1. Reporter :Liang, Min-Chen Date :2003/05/06
Improved Hiding Data in Images by Optimal Moderately-Significant-Bit Replacement Author:Chi-Kwong Chan and L.M. Cheng Source:IEE ELECTRONICS LETTERS,VOL.37, NO. 16, AUGUST 2001, pp
Adviser :Dr. Chang, Chin-Chen
Reporter :Liang, Min-Chen
Date :2003/05/06
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2. Outline PREVIOUS WORK PROPOSED METHODS EXPERIMENTAL RESULTS
CONCLUSIONS
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3. PREVIOUS WORK – Wang-Lin-Lin Scheme
temporal image (1bit/pixel)
The cipher process GA
important image
(1 bit/pixel)
perturbed image
(1 bit/pixel)
replacement
Improve H R Z Z1
pixel adjustment
host image
(8 bits/pixel)
residual image
(1 bit/pixel)
PSNR=33.02dB
PSNR=38.75dB
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4. The Cipher Process
Ex. F(X)=(5+3*X) mod (4*4)
F(0)=5, F(1)=8, F(2)=11, F(3)=14, F(4)=1,….. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 9 4 15 10 5 11 6 1 12 7 2 13 8 3 14
The location of important image
The location of perturbed image
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5. The Cipher Process (cont.)1 1
important image
perturbed image
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6. GA (Genetic Algorithm)1
G=g0g1….g15=g0000g0001….g1111
EX. we get the best replacement :
E1 E2
perturbed image
{1111}  {1100}
{1001}  {0001}
{0101}  {1101}
{0000}  {1111}
residual image 1
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perturbed image

7. Pixel Adjustment H Z 10 29 31 5 16 22 43
100 79
213
176
162 27 93
121
200 10 29 23 5 16 22 35
108 79
221
176
170 27 93
121
200
host image
optimal substitution image δ
1. If δ>=4 then add 8- δ-1
EX. 7>=4 then 23+0
2. If δ<4 and if the 4th bit is 0 then 0
is changed to 1 and subtracted δ
3. Do nothing otherwise
=31
=23
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8. Pixel Adjustment (cont.)H Z 10 29 31 5 16 22 43
100 79
213
176
162 27 93
121
200 10 29 23 5 16 22 35
108 79
221
176
170 27 93
121
200
optimal substitution image
host image δ
1. If δ <4 then subtract δ
2. If δ >=4 and if the 4th bit is 1 then 1
is changed to 0 and add 8- δ -1
3. Do nothing otherwise
=100
=108
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9. PROPOSED METHODS H Z 10 29 31 5 16 22 43
100 79
213
176
162 27 93
121
200 10 29 23 5 16 22 35
108 79
221
176
170 27 93
121
200
host image δ
optimal substitution image
1. If δ >=4 then add 8- δ -1
EX. 7>=4 then 23+0
2. If δ <4 and if the 4th bit is 0 then 0
is changed to 1 and subtracted δ
3. Do nothing otherwise
absolute error ε=31-23=8
If ε=32-31=1
32=
=31
=23
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10. PROPOSED METHODS (cont.)
O are the possible pixel values of H(Host image)
S are the pixel values used for the substitution H E1 10 29 31 5 16 12 43
100 79
213
176
162 27 93
121
200 1
12= is replaced by 16=
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11. PROPOSED METHODS (cont.)ε
Mean ε 8 7 6 5 4 3 2 1
4.5 . . 1 2 3 4 .
2.5 .
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12. EXPERIMENTAL RESULTS
Resulting stego-image with PSNR=42.352
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13. CONCLUSIONS
An improvement of the Wang-Lin-Lin data hiding scheme is proposed.
The improvement demonstrates better performance than the Wang-Lin-Lin scheme with respect to computational cost and image quality.
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