- 學位論文
一種實作於影像區塊截短編碼之可逆式資料隱藏方法
A Reversible Data Hiding Scheme Implemented on Block Truncation Coding of Image
摘要
近年來隨著網際網路的進步，再加上智慧型手機的蓬勃發展，讓社群網站的使用人數直線攀升。網際網路帶來許多便利性，但也帶來許多資訊安全上的問題。現今網路的普及，讓資訊安全這一研究領域令人格外重視。目前許多產業會藉由網路來傳遞機密資訊，例如：軍事、商業和醫學等不同領域上。所以傳遞機密資訊的安全機制就顯得格外重要。 本論文提出一種基於區塊截短編碼(Block Truncation Coding, BTC)之可逆式的資料隱藏技術。首先把影像切割成n×n大小不重疊的區塊做區塊截短編碼，根據區塊截短編碼特性，編碼後的每個區塊會產生一對重建階值XH與XL和一個位元圖(Bitmap)。本論文提出的資料隱藏技術在機密資料藏入部份分成二個階段。第一階段之藏入方法為把機密資料藏入於每個區塊的重建階值XH與XL裡。第二階段之藏入方法為本論文所提出之利用格雷碼(Gray code)與直方圖位移(Histogram Shifting)技術的資料隱藏法。此方法把機密資料藏入於位元圖裡。本方法所使用的直方圖位移技術有做些改良，改良之方法會選擇最適合的峰值點與低值點進行位移及機密資料藏入。運用直方圖位移技術主要可以達到可逆性的目的，而應用格雷碼主要可以提高偽裝影像的品質。實驗結果證明提出的方法具有不錯的資料藏入量與視覺品質良好的重建影像。
並列摘要
The number of social network users has been rising thanks to the improvement of the Internet and the booming development of smartphones. The Internet has made lives easier, but it has also brought concerns on information security. Because the Internet is everywhere now, people put more emphasis on information security. In many areas such as military, business, and medicine, etc., people exchange classified information through the Internet, which shows the importance of a mechanism to secure the information. This paper proposed a reversible data hiding technique based on block truncation coding (BTC). By means of this technique, an image is divided into n×n non-overlapping blocks of pixels for block truncation coding. Each coded block generated two reconstruction level values XH and XL and one bitmap. The proposed data hiding technique secures secret data in two phase. The secret data is firstly embedded into the reconstruction level values of each coded block, and then embedded into bitmaps derived from a hybrid data embedding scheme using gray-code and histogram shifting. The histogram shifting technique employed in the research was slightly modified to shift between the best-fitting peak and low points and hide the data . This technique renders data reversible. The gray-code improves the quality of stego images. The experimental results demonstrate that this proposed technique yielded enhanced data hiding capacity, coupled with fine reconstructed images.