Content based Public Key Watermarking Scheme for Image Verification and Authentication

A semi fragile, public key based digital signature scheme to verify and authenticate digital images is proposed. The scheme computes a content dependent feature value for each block of DCT coefficients of the original image. This feature is signed and then embedded into the selected DCT coefficients of the image as watermark. The technique aims to circumvent the cut and paste attacks by incorporating inter block dependence during the watermarking procedure. The watermarked image demonstrated high perceptual quality and robustness. It also proved to be robust against many common image processing operations and JPEG compression. The scheme not only can verify the authenticity and the integrity of images, but also can locate the illegal modifications. General Terms Image watermarking, authentication, content based watermarking