Image watermarking with zero-mean patches

We describe a new technique for robust watermarking of digital images for copyright protection. The proposed technique involves modulating the image signal with random zero-mean patches at random locations, the randomness being determined by a pseudorandom number generator seeded with a public-key digital signature. Watermark verification is done using correlation measurements on a candidate image, and does not require the original image. The watermark is robust against a wide range of geometric manipulations and image processing. However; like other watermarking schemes that do not use any transformation-invariant domain for applying the watermark, our scheme also requires a registration search prior to detection. The search procedure, which can be made faster by retaining the original image, is also discussed.