随着计算机信息技术和互联网的飞速发展，数字文档的应用领域不断扩大，其版权保护和防篡改问题变得越来越重要，文档水印技术是解决这一问题的有效方法。本文介绍了文档水印的基本概念、应用领域及常见攻击，并利用TrueType造字程序的特点，实现了基于TrueType新造字的文档水印算法，提出了基于新造字的秘密通信和数字签名的方法。 基于新造字的文档水印算法根据所有者的相关信息创建TrueType新字符，将这些新造字字符按照一定的规则嵌入到文档中，利用原始文档中的字符覆盖新造字字符，在接收端通过水印提取进行所有权的认定。该算法适用于DOC格式文档，能有效检测篡改和认证所有权。仿真结果表明算法具有完全不可见性，抗攻击性强，还能对篡改进行定位。 在秘密通信方面，作者充分利用TrueType新造字的特点，将某一机密信息隐藏于另一公开的、无关紧要的信息之中，然后通过公开信息的传输来传递隐藏信息。非法拦截者难以从公开信息中判断机密信息的存在性和存在位置，难以截获机密信息，从而有效保证机密信息的安全。仿真实验也进一步证明了这一点。 在数字签名方面，作者利用TrueType的造字功能，输入所有者的个性签名，然后嵌入到文档指定位置，在接收端通过水印提取进行所有权的认定。它具有完全不可见性，抗攻击性强。

With the rapid development of the computer information technology and Internet, the application fields of digital documents are increasing expanding. The copyright protection and the tamper-proofing of the documents are becoming more and more significant. Document watermarking technique is the most effective way to solve this problem. The thesis describes the basic concepts, applications area and common attacks of the document watermarking. By using TrueType new-defined characters, a document watermarking algorithm is implemented and its applications in the secrete communication and digital signature are proposed. In the document watermarking algorithm based on TrueType new-defined characters, some TrueType new characters are created according to the information of the owner. these characters are embedded in the document by a specified rule and are covered by the characters in the original document. In the receiving end, the ownership authorization can be done by extracting the watermark in the test document. This algorithm can be applied in the documents whose file extension name is DOC. It can detect tampering and authenticate the ownership efficiently. Simulation results show that the algorithm has a complete imperceptibility, a high robustness to attacks, and can locate the tampering. In the field of secret communication, a piece of certain confidential information is transmitted by hiding it in the open, irrelevant information according to the features of the new-defined TrueType characters. It is difficult for the illegal interceptor to determinewhether there is confidential information and where it is, which can effectively guarantee the security of confidential information. It can also be seen from the simulation experiments. In the field of the digital signature, the author took advantage of the character-creating function of the TrueType, inputted the owner's personal signature, which would be embeddedin the specified location of a document. In the receiving end the ownership is authorized by extracting the watermark. It's not visible and anti-attack efficiently.