The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 12, 2011
Filed:
May. 24, 2004
Toshihisa Nakano, Neyagawa, JP;
Attrapadung Nuttapong, Koto-ku, JP;
Kazukuni Kobara, Mitaka, JP;
Hideki Imai, Yokohama, JP;
Toshihisa Nakano, Neyagawa, JP;
Attrapadung Nuttapong, Koto-ku, JP;
Kazukuni Kobara, Mitaka, JP;
Hideki Imai, Yokohama, JP;
Panasonic Corporation, Osaka, JP;
Abstract
A copyright protection system is provided that keeps manufacturing costs down regardless of the total number of playback apparatuses belonging to the system. In this system, a device key generating unit of a key management apparatus performs a modular exponentiation operation on a random number with an inverse element of a product of predetermined prime numbers, so as to generate and distribute device keys to playback apparatuses in one-to-one correspondence. A key revocation data generating unit generates, as key revocation data, information identifying the prime numbers used by an unrevoked playback apparatus to generate a decryption key from its device key and distributes the key revocation data along with an encrypted content to each playback apparatus. Playback apparatuses each attempt to generate a description key based on the key revocation data, and only those playback apparatuses that have successfully generated a decryption key are able to decrypt the encrypted content.