基於 (7,4) 漢明碼的隱寫技術 Chair Professor Chin-Chen Chang ( 張真誠 ) National Tsing Hua University National Chung Cheng University Feng Chia University

2 Introduction Information Hiding Cover image Hiding system Secret message Stego image

3 Introduction (Cont.) Cover Carriers Image Video Sound Text

4 Data: SenderReceiver 1 1 ?.... Data: Corrected data:

5 (7, 4) Hamming Coding Encoding Data: p 1 p 2 d 1 p 3 d 2 d 3 d d 1  d 2  d 4 = p 1 1  1  1 = 1 d 1  d 3  d 4 = p 2 1  0  1 = 0 d 2  d 3  d 4 = p 3 1  0  1 = 0 d1 d2 d3 d4d1 d2 d3 d4 Encoded data Encoding p 1 p 2 d 1 p 3 d 2 d 3 d 4

6 (7, 4) Hamming Coding (Cont.) Error Detection Received data: Error Position Corrected data: Correcting Parity check matrix H Error bit

(7, 4) Hamming Coding (Cont.)  The (7,4) Hamming code can be applied to data hiding based on the pixel domain and AMBTC domain. 7

Matrix Coding Method 8 Example: [7,4] Hamming code, the parity check matrix H is : Embedding process: Cover vector Extraction process: Stego vector y = Change one bit in x according to coset leader associated to syndrome = Change one bit in x according to coset leader associated to = Change one bit in according to coset leader associated to = [ ]

9 Matrix Coding Method – based on the pixel domain Cover Image Parity check matrix H ( ) T = (1 1 1) T Secret data: …  Stego Image Embedding

10 Matrix Coding Method (Cont.) – based on the pixel domain ( ) T = (1 1 0) T Extracted secret data: … Stego Image Extracting ■ 7 pixels embed 3 bits

Matrix Coding Method – based on the AMBTC algorithm

Matrix Coding Method – based on the AMBTC algorithm AMBTC algorithm (Absolute moment block truncation coding) Reconstructed block 0/1 bitmap Original block Average=100 High mean value = 160 Low mean value = 64

The flowchart of the proposed scheme – embedding phase 13

An example of the proposed scheme – embedding phase 14

An example of the proposed scheme – embedding phase 15  Phase 1  Embed secret into the bitmaps

An example of the proposed scheme – embedding phase 16  Phase 2  Embed secret into (H, L) Final Result

An example of the proposed scheme – extraction phase 17  Phase 1  Extract secret from bitmaps

An example of the proposed scheme – extraction phase 18  Phase 2  Extract secret from quantization pairs

Experimental results 19 Test images

Experimental results SchemeCriteriaLenaZeldaElainJetBoatGoldhillAverage AMBTCPSNR (dB) Proposed scheme PSNR (dB) HC (bits)169, ,479168,388170,103172,771170,245 Chang et al.’s scheme [1] PSNR (dB) HC (bits)114,688 Chuang and Chang’s scheme [2] PSNR (dB) HC (bits)13,05113,16913,24812,63711,98912,48612, [1] C.C. Chang, Y.J. Liu, and S.T. Nguyen, “Hiding Secret Information in Block Truncation Code Using Dynamic Programming Strategy,” In Proceedings of 6th International Graphic and Image Processing, vol. 9443, Beijing, China, [2] J.C. Chuang and C.C. Chang, “Using a simple and fast image compression algorithm to hide secret information,” International Journal of Computers & Applications, vol. 28, no. 4, pp , 2006.

21 Conclusions Based on the property of Hamming code, the embedding and the extracting are very simple. The proposed steganographic scheme achieves much higher payload with a slightly lower visual quality of stego images compared with the related works.