目前多媒體資料的驗證依其功能性分成兩種方法，其中一個稱為數位簽章驗證法，主要的功能為驗證資訊來源的正確性，確保資訊是來自特定的一端；另一個則稱為數位浮水印，主要的功能為驗證資訊內容的正確性，確保資訊沒有被竄改或遺失。本篇論文的主要研究目的，就是如何結合上述兩種方法，以達成影像驗證與影像回復的技術。
本論文中提出了一個易碎浮水印的影像驗證和回復技術。關於影像驗證方面，在金鑰交換系統架構下使用加密與循環冗餘碼檢測，使得接收到影像的另一端能夠快速驗證影像的來源與內容是否正確，並且能夠免去密鑰在網路上傳輸的麻煩。在影像還原方面，本方法使用嵌入在另一區塊中的區塊平均值來還原被竄改的區塊。本方法使用雙重循環冗餘碼檢測以及3DES-ECB加密法來達到安全性的要求；另外，本論文的方法也以浮水印中的區塊絕對位置來偵測影像被裁剪或遺失邊緣。實驗的結果表示本方法能夠偵測影像的任何改變，包括VQ攻擊或Holliman-Memon[11]提出的攻擊，並且能指出改變的位置正確至8x8範圍內，最後也能將錯誤的區塊還原。
與Celik[14]中所提出的方法比較，本論文在指出竄改位置的正確範圍比他們的10x10更精準，並且能夠更進一步偵測出影像四邊均被裁剪或遺失的情形，另外本方法以降低3dB的浮水印影像品質換取竄改部位的還原能力。

Current multimedia authentication schemes can be divided into two categories: digital signature-based and digital watermarking-based. In this paper, a fragile, block-wise, and content-based watermarking for image authentication and recovery is presented. In this scheme, the watermark of each block is an encrypted form of its signature, which includes the block location, a content-feature of another block, and two CRC checksums. While the CRC checksum is to authenticating the signature, the mixture of the location indices of one block with the feature of a randomly selected block complicates the VQ attack. The encryption further strengthens the security. That all security parameters are user dependent and can be computed at both ends individually based on Diffie-Hellman key exchange method not only makes the scheme robust against collage attack but truly oblivious, as well. The experiments demonstrate that our scheme can detect and localize any tampering of size 8x8 pixels and can recover an image with 40% damage to an intelligible one with 24dB. As for incidentally manipulated images, our scheme can invalidate all the blocks but will not further degrade the images.
Comparing with the scheme of Celik et al. [14], ours has better tampering localization accuracy and surviving on cropping of four boundaries while trading off 3 dB of the watermarked image for recovery.

中文摘要…………………………………………………………………4
英文摘要…………………………………………………………………5
圖目錄……………………………………………………………………8
表目錄……………………………………………………………………9
第一章、緒論……………………………………………………………10
1.1研究動機………………………………………………………………11
1.2研究目標………………………………………………………………12
1.3論文架構………………………………………………………………13
第二章、研究背景………………………………………………………14
2.1數位影像格式…………………………………………………………14
2.2數位浮水印簡介………………………………………………………16
2.3目前浮水印的相關方法介紹…………………………………………18
2.3.1 Walton提出的影像驗證方法………………………………………19
2.3.2 Yeung與Mintzer提出的影像驗證方法……………………………20
2.3.3 Memon與Wong[5]提出的影像驗證方法……………………………21
2.3.4 Holliman與Memon提出關於區塊式浮水印的弱點………………23
2.3.5 Fridirch提出的影像驗證方法……………………………………24
2.3.6 Lin與Chang提出的影像驗證方法…………………………………24
2.3.7 Celik、Sharma、Saber與Tekalp提出的影像驗證方法…………27
2.4三重DES演算法…………………………………………………………31
2.5 Diffie-Hellman金鑰交換系統………………………………………33
第三章、影像驗證與回復之浮水印技術…………………………………35
3.1方法動機…………………………………………………………………35
3.2循環冗餘碼檢測…………………………………………………………36
3.3浮水印的產生與嵌入方法………………………………………………37
3.4影像驗證的方法…………………………………………………………41
3.5影像錯誤的回復…………………………………………………………44
3.6影像切割偵測……………………………………………………………45
第四章、實驗結果與分析…………………………………………………47
4.1實驗方向…………………………………………………………………47
4.2惡意竄改的實驗…………………………………………………………49
4.3非惡意竄改的實驗………………………………………………………54
4.4影像回復效果的實驗……………………………………………………56
4.4 CRC錯誤區塊偵測的遺漏率與安全性的分析…………………………59
第五章、結論與未來研究方向………………………………………………63
參考文獻………………………………………………………………………64

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