一种基于自相关函数的小波域数字水印算法

几何攻击是对数字水印技术最具威胁的攻击手段之一，而基于自相关函数的水印算法被认为是一种有效的解决手段，却有其局限性。研究发现，对用于评价几何攻击起很重要作用的水印的自相关峰值（以下简称AC峰值），也可从小波域提取出来。这里介绍一种小波域基于ACF的数字水印算法，该算法在考虑到AC峰值和噪声能见度的影响的同时，把一个周期性水印信号嵌入小波域。仿真实验结果表明，算法能产生更显著的AC峰值，从而提高了抗几何攻击的鲁棒性。

An algorithm of digital watermark based on auto-correlation function in the discrete wavelet transform domain

Geometric attack is regarded as one of the most dangerous attacks to the watermark system.The auto-correlation based algorithms are considered as an efficient method,but they have certain defects.Research results show that the auto-correlation (AC)peaks,which play an important rote in estimating the geometric attacks in ACF-based watermarking,can also be extracted by embedding the watermark in the DWT domain.In this paper,an auto-correlation function based digital watermark algorithm in the wavelet domain is presented.A periodic watermark signal was embedded into the wavelet domain by considering the AC peak strength and noise visibility.Experimental result show that the algorithm yields stronger AC peaks to improve the robustness of the watermark system against geometric attacks.