| 摘要 |
<p>A license administration device administers permissions of an option function for a plurality of licensee devices. A licensee device stores key information which is encrypted with an encryption key and issues a license change request which denotes either restricting or releasing a prescribed option function. Upon receiving the license change request which denotes restricting the prescribed option function, a license administration device overwrites a default key with the key information of the licensee device. Upon receiving thereafter the license change request which denotes releasing the prescribed option function, the license administration device applies an upgrade key to the key information of the licensee device. The default key and the upgrade key can be decrypted only by an encryption key which is unique to the licensee device. The license administration device administers the prescribed option function upper bound number of permissions, and reflects the change value of the upper bound of the number of permissions, said upper bound value being changed by applying the default key and the upgrade key.</p> |
