Wavelet packet and adaptive spatial transformation of watermark for digital image authentication

A general watermarking scheme which adopts the multiresolution wavelet packet transform and content based watermarking scheme has been developed for digital image in this paper. The systematic approach of the watermarking includes the selection of the image content, the wavelet packet transform and the implementation of toral automorphism as the spatial transform for the watermark. To efficiently embed the watermark within the images and provide the robustness for the watermark detection under attacks, a modular based element classification and adjustment of the wavelet transformed coefficients has been utilized in this research. Instead of using the random number generator to create the watermark, the meaningful and recognizable seal image has been used as the watermark which provides immediately strong authentication information. In addition, the parameter settings of the choices among the transforms serve as the key information in decipher an watermarked image without referring to the original image. Compared with other watermarking methods, our technique provides a generalized approach for watermarking with robustness.