US Patent 7979719 Data authentication method and data authentication system

A storage means which can be accessed by an authentication apparatus stores content data, a first digest table including primary digest values corresponding to a plurality of data portions constituting the content data, a second digest table including secondary digest values corresponding to a plurality of data portions of the first digest table, and a digital signature generated from the second digest table. In a first reading step, the second digest table and the digital signature are read out from the storage means into a memory of the authentication apparatus. In a first authentication step, the authenticity of the content data is verified using the digital signature read out into the memory and the second digest table read out into the memory.