Referring to FIG. 2, DRM A-to-DRM B conversion is a process of converting content Cont_A which has been created using a DRM system DRM A installed in a device Dev_A, so that a device Dev_B, in which a DRM system DRM B is installed, can reproduce the content Cont_A received from the device Dev_A. The devices Dev_A and Dev_B belong to the same home network, i.e., a home network 200.