由於電腦與通訊網路的進步，使得電子文件交換、電子商務、隨選視訊、數位圖書館等數位服務廣為流行。由於數位化資料很容易被複製，所以需要能防止竊取或篡改的保護機制。數位浮水印技術為近年來新興的技術，它能將資訊隱藏於多媒體資料中用來宣告所有權、著作權或認證。
在我們的研究上，我們是使用通訊系統中的展頻通訊原理來實現數位浮水印。本文將數位浮水印系統比擬成通訊系統，原始媒體資訊(影像)之頻率域為傳輸通道，而浮水印資料為傳輸訊號，可能遇到的攻擊或破壞則視為通道雜訊[4][9]。
JPEG壓縮是現今普遍使用的壓縮格式，因它有著高壓縮特性，以及壓縮後影像品質仍很高，所以普遍被大眾使用。由於慢速跳頻展頻浮水印技術主要是設計對抗JPEG壓縮。在多重傳送(Multicast)的環境下，我們想在同一張影像中放入二個不同的資訊，以提升影像的安全性，在本論文中，我們利用慢速跳頻展頻技術提出雙浮水印的嵌入構想，將浮水印嵌入於不同的頻帶中，實現將二個重要的資訊嵌入於同一張影像。
本論文最後提出利用二張不同的量化表，可讓二組key順利且無干擾的嵌入於同一張影像中，實現利用影像浮水印嵌入安全金鑰。The advances of computers and communication networks make digital content service such as digital document exchange, E-commerce, video on demand, and digital library very popular. Since digital data can be easily reproduced without any loss, copyright protection becomes an imperative requirement to prevent piracy. Digital watermarking has been proposed as one of the techniques to prevent data piracy and plagiarism. Digital watermarking is a novel and emerging technology. It has developed very quickly for the past few years. A digital watermark is a set of information that is robustly and imperceptibly embedded in the data to be protected. Applications include copyright protection and authentication.
In the thesis, we developed two watermarking techniques using spread-spectrum technique. We interpreted the watermarking technology based on communication theory. The watermark was the signal to be transmitted. The frequency domain of the original image was the transmission channel. The attacks were regarded as channel noise.
JPEG compression is the most widely used image compression technique because of its high compression ratio and reasonable image quality. In the multicast environment, we wanted to embed two different information to increase the security of images. Here, we developed an embedding method to embed two watermarks in the different bands. We used two different quantization tables to embed two keys in the same image, and realize embedding security keys in images using digital watermarks.中文摘要......................................................I
英文摘要....................................................III
致謝.........................................................V
目錄........................................................VI
圖目錄.......................................................X
表目錄.....................................................XIV
第一章 緒論...................................................1
1.1 影像保密..............................................1
1.2 何謂數位浮水印........................................1
第二章 數位浮水印的背景.......................................4
2.1 數位浮水印的評估標準..................................4
2.2 數位浮水印架構........................................5
2.3 數位浮水印特性........................................7
2.3.1數位浮水印之種類.....................................7
2.3.2浮水印影像...........................................8
2.4 影像品質定義.........................................10
2.5 浮水印相似度衡量.....................................11
2.6 浮水印嵌入之領域.....................................13
2.6.1 嵌入浮水印於空間域...............................14
2.6.2 嵌入浮水印於頻率域...............................14
2.7 展頻通訊介紹與展頻數位浮水印研究方向.................16
2.7.1 跳頻展頻.........................................17
2.7.2 直接序列展頻.....................................19
2.8 展頻數位浮水印研究方向...............................21
第三章 多路徑數量量化器......................................22
3.1 多路徑數量量化器介紹.................................22
3.2 多路徑數量量化器的公式化與表示法.....................23
3.3 多路徑數量量化器失真問題.............................25
3.4 理想狀況的條件.......................................26
3.5 在多路徑數量量化器性能下的失真率範圍.................28
3.6 標籤指定.............................................30
3.6.1 標籤指定介紹.....................................30
3.6.2 設計好的標籤指定條件.............................30
3.6.3 修正的巢狀標籤指定...............................31
3.6.4 修正的線性標籤指定...............................33
3.6.5 MN和ML標籤指定特性比較...........................35
第四章 跳頻展頻與多路徑數量量化器於數位浮水印上的應用........36
4.1 前言.................................................36
4.2 快速跳頻展頻浮水印...................................36
4.3 慢速跳頻展頻浮水印...................................38
4.4 嵌入浮水印方法.......................................39
4.4.1 產生跳頻碼與建立慢速跳頻表.......................41
4.5 取出浮水印方法.......................................47
4.6 加入MDSQ的浮水印.....................................49
4.7 MDSQ解碼器應用於浮水印的問題.........................53
4.7.1 問題產生原因.....................................53
4.7.2 問題解決方式.....................................53
4.8 模擬結果.............................................55
第五章 雙浮水印嵌入的展頻浮水印架構..........................60
5.1 研究動機.............................................60
5.2 雙浮水印嵌入.........................................60
5.3 雙浮水印取出.........................................63
5.4 模擬結果.............................................63
第六章 利用影像浮水印嵌入安全金錀............................66
6.1 研究方向.............................................66
6.2 重新修改量化表.......................................67
6.3 模擬結果.............................................70
第七章 結論與未來工作........................................76
7.1 結論.................................................76
7.2 未來方向.............................................77
參考文獻.....................................................7
