應用差值擴張法於區塊截短編碼法之可回復式資料隱藏技術

Reversible Data Hiding Based on Block Truncation Coding Using Difference Expansion

劉怡傑(Yi-Jie Liu)

指導教授 ： 莊潤洲 ； 詹啟祥

亞洲大學/資訊學院/資訊科學與應用學系碩士班/碩士(2008年)

摘要

本篇碩士論文提出基於區塊截短編碼法(Block Truncation Coding, BTC)之可回復式資料隱藏技術。在我們所提的方法中，我們應用差值擴張(Difference Expansion, DE)的技術，將秘密訊息藏入BTC中的兩個重建階數值內。然而，若只應用差值擴張法於區塊截短編碼法，當二個重建階的值相差太大，並強行藏入祕密訊息，會對影像造成相當大的傷害。為了能夠改善影像品質與增加可藏的資訊量，我們進而提出二個改善方法。第一個方法為二階段差值擴張法，此方法利用二個門檻值的設定，來決定利用差值擴張法時藏入的資料容量。第二個方法為多階段差值擴張法，此方法除了利用門檻值的設定之外，再加上單邊擴張方法，將秘密資訊潛藏至兩個重建階之中。根據實驗結果，在使用二階段的方法後，藏入量增加了500~3000個位元，而使用單邊擴張法，則使影像品質增加了1~3db。由實驗可知，我們所提之方法，不只改善了影像品質，並增加可藏入的秘密訊息。

關鍵字

區塊截短編碼法 ； 差值擴張法 ； 可回復式資料隱藏

並列摘要

In this thesis, we propose a reversible data hiding scheme based on Block Truncation Coding (BTC). In our proposed methods, we apply Difference Expansion Method to hiding secret data in reconstruction pixels of BTC codes. However, applying Difference Expansion Method may damage the quality of stego-images when the difference between two reconstruction pixels is too large. In order to improve the quality of stego-images and the quantity of hiding data, we go further to propose two modified methods. The first one is Two-Stage Difference Expansion Method. In this method, we set and adjust two thresholds to control the quantity of hiding data when applying Difference Expansion Method. The second method is Multi-Stage Difference Expansion Method. This method not only uses the threshold but also brings the concept of one-side expansion in the method when hiding secret data. According to experimental results, after using Two-Stage Difference Expansion Method, the capacity of hiding data increases 500~3000 bits. Moreover, applying one-side expansion raises the quality of image about 1~3 dB. Through experimental results, our proposed methods improve not only the quality of stego-images but also the quantity of hiding data.

並列關鍵字

block truncation coding ； difference expansion ； reversible data hiding

參考文獻

[5]R. Rivest, A. Shamir, and L. Adleman, “A Method for Obtaining Digital Signature and Public-key Cryptosystems,” Communications of the ACM, Vol. 21, No. 2, pp. 120-126, Feb. 1978.

[6]N. Bourbakis, and C. Alexopoulos, “Picture Data Encryption Using Scan Patterns,” Pattern Recognition, Vol. 25, No. 6, pp. 567-581, June 1992.

[7]H. K. C. Chang, and J. L. Liu, “A Linear Quadtree Compression Scheme for Image Encryption,” Signal Processing: Image Communication, Vol. 10, No. 4, pp. 279-290, Sep. 1997.

[8]T. S. Chen, C. C. Chang, and M. S. Hwang, “Virtual Image Cryptosystem Based Upon Vector Quantization,” IEEE Transactions on Image Processing, Vol. 7, No. 10, pp. 1485-1488, Oct. 1998.

[10]S. Dumitrescu, X. Wu, “A New Framework of LSB Steganalysis of Digital Media,” IEEE Transactions Signal Process, pp. 3936–3947, 2005.