Patent ID: 7484090

Claim:
An encryption apparatus that encrypts a digital work and outputs the encrypted digital work to a storage medium or a transmission medium, the encryption apparatus comprising: a digital work storage unit operable to store a digital work; a first secret key storage unit operable to store a first secret key, the first secret key being for encrypting the digital work; a second secret key storage unit operable to store a second secret key associated with a decryption apparatus that decrypts an encrypted digital work; a certificate revocation list (CRL) storage unit operable to store a CRL, the CRL including a list of information specifying revoked public key certificates; an attribute value calculation unit operable to calculate an attribute value associated with the information included in the CRL, the attribute value being calculated based on the CRL stored in the CRL storage unit; a modification unit operable to generate a modified second secret key by modifying the second secret key stored in the second secret key storage unit, the second secret key being modified using the attribute value calculated by the attribute value calculation unit and being modified without using the CRL stored in the CRL storage unit; a first encryption unit operable to generate an encrypted first secret key by encrypting the first secret key stored in the first secret key storage unit, the first secret key being encrypted using the modified second secret key generated by the modification unit; a second encryption unit operable to encrypt the digital work stored in the digital work storage unit, the digital work being encrypted using the first secret key stored in the first secret key storage unit; and an output unit operable to output, to the storage medium or the transmission medium, the attribute value calculated by the attribute value calculation unit, the encrypted first secret key generated by the first encryption unit and the digital work encrypted by the second encryption unit.