【作者】 文志强；

【导师】 张增芳； 李陶深；

【作者基本信息】 广西大学 ， 计算机应用技术， 2004， 硕士

【摘要】 网络技术的发展使得网络传输的数字产品在没有授权的情况下容易被有恶意的人们随意篡改、拷贝。近几年来提出的数字水印技术可以解决这个问题。虽然研究者们为研究该项技术付出了大量的精力，并取得了一定的成果，但是数字水印技术的研究正处在起步阶段，还存在许多问题，这限制了它的应用。 本文从三个不同的角度来研究数字水印技术，其目的是在保证不可见性的前提下，提高数字水印的鲁棒性。主要完成以下工作： (1)本文利用混沌系统和离散柯尔莫哥罗夫变换，提出两种水印序列生成算法。该算法安全性好，且生成的水印序列均值近似于零，为后面两种水印技术做准备。 (2)提出一种基于离散余弦变换(DCT)的自适应水印技术。该技术首先采用边缘检测方法确定边缘块；根据DCT系数方差确定纹理块；然后根据人的视觉特性把图像的DCT块分成六类。不同强度的水印成分自适应地嵌入在低频域系数上，保证了水印抗攻击鲁棒性。实验结果表明此方法比同类方法要好。 (3)提出一种基于离散小波变换(DWT)的公有水印技术。该技术在公广西大学硕士论文基于变换域的数字水印技术研究有水印模型中引入了混沌系统，水印嵌入在DWT域的低频系数，并且在水印嵌入时引入一个指数因子，本文对使用不同指数因子嵌入的水印抗攻击鲁棒性进行了实验分析，实验结果表明:指数因子在0.1一0.2之间的水印鲁棒性要更好些。更多还原

【Abstract】 With the development of network technology, the digital products transmitted through the Internet are easier to be modified or copied by vicious people at will without authorization. The digital watermarking technology was presented several years ago to resolve this problem. Though researchers pay out a mass of vigor for this technology and acquire some achievements, the digital watermarking technology is still on road to development and many existing problems hold back its application.The digital watermarking technology is studied from three different points of view to improve the robustness under the precondition of invisibility. The primary contributions of this paper contain the following points:(1) Two algorithms are presented using chaotic system and discrete Kolmogorov flows to create watermark sequences .The algorithms have good security and the mean of watermark sequences is close to zero, preparing for following two algorithms.(2) The proposed method is an adaptive watermarking technology based on Discrete Cosine Transformation (DCT). This method discerns the edge blocks using the edge detection method and texture blocks using the deviations of DCT coefficients at first, and then the DCT blocks of image are classified into 6 blocks based on Human Visual System (HVS). Watermark components with different strengths are adaptively embeded into some low-frequency coefficients according to the classification to ensure good robustness against attacks. The experimental results show this algorithm possesses better robustness than the similar algorithms.(3) A public watermarking technology based on Discrete Wavelet Transformation (DWT) is proposed, which introduces Chaos systems into the modified public watermarking model. The watermark is embedded into the low-frequency coefficients ofDWT domain and an index factor is used in this technology. In the experiment, this paper analyses the robustness of watermark against attacks using the different index factors and concludes when the value of the index factor is between 0.1 and 0.2,the robustness of watermark against attacks is better.更多还原