A novel zero-watermark algorithm based on LU decomposition in NSST domain

A novel zero-watermark algorithm is proposed based on LU decomposition and Non-Subsampled Shearlet Transform(NSST) for copyright protection of digital images. In this method, firstly the host image is performed with NSST, and a sub-image is extracted from the low-frequency approximation image randomly by Logistic chaotic system, then the sub-image is divided into non-overlapping sub-blocks. Next, each sub-block is performed with LU decomposition, the zero-watermark is derived by judging the numerical relationship between the sum from the first row elements of each sub-block´s U matrix and the mean of the sums from the first row elements of all sub-block´s U matrix. Experimental results show that the method is robust to adding noise, filtering and JPEG compression, and can resist the Cropping and RST attack to some extent.