A Web-Based Privacy-Secure Content Trading System for Small Content Providers Using Semi-Blind Digital Watermarking

A privacy-secure content trading system based on semi-blind fingerprinting is presented. Semi-blind fingerprinting provides privacy-secure content trading as secure as blind fingerprinting at feasible processing cost with sufficient robustness. This system assures a fair trading for both a content provider and a purchaser which is effective for a market where a number of small or not so reliable content providers deal with purchasers. We have been aiming at providing a useful tool for the market by overcoming the following defects. In the basic models of conventional fingerprinting, the user´s security could be guaranteed only under the premise that a content provider was perfectly trustworthy. Such premise makes a system unpractical. To overcome this defect, various scheme of blind fingerprinting have been proposed in which cryptography technique is used in order to protect user´s privacy. However, these are not practical due to heavy computation cost and insufficient robustness of watermark against manipulations. The semi-blind fingerprinting fulfills the need for both feasibility and robustness by altering encryption with image decomposition that blinds up an image to be unrecognizable. Image decomposition and a customized embedding algorithm are implemented to a web-based system, whose perceptual condition of decomposed images and robustness of watermark is evaluated.