Image service system

摘要

Illegal use of a playlist can be prevented. A laboratory generates a playlist and encodes the playlist with a public key. The encoded playlist is recorded in a DVD. When a user carries out reproduction using the playlist on a personal computer, the personal computer compares token information thereof and token information included in an access ticket issued by an access ticket issuing center according to the token information of the personal computer. The personal computer carries out the reproduction by decoding the playlist with the private key in the access ticket only in the case where the token information thereof agrees with the token information in the access ticket.