A Secret Information Hiding Scheme Based on Switching Tree Coding

1. A Secret Information Hiding Scheme Based on Switching Tree Coding Speaker: Chin-Chen Chang Department of Computer Science and Information Engineering National Chung Cheng University Chiayi, Taiwan 62107, R.O.C. E-mail:ccc@cs.ccu.edu.tw URL: http://www.cs.ccu.edu.tw/~ccc

2. Outline • VQ image compression • Watermarking • Search order coding (SOC) • Switching tree coding (STC)

3. VQ Image Compression

4. VQ Compression w h Image Index table Vector Quantization Encoder

5. VQ Compression w h Image Index table Vector Quantization Decoder

6. Finds the nearest pairs

7. CW1 ,CW2 CW4, CW5 CW6, CW7 CW0, CW8, CW13, CW14 hide 1 ,CW3 CW11 CW15, CW10 CW12, CW9 Unused hide 0 • Find d(CW0, CW8) > TH d(CW13, CW14) > TH

8. CW0, CW8, CW13, CW14 Unused Encode Index Table Index Table

9. 1 0 0 1 • Water mark: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0 1 0 0 1 1 1 0 1 1 0 0 Index Table Water mark CW1, CW2, CW4, CW5 CW6, CW7 CW11, CW3 CW15, CW10 CW12, CW9 hide 1 hide 0

10. 1 0 0 1 • Water mark: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0 1 0 0 1 1 1 0 1 1 0 0 Index Table Water mark CW1, CW2, CW4, CW5 CW6, CW7 CW11, CW3 CW15, CW10 CW12, CW9 hide 1 hide 0

11. 1 0 0 1 • Water mark: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0 1 0 0 1 1 1 0 1 1 0 0 Index Table Water mark

12. Search-Order Coding (SOC)

13. An example for indices of VQ

14. Search-Order Coding (SOC) Searched point Non-searched point

15. Search-Order Coding (SOC) Indicator The compressing steps P1 = 1 00011111 P2 = 1 11001111 P3 = 0 00 … P6 = 0 10 Compression codes = 100011111 111001111 000 …

16. Information hiding on the SOC codes • The proposed scheme: - Information hiding: to embed secret data into host image - Steganography : to embed secret data into host image and the interceptors will not notice the existence of secret data - Based on SOC

17. OIV (original index value) Information hiding on the SOC codes • Main idea: Ex. receiver receives the compression codes : 010101101110110110011000011 SOC OIV SOC SOC It means that the embedded secret data is “01100” if SOC is represented to hide “0” and OIV is represented to hide “1”.

18. Information hiding on the SOC codes • Method: ex. A 3*3 index table: If the secret data is “111110100”, then the hiding position of each bit will be in the raster scan order.

19. hide “0” SOC ====> there is nothing that needs to change for its compression codes hide “1” SOC ====> translate SOC into OIV (give up SOC coding and keep the OIV) hide “1” OIV ====> there is nothing that needs to change hide “0” OIV ====> translate OIV into SOC ex. 11 (SOC) Information hiding on the SOC codes Defined: “0”  embedded into SOC and “1”  embedded into OIV. • Embedding phase: + OIV

20. compression codes are still OIV: 100010010 translate SOC into OIV : 000 => 100011110 translate OIV into SOC : 100100000 => 01100100000 Information hiding on the SOC codes • Ex.

21. Information hiding on the SOC codes • Cost table (bits):

22. Information hiding on the SOC codes • Security: For enhancing the security of our method, the position in the index table for hiding each bit of secret data can be determined by using pseudo random number generator, and the secret data can be encrypted by using traditional cryptography system such as DES or RSA in advance.

23. Experimental results

24. Experimental results

25. Experimental results

26. Experimental results

27. Switching tree coding (STC)

28. Switching-tree coding (STC) • Sheu proposed the STC algorithm in 1999 • Re-encode the index table U L the current index

29. Switching-tree coding (STC) • If P = 7, then P = U • P’ = ‘11’ • If P = 10, then P = L • P’ = ‘10’

30. If P = 14, then P = A in index (3) • P’ = ‘01’ || index (3) = ‘0100011’ • If P = 17, then • P’ = ‘00’ || (17) = ‘0000010001’ n=5

31. Information Hiding on the STC codes (IHSTC)

32. Information Hiding on the STC codes (IHSTC) • Watermark: 0 1 0 0 1 1 0 0 0 1 1 0 1 0 … Index table

33. P’ = ‘00’||(10) ‘00’||(25) ‘00’||(21) … ‘00’||(17) Information Hiding on the STC codes (IHSTC) • Watermark: 0 1 0 0 1 1 0 0 0 1 1 0 1 0 …

34. ‘10’ Information Hiding on the STC codes (IHSTC) • Watermark: 0 1 0 0 1 1 0 0 0 1 1 0 1 0 … P’ = ‘00’||(10) ‘00’||(25) ‘00’||(21) … ‘00’||(17)

35. ‘10’ Information Hiding on the STC codes (IHSTC) • Watermark: 0 1 0 0 1 1 0 0 0 1 1 0 1 0 … P’ = ‘00’||(10) ‘00’||(25) ‘00’||(21) … ‘00’||(17) ‘10’‘00’||(128) …

36. ‘11’ Information Hiding on the STC codes (IHSTC) • Watermark: 0 1 0 0 1 1 0 0 0 1 1 0 1 0 … P’ = ‘00’||(10) ‘00’||(25) ‘00’||(21) … ‘00’||(17) ‘10’‘00’||(128) … ‘10’

37. Three binary connection tree

38. Three binary connection tree • If U-length > L-length • Tree B • If U-length < L-length • Tree C • Otherwise Tree A Tree B Tree C

39. Experiment results Image size = 512*512, n = 3 and |H| = 1024 NSTC: 在 image 中，可藏入之點 |H|: Secret Information 之長度 Difference: 藏入前與藏入後image bit 數的差異

40. Experiment results Image size = 512*512, n = 3 and |H| = 2048 Image size = 512*512, n = 3 and |H| = NSTC

41. Image size = 512*512, n = 5 and |H| = 1024 Image size = 512*512, n = 5 and |H| = 2048 Image size = 512*512, n = 5 and |H| = NSTC

42. Conclusions • A novel information-hiding scheme based on a switching-tree coding • The IHSTC system can hide a huge amount of information in the index table • Only a few extra bits are needed to record the corresponding information • The average time needed to hide an information character is 0.077seconds • IHSTC -- an efficient and effective scheme for hiding secret information