COPYRIGHT PROTECTION SYSTEM, POWER RESIDUE CALCULATION DEVICE, AND METHOD

摘要

There is provided a copyright protection system capable of suppressing a manufacturing cost regardless of the total number of reproduction devices belonging to a system. In the copyright protection system, a key management device has a device key generation section for performing power residue calculation with an inverse element of a product of predetermined primes for a random number, thereby generating a device key and distributing one unique key to each reproduction device. The key management device also has a key disabling data generation section for generating information instructing a prime to be used for generating a decryption key from a device key by a reproduction device not disabled, together with key disabling data, and distributing it together with the encrypted content to the reproduction device. The reproduction device attempts generation of a decoding key according to the key disabling data. Only the reproduction device which could generate a decryption key decrypts the encrypted content.