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Presenting a new method for identifying LSB steganography in images based on difference image histograms and transition coefficients. This study explores the proposed steganalysis approach, outlining the detection process and embedding ratios to enhance image security.
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A new approach to reliable detection of LSB steganography in natural images Sources: Signal Processing, Vol. 83, Issue 10, October 2003, pp. 2085-2093 Authors: Tao Zhang, Xijian Ping Speaker: Jui-Yi Kuo Date: 2004/06/12
Outline • Introduction • LSB steganography • Difference image histogram • The proposed Steganalysis • Conclusions
LSB steganography Cover image Embedded Image Stego-image
20-35=(-15) Difference image histogram D(i,j)=I(i+1,j)-I(i,j) Difference image Difference image histogram Original image
The proposed steganography i: different value between two pixel hi: amount of difference i generated by stego-image fi: amount of difference i generated by stego-image which is after flipping all bits in the LSB plane gi: amount of difference i generated by stego-image which is after setting all bits in the LSB plane to zero ai,j: transition coefficient from gi to hj
Difference image histogram (Ex.) (a) Cover image (c) After flipping of cover image (b) Stego-image (d) After flipping of Stego-image
1 1 0 0 0 0 0 0 0 0 0 0 1 0 0 1 1 0 0 0 0 0 0 0 0 1 0 0 g g 2 1 0 1 gi : set to zero of LSB plane Difference = Even g g Difference = Odd
1 1 0 1 1 0 0 0 0 0 0 0 1 0 0 1 1 1 0 0 0 1 0 0 f 1 3 1 fi : flipping all bit of LSB plane Difference = Even f f 0 0 0 1 Difference = Odd f -1
8 6 g2i+2 0.5 0.5 0.25 0.33 a2i,2i+1 a2i,2i+3 a2i+2,2i+2 3 4 4 h2i+2 h2i+3 =0.5*8=4 =0.25*8+0.33*6=4 =0.25*8+0.17*6=3 Transition diagram a2i,2i-1+a2i,2i+a2i,2i+1=1 g2i a2i,2i-1 a2i,2i+1 a2i,2i h2i-1 h2i h2i+1 h2i=f2i=a2i,2i g2i h2i+1=a2i,2i+1 g2i+a2i+2,2i+1 g2i+2 f2i+1=a2i,2i-1 g2i+a2i+2,2i+3 g2i+2
Transition coefficients a0,1=a0,-1=(g0-h0)/(2g0) a2i,2i=h2i/g2i a2i,2i-1=(h2i-1-a2i-2,2i-1 g2i-2)/g2i a2i,2i+1=1-a2i,2i-a2i,2i-1
Embedding Ratio 2d1*P2+(d3-4d1-d2)*P+2d2=0 P is embedding ratio
Conclusions • detection of LSB steganography • Embedding ratio of an image with LSB steganography