【作者】 侯振华；

【导师】 陈生潭；

【作者基本信息】 西安电子科技大学 ， 信号与信息处理， 2004， 硕士

【摘要】 数字水印技术是保护多媒体数据版权和图像可靠性认证的一种新技术。DCT（离散余弦变换）及小波变换分别是已有的信源压缩编码标准 JPEG 和信源压缩编码标准 JPEG-2000 的核心技术。本文比较系统地研究了数字水印的重要分支──认证水印的发展情况，论述了认证水印（脆弱数字水印和半脆弱数字水印）的提出背景及概念，原理和研究动态，重点分析了认证水印按空间域和变换域分类的各种算法，比较了它们的优缺点，总结了认证水印有可能受到的攻击行为；提出了两类 DCT 域与 DWT 域相结合的静止图像半脆弱数字水印算法，这两类算法都是基于图像内容生成水印信息，利用混沌密钥，结合 DCT 域定义水印及其嵌入位置，在小波变换域完成水印的嵌入，在检测算法中不需要原始图像。实验结果表明这两类半脆弱水印算法在保持对常见的 JPEG 压缩稳健的同时，还能有效的区分偶然失真与恶意篡改。本文所提出的水印算法，最大的特点就是安全性与实用性。作者认为，针对多媒体数据认证的研究，应该针对具体的场合而进行。同时指出，将半脆弱水印和现代密码学有机地结合起来，以之为基础构造水印方案，将是多媒体认证技术发展的一个很有前景的方向。更多还原

【Abstract】 Digital watermarking has recently been proposed as a new mean to providecopyright protection of multimedia data and still image authentication. DiscreteCosine Transform and Wavelets are respectively the key technique in the subsistentsource compression coding standard JPEG and source compression codingstandard JPEG-2000, the background, the concept, the general framework and theresearch trend of authentication watermarking (known as fragile watermarking andsemi-fragile watermarking) technology is roughly described, the emphasis is on theanalysis of authentication watermarking classified by the spatial and the transformdomain, also their advantages and disadvantages are analyzed, in addition, commonattacks applied to authentication watermarking are summaried. Two novel semi-fragile watermarking algorithms based on DCT-DWT domain combining areproposed separately in this paper, both algorithms generate the watermarks in theDCT domain and embed the watermarks into the original image in the DWT domainby using private chaos keys which are designed to define watermarks to be embeddedand determine the position for watermarking. Both algorithms can renew thewatermarking completely without original image. Experimental results show that theproposed algorithms are robust against JPEG compression, and provide very goodclassification of intentional and incidental tampering. We can know that what mostly characterize the algorithms presented in this paperare security and practicality. It’s also suggested that the research on multimedia dataauthentication should aim at concrete situation. It’s undoubtedly that designing thewatermark scheme based on semi-fragile watermarking and cryptology should bepromising.更多还原