Patent ID: 7203312

Claim:
A data reproduction apparatus decrypting encrypted content data to reproduce content data, comprising: a data reproduction unit to reproduce said encrypted content data, and a data storage unit storing said encrypted content data and an encrypted content key, and providing said encrypted content data and said encrypted content key to said data reproduction unit, wherein said encrypted content key is a content key directed to decrypt said encrypted content data in an encrypted form decryptable with a first decryption key unique to said data reproduction unit; wherein said data reproduction unit comprises a session key generation unit generating a session key updated at every access to obtain said content key with respect to said data storage unit, a first encryption processing unit encrypting said session key using a public encryption key that can be decrypted at said data storage unit and that is unique to said data storage unit, and providing said encrypted session key to said data storage unit, a first decryption processing unit using said session key to decrypt said encrypted content key that is an encrypted version of said content key using said session key, said encrypted content key formally obtained from said data storage unit, a first key hold unit prestoring said first decryption key, a second decryption processing unit extracting said content key by applying a decryption process on an output from said first decryption processing unit using said first decryption key stored in said first key hold unit, and a third decryption processing unit receiving said encrypted content data read out from said data storage unit to decrypt said encrypted content data using a content key extracted by said second decryption processing unit to extract content data.