Publications

Abstract : The advent of internet and hence multimedia communication has been very useful to quickly transmit data, in all fields, including the medical field. In this scenario, security breach becomes a major concern. Watermarking is one of the schemes used for authentication purposes, copyright protection etc. Watermarking involves two images, one watermark and one cover-image. The watermark is embedded into the cover-image imperceptibly and has to be extracted later for it to be authenticated. Both the cover image and the watermark undergo various transforms. A non-blind, robust, imperceptible watermarking, in the frequency domain is presented here. Two different frequency domain transforms have been applied on the cover-image successively followed by a mathematical decomposition to improve the robustness, they are, namely, DWT (Discrete Wavelet Transform), DCT (Discrete Cosine Transform) and Schur decomposition. A two level DWT is applied to the encrypted watermark before embedding it to the cover image. This method is highly effective on X-ray images and color images alike. This can be used on medical images for authentication purposes. Robustness and imperceptibility of the image under various attacks have been simulated on Matlab and examined.