Patent ID: 8250664

Claim:
A content playback device for playing back a digital content, the content playback device comprising: at least one processor configured to operate as: an information acquisition unit operable to acquire a content playback program that is a computer program for playing back the digital content on a recording medium in which the digital content, the content playback program, and a digital signature generated for the content playback program are recorded; a medium type judgment unit operable to judge whether a type of the recording medium is a read-only type or a recordable type; a signature verification unit operable to perform verification of the digital signature using different signature verification methods depending on whether the type of the recording medium is judged to be the read-only type or the recordable type; and a playback permission determination unit operable to stop a processing relating to playback of the digital content by execution of the content playback program if the verification is unsuccessful.