| US 7,555,129 B2 | ||
| Content playback apparatus, content playback method, and program | ||
| Masaya Yamamoto, Arcadia, Calif. (US); Motoji Ohmori, Hirakata (Japan); Masato Yamamichi, Kodama (Japan); Masami Yamamichi, legal representative, Satomi Yamamichi, legal representative, and Keiko Yamamichi, legal representative; Kazuhisa Watanabe, Yokohama (Japan); Atsushi Saso, Yokohama (Japan); and Naoaki Yamamoto, Tokyo (Japan) | ||
| Assigned to Panasonic Corporation, Osaka (Japan) | ||
| Filed on Jun. 17, 2004, as Appl. No. 10/868,872. | ||
| Claims priority of application No. 2003-173908 (JP), filed on Jun. 18, 2003. | ||
| Prior Publication US 2005/0018854 A1, Jan. 27, 2005 | ||
| Int. Cl. H04L 9/00 (2006.01) | ||
| U.S. Cl. 380—277 [380/54; 380/200; 380/210; 713/193; 726/27] | 20 Claims |
| 1. A content playback apparatus comprising:
a key storage unit operable to store a device key pre-assigned to said content playback apparatus;
an information reading unit operable to read, from a recording medium having a pre-assigned media key and pre-storing main
content, (i) key management information obtained by encrypting, based on the device key, one of (a) the media key and (b)
a piece of revocation information, the piece of revocation information indicating that said content playback apparatus has
been revoked, and (ii) the main content;
a sub-content obtaining unit operable to obtain encrypted sub-content, the encrypted sub-content being data generated by encrypting
sub-content based on a content key, the sub-content being content relating to the main content recorded on the recording medium,
and the content key being a key generated by applying a predetermined operation to key generation information based on the
media key;
a key obtaining unit operable to decrypt, based on the device key, the key management information to obtain one of (a) the
media key and (b) the piece of revocation information;
an information obtaining unit operable to obtain key generation information from an information source other than the recording
medium;
a key generation unit operable to, when said key obtaining unit has obtained the media-key, apply a predetermined operation
to the obtained key generation information to generate a content key, the predetermined operation being applied to the obtained
key generation information based on the media key;
a decryption unit operable to decrypt the encrypted sub-content based on the content key; and
a playback unit operable to play the main content and the decrypted sub-content.
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