Improved Hiding Data in Images by Optimal ModeratelySignificantBit

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 1

Outline n n PREVIOUS WORK PROPOSED METHODS EXPERIMENTAL RESULTS CONCLUSIONS 2003/05/06 2

PREVIOUS WORK – Wang-Lin Scheme E E 1 The cipher process important image (1 bit/pixel) H perturbed image (1 bit/pixel) R E 2 GA temporal image (1 bit/pixel) replacement Improve Z Z 1 pixel adjustment host image (8 bits/pixel) 2003/05/06 residual image (1 bit/pixel) PSNR=33. 02 d. B PSNR=38. 75 d. B 3

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, …. . 0 4 8 12 1 5 9 13 2 6 10 14 3 7 11 15 The location of important image 2003/05/06 9 5 1 13 4 0 12 8 15 11 7 3 10 6 2 14 The location of perturbed image 4

The Cipher Process (cont. ) E E 1 0 0 1 1 1 1 0 1 0 1 1 0 0 0 0 important image 2003/05/06 perturbed image 5

GA (Genetic Algorithm) G=g 0 g 1…. g 15=g 0000 g 0001…. g 1111 EX. we get the best replacement : E 1 perturbed image {1111} {1001} {0101} {0000} . . 2003/05/06 E 2 {1100} {0001} {1111}. . 1 0 1 1 1 0 1 0 0 0 1 1 1 0 0 1 0 1 0 0 0 1 1 1 0 residual image perturbed image 6

Pixel Adjustment H Z 10 16 79 29 31 5 22 43 100 213 176 162 27 93 10 16 79 27 121 200 host image δ 23 35 176 121 5 108 170 200 optimal substitution image 00011111=31 00010111=23 2003/05/06 29 22 221 93 1. If δ>=4 then add 8 - δ-1 EX. 7>=4 then 23+0 2. If δ<4 and if the 4 th bit is 0 then 0 is changed to 1 and subtracted δ 3. Do nothing otherwise 7

Pixel Adjustment (cont. ) H Z 10 16 79 29 31 5 22 43 100 213 176 162 27 93 10 16 79 27 121 200 host image 23 35 176 121 5 108 170 200 optimal substitution image δ 01100100=100 01101100=108 2003/05/06 29 22 221 93 1. If δ <4 then subtract δ 2. If δ >=4 and if the 4 th bit is 1 then 1 is changed to 0 and add 8 - δ -1 3. Do nothing otherwise 8

PROPOSED METHODS H Z 10 16 79 29 31 5 22 43 100 213 176 162 27 93 10 16 79 27 121 200 host image absolute error ε=31 -23=8 δ 23 35 176 121 5 108 170 200 optimal substitution image If ε=32 -31=1 00011111=31 32=00100000 00010111=23 2003/05/06 29 22 221 93 1. If δ >=4 then add 8 - δ -1 EX. 7>=4 then 23+0 2. If δ <4 and if the 4 th bit is 0 then 0 is changed to 1 and subtracted δ 3. Do nothing otherwise 9

PROPOSED METHODS (cont. ) O are the possible pixel values of H(Host image) S are the pixel H values used for the substitution E 1 10 29 31 5 1 1 16 12 43 100 1 0 0 1 79 213 176 162 0 1 27 93 0 0 121 200 12=00001100 is replaced by 16=00010000 2003/05/06 10

PROPOSED METHODS (cont. ) O 2003/05/06 S ε Mean ε 4. 5 00000001 00000010 00000011 00000100 00000101 00000110 00000111 00001000 00001000 8 7 6 5 4 3 2 1 00001000 00001001 00001010 00001011. . 00000111. . 1 2 3 4. . 2. 5. 11

EXPERIMENTAL RESULTS Resulting stego-image with PSNR=42. 352 2003/05/06 12

CONCLUSIONS n n An improvement of the Wang-Lin data hiding scheme is proposed. The improvement demonstrates better performance than the Wang-Lin scheme with respect to computational cost and image quality. 2003/05/06 13