具有自适应性的半脆弱数字水印算法*

为了解决数字水印算法的鲁棒性与脆弱性之间的矛盾，提出了一种新的具有自适应性的半脆弱数字水印算法，重点介绍数字水印的嵌入算法。该算法通过采用改进的低通滤波器，调整中间像素灰度、改变两端的灰度差分来实现水印的嵌入。实验结果表明：该算法对photoshop下所有级别的JPEG压缩均具鲁棒性，而对所有几何变换等恶意攻击具有脆弱性，并可根据所提取水印可判断出恶意攻击的类型、程度、区域等特征，具有较好的自适应性。

Self-adaptive semi-fragile digital watermarking algorithm

In order to solve the contradiction between robustness and vulnerability of digital watermarking algorithm, this paper proposes a new self-adaptive semi-fragile digital watermarking method, with emphasis on digital watermarking embedding algorithm. By using improved low-pass filter, this algorithm adjusts gray value of middle pixel and changes gray-value differential of two terminal to embed the digital watermark. The experimental results show that this algorithm has strong robustness on all JPEG compression of Photoshop and has vulnerability for all geometric transformation malicious attacks. And from the extracted watermark, it can judge the characteristics of malicious attacks, such as types, extent and region. This algorithm shows good adaptability.