Patent ID: 7979719
Filing Date: 2011-07-12
Classification: G06F

Abstract:
1. A method for use in an authentication apparatus for authenticating content data, wherein the authentication apparatus can access a storage medium configured to store: the content data, a first digest table including stored primary digest values which are digest values corresponding to content data portions of the content data, a second digest table including stored secondary digest values which are digest values corresponding to first digest table portions constituting the first digest table, each one of the first digest table portions including a plurality of stored primary digest values and a digital signature generated from at least a secondary digest value included in the second digest table, the method comprising: reading out the second digest table and the digital signature from the storage medium into a memory of the authentication apparatus; and verifying the authenticity of the content data using the digital signature read out into the memory and a stored secondary digest value included in the second digest table read out into the memory; designating a content data portion via a random access method in accordance with a computer process; calculating a secondary digest value from a group of primary digest values that includes a stored primary digest value that corresponds to the designated content data portion; checking the calculated secondary digest value against a stored secondary digest value to verify the authenticity of the designated content data portion; reading out the designated content data portion into a content storage memory; calculating a calculated primary digest value from the designated content data portion, when the check of the calculated secondary digest value against a stored secondary digest value is successfully verified; and checking the calculated primary digest value against the stored primary digest value to verify the authenticity of the designated content data portion.