1. Hiding Information in VQ Index Tables with Reversibility
Chair Professor Chin-Chen Chang
Feng Chia University
National Chung Cheng University
National Tsing Hua University

2. Outline Introduction The proposed scheme Experimental results
Conclusions

3. Introduction VQ compression Index table Original Image Codebook 1
(16, 200, …, 90) 2
(35, 22, …, 100) 3
(40, 255, …, 59) . 14
(90, 102, …, 98) 15
(145, 16, …, 99) 2 60 61
175 …
100 95
203 .
. . .
Index table
Original Image
Codebook

4. The Proposed Scheme Embedding Processes
Selecting the three preserved indices F, L, and I F
(40, 69, …, 88) 2
(35, 22, …, 100) 3
(40, 255, …, 59) . 14
(90, 102, …, 98) L
(65, 79, …, 200) 2 60 61
175 …
100 95
203 .
. . .
Two least frequently used indices
Index table

5. The Proposed Scheme Embedding ProcessesF
(40, 69, …, 88) 2
(35, 22, …, 100) 3
(40, 255, …, 59) . 14
(90, 102, …, 98) L
(65, 79, …, 200)
Select I by a pseudo random number generator with key K

6. The Proposed Scheme Embedding Processes
2. Compress original images with the modified codebook (assume I = 3) F
(40, 69, …, 88) 2
(35, 22, …, 100) I
(40, 255, …, 59) . 14
(90, 102, …, 98) L
(65, 79, …, 200) 2 60 61 …
100 95
203 .
. . .
Index table
Original Image
Modified Codebook

7. The Proposed Scheme Embedding Processes
3. Bound each two indices as a index pair (i1, i2) 2 60 61 …
100 95
203 .
. . .
Index table

8. The Proposed Scheme 4. Analyzing all index pairs i1 > i2
n1: the number of index pairs (i1, i2) in which
i1 > i2
n2: the number of index pairs (i1, i2) in which
i1 < i2
Case A: n1 ≧ n2
Case B: n1 < n2

9. The Proposed Scheme 5.1 Embedding rules (Case A)
To Embed secret bit s into index pair (i1, i2)

10. The Proposed Scheme 5.2 Embedding rules (Case B)
To Embed secret bit s into index pair (i1, i2)

11. The Proposed Scheme Example (Case A)；
Codebook size = 256, I = 3, F = 0, L = 255,
and s = 1101
(90, 30)
(50, 60)
(70, 70)
(254, 1)
Original VQ index table

12. Watermarked index pair:
The Proposed Scheme s: 1
Index pair:
(90, 30)
(50, 60)
(70, 70)
(254, 1)
(j1, j2) = (i1, i1 – i2)
=(90, 90-30)
(j1, j2) = (I, i1)
=(0, 70)
(j1, j2) = (i1, i1 – i2)
=(254, 254-1)
(j1, j2) = (L, i1, i2)
Watermarked index pair:
(90, 60)
(255, 50, 60)
(0, 70)
(254, 253)

13. The Proposed Scheme Extracting procedure
1.1 The extracting rules (Case A)
index by index

14. The Proposed Scheme Extracting procedure
1.2 The extracting rules (Case B)
index by index

15. Watermarked index pair:
The Proposed Scheme
Extracting procedure
Example (Case A):
Watermarked index pair:
(90, 60)
(255, 50, 60)
(0, 70)
(254, 253)
(i1, i2) = (j1, j1 – j2)
=(90, 90-60)
(i1, i2) = (j2, j3)
=(50, 60)
(i1, i2) = (j2, j2)
=(70, 70)
(i1, i2) = (j1, j1 – j2)
=(254, )
Recovered index pair:
(90, 30)
(50, 60)
(70, 70)
(254, 1)
j1 ≠L; j1 ≠I; j1 > j2
j1 =L; j2 < j3
j1 ≠L; j1 ≠I; j1 > j2
j1 =I 1 1
Secret bits: 1

16. Experimental results Original VQ-coded Images
Recovered VQ-coded Images

17. Experimental results Bit rate =
[11] C. C. Chang, Y. H. Chen, Z. H. Wang, and M. C. Li, "A reversible data embedding scheme based on Chinese remainder theorem for VQ index tables," submitted to 2009 ISECS International Colloquium on Computing, Communication, Control, and Management (CCCM 2009), Sanya China, August 2009.

18. Conclusions
Simple
Efficient
Reversible

19. Thanks for your listening~