REVERSIBLE WATERMARKING USING VARIOUS TECHNIQUE

Abstract

Reversible watermarking has been proposed as a viable solution to the need of copyright protection and authentication of multimedia data in a networked environment, since it makes possible to identify the author, owner, distributor or authorized consumer of a document. A novel image authentication scheme based on reversible watermarking is presented here. Reversible watermarking scheme is based on the invariant sum values of pixel pairs. Standard digital signature scheme is used to generate digital signature of image and hide it behind the image. For verification of image ownership, the watermark and original image is extracted from watermarked image, digital signature is recomputed on extracted image and then compared with extracted watermark for verification. The watermarking scheme used here works for pair of pixels. For each pixel pair, if a certain value is added to one pixel while the same value is subtracted from the other pixel, then the sum of these two pixels will remain unchanged. This value is selected as the half of difference plus 1-bit watermark considering the distortion control and the reversibility of the algorithm. The watermark bit can be extracted by using the invariability of the sum values and the equality property between the parities of the sum values and the difference values