随着因特网的日益普及和多媒体技术的发展，多媒体信息的交流达到了前所未有的深度和广度，但对多媒体作品的侵权也随之更加容易，篡改也更加方便，极大的损害了作者及版权所有者的利益，如何有效的保护多媒体信息的版权成为安全研究领域的一个热门问题。作为信息隐藏在计算机多媒体领域的一个重要应用，数字水印技术使得人们能够在多媒体信息(如图像、声音、视频)中嵌入不可见的信息(水印)，并且在多媒体信息经过一定程度的处理之后，嵌入的水印信息不会丢失。数字水印技术为多媒体版权保护提供了一个崭新的方法，近年来在国际上引起了人们极大的兴趣和注意，得到广泛的研究和应用。论文首先介绍了数字水印技术及其原理、特点、以及目前的应用状况等等。然后对数字水印算法模型、分类以及典型算法进行了简要的分析。在此基础上，论文遵循国际JPEG静态图像压缩标准的原理，分析了两个“基于DCT变换的数字水印算法”，其中算法I采用私有水印的设计思想，即在提取检测水印信息时需要原始图像；算法II则是半私有水印算法，在提取检测水印时无需原始图像。

关键词： 数字水印； 算法； DCT变换；

 

 

 

 

 

 

 

 

 

 

 

 

 

      With the popularization of Internet and the development of multimedia techniques, the digital media, including image, graphics，audio and video etc., has become a main way for information communication. People can get almost information through the Internet, but this also gives rise to serious problems including wide spread copying violation, illegal copying, easy forging etc. which harm the advantage of the author or the copyright owner most . How to provide copyright protection for multimedia data has became an important issue. As a main application in computer multimedia of information hiding, the digital watermarking technique makes it possible embed an invisible signal (watermark) to the multimedia data such as image, audio and video. The digital watermarking technique has been proposed as a valid solution for the need of copyright protection and authentication of multimedia data in a networked environment, since it makes possible to identify the author, owner, distributor or authorized consumer of a multimedia data. So it has drawn extensive attention in recent years. In this paper, the author first makes an introductory review on the digital watermarking techniques including the definition, chrematistics and main application domains of digital watermarking. Then the author analyzes fundamental principles of digital watermarking algorithm in detail such as the general framework, classification and the typical algorithm, puts forward two DCT domain image digital watermarking algorithms based on the principles of JPEG. The algorithm I is a private watermarking algorithm which need the original image in the process of extract the watermark, while the algorithm II don’t need because it is semi-private watermarking algorithm.