Patent ID: 8108936

Claim:
A content playback control method comprising: storing in a memory, information describing: a content key; a usage condition; special sections subject to a restriction of a special playback of content; and a playback mode permitted in each of the special sections; the usage condition specifying whether or not a playback is performed with respect to the special sections and the playback mode, and an electronic signature assigned to at least one of the special sections and the playback mode; at least one of the special sections and the playback mode is assigned the electronic signature and stored in a non-tamper-proof memory; the content key and the usage condition are stored in a tamper-proof security module; decoding encrypted content using the content key to generate decoded content, only when the usage condition is met; checking a validity of the at least one of the special sections and the playback mode to which the electronic signature is assigned, when an instructed special playback of the decoded content is performed; determining, when the at least one of the special sections and the playback mode to which the electronic signature is assigned is valid and the usage condition specifies the special sections of the decoded content described in the information stored in the memory, whether the special sections of the decoded content described in the information stored in the memory include a point at which the instructed special playback is performed, and controlling the instructed special playback for the decoded content, when the special sections include the point at which the instructed special playback is performed, and when the usage condition specifies that the playback is performed based on the playback mode described in the information stored in the memory, and a playback mode of the instructed special playback corresponds to one of the playback mode described in the information stored in the memory.