1. Steganography of Reversible Data Hiding Producer: Chia-Chen Lin Speaker: Paul 2013/06/26

2. 2 Outline ♠ Introduction ♠ Histogram shifting vs. reversible data hiding ●Three solutions ♠ Conclusions

3. 3 Introduction ♠ Technical Steganography ●Types Loss Lossless (reversible) ●General Criteria Image quality Payload Reversibility  lossless steganography reversible data hiding

4. 4 Histogram shifting vs. reversible data hiding  Zhicheng Ni, Yun-Qing Shi, Nirwan Ansari, and Wei Su, “Reversible data hiding,” IEEE Transactions on Circuits and Systems for Video Technology, Vol. 16, No. 3, 2006, pp. 354-362.

5. 5 Histogram Original gray-scale image Histogram of Lena image Source: Zhicheng Ni, Yun-Qing Shi, Nirwan Ansari, and Wei Su, “Reversible Data Hiding”, IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY(16:3), 2006. (P) (Z) Step 1: Generate an image histogram Ni et al.’s proposed method (1/7)

6. 6 Step 2: To shift the pixels of histogram (1)If P>Z → To shift the range of the histogram, [Z+1, P-1], to the left-hand side by 1 unit. (2)If P<Z → To shift the range of the histogram, [P+1, Z-1], to the right-hand side by 1 unit. ------------------------------------------------------------------------------------- Step 3: To hide the secret data by pixels P (1)If P>Z → To be embedded bit is “1”, the pixel value is changed to P-1. If the bit is ”0”, the pixel value remains. (2)If P<Z → To be embedded bit is “1”, the pixel value is changed to P+1. If the bit is ”0”, the pixel value remains. Ni et al.’s proposed method (2/7)

7. 7 Original image 26311 52611 23551 33126 33332 Peak pointZero point [3+1,6-1] 4 → 5 5 → 6 25311 42511 23441 33125 33332 P=3, Z=6 and P<Z shift to right-hand Ni et al.’s proposed method (3/7)

8. 8 26411 52611 24551 33126 44342 Using P=3, 0 → 3 1 → 4 Secret bits: 1 1 0 0 1 1 0 1 26311 52611 23551 33126 33332 Stego-image Ni et al.’s proposed method (4/7)

9. 9 26411 52611 24551 33126 44342 3 → 0 4 → 1 Stego-image P=3, Z=6 Extract 26411 52611 24551 33126 44342 Extracted secret bits: 1 1 0 0 1 1 0 1 25311 42511 23441 33125 33332 6 → 5 5 → 4 4 → 3 3 → 3 Recover Original image Ni et al.’s proposed method (5/7)

10. 10 Maximum and minimum points maximum point minimum point Original image 25300 42516 23447 33125 33332 Ni et al.’s proposed method (6/7)

11. 11 Multiple pairs Original image 25300 42516 23447 33125 33332 Example of 2 pairs. P2Z1Z2P1 Ni et al.’s proposed method (7/7)

12. 12 ♠ Summary of Ni et al.’s scheme ●It is simple and efficient. ●The PSNR of the marked image is above 48dB. ●The pure payload is about 5k-80k bits for a 512*512 grayscale image

13. 13 Questions: ♠ How to increase the pixel number of peak point? ●Difference image ♠ Is there any different way to generate a difference image

14. 14  Chia-Chen Lin, Wei-Liang Tai and Chin-Chen Chang, “Multilevel reversible data hiding based on histogram modification of difference images,” Pattern Recognition, Vol. 41, Issue 12, December, 2008, pp. 3582-3591. Solution :

15. 15 Basic idea

16. 16 ♠ Hiding Phase Original Block 162156163160 161159158159 160161159155 158 156157 |162 – 156| = 6 |161 – 159| = 2 673 211 124 021 Message = “0110” 784 311 135 031 784 311 135 031 784 312 135 031 784 312 235 031 Original Image Difference Image Peak Point Lin et al.’s proposed method

17. 17 Lin et al.’s proposed method 1.For the first two pixels in each row 2.For any residual pixels

18. 18 ♠ Hiding phase 162156163160 161159158159 160161159155 158 156157 784 312 235 031 156 + 7 = 163 163156163160 161159158159 160161159155 158 156157 159 + 3 = 162 163156163160 162159158159 160161159155 158 156157 163156163160 162159158159 160162159155 158 156157 163156164160 162159158159 160162159155 158 156157 156 + 8 = 164 163156164160 162159158159 160162159155 158 155157 160 + 4 = 164 163156164160 162159158160 162159154 158 155156 Original image Stego-image Difference image Lin et al.’s proposed method

19. 19 ♠ Extracting and reversing phase 163156164160 162159158160 162159154 158 155156 784 312 235 031 Stego imageDifference image Peak Point = 1 784 312 235 031 784 311 135 031 0110 673 211 124 021 162156164160 162159158160 162159154 158 155156 162156164160 161159158160 161159154 158 155156 162156163160 161159158160 161159154 158 155156 162156163160 161159158160 161159154 158 156 162156163160 161159158159 160161159155 158 156157 Original image Message = Lin et al.’s proposed method (1/2)

20. 20 Conclusions ♠ Simple is good. ♠ Possible improvements ●Different shifting methods ●Apply different prediction algorithms

21. Thanks for your attention !