1. 一種兼顧影像壓縮與資訊隱藏之技術 張 真 誠 國立中正大學資訊工程學系 講座教授 http://www.cs.ccu.edu.tw/~ccc

2. Outline Search order coding (SOC) Switching tree coding (STC)
Experimental results
Conclusions

3. Search-Order Coding (SOC)

4. An example for indices of VQ

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

6. Search-Order Coding (SOC)
Indicator
The compressing steps 31
207
211 8 7 35
P1 =
P2 =
P3 = 0 00 …
P6 = 0 01
Compression codes = …

7. 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

8. 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”.

9. 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.

10. 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

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

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

13. 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.

14. Experimental results

15. Experimental results

16. Experimental results

17. Experimental results

18. Switching tree coding (STC)

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

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

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

22. Information Hiding on the STC codes (IHSTC)

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

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

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

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

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

28. Three binary connection tree

29. 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

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

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

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

33. 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

34. Questions ??

35. Thank You !!