METHOD FOR PROVIDING DIGITAL CONTENTS, METHOD FOR MONITORING ITS ILLEGAL USAGE, ITS PROVIDING DEVICE AND DEVICE FOR MONITORING ITS ILLEGAL USAGE

摘要

PROBLEM TO BE SOLVED: To prevent a secondary usage violating usage condition and an illegal re-distribution and also to prevent an illegal usage even against digital contents which are partially segmented. SOLUTION: The digital contents providing means 21 inserts a transaction identifier for identifying a transaction to the digital contents as electronic watermark, generates transaction information including license defining information concerning the usage of the digital contents, preserves it in correspondence to the transaction identifier and offers the digital contents, in which the electronic watermark is inserted, to a user. A digital contents illegal usage monitoring means 25 extracts the electronic watermark from the digital contents, obtains preserved transaction information through the use of the transaction identifier in the electronic watermark and judges whether the digital contents are illegally used or not, based on the license defining information obtained from the transaction information and based on the digital contents from which electronic watermark is extracted or on their presence forms.