【作者】 刘铁柱；

【导师】 张建伟；

【作者基本信息】 南京信息工程大学 ， 应用数学， 2008， 硕士

【摘要】 伴随着网络技术和多媒体技术的飞速发展,多媒体数据逐渐成为人们获取信息的重要来源,并因其方便快捷而成为人们生活的重要组成部分,多媒体信息的交流达到了前所未有的深度和广度。多媒体数据发布形式愈加丰富,其暴露出的问题也十分明显:作品侵权更加容易,篡改更加方便。因而,如何保护多媒体信息的安全成为国际上研究的热门课题。本论文主要探讨有关数字图像信息安全中的数字水印技术。数字水印技术作为版权保护的重要手段是数字信息安全中重要的一个分支,它通过在原始数据中嵌入秘密信息——水印来证实该数据的所有权或完整性,以此来抵制对数字作品的盗版或篡改等,其凭借优于数字加密技术的特点,得到广泛的研究和应用。。本文以静态的数字图像为例,在总结数字水印技术的发展背景及基本理论框架的基础之上,从不同侧重点提出两种基于频域的鲁棒性水印算法,并对数字(图像)水印算法和不同水印之间的结合应用进行了研究和讨论。主要工作有以下几个方面:首先,数字水印技术研究的一个重要内容就是鲁棒性数字水印算法的研究和设计,因此,对现有数字水印技术进行了概述,并重点分析了鲁棒水印和易脆水印的研究现状。其次,通过利用分块DCT技术,采用混沌加密技术对水印图像预处理,提高抗剪切能力,根据人眼视觉系统的掩蔽特性选择合适的分块,然后利用余数的周期特性在选择较好分块的中频系数上进行水印嵌入,在检测水印时实现了盲检测。经过仿真实验,该算法对剪切攻击,滤波攻击,JPEG压缩等有较强鲁棒性,但在旋转变换和强噪声攻击时尚待改进。最后,介绍了新的数字水印技术——零水印的应用,结合小波水印同时实现了鲁棒性和易脆性,这是其他多功能数字水印技术算法无法独立完成的,并针对传统的相关值检测盲水印方法嵌入容量小,鲁棒性较差的缺点,提出了实现鲁棒性和易脆性相结合的基于小波零树结构和奇异值分解的零水印算法。该方法具有实现简单,运算复杂度低的特点,并对常见的攻击具有鲁棒性。仿真实验结果表明该算法不仅具有较强的鲁棒性,而且能够达到易脆水印的图像篡改定位能力,即同时实现了水印的鲁棒性和易脆性。更多还原

【Abstract】 With the rapid development of internet and multimedia technique, the multi-media data is becoming the important source that the people obtain information gradually, and it constitutes an important part of people’s live because of its convenience and speediness. The exchange of the multi-media information has come to an unprecedented depth and wide degrees. The forms of multi-media data release are much abundant, but there are many obvious problems: it is much easier to infringe copyright; it is more convenient to sophisticate etc. As a consequence, how to protect the security of multi-media information turns into a popular topic all over the world.This paper mainly discusses the watermark technique applied in information security concerning digital image. The watermark technique is one of the important branches in digital information security which servers to protect copyright and it is researched and applied extensively because of its characteristics that are more excellent than digital encryption. It is used to confirm the ownership or integrities of the data by the watermark with secret information, which is imbed into the original data, to boycott the pirate edition or distort to the digital work.This paper discussed and researched thoroughly in the combination between image waterworks and other watermark based on summarizing the background and the theories frame of the digital watermark technical development. It takes the digital image of the static as an example, the main work contain followings:Firstly, an important content of the digital watermark technique research is the research and design of the robust watermark. This paper advances two robust watermark arithmetic base on frequency field from different particular emphasis, and stress to analyze the present conditions research of the robust watermark and fragile watermark.Secondly, pass to make use of to divide the DCT technique, adopt the Chaotic Encryption to do the pretreatment of the digital watermark image, raise the ability of resist cutting, choice the right block according to the human visual system, then imbed the watermark into the better block of the coefficient of intermediate frequency by the period characteristic of remainder, carrying out the blind detection while examine watermark. After the experimentation, the arithmetic has the stronger robust to the attacks of shear , filter and the JPEG compresses etc, but it needs the improvement on the attacks of revolve transformation and the strong yawp.Finally, it introduced the latest digital watermark technique--zero watermarks, andconcludes the stronger characteristic, which carries out the combining robust with frangibility, and which is other multi-function digital watermarks technique can’t complete independently. It advances the zero watermark arithmetic, which is based on EZW and SVD and carrying out the combining robust with frangibility. This method has the characteristic which is simple and low complication, and has the robust to familiar image processing. The experimentation result indicate that method not only have the robust, but also can attain the orientation ability of fragile watermark, then carried out the robust and frangibility at the same time.更多还原