Unauthorized contents detection system

摘要

A data processing device for playing back a digital work reduces the processing load involved in verification by using only a predetermined number of encrypted units selected randomly from multiple encrypted units constituting encrypted contents recorded on a DVD. In addition, the data processing device improves the accuracy of detecting unauthorized contents by randomly selecting a predetermined number of encrypted units every time the verification is performed.

主权项

1. A data processing device for using a digital work recorded on a recording medium having also recorded thereon (i) a plurality of record digest values generated from a plurality of data blocks constituting the digital work, (ii) record signature data generated by applying, with use of a signature key, a signature generating algorithm to a first combination made of at least some or all of the plurality of record digest values and (iii) a predetermined number of data blocks, the data processing device comprising:
a non-transitory memory device that stores a program; and a hardware processing device that executes the program and causes the data processing device to operate as: a verification key storing unit configured to store a verification key corresponding to the signature key; a using unit configured to use the digital work; an acquiring unit configured to acquire the predetermined number of data blocks, the predetermined number being smaller than the number of all the plurality of data blocks; a selecting unit configured to, each time the digital work is used, randomly select the predetermined number of data blocks from all of the plurality of data blocks; a calculating unit configured to calculate a plurality of calculation digest values from the selected data blocks; a reading unit configured to read remaining record digest values corresponding to unselected data blocks from among the plurality of record digest values; a generating unit configured to generate a second combination based on calculation digest values and the remaining record digest values, the second combination being the same as data which is generated from the first combination by replacing record digest values corresponding to the selected data blocks with corresponding calculation digest values; and a signature verifying unit configured to verify the record signature data by applying, with use of the verification key, a signature verification algorithm to the second combination and the record signature data.