Information hiding in stationary images

staff corporal Piotr LenarczykMilitary Uniwersity of Technology Institute of Electronics and Telecomunication

Watermarking

„Digital image watermarking means embedding information into image in such a way that it is imperceptible to a human observer, but can be easily detected by special computer algorithm.”

Ingemar J. Cox

Applications of watermarking

• Owner Identification• Proof of Ownership • Copy Control• Device Control• Broadcast Monitoring• Content Authentication

Method of changing Discrete Cosine Transform coefficients in

frueqency domain

2-Dimensional Discrete Cosine Transform DCT 2D

M,N = 8

m,n – discrete index of pixel position

k,l discrete index of DCT coefficient

DCT 2D Basis Functions

Basis functions matrices of Discrete Cosine Transform for block 8x8 pix

2 dimensional Discrete Cosine Transform coefficients

Standard quantization matrix used in JPEG algorithm

16 11 10 16 24 40 51 61

12 12 14 19 26 58 60 55

14 13 16 24 40 57 69 56

14 17 22 29 51 87 80 62

18 22 37 56 68109

103

77

24 35 55 64 81104

113

92

49 64 78 87103

121

120

101

72 92 95 98112

100

103

99

Q=

162 162 162 161 162 157 163 161162 162 162 161 162 157 163 161162 162 162 161 162 157 163 161162 162 162 161 162 157 163 161162 162 162 161 162 157 163 161164 164 158 155 161 159 159 160160 160 163 158 160 162 159 156159 159 155 157 158 159 156 157

1283,5 4,77 3,24 -0,2 0,25 -0,55 -4,59 5,647,95 -0,79 -4,93 1,96 2,98 -3,8 3,32

-5,03 -0,3 -1,55 1,72 -0,68 -0,45 1,85 -2,22,26 1,14 1,7 0,92 -0,76 -1,37 0,21 1,14

-1 -1,15 -0,34 -1,36 1,75 1,12 -1,48 -0,671,21 0,46 -1,8 -0,11 -2,01 0,71 1,69 0,76-1,7 0,26 3,1 1,64 1,63 -2,25 -1,2 -0,91,33 -0,42 -2,38 -1,59 -0,88 1,97 0,55 0,65

Matrix A represents block of 8 x 8 pixel values

Matrix B represents DCT 2D calculated on matrix A:

A =

B =

0,5523,55

Original image

Watermarked image

Perceptual transparency

Data payloadRobustness

Original picture Watermarked picture for scalling coefficient k=23

Watermarked picture for scalling coefficient k=3000

BCH code influence on Bit Error Rate

Algorithm CharacteristicSupported formats BMP 16, 24 bits

PNG, JPG 24 bits

Minimal picture size [pix x pix] 256 x 256

Data payload [bits] 130

Error correction BCH – correction capability of 14 bits

Redundancy of embedded information At least four times

Method advantages Robust against multiply rotation of 90 degrees

Robust against high-pass filtering

Robust against picture distortion like text embedding, painting

Robust against lossy JPG compression - approximately 70%

JPEG format popularity

Program execution time [sec] BMP format, picture size 400 x 400 pix

Coder - 0,12

Decoder - 0,07

Program execution time [sec]JPG format, picture size 400 x 400 pix

Coder - 0,63

Decoder - 0,29

Thank you for your attention.

Questions?