臺灣博碩士論文加值系統

藏密學是用於資訊隱藏的一種方法，隨著網路通訊的持續成長，愈益凸顯它的重要性。現在，已經有非常多的藏密演算法或藏密軟體已經被開發出來了，其中也包括了把資訊藏入於JPEG 影像之隱藏技術。JPEG是數位相機常使用的影像格式並廣泛應用在網路上。
這篇論文提供了兩個方法改進F5資訊隱藏演算法的藏密容量。第一個方法屬於前處理的方法，在F5資訊隱藏演算法執行前，我們會隨機修改量化後的DCT係數去得到更多的非零的量化後的DCT係數來藏訊息。第二個方法裡，在F5資訊隱藏演算法執行後，我們在JPEG影像裡會稍微修改每個DCT區塊的結束位置的資訊去增加藏密容量。我們只要在量化後的DCT 8×8 區塊內修改一個DCT係數就能多儲存三位元的資料。縱使PSNR的數值有一點降低，我們提出的演算法跟許多經典的資訊隱藏演算法相比，藏密容量卻有顯著的進步。

Steganography is a method of data hiding. It is more and more important while the Internet communication grows up. Now, many steganographic algorithms or software have already been developed including image hiding techniques for JPEG images. JPEG is the most common image format used by digital cameras and transmitted in the Internet.
This thesis proposes two methods to increase the capacity of F5 embedding algorithm. The first method is a pre-processing method, we randomly modifies the qDCT coefficients before the F5 embedding algorithm to get more nonzero qDCT coefficients to embed message. In the second method, we slightly modify the end of block (EOB) information in a JPEG image to increase the capacity of embedding after the F5 embedding algorithm. We change a qDCT coefficient on each qDCT 8×8 block to embed 3 more bits of message. Although the PSNR value is slightly decreased, our proposed algorithm significantly increases the capacity of embedding compared with many classical steganographic algorithms.

Chapter 1 Introduction 1
Chapter 2 Review of DCT-Based Steganographic Algorithms 3
2.1 The JPEG Image Format 3
2.2 Some Classical Steganographic Algorithms 5
2.2.1 J-Steg 5
2.2.2 JPhide 6
2.2.3 F5 6
2.2.4 OutGuess 8
2.2.5 JPEG-CES 8
2.3 Steganalysis 10
2.3.1 χ^2-test 10
2.3.2 S1 attack 11
2.3.3 S2 attack 12
Chapter 3 Proposed Data Hiding Method 13
3.1 Method 1: Random Modification of DCT Coefficients 13
3.2 Method 2: Adding One More Coefficient 15
3.3 Embedding and Extraction 16
Chapter 4 Experimental Results 18
4.1 Image Quality 18
4.2 S1 attack test 22
Chapter 5 Conclusion and Future Work 23
References 24

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