Covert Encryption and Document Authentication using Texture Coding

With the improvements in the quality of Commercial-Off-The-Shelf (COTS) printing and scanning devices, the ability to counterfeit documents has become a widespread problem. Consequently, there has been an increasing demand to develop digital watermarking techniques which can be applied to both electronic and printed images (and documents) that can be authenticated, prevent unauthorized copying and withstand abuse and degradation. In this paper , a new approach to digital watermarking is presented and a range of possible applications are considered. The process is defined by using concepts and techniques borrowed from Cryptography. It is based on computing a \u27scramble image\u27 by diffusing a watermark image with a noise field (a cipher). The cover image (covertext) is then introduced using a simple additive process (confusion). The watermark is subsequently recovered by removing the covertext and then correlating the output with the original (key dependent) noise field. For covert encryption, this approach provides the user with a method of hiding ciphertext (the scrambled image) in a host image before the transmission of the data. With regard to document authentication, a diffusion only or \u27texture coding\u27 approach that is robust to a wide variety of attacks including geometric attacks, crumpling and print/scan attacks are considered