基于DCT系数重构的分层认证水印算法

提出了一种新的半脆弱认证水印算法——基于DCT系数重构的分层认证水印算法. 基于DCT系数重构的分层认证水印算法利用了分层的思想，通过不同层分块间的相关性实现了抵抗矢量量化攻击的目的；给出了一种基于多分辨率的篡改定位技术，实现对篡改的分层渐进定位，提高了定位效率. 基于DCT系数重构的分层认证水印算法利用预量化原理来实现对有损压缩后的DCT系数的重构，水印达到了对正常的JPEG有损压缩鲁棒，对恶意篡改脆弱的目的. 实验结果表明，该算法是一种行之有效的半脆弱认证水印算法.

Hierarchical semi-frigile watermarking based on the reconstruction of DCT coefficients

Digital image manipulation software is now readily available on personal computers. It is therefore very simple to tamper with any image and make it available to others. Insuring digital image integrity becomes a major issue. In this paper, a new semi-fragile watermarking algorithm, called HSFW, is presented. Using a hierarchical structure and the idea of multi-resolution, HSFW can avoid the vector quantization (VQ) counterfeiting attack and identify the positions of corrupted blocks under different resolutions without the source image. By the reconstruction of DCT coefficient, HSFW can accept JPEG lossy compression on the watermarked image to a pre-determined quality factor, and reject malicious attacks. The experimental results show its effectiveness in protecting the content-integrity of images.