A Design of Secure Watermarking Scheme for Images in Spatial Domain

Digital watermarking (DWM) technology has been proposed for the implementation of digital right management (DRM) system that can be used for establishing ownership right, ensuring authorized access and content authentication. The goal of this paper is to protect copyrights and content authentication of digital still images with the consideration of high level of robustness against changes made to invisible watermark contents in context to spatial domain. The proposed scheme combines the advantages of cryptographic concept and imperceptibility feature of digital image watermarking. The watermark is first generated based on hash function with the use of user key. Each bit of this new generated watermark is then encoded into respective blocks of 4times4 pixels of the original image, in raster scan order. The encoding is performed by modifying the average value of pixel intensity of each block with in a range specified by the contrast value for a given block. This reduces the effects of the modification as perceived by the human eyes. The experimental results show the robustness of scheme against common image processing operations. The results also demonstrate the location of modification as corresponding error in the extracted watermark