【作者】 潘伟；

【导师】 孙艳蕊；

【作者基本信息】 东北大学 ， 应用数学， 2008， 硕士

【摘要】 数字化技术在为信息处理、复制、传播以及销售提供便利的同时,也随之带来了潜在的安全隐患。数字水印技术通过在数据中嵌入认证信息,能够有效地识别数据所有者并验证数据的真伪,是保证数字媒体真实性与完整性的一种重要手段。本文对数字水印算法进行了研究,主要工作如下：首先对图像认证水印作了一个简单的介绍,并对现有图像认证水印算法的安全性进行了分析,发现现有水印算法存在的主要问题是无法同时满足具有高的定位精度和安全性。针对这一问题,本文提出并实现了一个基于混沌映射的数字水印算法。在本算法中,图像块的水印选择Logistic映射作为混沌系统从该图像块本身产生作用于水印的嵌入,这提高了算法的定位精度；且每个图像块产生的水印按照Torus自同构映射嵌入另一个映射块的LSB(Least Significant Bit),其对应关系通过密钥来确定,这样建立起图像块之间的相关性,增强了算法抵抗拼贴攻击的能力。利用Matlab实验仿真,结果表明,该算法保证嵌入水印后图像具有良好的视觉质量；很强的图像篡改定位能力；算法简单,安全性高；水印提取时不需要原始图像,具有较好的实用性。更多还原

【Abstract】 The revolution of digital technology has increased the ease of manipulation, reproduction and distribution of digital media; meanwhile, it also leads to potential security problems. Digital watermarking is an important technique to verify the authenticity and integrity of digital images through embedding secret data-watermark in the original data, thus it can protect the digital product from pirate and tamper. In the paper, the main work is as follows:At first, authentication watermarking technology is roughly described.Throughout the analysis on the existing authentication watermarking schemes, the crucial shortcoming inhered in the current schemes can be concluded as follows:accuracy localization and high security cannot be hold at the same time. In order to resolve this problem, a new watermarking algorithm based on chaotic mapping is presented. In this scheme, for the sake of improving the accuracy of localization, the image block’s watermark is generated from the block itself, using chaotic system,the Logistic mapping to generate chaotic sequence for embedding the watermark; in order to enhance the security arid resist against collage attack completely, the block’s watermark information is embedded into LSB plane of another image block with Torus Automorphism mapping and the secret key; so as to establish the correlation among the image blocks. Experiments are done by Matlab, the results show that watermarked images obtained have good subjective quality, precise localization of tampered areas; the algorithm is simple and safe, and the experiment results illustrate that it is validity.更多还原