Robust Zero-Watermark Algorithms in Hybrid Transform Domains Based on the Parity of Norm’s Highest Digit

Abstract

Two robust zero-watermark algorithms in hybrid transform domains are proposed. The first one is realized in hybrid transform domains of discreet cosine transform (DCT) and singular value decomposition (SVD), and the other one is realized in hybrid transform domains of discreet wavelet transform (DWT), DCT and SVD. The first algorithm divides an image into non-overlapping blocks, transforms every block with DCT, and conducts SVD on the upper left corner of every block’s DCT matrix. Finally, it produces the zero-watermark sequence by judging the parity of norm’s highest digit. The second algorithm transforms an image with DWT, divides its LL band into non-overlapping blocks, and transforms every block with DCT, then conducts SVD on the upper left corner of every block’s DCT matrix. Finally, it produces the zero-watermark sequence by judging the parity of norm’s highest digit. It is easy to find out that both of them have perfect visual effect. Experimental results show that as to images with different textures, both of them have good robustness against various attacks.