The risk of a third party referring to or using backup data without authorization upon restoring such backup data in an HDD recorder is mitigated. First authentication information of a user as the HDD owner and second authentication information of an engineer of a repair plant are registered in an online backup service system. The first authentication information is used when backing up data recorded in the HDD to the online backup service system, and the second authentication information is used when restoring the data backed up to the online backup service system. The data backup processing and data restoration processing are executed only when the authentication information is appropriate. Since the user will directly receive an email from the online backup service system regarding who restored which data at what time, such user will be able to audit the data restoration process independently from the person recovering the data.