近年來，由於電腦與網際網路發展持續進步，使得人們取得各方面資訊越來越方便，大量的數位化資料在網際網路間公開的流通。不過由於數位化資訊太容易取得，導致不肖人士利用電腦及網際網路竊取、修改他人資訊也變得比以往簡單太多，因此如何將數位資產的智慧財產權保護就顯得非常重要。而數位浮水印技術即是一種用來保護數位影像的智慧財產權的一種方法。其目的為將個人資訊加入到欲保護的數位資產中的方法，日後受保護的數位資產發生爭議時，便可取出以證明其所有權，達到保護資產與驗證所有權目的。而Naor 及Shamir於1994年提出視覺密碼後，陸續有研究以結合視覺密碼與浮水印技術進行影像所有權的保護方案。本研究以視覺密碼及頻率域小波轉換的資訊為基礎，不論是灰階影像或全彩影像皆發展出一個數位浮水印的技術，利用統計學的中位數來產生視覺密碼所需要的分享影像，以期不需要利用大量的統計複雜理論及運算也能得到相同的良好結果。實驗結果得知，本研究在經過各種影像攻擊都能有良好的抵抗性。

In recent era, with the continuous advancement of computer and internet technology, it becomes much easier for common folks to obtain various information. Enormous amount of digital data are roaming in public access. As great convenience often came with price, it also becomes much easier for malicious third party members to steal, forge information. Therefore it becomes evidently important to protect the digital intellectual property, and the digital watermark technology is one of the many methods. The sole purpose of digital watermark technology is to inject personal data to the intellectual property that ones want to protect, and when the protected intellectual property faces controversy, one will be able to prove ownership from the injected information. Since Naor and Shamir published the idea of visual encryption in 1994, many researches on the same topic start to broom over the years. This purposed research will be based on visual encryption and frequency transfer, to develop a brand new digital watermark technology, whether it is a full color or gray scale image, and use statistical median to obtain the actual visual encryption so that in the absence of complex statistical theory and calculation, one can still achieve well-accepted result. As result of this research, the outcome has great resistance to various visual attacks.

目錄
第一章 緒論 1
1.1 前言： 1
1.2 研究目的 3
第二章 文獻探討 5
2.1 視覺密碼 5
2.2 數位浮水印 6
2.3 離散小波轉換 9
2.4 中位數 11
2.5 影像形成原理 12
第三章 相關研究 14
3.1 空間域之相關研究 14
3.2 頻率域之相關研究 17
4.1 視覺密碼與浮水印之結合 21
4.2 數位影像資產的保護方式 23
4.2.1 灰階影像所有權產生-浮水印嵌入過程 23
4.2.2 灰階影像所有權驗證-浮水印取出過程 25
4.2.3 全彩影像所有權產生-浮水印嵌入過程 26
4.2.4 全彩影像所有權驗證-浮水印取出過程 29
4.4 驗證浮水印的相似程度 31
第五章 實驗結果與討論 33
5.1 實驗環境 33
5.2 攻擊實驗 34
5.3 與劉馨茹的比較 37
第六章 結論 40
參考文獻 41

表目錄
表 3-1  沈昌興的黑白視覺密碼模型 14
表 3-2  Hsu之視覺密碼加密規則 15
表 3-3  黃培修的浮水印分享規則 16
表5-1 灰階影像(花)各種攻擊的實驗結果 35
表5-2 全彩影像(風景)各種攻擊的實驗結果 37
表5-3 針對攻擊抵抗與許慶昇、劉馨茹比較(灰階圖Flower) 38
表5-4 各實驗所花費的時間(灰階圖Flower) 38

圖目錄

圖2-1  Noar & Shamir的視覺密碼分享影像的色彩配置 6
圖2-2 (2,2)-threshold分享影像產生與疊合過程 6
圖2-3 第一次水平小波轉換 9
圖2-4第一次垂直小波轉換 10
圖2-5 三階離散小波轉換流程 10
圖2-6 三階離散小波轉換示意圖 11
圖2-7 色光三原色及顏料三原色 13
圖 3-1  Hsieh等人的Mapping Table 18
圖 3-2  Lou等人所提出的密碼簿(codebook) 19
圖 3-3 劉馨茹的浮水印分享規則 20
圖4-1 視覺密碼應用於浮水印之模型 22
圖4-2 數位資產之驗證過程 22
圖4-3灰階影像浮水印之嵌入過程 24
圖4-4灰階影像浮水印之驗證過程 26
圖4-5全彩影像浮水印之嵌入過程 27
圖4-6全彩影像浮水印之驗證過程 30
圖4-7  NC值計算公式	 31
圖5-1 受保護的影像(512x512)  a.花(灰階) b.風景(全彩) 33
圖5-2 浮水印新年快樂(256x256) 33

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