In an internal circuit type, an encryption circuit is included in a device. Information specific to the device including the encryption circuit is preregistered to a net authentication site. A portable storage medium is inserted into an information recording/reproduction mechanism of the device, and an access is made to the net authentication site with a host PC. When a right to access to the net authentication site is obtained, the net authentication site reads shared information stored on the portable storage medium, and makes a comparison between the shared information and the contents of a database. If a match is found as a result of the comparison, the net authentication site writes devices-specific information to the shared information on the portable storage medium, so that encrypted data on the portable storage medium can be read with the device.