Patent ID: 8204227

Claim:
An information processing apparatus comprising: an encryption unit constructed to generate a plurality of encrypted files by encrypting each of a plurality of original files are stored in a first rewritable storage device, wherein the plurality of encrypted files is generated using each of a plurality of unique cryptographic keys stored in a second rewritable storage device, and wherein each of the plurality of the encrypted files is associated with a respective one of the plurality of the unique cryptographic keys; a writing unit constructed to write the plurality of the encrypted files into a single write-once storage device which consists of unrewritable blocks; an acceptance unit constructed to accept an instruction which instructs to update one of the plurality of the original files; an update unit constructed to update the one of the plurality of the original files in accordance with the accepted instruction; and a deletion unit constructed to delete one of the plurality of the unique cryptographic keys, wherein the key to be deleted is associated with the one of the plurality of encrypted files which was generated by encrypting the one original file which is the subject of updating in accordance with the accepted instruction, without deleting others of the plurality of unique cryptographic keys from the second rewritable storage device and without updating the encrypted files which have been written in the single write-once storage device, so that the encrypted files become partially unavailable and are kept as partially available and so that both the unavailable encrypted files and the available encrypted files are written in the same single write-once storage device, wherein at least one processor executes steps stored in a memory to function as at least one of the units.