一种几何攻击下的数字图像水印检测方法

几何攻击是数字图像水印众多攻击的一种，它不试图破坏图像中的水印信号，而是使水印检测器与水印信号失去同步，致使水印检测器检测不到水印信号，是一种有效的水印攻击方法。该文介绍了一种基于标准化的互相关NCC(normalized-cross correlation)图像固有特征提取及特征点匹配方法，进而利用图像固有特征恢复经几何变换的水印图像，使水印检测器与水印同步以达到有效检测水印的目的。实验表明，使用该方法能较好地恢复图像，有效地同步水印检测器与水印信号，从而使水印对仿射变换攻击具有鲁棒性。

A Detecting Method of Digital Image Watermark Attacked by Geometric Transformation

The geometric attack is a kind of attack on the digital image watermark. It doesn't intend to remove the watermark embedded in the image. However it distorts the watermark detector synchronization with the embedded information (watermark), as a result, the watermark detector can't detect the watermark. It is a very effective attack method to the watermark. This paper presents a synchronization method based on image salient features, which is selected and matched using NCC (normalized-cross correlation) and used to recover image size and aspect. So that the watermark detector can detect the watermark. The experiment result shows that the synchronization method can synchronize the detector with the watermark perfectly and that the watermark is robust to global geometric attacks.