【作者】 王建洪；

【导师】 熊淑华；

【作者基本信息】 四川大学 ， 通信与信息系统， 2005， 硕士

【摘要】 近年来,随着网络技术的飞速发展,数字多媒体的存储、复制与传播变得非常方便。人们可以通过互联网和CD-ROM方便快捷地获得多媒体信息,还可以得到与原始数据完全相同地复制品。因此对多媒体内容的版权保护与内容认证已成为亟待解决的问题。数字水印技术在这种背景下产生,并得到了飞速地发展。数字水印技术通过在被保护数字对象中嵌入某些秘密信息即水印(watermark)来证明版权归属或跟踪侵权行为。水印的嵌入不会影响原内容的价值和使用,且不能被人感知系统察觉和很难被清除。由于数字水印是实现版权保护和内容认证的有效方法,因此已成为多媒体信息安全领域的一个研究热点。特别对鲁棒性水印进行了广泛、深入地研究,提出了许多好的算法,用以实现多媒体的版权保护,相对来说,对实现多媒体内容完整性认证和篡改提示的脆弱水印研究要少一些,把两者结合起来的多功能数字水印研究就更少了。 本文提出的一种多功能数字水印算法是基于静止图像内容的版权保护和内容完整性认证功能的结合。多功能水印被分为两个部分,鲁棒水印和脆弱水印,其中鲁棒水印实现内容的版权保护;脆弱水印实现内容完整性认证。鲁棒水印嵌入到小波变换基础上的离散余弦变换大系数上,此方法结合了小波变换和离散余弦变换的优点,使水印更加稳健。脆弱水印是在分块离散余弦变换系数的高频部分嵌入,实现图像内容完整性认证和篡改定位。仿真结果表明多功能数字水印具有图像内容版权保护和完整性认证的功能。多功能水印算法在抗噪声攻击,剪切,压缩攻击时,其鲁棒水印部分具有很好的稳健性,能够完成保护图像内容版权的功能,脆弱水印部分则发挥其易损的特性,图像受到攻击即水印被破坏,而还在剪切攻击时,提示图像剪切的位置和大小,从实现图像内容完整性认证和篡改定位的功能。更多还原

【Abstract】 In recent years, with the development at full speed of the network technology, the storage and copy of the digital multimedia become very convenient. People can obtain information of multimedia conveniently through Internet and CD-ROM, which may influence the multimedia copyright protection and economic benefits of the authors. Therefore, multimedia copyright protection and content authentication have become serious problems that need to be solved urgently. Digital watermarking is developed to resolve these problems. Digital watermarking protects the copyright and content authentication by embedding some secret information, which is called watermark. The existence of the watermark in the digital products should not influence the quality of the original digital product obviously and it is difficult to remove the watermark. There are many papers about robust digital watermarking, but papers about fragile digital watermarking are fewer. Thus, the research of multi-functional digital watermarking is usually ignored.In this paper, a kind of multi-functional digital watermarking is provided, which can be applied to copyright protection and content authentication at the same time. The multi-functional watermark is divided into two parts: robust watermark and fragile watermark. The robust watermark is used to provide the copyright protection of image; The fragile watermark is used for authentication of the content . The embedding of robust watermark is based on wavelet transform and discrete cosine transform. Since this algorithm combines the merits of two transforms, it can get better performance. The fragile watermark is embedded in the high-frequency DCT coefficients. The simulation results show that this kind of multi-functional digital watermarking provides copyright protection as well as content authentication, and it also perform well under the attacks, such as noise, shear, compression.更多还原