Photo editing software permits image files to readily be manipulated in a variety of ways. Various alterations, be it cropping, color adjustment, or replacement of portions of pictures with other images, can be characterized as an attack on the integrity of the image. This technology establishes a method and a system to watermark an electronically depicted file so that unauthorized alterations made to the file can be detected. The technology uses predetermined selection rules and calculations to generate a signature of the original image to readily detect any such attack.
Using a predetermined, undisclosed selection procedure, this technology selects coefficient pairs at multiple locations in an image. The difference between the coefficient pairs is used to generate a multi-bit raw signature to characterize the authentic image. A similar procedure is carried out to generate raw signature values of another image file, and the new image's signature values are compared to those values derived from original image. Using predetermined calculations, unauthorized alterations can be identified. Because this watermarking system is kept secret, it is unable to be attacked and altered. Furthermore, this technology is sufficiently flexible to accommodate acceptable image adjustments, such as slight file compression, but has a low tolerance for other, more distinct image revisions to lower the error rate of falsification recognition.
A prototype of this technology has shown to be robust in image manipulation detection.
Patent Pending (WO/2003/003285)
Tech Ventures Reference: IR M02-013