Content protection in adaptive content delivery

This paper considers environment-adaptive content delivery in which an intermediary modifies the content between the content provider and the content user, and proposes a system in which the provider can securely control content modification by the intermediary in accordance with usage rules defined in the content. In order to have the intermediary follow the usage rules strictly, it is indispensable to provide a content protection technique in which tampering with content or usage rules by a third party is prevented while permitting content modification by intermediaries approved by the provider within the scope of the usage rules. The authors consider the hash-tree signature method in which data deletion by the intermediary is permitted, and propose a signature system with a place holder extension permitting data addition. A highly efficient realization of the proposed signature system based on the hash-sign-switch (HSS) method is presented. The effectiveness of the approach is shown by a quantitative evaluation using the implemented system. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(9): 54–66, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20341