A Hierarchical Fragile Watermarking with VQ Index Recovery

Abstract

This paper proposes a hierarchical fragile watermarking scheme for image authentication with localization and recovery. Two phases are exploited for pixel-wise and block-wise authenticity. By applying the singular value decomposition (SVD), only a few pixels need to be modified to carry these watermark bits so we can produce high quality of the watermarked image and achieve the integrity verification of blocks. Pixel-wise tampering detection and recovery is also realized in this proposed scheme. Altered pixels in each block can be exactly localized using the authentication bits. Accordingly, unaltered pixels remain unchanged but only altered pixels need to be recovered. In the image recovery stage, instead of replacing the whole block identified as tampered, elements belonging to associated VQ codeword are restored for those altered pixels. In this way, the quality of recovered image is better than replacing whole altered block by a whole vector quantization block. The experimental results reveal that the average PSNR values of reconstructed images are higher than that of other schemes.