Copyright protection system, modular exponentiation...

Electrical computers and digital processing systems: support – Data processing protection using cryptography – By stored data protection

Reexamination Certificate

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C380S028000, C726S026000

Reexamination Certificate

active

07925893

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.

REFERENCES:
patent: 2002/0076204 (2002-06-01), Nakano et al.
patent: 2003/0142826 (2003-07-01), Asano
patent: 2003/0182565 (2003-09-01), Nakano et al.
patent: 2004/0030905 (2004-02-01), Chow et al.
patent: 2002-281013 (2002-09-01), None
patent: 2003-169048 (2003-06-01), None
patent: 2003-273862 (2003-09-01), None
Tomoyuki Asano, “Efficient Broadcast Encryption Methods Based on a Key Tree Structure”, Proceedings of the 2003 Symposium on Cryptography and Information Security, vol. I of II, pp. 209 to 214, Jan. 26, 2003 (along with partial English translation).
Tomoyuki Asano, “A Revocation Scheme with Minimal Storage at Receivers”, Lecture Notes in Computer Science, vol. 2501, pp. 433 to 450, Apr. 17, 2003.

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