臺灣博碩士論文加值系統

近年來網際網路的發展越來越蓬勃，而由於影像可以被用來作為公司行號的商標、電子商務的廣告圖樣、多媒體的主要內容等，因此在網際網路上經常舉目可見。但就在藉由網路來提供這些影像的同時，也衍生出許多影像的安全問題，例如影像被非法拷貝與更改。那是由於影像非常容易被複製及竄改的緣故，因此如何去保護影像的智慧財產權將是一個重要的研究主題。在這一篇論文中，我們將會採用影像認證法來保護影像，當影像被竄改時，透過影像認證法，就可以指出影像被竄改之處，因而達到偵測影像完整性之目的。
在本碩士論文之中，我們將推出兩種新的影像認證法。第一種方法是植基於RSA的數位簽章以及四元樹的結構來達成影像完整性之偵測，透過數位簽章我們可以證明這些影像的所有權並且也可以指出影像中何處曾被竄改過，在另一方面，我們利用四元樹結構來組織這些數位簽章，因此在影像的偵測部分將會更有效率。
由於傳統的影像認證法是不允許JPEG的失真壓縮，那是因為JPEG失真壓縮法會將藏入影像的簽章給破壞掉。可是JPEG的失真壓縮在網際網路中卻是經常被使用的，因此我們希望所提出影像認證技術可以禁得起JPEG的失真壓縮。為了改進傳統的影像驗證法之效益，在第二個方法我們提出了另一個新的影像認證技術，不僅可以偵測影像中何處被竄改處又可以允許JPEG的失真壓縮。我們的方法會去取出一些重要的DCT係數，並且在這些重要的係數上設定一個可以容許壓縮的範圍，當這張影像沒有被過度修改或是過度壓縮時，其DCT係數將可以被正確地取回。如此這個影像認證法就可以禁得起JPEG的失真壓縮。

Nowadays, Internet has become more and more popular. However, images are most oftenly used in Internet. Images can be used as the trademarks of company symbolization, electronic commerce (EC), multimedia, etc. However, there are also some security issues of images. Among them, the illegal like illegal copy and modification of image is a popular security problem which oftenly occurs in our daily life. Therefore, how to protect the intellectual property of images is an important research topic. The thesis planes to use image authentication to protect the images. Based on the image authentication, the modified places of the images will be pointed out; thus the images can preserve the image integrity.
This thesis proposes two new methods for image authentication. The first method uses the RSA signatures and quadtree structure to achieve the image integrity. Based on those digital signatures, we can claim the authorship of the image and detect efficiently whether the image has been modified or not. On the other hand, we use quadtree structure to organize digital signatures; thus the detection procedure will be more efficient.
The traditional image authentication methods cannot allow JPEG lossy compression since the JPEG lossy compression may destroy the signatures embedded in images. However, JPEG lossy compression method is often required and popularly used everywhere. Thus, the JPEG lossy compression should be taken into consideration. To improve the traditional methods, we propose a new image authentication that not only can prevent images tampered with but also allow reasonable JPEG lossy compression. Our method will extract some significant DCT coefficients and set a compression tolerant range of them. An extracted DCT coefficient will be survived after the image is not further modified or lossily compressed.

Contents
Abstract (in Chinese)ii
Abstract (in English)iv
Acknowledgmentsvi
List of Figuresvii
List of Tablesviii
Chapter 1Introduction1
1.1 Motivation1
1.2 A Survey of Image Authentication2
1.3 Organization of this thesis2
Chapter 2An Efficient Image Tampering Detection Algorithm
Based on Quadtree Structure4
2.1 The Previous Work6
2.1.1 The Signing Procedure of TDDA6
2.1.2 The Verification Procedure of TDDA7
2.2 The Propose Method8
2.2.1 The Signing Procedure of FITDA9
2.2.2 The Verification Procedure of FITDA13
2.3 Discussions and Analyses18
Chapter 3An New Image Authentication for Tolerating
JPEG lossy compression23
3.1 JPEG lossy compression technique 25
3.2 The Propose Method26
3.2.1. The Signing Procedure26
3.2.2. The Verification Procedure32
3.3. Discussions and Analyses36
Chapter 4Conclusions47
Bibliography49

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