Robust Zero-Watermarking Algorithm Based on Invariant Centroid

In order to effectively resist geometric attacks and protect the security of information and copyrights of digital products, a digital image zerowatermarking algorithm based on geometric correction is proposed. According to the stability of the invariant centroid, we select the invariant centroid as a stable geometric reference point. The algorithm finds out the specific SIFT point which is the farthest to the reference point in image, then calculates geometric transformation parameters by changes of these two points´ positions. To hide information in image, we divide the image into blocks and apply QR decomposition in each block. After this, we extract the 2-Norm of the first row vector of matrix R in each block to form a sequence, and then transform it into a matrix after binary quantization. Finally, we make the XOR operation between the watermark and the matrix, and the result of the operation is the zero-watermarking. Experimental results show that the algorithm can effectively resist geometric attacks, with a high degree of correction accuracy and a strong robustness. By using the zero-watermarking method, the algorithm can also avoid the contradiction between invisibility and robustness.