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LSB Matching Revisited

LSB Matching Revisited. Source: IEEE Signal Processing Letters (Accepted for future publication) Authors: Jarno Mielikainen Speaker: Chia-Chun Wu ( 吳佳駿 ) Date: 2006/03/13. Outline. Introduction LSB replacement The proposed scheme Experimental results Conclusions Comments.

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LSB Matching Revisited

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  1. LSB Matching Revisited Source: IEEE Signal Processing Letters (Accepted for future publication) Authors: Jarno Mielikainen Speaker: Chia-Chun Wu (吳佳駿) Date: 2006/03/13

  2. Outline • Introduction • LSB replacement • The proposed scheme • Experimental results • Conclusions • Comments

  3. Internet Introduction • Steganographic Stego image Cover image Secret message: 01011001110…

  4. LSB replacement xi xi+1 mi mi+1 yi yi+1

  5. Example: f (161, 150) = 0 f (163, 150) = 1 f (162, 150) = 1 f (162, 150) = 1 f (162, 151) = 0 The proposed scheme • Modified version of the LSB method • Binary function f (l, n) Property 1: Property 2:

  6. Embedding algorithm Embedding algorithm for a pair of pixels.

  7. Case 1: embedding “0”, “0” 10100010 10010111 0 0 162 151 yi yi+1 mi mi+1 Case 2: embedding “0”, “1” 162 150 0 1 10100010 10010110 yi yi+1 mi mi+1 Embedding messages (1/3) xi xi+1

  8. Embedding messages (2/3) Case 3: embedding “1”, “0” xi xi+1 mi+1 mi yi yi+1 f (163, 150) = 1 f (161, 150) = 0

  9. Embedding messages (3/3) Case 4: embedding “1”, “1” xi xi+1 mi mi+1 yi yi+1 f (163, 150) = 1 f (161, 150) = 0

  10. Extracting messages xi xi+1

  11. Example - 1

  12. Example - 2

  13. Experimental results (1/2) • 1000 JPEG images • All size 384×256 • HCF COM detectors The center of mass (COM) of the histogram characteristic function (HCF) introduced by Harmsen et al. [4] Ker [5] proposed using the adjacency histogram instead of the usual histogram.

  14. Experimental results (2/2) The x-axis has been scaled to focus on a region of interest. ROC curves for the calibrated adjacency HCF COM. ROC curves for the calibrated HCF COM.

  15. Conclusions • The proposed method allows an embedding of the same amount of information into the stego image as LSB matching but with fewer changes to the cover image. • The detection of the existence of the hidden messages using the HCF COM-based detectors is less efficient against the method compared to LSB matching.

  16. Comments • The embedding cannot be performed for saturated pixels, i.e., pixels that have either a minimal (0) or maximal (255) allowable value.

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