浏览器端定位篡改的网页脆弱水印算法

为及时阻止网页中篡改信息的传播且使真实信息得到有效利用，提出一种在浏览器端标示篡改的分块网页脆弱水印算法.算法首先按浏览器显示字符所在标签将网页分块，然后将基于块内容生成的水印信息置乱加密后嵌入在网页的颜色属性中.认证时，通过比较网页块提取水印和重构水印的不同比特个数与阈值的关系判定网页块的有效性.对判定为篡改的网页块，通过修改其浏览器端显示字符和尾标签的属性使其在浏览器端屏蔽并标示篡改，阻止伪造信息传播的同时不影响其他信息的继续使用.实验结果表明，算法在水印嵌入方法上有较好的隐蔽性，文件增量较小.当阈值为2时，算法能够较准确地检测出篡改并在浏览器端合理准确地定位标示网页块，且有效提高了算法的时间效率.

Webpage Fragile Watermarking Algorithm for Tamper Localization on the Browser

To timely prevent the diffusion of tampered information and make full use of authentic information, a fragile watermarking scheme is proposed to detect the validity of webpage and mark the tampered parts of it on the browser. To locate the tampered locations, a webpage is firstly divided into webpage-blocks according to the labels which include the displayed characters on the browser. For each webpage-block, the watermark data is generated based on the content of it and randomly hidden into the color attributions of other webpage-blocks according to the secret key, which will further improve the secrecy of watermark data. The validity of a webpage-block is determined by comparing the number of the inconsistent bits with the given threshold. If a webpage-block is judged as tampered, the displayed characters of the webpage-block are replaced with the given symbol to shield the tampered information, and the last-label attributions of it are changed to highlight the tampered webpage-block. These strategies not only prevent the spread of tampered information in webpage, but also make efficient use of the unmodified ones in it. Experimental results show that the file delta of watermarked webpage is smaller. The proposed method achieves good imperceptibility and the tampered webpage-blocks are reasonably and accurately localized on the browser when the threshold value is two. Whats more, time efficiency is also improved.