Patent ID: 7058819

Claim:
A data processing apparatus for generating a verifying value for verifying an individual contents data to be stored in a memory device, storing said verified value in said memory device in correspondence with said contents data, and checking to probe actual occurrence or absence of the act of tampering with said contents data by referring to said verifying value, comprising: a ciphering unit for generating said verifying value; and one or more keys for use by said ciphering unit to generate said verifying value; whereby said processing apparatus is operable to generate a verifying value for each category of a plurality of categories of contents data stored in said memory device; and whereby said keys are arranged in a hierarchical structure having a plurality of levels, said memory device is associated with a device level of said structure, and said memory device stores, in unencrypted form, at least one key corresponding to a level of said structure above said device level.