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. 1017-1018. Adviser :Dr. Chang, Chin-Chen Reporter :Liang, Min-Chen Date :2003/05/06 2003/05/06

Outline PREVIOUS WORK PROPOSED METHODS EXPERIMENTAL RESULTS CONCLUSIONS 2003/05/06

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 2003/05/06

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 2003/05/06

The Cipher Process (cont.) 1 1 important image perturbed image 2003/05/06

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 2003/05/06 perturbed image

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 00011111=31 00010111=23 2003/05/06

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 01100100=100 01101100=108 2003/05/06

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=00100000 00011111=31 00010111=23 2003/05/06

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=00001100 is replaced by 16=00010000 2003/05/06

PROPOSED METHODS (cont.) ε Mean ε 00000000 00000001 00000010 00000011 00000100 00000101 00000110 00000111 00001000 8 7 6 5 4 3 2 1 4.5 00001000 00001001 00001010 00001011 . 00000111 . 1 2 3 4 . 2.5 . 2003/05/06

EXPERIMENTAL RESULTS Resulting stego-image with PSNR=42.352 2003/05/06

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. 2003/05/06