In the Local Storage (18), a plurality of files, merge management information which specifies a file out of the plurality of files to be used in combination with what is recorded on a Read-Only recording medium, and signature information used for judging the authenticity of the merge management information. The Virtual File System unit (38) judges the authenticity of the merge management information based on the signature information. In the case where the merge management information is judged to be authentic, the Virtual File System unit (38) generates package information which indicates a new file structure obtained by adding the file specified by the merge management information to the file structure of the Read-Only recording medium.