Patent ID: 7555779

Claim:
A copyright protection system comprising: a recording device for recording encrypted content on a recording medium loaded to said recording device, the recording medium being removable from said recording device and having an unrewritable area in which a media number for identifying the removable recording medium is recorded; and a reproduction device for reproducing the encrypted content, wherein said recording device includes: content key storing unit configured to store a content key; a first master key storing unit configured to store a first master key assigned to said recording device; a content key encrypting unit configured to encrypt the content key based on the first master key stored in said first master key storing unit, the content key to be used to decrypt the encrypted content; a generating unit configured to obtain the media number from the removable recording medium, and generate license information based on the media number and the content key; and a recording unit configured to record the license information, the encrypted content key, and the encrypted content on the removable recording medium, wherein said reproduction device includes: a second master key storing unit configured to store a second master key assigned to said reproduction device; a computing unit configured to obtain a media number from an unrewritable area and an encrypted content key that are recorded on a removable recording medium loaded to said reproduction device, and generate reference license information based on the media number and the encrypted content key; a comparing unit configured to (i) obtain the license information from the removable recording medium loaded to said reproduction device and the reference license information from said computing unit, and (ii) compare the license information and the reference license information to determine whether or not the license information and the reference license information match each other, thereby determining whether or not at least one of (a) the removable recording medium loaded to said reproduction device is a copied medium, the copied medium having a different media number from the removable recording medium loaded to said recording device and having recorded therein copies of the license information, the encrypted content key, and the encrypted content, and (b) the content key has been tampered with; a decrypting unit configured to obtain the encrypted content and the encrypted content key from the removable recording medium loaded to said reproduction device, obtain the second master key stored in said second master key storing unit, decrypt the encrypted content key by using the second master key, and decrypt the encrypted content by using the content key to generate decrypted content; a reproduction unit configured to reproduce the decrypted content; and a suppressing unit configured to suppress the reproduction of the decrypted content when said comparing unit determines that the license information does not match the reference license information.