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.

许可管理装置管理针对多个被许可方装置的选项功能的允许与否。被许可方装置对通过加密密钥而加密的密钥信息进行存储，发出对规定的选项功能的限制或者开放进行表示的许可变更请求。在接收到对规定的选项功能的限制进行表示的许可变更请求时，许可管理装置对被许可方装置的密钥信息重写默认密钥。之后，在接收到对规定的选项功能的开放进行表示的许可变更请求时，许可管理装置将升级密钥应用于被许可方装置的密钥信息。默认密钥以及升级密钥只能通过被许可方装置所固有的加密密钥来进行解密。此外，许可管理装置对规定的选项功能的允许上限数进行管理，将基于应用默认密钥、升级密钥所带来的允许数的增减值反映到允许上限数。