pass phrase of the user and the key and a key managing database for registering the second keys.

The user registers his pass phrase 208 in the user information managing database 211 of a server together with his information (an address and a name, etc.), 11. When the pass phrase 208 is registered, the key B generating function 212 at the side of the server fetches the keys A and the pass phrases 208 at every user, generates the keys B 209 at every user and registers them in the key managing database 213. When the register of the keys B209 at every user is ended, a mail is transmitted from a server operating organization or automatically transmitted by the register function to the user. Thus, danger that the keys B 209 are tapped simultaneously with the pass phrases 208 is avoided and the user can always use a software by using a network.