1. 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 http://msn.iecs.fcu.edu.tw/~ccc

2. 2 Introduction Information Hiding Cover image Hiding system Secret message Stego image 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0

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

4. 4 Data: 1 1 0 1 SenderReceiver 1 1 ?.... Data: 1 0 1 0 1 0 1 1 0 1 0 1 1 1.... Corrected data: 1 0 1 0 1 0 1

5. 5 (7, 4) Hamming Coding Encoding Data: 1 1 0 1 2 p 1 p 2 d 1 p 3 d 2 d 3 d 4 1 0 1 0 1 0 1 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. 6 (7, 4) Hamming Coding (Cont.) Error Detection Received data: 1 0 1 0 1 1 1 Error Position Corrected data: 1 0 1 0 1 0 1 Correcting Parity check matrix H Error bit

7. (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

8. 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 = [0010100] 100000000000100010000000010000010000100000

9. 9 Matrix Coding Method – based on the pixel domain 000010110000101000001001 000001100000001100000100 000011000000100100001011 11109 634 12911 Cover Image Parity check matrix H (1010100) T = (1 1 1) T Secret data: 1 1 0 0…  0 0 1 00001010 00001001 000001100000001100000100 000011000000100100001011 10 9 634 12911 Stego Image Embedding

10. 10 Matrix Coding Method (Cont.) – based on the pixel domain (0010100) T = (1 1 0) T Extracted secret data: 1 1 0 0… 00001010 00001001 000001100000001100000100 000011000000100100001011 10 9 634 12911 Stego Image Extracting ■ 7 pixels embed 3 bits

11. Matrix Coding Method – based on the AMBTC algorithm 11 248764962 572496118 1251445641 8297211114

12. Matrix Coding Method – based on the AMBTC algorithm AMBTC algorithm (Absolute moment block truncation coding) 12 248764962 572496118 1251445641 8297211114 1000 0001 1100 0011 16064 160 64 160 Reconstructed block 0/1 bitmap Original block Average=100 High mean value = 160 Low mean value = 64

13. The flowchart of the proposed scheme – embedding phase 13

14. An example of the proposed scheme – embedding phase 14

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

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

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

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

19. Experimental results 19 Test images

20. Experimental results SchemeCriteriaLenaZeldaElainJetBoatGoldhillAverage AMBTCPSNR (dB)33.2336.7433.8333.2531.7632.8733.61 Proposed scheme PSNR (dB)28.9232.2529.4128.1127.56.28.7429.17 HC (bits)169,250168480172,479168,388170,103172,771170,245 Chang et al.’s scheme [1] PSNR (dB)30.7134.2631.2630.9931.0230.4931.45 HC (bits)114,688 Chuang and Chang’s scheme [2] PSNR (dB)30.4533.9831.0730.5229.8430.5231.06 HC (bits)13,05113,16913,24812,63711,98912,48612,763 20 [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, 2014. [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. 329-333, 2006.

21. 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.