1. Reversible Data Hiding Scheme Using Two Steganographic Images
Chair Professor Chin-Chen Chang
Feng Chia University

2. Data Hiding Hiding system Stego image Cover image
Secret message

3. Cover Carriers
Image
Video
Sound
Text

4. VQ Encoding Index table Original Image Codebook … (120,155,…,80) 11 2 3 4 5 6 7 8 9 10 11 12 13 14 15
(90,135,…,120)
(100,125,…,150) …
Index table
Original Image
(49,117,…,25)
(50,42,…,98)
(20,65,…,110)
Codebook

5. Previous Work of Steganography on VQ
To find the closest pairs

6. d(CW0, CW8) > TH d(CW13, CW14) > TH Unused CW0, CW8, CW13, CW14

7. Encode Index Table CW0, CW8, CW13, CW14 Unused Index Table
Original Image
Index Table
Unused
CW0,
CW8,
CW13,
CW14

8. A secret message: 1 1 1 1 1 1 1 1
Index Table
Secret bits
CW1, CW2,
CW4, CW5
CW6, CW7
CW11, CW3
CW15, CW10
CW12, CW9 1

9. A secret message: 1 1 1 1 1 1 1 1
Index Table
Secret bits
CW1, CW2,
CW4, CW5
CW6, CW7
CW11, CW3
CW15, CW10
CW12, CW9 1

10. A secret message: 1 1 1 1 1 1 1 1
Index Table
Secret bits

11. Zhang and Wang’s Method (Embedding)
Extracting function: 8 7 9 4 79 54 55 11 20 21 12 24 10
Secret data: … p2
255 1 2 3 4 1 2 3 4 1 : : : : : : : : : : : : :
10002
1 35 … 11 2 3 4 1 2 3 4 1 2 3 2 … 10 1 2 3 4 1 2 3 4 1
Cover image … 9 3 4 1 2 3 4 1 2 3 4 3 … 8 1 2 3 4 1 2 3 4 1 2 1 … 7 4 1 2 3 4 1 2 3 4 4 … 6 2 3 4 1 2 3 4 1 2 3 2 … 5 1 2 3 4 1 2 3 4 1 7 10 4 … 4 3 4 1 2 3 4 1 2 3 4 3 … 3 1 2 3 4 1 2 3 4 1 2 1 … 2 4 1 2 3 4 1 2 3 4 4 … 1 2 3 4 1 2 3 4 1 2 3 2 … 1 2 3 4 1 2 3 4 1
Stego image 1 2 3 4 5 6 7 8 9 10 11 …
255 p1
Magic Matrix

12. Zhang and Wang’s Method (Extracting)p2 7 10 4
255 1 2 3 4 1 2 3 4 1 : : : : : : : : : : : : : … 11 2 3 4 1 2 3 4 1 2 3 2 … 10 1 2 3 4 1 2 3 4 1 … 9 3 4 1 2 3 4 1 2 3 4 3 … 8 1 2 3 4 1 2 3 4 1 2 1
Stego image … 7 4 1 2 3 4 1 2 3 4 4 … 6 2 3 4 1 2 3 4 1 2 3 2 … 5 1 2 3 4 1 2 3 4 1 … 4 3 4 1 2 3 4 1 2 3 4 3 … 3 1 2 3 4 1 2 3 4 1 2 1 … 2 4 1 2 3 4 1 2 3 4 4
1 35 … 1 2 3 4 1 2 3 4 1 2 3 2 … 1 2 3 4 1 2 3 4 1 p1 1 2 3 4 5 6 7 8 9 10 11 …
255
Extracted secret data: 10002
Magic Matrix
Irreversibility

13. Proposed Method Magic Matrix Restored Image Stego 1 Original Image
Embedding
Extracting
Restored Image
Stego 1
Original Image
Extracted
Secret
Secret
Stego 2

14. The Proposed Method (Embedding)10 9 8 7 9 4 79 54 55 11 20 21 12 24 10 p2
255 1 2 3 4 1 2 3 4 1 : : : : : : : : : : : : : …
Stego 2 11 2 3 4 1 2 3 4 1 2 3 2 …
Cover image 10 1 2 3 4 1 2 3 4 1 … 9 3 4 1 2 3 4 1 2 3 4 3 … 8 1 2 3 4 1 2 3 4 1 2 1 …
Secret message
10002
1 35 9 6 7 4 1 2 3 4 1 2 3 4 4 … 6 2 3 4 1 2 3 4 1 2 3 2 … 5 1 2 3 4 1 2 3 4 1 … 4 3 4 1 2 3 4 1 2 3 4 3 … 3 1 2 3 4 1 2 3 4 1 2 1 … 2 4 1 2 3 4 1 2 3 4 4
Stego 1 … 1 2 3 4 1 2 3 4 1 2 3 2 … 1 2 3 4 1 2 3 4 1 p1 1 2 3 4 5 6 7 8 9 10 11 …
255
Magic Matrix

15. The Proposed Method (Extracting)10 9 9 6 p2
255 1 2 3 4 1 2 3 4 1 2 : : : : : : : : : : : : : : …
Stego 2 11 2 3 4 1 2 3 4 1 2 3 4 2
Stego 1 … 10 1 2 3 4 1 2 3 4 1 2 … 9 3 4 1 2 3 4 1 2 3 4 3 … 8 1 2 3 4 1 2 3 4 1 2 3 1 … 7 4 1 2 3 4 1 2 3 4 1 4 8 7 … 6 2 3 4 1 2 3 4 1 2 3 4 2 … 5 1 2 3 4 1 2 3 4 1 2 … 4 3 4 1 2 3 4 1 2 3 4 3 …
1 35
10002
Secret message 3 1 2 3 4 1 2 3 4 1 2 3 1 … 2 4 1 2 3 4 1 2 3 4 1 4 …
Restored image 1 2 3 4 1 2 3 4 1 2 3 4 2 … 1 2 3 4 1 2 3 4 1 2 p1 1 2 3 4 5 6 7 8 9 10 11 12 …
255
Magic Matrix

16. Experimental Results (a) Original image (b) Stego 1
(PSNR = dB)
(c) Stego 2
(PSNR = dB)
(d) Restored image

17. Experimental Results (cont.)
Methods
Images
Zhang and Wang’s method
The proposed method
PSNR
Capacity (bpp)
PSNR (Stego 1)
PSNR (Stego 2)
Baboon
52.11 1
Barbara
Lena
52.12
Pepper
0.9999
Average p2
255 1 2 3 4 1 2 3 4 1 2 : : : : : : : : : : : : : : … 11 2 3 4 1 2 3 4 1 2 3 4 2 … 10 1 2 3 4 1 2 3 4 1 2 … 9 3 4 1 2 3 4 1 2 3 4 3 … 8 1 2 3 4 1 2 3 4 1 2 3 1 … 7 4 1 2 3 4 1 2 3 4 1 4 … 6 2 3 4 1 2 3 4 1 2 3 4 2 … 5 1 2 3 4 1 2 3 4 1 2 … 4 3 4 1 2 3 4 1 2 3 4 3 … 3 1 2 3 4 1 2 3 4 1 2 3 1 … 2 4 1 2 3 4 1 2 3 4 1 4 … 1 2 3 4 1 2 3 4 1 2 3 4 2 … 1 2 3 4 1 2 3 4 1 2 p1 1 2 3 4 5 6 7 8 9 10 11 12 …
255
Magic Matrix

18. Conclusions
The proposed method embeds two digits into one pixel pair by generating two stego pixel pairs.
Generating two stego images achieves the purpose of secret sharing
We provide a reversible data hiding scheme with the same embedding capacity and lower visual quality (i.e. PSNR ≈ 45dB) in comparison with the related work.