臺灣博碩士論文加值系統

本論文提出一個容忍JPEG失真壓縮之資訊隱藏方法。我們的方法除了能隱藏大量的資訊於掩護影像（Cover image）內，產生的偽裝影像（Stego-image）與掩護影像於外觀上並無太大差異，從視覺觀察無法分辨兩者之間的差別，攻擊者亦無法偵測出該偽裝影像隱藏機密資料。由於數位影像需要佔用大量的儲存媒體，一般傳輸或儲存上皆會採用例如JPEG壓縮法等失真壓縮技術以減小影像之儲存空間，我們的方法產生的偽裝影像，可以使用JPEG來進行失真壓縮處理，增加實用上的價值，但即便如此，從壓縮過並解壓縮後的偽裝影像中萃取出的機密資料，仍然可以達到百分之百的正確率。這對如文、數字與程式等萃取出來有任何一位元發生錯誤將造成意義失真或不可執行的隱藏資料而言是非常重要的。本論文所提出之方法，提供這類資料一個安全隱密的傳輸管道，而這是過去學者們的方法所較少考慮的特質。

In this paper, we present a new steganographic scheme used to embed secret text data into color images. Not only preserve the visual quality, we can use JPEG to com-press the stego-image. JPEG is the most common used image compression technique which reduces the image size drastically without losing the image quality seriously. There are many steganographic scheme have been proposed, but most of them can’t tolerate JPEG compression. That is, after JPEG compressing, the hidden data will be damaged critically. If the embedding data are pictures, accuracy losing would be ac-cepted. But for text data embedding approaches, even one bit error will lead the ex-tracted data to be totally useless. In our scheme, the hidden data are encoded by error correction technique first. Then we embed the encoded data in the spatial domain di-rectly by adjusting the pixel relation in each 3×3 image block. We also adopt the concept of error diffusion method used in halftone technique to improve the image quality to human visual system. By this way, the extracted data from a compressed stego-image could be completely correct.

目錄
第1章 緒論 1
1.1 資訊隱藏的歷史與背景 1
1.2 資訊隱藏技術之演變 5
1.3 研究動機與目的 11
1.4 論文結構 13
第2章 相關研究工作 14
2.1 低位元隱藏法（LSB-based embedding） 14
2.2 Wu和Tsai的方法 15
2.3 Wang和Pearmain的方法 17
第3章 容忍失真壓縮之資訊隱藏技術 19
3.1 隱藏方法（Embedding process） 21
3.2 萃取方法（Extracting process） 27
第4章 實驗結果 29
第5章 討論與分析 40
5.1 隱藏量分析 40
5.2 影像品質與壓縮率探討 41
5.3 安全性討論 42
5.3.1 Steganalysis based on JPEG compatibility 43
5.3.2 Visual attack 43
5.3.3 Chi-square attack 50
第6章 結論與未來方向 59
參考文獻 61
附錄A：英文論文稿 65

圖目錄
圖1-1：以加密方式進行秘密通訊的流程 2
圖1-2：以資訊隱藏方法進行秘密通訊的流程 4
圖1-3：資訊隱藏技術之分類 6
圖2-1：灰階度示意圖 14
圖2-2：差值表範例 16
圖2-3：由差值表判斷所能隱藏的資訊量 16
圖2-4：3×3區塊中間像素Pc與其八個相鄰像素 17
圖3-1：整體方法架構圖 21
圖3-2：區塊分割示意圖 23
圖3-3：區塊Bi像素值經過排序過後的結果 23
圖4-1：掩護影像Airplane（512×512） 30
圖4-2：藏入資料後的偽裝影像Stego-Airplane 30
圖4-3：掩護影像Airplane（512×512） 31
圖4-4：藏入資料後的偽裝影像Stego-Baboon 31
圖4-5：掩護影像Fruits（512×512） 32
圖4-6：藏入資料後的偽裝影像Stego-Fruits 32
圖4-7：掩護影像Lena（512×512） 33
圖4-8：藏入資料後的偽裝影像Stego-Lena 33
圖4-9：掩護影像Peppers（512×512） 34
圖4-10：藏入資料後的偽裝影像Stego-Peppers 34
圖4-11：以JPEG壓縮過的Stego-Airplane 37
圖4-12：以JPEG壓縮過的Stego-Baboon 38
圖4-13：以JPEG壓縮過的Stego-Fruits 38
圖4-14：以JPEG壓縮過的Stego-Lena 39
圖4-15：以JPEG壓縮過的Stego-Peppers 39
圖5-1：掩護影像Airplane的位元平面 45
圖5-2：偽裝影像Stego-Airplane的位元平面 45
圖5-3：掩護影像Baboon的位元平面 46
圖5-4：偽裝影像Stego-Baboon的位元平面 46
圖5-5：掩護影像Fruits的位元平面 47
圖5-6：偽裝影像Stego-Fruits的位元平面 47
圖5-7：掩護影像Lena的位元平面 48
圖5-8：偽裝影像Stego-Lena的位元平面 48
圖5-9：掩護影像Peppers的位元平面 49
圖5-10：偽裝影像Stego-Peppers的位元平面 49
圖5-11：Airplane經Chi-square attack分析的結果 52
圖5-12：Baboon經Chi-square attack分析的結果 53
圖5-13：Fruits經Chi-square attack分析的結果 54
圖5-14：Lena經Chi-square attack分析的結果 55
圖5-15：Peppers經Chi-square attack分析的結果 56
圖5-16：Airplane以亮度做Chi-square attack分析之結果 57
圖5-17：Baboon以亮度做Chi-square attack分析之結果 57
圖5-18：Fruits以亮度做Chi-square attack分析之結果 58
圖5-19：Lena以亮度做Chi-square attack分析之結果 58
圖5-20：Peppers以亮度做Chi-square attack分析之結果 58

表目錄
表4-1：使用不同的秘密金鑰產生的偽裝影像的影像品質 36
表4-2：使用JPEG壓縮過後的影像品質與壓縮率 37
表5-1：α=3與t=15時的影像品質與所能容忍的最大壓縮率 42

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