1. High Capacity Data Hiding for Grayscale Images
Author: Chin-Chen Chang, Yung-Chen Chou and The Duc Kieu
Speaker: Yung-Chen Chou

2. Outline Introduction Zhang and Wang’s method The proposed method
Experimental result
Conclusions
Yung-Chen Chou

3. Introduction Sender Receiver Stego-Image Stego-Image Host Image
Secret data:
Secret data:
Yung-Chen Chou

4. Introduction (cont.) Data hiding: Requirement: Spatial domain
Frequency domain
Compression domain
Requirement:
Low distortion
High capacity
Yung-Chen Chou

5. Zhang and Wang’s method12 19 15 23 79 54 55 11 20 21 24 10 9
Translate binary secret message to (2n+1)-ary notification system
image
Secret data: …
01112  125
01012  105
Yung-Chen Chou

6. Zhang and Wang’s method (cont.)
Extracting function:
n=2 19 12 19 13 12 19 15 23 79 54 55 11 20 21 24 10 9
f(13,19)=(13+19*2) mod 5 = 1
f(11,19)=(11+19*2) mod 5 = 4
f(12,19)=(12+19*2) mod 5 = 0
f(12,18)=(12+18*2) mod 5 = 3
f(12,20)=(12+20*2) mod 5 = 2 19 13 11 18 12 20
image x1 x2
… … 1 3 4 2 : 20 19 18
Secret data:  125
Yung-Chen Chou

7. Zhang and Wang’s method (cont.)2 x1 x2
… … 3 1 4 : 22 21 20
n=2 13 19 15 21 79 54 55 11 20 12 24 10 9 21 15
f(16,21)=(16+21*2) mod 5 = 3
f(14,21)=(14+21*2) mod 5 = 1
f(15,21)=(15+21*2) mod 5 = 2
f(15,20)=(15+20*2) mod 5 = 0
f(15,22)=(15+22*2) mod 5 = 4 21 16 14 20 15 22
image
Low embedding rate
Secret data:  125
Yung-Chen Chou

8. The proposed method Magic matrix construction Extracting function:
f(0,0)=(0+0*2) mod 5 = 0
f(1,0)=(1+0*2) mod 5 = 1 :
f(2, 1)=(2+1*2) mod 5 = 4 :
f(3,252)=(3+252*2) mod 5 = 2 :
f(252,3)=(252+3*2) mod 5 = 3 :
Yung-Chen Chou

9. The proposed method (cont.)
x1 = 2
x2 = 255-x1 = 253 2 3 15 23 79 54 55 11 20 21 12 24 10 9 4
x1=3
x2=255-x1 = 252
Secret data: …
01112  125
01012  105
image
Yung-Chen Chou

10. The proposed method (cont.)
Data extraction
f(4, 255-4) = (4+251*2) mod 5 = 1 4 3 15 23 79 54 55 11 20 21 12 24 10 9
f(3, 255-3) = (3+252*2) mod 5 = 2
Stego-image
125=01112
Yung-Chen Chou

11. Experimental Results
The proposed method embeds two secret bits per pixel
Zhang and Wang’s method using two pixels to embed two secret bits
Yung-Chen Chou

12. Experimental results Original image Stego-image with 524288
bits secret message
Yung-Chen Chou

13. Conclusions The proposed method embeds one digit into one pixel.
We provide a simple and efficient data embedding method to achieve secret message delivery purpose with high capacity.
Yung-Chen Chou