9 May 2000 Automatic recovery of invisible image watermarks from geometrically distorted images
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One method of attacking an imbedded invisible watermark is to create a derivative image that is geometrically distorted relative to the original. One attack, developed at Cambridge University, is called 'StirMark.' Image-distorting methods modify images so subtly that the changes are essentially unnoticeable to a viewer. However, their effect on invisible watermarks can be devastating, rendering them unextractable. In this paper, an automated countermeasure to image-distorting attacks will be described. Employing an unmarked copy of the original image as a reference, the possible distortion in a suspect image is first detected by the method, then measured, and finally reversed, producing a restored image approximately geometrically aligned with the original. Using a robust invisible watermarking method presented previously by one of the authors to produce a watermarked image, 'StirMark' to distort the watermarked image, and a copy of the original unmarked image for reference, the restoration method is demonstrated to be sufficient by showing successful extraction of the imbedded watermark from a restored image.
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Gordon W. Braudaway, Gordon W. Braudaway, Frederick C. Mintzer, Frederick C. Mintzer, "Automatic recovery of invisible image watermarks from geometrically distorted images", Proc. SPIE 3971, Security and Watermarking of Multimedia Contents II, (9 May 2000); doi: 10.1117/12.385010; https://doi.org/10.1117/12.385010


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