中文水印字库的自动生成方法  

Automatic generation of Chinese document watermarking fonts

作　　者：孙杉 张卫明[1,2] 方涵 俞能海 Sun Shan;Zhang Weiming;Fang Han;Yu Nenghai(School of Cyber Security,University of Science and Technology of China,Hefei 230027,China;Key Laboratory of Electromagnetic Space Information,Chinese Academy of Sciences,Hefei 230027,China)

机构地区：[1]中国科学技术大学网络空间安全学院,合肥230027 [2]中国科学院电磁空间信息重点实验室,合肥230027

出　　处：《中国图象图形学报》2022年第1期262-276,共15页Journal of Image and Graphics

基　　金：国家自然科学基金项目(62072421,U1636201,62002334)。

摘　　要：目的文档水印技术是一种用以解决文档泄密溯源的信息隐藏技术。传统的基于字库的文档水印方案需要手动生成字库,极大地影响了水印的使用效率。为此本文设计了一种基于自动生成字库的鲁棒文档水印方案。方法该方法由一个端到端的编码—解码器结构的自动字库生成网络、一个字符筛选嵌入端和一个神经网络提取端组成,可自动完成变形字库的生成,而后进行水印的嵌入和提取。为了抵抗传输过程中可能存在的失真,在编码器和解码器之间加入可导噪声层用以模拟失真过程,使得水印模型获得对应的鲁棒性。结果本文方法在含252个中文字符的真实文档中嵌入252 bit水印信息,与其他文档水印方法的视觉质量和鲁棒性进行了对比。结果表明,相对于现有的基于字符特征的中文文档水印方法,本文方法的峰值信噪比(peak signal to noise ratio,PSNR)、结构相似性(structural similarity,SSIM)和主观质量评分分别提升了11.68 dB、0.08和5.8%,说明其有更好的视觉质量。对于数字信道传输场景,本文方法达到了与其他方法大致相当的性能;对于打印扫描场景,本文方法在三号、四号、小四号和五号字体下的水印提取率分别提升了2.4%、3.07%、1.34%和0.02%,在打印、扫描分辨率失配的场景下也具有较好性能,说明其在抗打印扫描上具有更高的鲁棒性。结论与基于人工设计字库的中文字符水印相比,本文方法充分利用了字符的几何特征并且能够自动生成字库,降低了中文文档水印方案的复杂度。Objective The copyright protection has been the hotspot with the amount of digital documents increased dramatically.In order to protect the document copyright and locate the source of the leaked document,watermarking technology innovation for documents has been widely focused on.The protection can be realized via adding invisible digital watermark information(e.g.,device number,date,etc.)to the document.To realize the traceability of document leakage,the leaked source can be located by extracting the watermark from the document once the watermarked document is leaked.Meanwhile,the current watermarking technology can also act as a deterrent which effectively reduce the occurrence of the leaking events.The current document watermarking methods can be divided into five categories:document structure based methods,natural language processing based methods,grid pattern based methods,image based methods and font based methods.Among them,the font based methods guarantee the best performance in the view of robustness and transparency.The main idea of such methods is representing the watermark information into the characteristics of the fonts(e.g.,the size,shape or brightness)while the modified fonts maintain the high visual consistency with the original one.The robustness,transparency,capacity as well as the integrity can be achieved simultaneously.However,the existing font based methods need to design the modification features manually,and cannot automatically generate the new fonts.For the Chinese character system which contains a large number of characters,such methods will cause a labor cost workload and severely less efficiency.To overcome such drawbacks,this research proposes an automatic font generation based robust document watermarking scheme.Method The framework of such scheme is comprised of an end-to-end encoder-decoder structure automatic font generation network,a character selection embedder and a neural network based extractor.With the designed font generation network,the deformed font library is further ut

关 键 词：文档水印 深度学习 中文字库生成 抗数字失真 抗打印扫描 

分 类 号：TP391[自动化与计算机技术—计算机应用技术]