以灰階影像區塊切割及模數函式為基礎之資訊隱藏技術

Information Hiding Schemes Based on the Block Segmentation and Modulus Function

張鈞名(Chun-Ming Chang)

指導教授 ： 呂慈純

朝陽科技大學/資訊學院/資訊管理系/碩士(2010年)

摘要

近年來已有非常多的資訊隱藏技術被提出來，如同位位元取代法、邊緣吻合技術、結合像素差異值與LSB取代之資訊隱藏方法及像素差異擴張與模數函式隱藏法等。上述之方法會造成擴張程度很大，而訊息藏量少。
為解決此問題本論文提出二個資訊隱藏方法，第一個方法以模數函式為基礎，以灰階影像作為媒介，將機密訊息藏於其中。所提方法首先將影像切割成數個不重疊區塊，區塊大小為 ，接著利用 函式計算每個區塊的能量，並將 個機密訊息轉換成十進制，若區塊能量與機密符號相等則無需修改像素;若不相等則計算訊息修改量，並且將訊息修改量平均分攤至像素中以產生偽裝像素。
第二個方法為以標準影像為對照基準的資訊隱藏技術，我們利用一張標準影像產生樣本區塊，以這些區塊做為資訊隱藏時之參考基準點，用以計算差異值，再將訊息藏入差異值中。由實驗結果顯示，所提方法可以有效提昇藏入量與減少因藏入而造成的失真。

關鍵字

資訊隱藏 ； 區塊分割 ； 邊緣吻合 ； 模數函式

並列摘要

There are plenty of information hiding technologies have been proposed recently, such as the parity bit replacement, the side match pixel value difference and LSB replacement, modulus function and so on. Most of then still can be improved.
This thesis proposes two information hiding technologies to enhance the hiding capacity. The first one is based on modulus function. We use grayscale image as cover medium to embed the secret information. The proposed method divides the image into several non-overlapping blocks and uses a G function to calculate the energy of each block. Then, we transform t bits secret information into a secret symbol in the decimal system. If the energy of the block equals to the secret symbol, then we do not modify the pixel. Otherwise, we calculate the quantity of the modification. The quantities of the modification are shared to each pixel of the block to generate the stego pixels.
The second method takes a gray image as a standard medium to generate block patterns. The cover image is divided into several blocks. The scheme compares each block with the block patterns to find a most similar pattern and calculate the difference between the block and the pattern. After that, the scheme embeds the information into the difference. The experimental results shows that the proposed method can increase embed capacity and reduce image distortion effectively.

並列關鍵字

Modulus Function ； Block Segmentation ； Information hiding ； Side Match

參考文獻

[1] C. C. Chang, J. Y. Hsiao, and C. S. Chan(2003), “Finding optimal least-significant-bit substitution in image hiding by dynamic programming strategy,” Pattern Recognition, Vol. 36, pp. 1583-1595.

[2] M. U. Celik, G. Sharma, A. M. Tekalp, and E. Saber(2005), “Lossless generalized-LSB data embedding,” IEEE Transactions on Image Processing, Vol. 14, No. 2, pp. 253-266.

[3] C. C. Chang and H. W. Tseng(2004), “A steganographic method for digital images using side match,” Pattern Recognition Letters, Vol. 25, No.12, pp. 1431-1437.

[4] W. C. Du and W. J. Hsu(2003), “Adaptive data hiding based on VQ compressed images,” IEE Proceedings on Vision, Image and Signal Processing, , Vol. 150, No. 4, pp. 233-238.

[6] M. Jarno(2006), “LSB matching revisited,” IEEE Signal Processing Letters, Vol. 13, No. 5, pp. 285-287.