Realization of a New Robust and Secure Watermarking Technique Using DC Coefficient Modification in Pixel Domain and Chaotic Encryption

The proliferation of information and communication technology has made exchange of information easier than ever. Security, Duplication and manipulation of information in such a scenario has become a major challenge to the research community round the globe. Digital watermarking has been found to be a potent tool to deal with such issues. A secure and robust image watermarking scheme based on DC coefficient modification in pixel domain and chaotic encryption has been presented in this paper. The cover image has been divided into 8×8 sub-blocks and instead of computing DC coefficient using Discrete Cosine Transform (DCTI, the authors compute DC coefficient of each block in spatial domain. Watermark bits are embedded by modifying DC coefficients of various blocks in spatial domain. The quantum of change to be brought in various pixels of a block for embedding watermark bit depends upon DC coefficient of respective blocks, nature of watermark bit (0 or 1) to be embedded and the adjustment factor. The security of embedded watermark has been taken care of by using chaotic encryption. Experimental investigations show that besides being highly secure the proposed technique is robust to both signal processing and geometric attacks. Further, the proposed scheme is computationally efficient as DC coefficient which holds the watermark information has been computed in pixel domain instead of using DCT on an image block.