| US 7,542,568 B2 | ||
| Encryption device a decrypting device a secret key generation device a copyright protection system and a cipher communication device | ||
| Motoji Ohmori, Hirakata (Japan); Makoto Tatebayashi, Takarazuka (Japan); Takahiro Nagai, Osaka (Japan); and Hideshi Ishihara, Katano (Japan) | ||
| Assigned to Panasonic Corporation, Osaka (Japan) | ||
| Appl. No. 10/490,346 PCT Filed Sep. 11, 2002, PCT No. PCT/JP02/09245 § 371(c)(1), (2), (4) Date Sep. 14, 2004, PCT Pub. No. WO03/030447, PCT Pub. Date Apr. 10, 2003. |
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| Claims priority of application No. 2001-298414 (JP), filed on Sep. 27, 2001; and application No. 2001-374856 (JP), filed on Dec. 07, 2001. | ||
| Prior Publication US 2005/0021941 A1, Jan. 27, 2005 | ||
| This patent is subject to a terminal disclaimer. | ||
| Int. Cl. H04N 7/167 (2006.01) | ||
| U.S. Cl. 380—201 [380/44; 380/277; 380/255; 726/2; 726/26; 713/158; 713/176; 713/156; 725/115] | 25 Claims |
| 1. A secret key generating device for outputting a secret key to a decrypting device, which decrypts, using the secret key,
an encrypted digital production, the secret key generating device comprising:
an obtaining unit operable to obtain an encrypted first secret key and a CRL, from one of a recording medium and a transmission
medium, the encrypted first secret key being generated by encrypting a first secret key using a transformed second secret
key, the first secret key being used for encrypting the digital production, the CRL being an information list specifying a
revoked public key certificate, the transformed second secret key being transformed from a second secret key using an attribute
value calculated based on the CRL, and the second secret key being specific to the secret key generating device;
a second secret key memory unit operable to store the second secret key that is specific to the secret key generating device;
an attribute value calculating unit operable to calculate the attribute value based on the CRL obtained from the one of the
recording medium and the transmission medium;
a transforming unit operable to transform the second secret key, using the attribute value calculated by the attribute value
calculating unit and using the second secret key stored in the second secret key memory unit, into the transformed second
secret key used for encrypting the first secret key;
a first decrypting unit operable to decrypt the encrypted first secret key, using the transformed second secret key transformed
by the transforming unit, to obtain the first secret key; and
an outputting unit operable to output, to the decrypting device, the first secret key obtained by the first decrypting unit,
as the secret key used for decrypting the encrypted digital production,
wherein the encrypted first secret key is associated with the CRL via the transformed second secret key.
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