Fragile watermarking addresses the recognition of manipulations. In the moment most fragile watermarks are very sensitive to changes. This is of interest for parties to verify that an image has not been edited, damaged, or altered since it was marked. However in many applications we have to expect several allowed post production editing processes which do not manipulate the content of the image or video data. The semi-fragile schemes address this problem. These techniques are moderately robust and the value identifying the presence of the watermark can serve as a measure of tampering. Unfortunately these schemes cannot recognize if the content or the message of the media was effected or manipulated. Approaches are necessary which can distinguish malicious changes from innocent image processing operations. Such techniques can be termed authentication of the visual content. We propose to extract the visual content, called feature, and embed the content features with a robust watermarking scheme into the image data, called content-fragile watermarking. An integrity decision is based on the extracted feature of the actual image and the embedded watermarking features. Our idea is based on edge characteristics, which are already known and used in several other approaches as content features. To minimize the length of the content feature we introduce and compare five new methods to encode the edge characteristic: two edge shape based feature codes, three statistical feature codes. Our first test results on a selected amount of images show that content fragile watermarking based on robust watermarking and feature extraction allows post production processes and recognizes manipulation.
Jana Dittmann, Jana Dittmann,
"Content-fragile watermarking for image authentication", Proc. SPIE 4314, Security and Watermarking of Multimedia Contents III, (1 August 2001); doi: 10.1117/12.435398; https://doi.org/10.1117/12.435398