Existing tamper detection techniques for document images use the textual information of the image to create a zero watermark. These techniques cannot authenticate a document image if the image is tampered with in non-textual regions. In order to resolve this problem, a tamper detection technique for document images is proposed using the concept of zero watermarking. The input document image is transformed by applying lifting wavelet transform to get its subbands. These subbands are further partitioned into non-overlapping blocks of the same size. Features of each blocks are extracted to create a zero watermark. This watermark is combined with the key watermark in order to create a meaningful watermark. This meaningful watermark is stored by a trusted authority. On the receiver side, the meaningful watermark is compared to the watermark generated using tampered image to check the authenticity of the cover image. The tampered regions of the cover image can also be localized using this technique. The experimental results demonstrate the effectiveness of the technique in comparison to the existing authentication techniques.

用于文档图像的现有篡改检测技术使用图像的文本信息来创建零水印。如果图像在非文本区域被篡改，则这些技术将无法认证文档图像。为了解决该问题，使用零水印的概念提出了用于文档图像的篡改检测技术。通过应用提升小波变换来变换输入文档图像以得到其子带。这些子带被进一步划分为相同大小的非重叠块。提取每个块的特征以创建零水印。该水印与关键水印相结合，以创建有意义的水印。此有意义的水印由受信任的机构存储。在接收方，将有意义的水印与使用篡改图像生成的水印进行比较，以检查封面图像的真实性。封面图像的篡改区域也可以使用此技术进行定位。实验结果证明了该技术与现有认证技术相比的有效性。