A Wavelet-Based Method of Zero-Watermark Utilizing Visual Cryptography

To protect the copyright of the digital image in the guarantee of image quality, a robust zero-watermarking scheme is proposed in the paper. The scheme selects the wavelet coefficients correctly to exploit the advantages of wavelet transform. Then the binary watermark is concealed into master share and ownership share by using the visual cryptography technique. Finally the ownership share is registered to certified authority (CA) for further protection. The scheme does not embedding the watermarking into the image actually, therefore it possesses both the invisibility and robustness. In the step of watermark extraction, the master share is first generated in the same way as embedding phase, then the watermark can be acquired by performing exclusive-OR (XOR) operation between the master share and ownership share. The experimental results show, that the proposed scheme not only can verify the copyright of the digital image, but also is highly robust for different attacks in terms of visual quality and Accuracy Ratio (AR).