CONTENTS DISTRIBUTING SYSTEM, DECODING DEVICE, ENCRYPTING DEVICE, DECODING PROGRAM, AND ENCRYPTING PROGRAM

摘要

PROBLEM TO BE SOLVED: To make it much more difficult to illegally decode encrypted contents by preventing any information embedded in an electronic watermark from being illegally erased in the distribution system of digital contents. SOLUTION: A decoding device 100 is provided with an encrypted contents reading part 10 for successively reading the data of digital contents by each decided block from the top of the data, an initial parameter holding part 30 for holding an encryption parameter being information for decoding the leading block of the encrypted contents, a decoding processing part 20 for decoding each block of the encrypted contents, an electronic watermark detecting part 40 for detecting electronic watermark information embedded in the block from the data of the block decoded by the decoding processing part 20, and a detected information processing part 60 for generating the encryption parameter being information for decoding the next block based on the electronic watermark information detected by the electronic watermark detecting part 40.