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.
URL:

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. Find d(CW0, CW8) > TH d(CW13, CW14) > TH hide 1 hide 0 CW1 CW11
Unused
CW0, CW8, CW13, CW14

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

9. Water mark: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0 1 1 1 1 1 1 1 1 Index Table1 1 1 1 1 1 1
Index Table
Water mark
CW1, CW2,
CW4, CW5
CW6, CW7
CW11, CW3
CW15, CW10
CW12, CW9
hide 1
hide 0

10. Water mark: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0 1 1 1 1 1 1 1 1 Index Table1 1 1 1 1 1 1
Index Table
Water mark
CW1, CW2,
CW4, CW5
CW6, CW7
CW11, CW3
CW15, CW10
CW12, CW9
hide 1
hide 0

11. Water mark: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0 1 1 1 1 1 1 1 1 Index Table1 1 1 1 1 1 1
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 31
207
211 8 7 35
P1 =
P2 =
P3 = 0 00 …
P6 = 0 10
Compression codes = …

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. Information hiding on the SOC codes
Main idea:
Ex. receiver receives the compression codes :
SOC
OIV
(original index value)
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: 1 2 3 18 21 31 30 29 32
If the secret data is “ ”, then the hiding position of each bit will be in the raster scan order.

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

20. Information hiding on the SOC codes
compression codes are still OIV:
Ex.
translate SOC into OIV : =>
translate OIV into SOC : =>

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) = ‘ ’
If P = 17, then
P’ = ‘00’ || (17) = ‘ ’
n=5

31. Information Hiding on the STC codes (IHSTC)

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

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

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

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

36. Information Hiding on the STC codes (IHSTC)
Watermark: …
‘11’
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| = 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 seconds
IHSTC -- an efficient and effective scheme for hiding secret information