A cross-correlation technique for cropping-invariant digital image watermarking

The development of electronic information and communication systems has significantly increased the need for digital multimedia security and copyright protection tools. A key technology in this context is in digital watermarking: a robust, secure and imperceptible identification code is secretly embedded into multimedia data as a digital watermark. Retrieving the watermark information will support the author's proof of ownership of the multimedia data. One of the major challenges in watermarking is robustness, since the watermarks need to survive multiple kinds of data processing. Image cropping is known as a common attack against digital watermarks. Some watermarking approaches have been developed in respect to robustness against cropping. However, the amount of watermark information is highly limited in most of these techniques. This paper introduces an innovative watermarking scheme that is extremely robust against cropping while still allowing high amounts of information to be embedded into the image.