外文翻译---基于数字水印技术的信息隐藏理论研究.docx

天津工业大学本科毕业论文外文资料Information Hiding Thieoretic Research Based on Digital Watermark TechnologySchool of Mathematics and Computer Science Ningxia Universit Yinchuan, ChinaAbstract-With rapidly growing interest in ways to hide information, a large number of schemes have been proposed for audio and other multimedia in digital pictures, video, audio and other multimedia objects.In an attempt to overcome this problem, watermarking has been suggested in the literrature as the most effective means for copyright protection and authentication .The main focus of this thesis is the problem of watermarking and compression of image due to bandwidth or storage constraints.Keywords: information hiding; digital watermarking; transparency; robustnessI. IntroductionDue to the rapidly development of the Interest and the World-Wide-Web(WWW),distribution of digital multimedia data to a large population of users can be done very easily.Moreover,digital data can be duplicated very fast and without any degration in quality-cinsider,for example,how common the copying of musical CDs has become in the last few years.Naturally,this situation has raised many concerns about possible violations of intellectual property rights.Unauthorized duplication and distribution of copyrighted material(photographs,music,movies,etc.),without appropriate compensation to the copyright holders,are becoming increasingly problemtic.In order to fight piracy,many companies(especially in the entertainment and news industries)have devoted considerable attention to the development of information hiding (or watermarking)techniques.In plain terms,a watermark is a signal which is hiden inside some multimedia data,and carries information about this data(e.g.,owner,title,data of creation,ect).Thus a watermark uniquely identifies the work being protected,and helps resolve disputes about the ownership of the data.There have been many instances of disputes or litigations on the intellectual ownership of multimedia data.A copyright violations lawsuit that received extensive publicity in the early 2000s,was that against Napster.And the Digital Video Disk,also known as Digital Versatile Disk(DVD)consortium called for proposals for a copyright marking scheme to enforce serial copy management.The idea is that the DVD players sold to consumers will allow unlimited copying of home videos and time-shifted viewing of TV programmers,but cannot easily be abused for commercial priacy.Electronic copyright management schemes have also been proposed by European projects such as Imprimatur and CITED,and American projects such as the proposed by the Working Group on Intellectual Property Rights.Due to its significance,the watermarking field has grown tremendously in the information hiding theoretic.There are numerous articles(the references therein)and books that explain the basic of watermarking,explore its many practical application,and evaluate the performance of various schemes under a variety of attacks.II. Digital Watermarking SystemA. WatermarkingIn the communication model for watermarking,the watermark embedder plays the role of the transmitter,the watermark detector plays the role of reciever and the attack represents the communication channel(Fig.1).The objective is to decode the hidden message reliably;the original image can be construed of as side information which is always available at the encoder,but is only available at the decoder in the private scenario(not the public one).In this paper, a transmitter sends a signal Xn to a receive (with n transmissions), through the following channel: Y=Xn+Sn+Zn, where Sn, Zn are independent, i.i.d.Gaussian random vectors.Here, Sn is known to the encoder, while Zn acts as noise known to neither encoder or decoder.It is proved that the capacity of this channel is the same as if Sn were known to the decoderas well.In general,this number grows linearly with the image size,and the constant of proportionality is known as the capacity C.Practical watermarking implementation embed at a rate R bits/image dimension,where RC.Namely,C=1/2 log（1+P/N）,where P is the average（per symbol）power of Xn and N is average of Zn.This result is quite surprising because one would expect Sn to act as inteference at the receiver,thus hidering the detection scenario,Sn would play the role of the covertext（known to the watermark embedder only),Xn would represent the watermark embedded, and Zn would be the noise added by the attacker.B. Characteristics of watermarkingIn the design of watermarking schemes,we mainly think about two key requirements.Transparency: The hidden message should not interfere perceptually with the host signal.This requirement is perfectly justified by the fact that watermarking aims at protecting multimedia data,which are sensitive,in general,to changes.In other words,an image or a musical piece could become useless if the introduced artifacts（due to watermarking）exceeded some perceptual threshold.The quality of the watermarked data must thus be comparable to that of the covertext,a requirement which is often expressed in terms of a distorition constraint.Robustness: The message must be detectable in the watermarked image（the covertext is assumed to be an image throughout this thesis,though similar techniques can be applied to other types of multimedia data）,even after degradation duo to malicious attacks or other processing（quantization,D/A conversion,etc）.Of course,detectability of the watermark is closely related to the maxinum amount of distortion that can be introduced by an attacker.A watermarking scheme is robust if it allows the hidden message to be accurately decoded in a distorted image whose quality is close to that of the watermarked image（this requriement is again expressed in terms of a distortion constraint）.C. Detection scenariosThere are two decetion scenarios:private and public.In the private decetion scenario,the original image is available to the decetor,in the public scenario,it is not.Although public detection scheme can be more useful in practice(since it is not always possible to have the original image availableduring the decetion),private schemes usually offer more robustness.III. Watermarking Rates In The Presence Of Memoryless Attacks And Gaussian AttacksWe choose that the memoryless attack is fixed (in terms of the conditional probability distribution of the attack channel), for both discrete and continuous alphabets.We establised the region achievable rates (Rq, Rw) under memoryless attacks.A. Discrete Alphabets.The general form of the watermarking system under consideration is shown in Fig.2.The watermark index W is uniformly distributed over a set of size 2nRw; Yn is the watermarked image which can be found in a source codebook of size 2nRw, the attack channel is memoryless.The watermark decode outputs W.We consider a private scenario here,so we assume that In is known at the decoder.A.Attacking ProcedureThe watermarker (who designs the encoder pair) tries to maximize the achievable rate region while the attacker tries to minimize it 12.The procedure of attack are expressed as follows:1. The encoder (watermark embedder) is designed without any knowledge of the attack conditional distribution p.Firstly; the watermark designs an encoding function f. The watermark must ensure that the rates are chosen such that the watermark is detected reliably for any attackd diatribution p chosen by the attacker.2. The attack, who knows k, plays second and chooses a conditional distribution p for the attack such that the distortion constraint is met.3. The watermark plays next, and designs his watermark decoding algorithm g with respect to the distribution p chosen by the attacker.IV. ConclutionIn this paper, we established the region of achievable rates under memory attacks.The paper is discussed the following case: 1. The memoryless attack is chosen independently of the embedding strategy and is known to both encoder and decoder.Results are obtained for two statistical models:the general discrete alphabet case for arbitrary image distributions and distortion constraints,as well as the Gaussian case where the original image and the attack channel are i.i.d.Gaussian,and the distortion metric is quadratic. 2. The information and the attacker play a game which is the attacking procedure. Specifically, the attacker knows the encoding function used by the watermarker, while the decoder knows the attack distribution. Finally, there are a number of direction for future research.All results derived in this thesis assume a private scenario.We were not able to astablised the region of achievable rates in a public scenario, even for the simple Gaussian case.Futhermore, it would be interesting to establish rate regions for joint watermarking and compression systems under distortion constraints that do not involve averaging of distortion measures.中文翻译基于数字水印技术的信息隐藏理论研究宋丽娟 （宁夏大学 数学与计算机科学，银川 中国，）摘要：随着信息隐藏技术的迅速发展，水印和其它一些在数码照片、视频、音频以及其它的多媒体设备等信息方面相继也提出了很多方案。为了解决版权保护盒认证的相关问题，有人提出了使用水印作为最有效的手段。鉴于带宽的限制和压缩存储的问题，本文的重点是研究水印和压缩方面的问题。关键字：信息隐藏；数字水印；透明度；鲁棒性I. 引言 由于互联网和计算机的迅速发展，数字多媒体迅速发展到数据同时共享于众多用户是很容易实现的。此外，数据可以被快速复试而不产生任何质量损耗。例如，最近几年里，音乐和唱片的拷贝变得非常普遍。理所当然，这种情形唤起了人们对知识产权侵害的关注。没有给予版权持有人适当的补偿，而进行未经许可的复制以及传播享有著作权的材料（照片，音乐，电影等），正变得越来越严重。为了打击盗版，许多公司（尤其是娱乐和新闻行业）相当重视信息隐藏（或数字水印）技术的发展。简单来说，水印作为一种信号隐藏技术在一些多媒体数据中，并携带有关数据（例如，所有者、标题、制作日期等）的信息。因此，水印就能唯一的标记受保护的作品，帮助解决有关数据所有权的纷争的问。 有很多的关于多媒体知识产权的纠纷或所有权的诉讼案件方面的例子。在2000年初一，关于Napster软件版权侵犯的诉讼案得到了普遍关注。数字视频光盘协会（即数字通用光盘协会）号召提出一些版权保护措施来加强资源的管理。该想法是，卖给消费者的DVD播放器将允许不受权限的复制家庭录影以及观看的是移电视节目，不能轻易将此行为定位商业侵权。像Imprimature和CITED的欧洲项目和Working Group 提议的关于知识产权的美国项目都提到了电子版权的管理。 由于其重要性，水印领域有了大量关于信息隐藏技术的研究。有很多文章（其中的参考文献）和书籍都解释了数字水印的基本知识，探索了它的许多实际应用，并评估在各种攻击下的性能。II. 数字水印系统A. 水印在水印的通信模型中，水印嵌入扮演的是发射机，水印检测器扮演的是接收机。攻击代表通信系统信道（图1）。目标是可靠检测出隐藏信息；原始图像可以被理解为一直用于编码器的隐藏信息。但是，仅仅是在隐藏（不公开）的情况下解码器可用。在本文中，发射机发出了一个信号Xn到一个接收机（有n个传输），通过以下途径：Yn=Xn+Sn+Zn,其中，Sn，Zn是独立分布高斯随机向量，这里Sn属于编码器，Zn既不属于编码器也不属于解码器的噪声。实验证明这里的信道容量相当于Sn在解码器中的角色。 一般而言，这个数字随图像尺寸的大小线性变化，其中C即比例常数，实际的水印以每幅图片Rbit的速度嵌入，其中RC，即C=1/2log(1+P/N),P是Xn的功率的平均值。结果相当出乎人们的意料是因为期望Sn扮演接收器的干扰的角色，这样就能阻碍信息的监测。这个对水印的比喻很明显：在公众的检测方，Sn是看不见的（仅仅是隐藏的水印），Xn代表嵌入的水印，Zn将是由攻击者添加的噪声。B. 水印特征在数字水印的设计方案中，我们主要考虑两个关键因素：可见性：隐藏的信息不能随意干扰主要的信号。因为水印的目的是保护那些在一般情况下很容易改变的多媒体数据，所以前面的要求是合理的。换句话说，如果做了改动一些作品允许的范围（由于水印的原因），那么这些图片和音乐作品将变得没用了，嵌入水印必须具有隐蔽性，这一要求通常出现在对失真具有的限制的情况中。鲁棒性：即使在因为恶意攻击或其它处理（量化，D/A转换等）导致降质之后，信息必须能在水印图像中被检测出来（在这篇论文中演示文本被假定是一幅图像，同样的技术能够被应用在多媒体数据的其它类型方面）。当然，水印的可检测