By recording a digital signature and a public key certificate when recording data on an information recording medium, a recording device having recorded content can be specified. If recording media including illegally recorded data are distributed, the recording device used for the recording can be specified and can be excluded from the system. An information playback device verifies the validity of the digital signature and public key certificate when reading data, specifies a content recorder, and verifies no falsification in the digital signature and the public key certificate before playing back the data. This structure can efficiently exclude the playback of content recorded by an invalid recording device.