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Capacity-Approaching Codes for Reversible Data Hiding

Capacity-Approaching Codes for Reversible Data Hiding. Weiming Zhang, Biao Chen, and Nenghai Yu Department of Electrical Engineering & Information Science University of Science and Technology of China Information Hiding Conference 2011. What is reversible data hiding?. Introduction.

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Capacity-Approaching Codes for Reversible Data Hiding

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  1. Capacity-Approaching Codes for Reversible Data Hiding Weiming Zhang, Biao Chen, and Nenghai Yu Department of Electrical Engineering & Information Science University of Science and Technology of China Information Hiding Conference 2011

  2. What is reversible data hiding? Introduction • The original cover can be losslessly restored after the embedded information is extracted. message data extraction & cover restoration message data embedding stego cover cover

  3. What is reversible data hiding? Introduction • The original cover can be losslessly restored after the embedded information is extracted. • Why is reversible data hiding needed? • In some applications, even any degradation of the original cover is not allowed, such as medical imagery, military imagery and law forensics. • Where is reversible data hiding applied? • Media annotation; • integrity authentication ...

  4. How to do reversible data hiding? Introduction • Type-I: Binary feature sequence, generic compression method (e.g., arithmetic coder); • Type-II: Integer operations: Difference Expansion (DE) or Histogram Shifting (HS)— specific compression manner for the histogram

  5. Type-I: Basic model [Kalker] Introduction d modifications • Embedding rate: • Distortion: • How to maximize embedding rate under any given distortion? A rate-distortion problem

  6. Introduction • Theoretical upper bound [Kalker]

  7. Introduction • RecursiveCode construction [Kalker] • Key idea: • the marked cover can be used to reconstruct the cover

  8. Observation I Two observations • Not only the marked cover can be used to reconstruct the cover, but also the reconstructed cover can help to extract message.

  9. Two observations • Observation II

  10. Observation II Two observations • The maximum capacity is achieved at D=p0－1/2; • When D≤p0－1/2, the optimal embedding manner is that only 0’s are allowed to be changed. (Corollary 1 of Theorem 2, [Kalker]) • Our strategy: • Only embed data into 0’s and skip 1’s; • At the decoder side, the embedding positions can be recognized with the help of reconstructed cover.

  11. RZL coding (reverse zero-run length) [Wong] How to embed data into all-zero cover • Message is divided into disjoint segments of k bits, each of which is converted to a integer d∈[0,2k-1]; skip d zeros in the cover, and flip the (d+1)th zero. • Our method: improve RZL by the idea of ZZW construction • A construction consists of two layers: • The outer layer: only embed one bit; • The inner layer: when embedding bit “1” in the outer layer, embed another k bits with RZL; otherwise skip 2k zeros.

  12. Example:k = 2 How to embed data into all-zero cover

  13. How to embed data into all-zero cover

  14. Proposed method Improved recursive construction Improved coding for all-zero cover x1: 0 1 y1: 0 1 1

  15. Proposed method Example 2 (follows Example 1)

  16. Comparison: Embedding efficiency vs. embedding rate Embedding efficiency e is defined as number of bits embedded by unit distortion, i.e. e=ρ/Δ=L/d.

  17. Comparison: Embedding efficiency vs. embedding rate

  18. Improving Type-I Schemes (embedding in binary feature sequences) 1. Improving RS method for spatial images [Fridrich] Texture complexity of pixel blocks is used to construct binary feature sequence.

  19. Improving Type-I Schemes 1. Improving RS scheme for spatial images [Fridrich]

  20. Improving Type-I Schemes 2. Improving the scheme for JPEG images [Fridrich] quantized DCT coefficients with value 0 and 1 are used as binary feature sequence.

  21. Improving Type-I Schemes 2. Improving the scheme for JPEG images [Fridrich]

  22. Improving Type-I Schemes 3. Improving PS scheme for binary images [Ho] Y.-A. Ho, et al., ``High capacity reversible data hiding in binary images using pattern substitution,” Computer Standards and Interfaces, 2009. Test images Patterns of 4-length vector in difference image are used as binary sequence.

  23. Improving Type-I Schemes 3. Improving PS scheme for binary images

  24. Improving Type-I Schemes 3. Improving PS scheme for binary images Embed 260 bits (a) Marked by PS (b) Marked by improved PS

  25. Improving Type-II Scheme Improving HS-based scheme for spatial images [Luo] L. X. Luo, et al., ``Reversible Image Watermarking Using Interpolation Technique," IEEE Trans. Inf. Forensics and Security, 2010. • The proposed codes is used at the second embedding stage. • Extension by embedding with two bins.

  26. Improving Type-II Schemes 3. Improving HS-based scheme for spatial images (a) Lenna

  27. Improving Type-II Schemes 3. Improving HS-based scheme for spatial images (b) Baboon

  28. Improving Type-II Schemes 3. Improving HS-based scheme for spatial images (c) Boat

  29. Conclusion: • An improved coding method for all-zero cover • An improved recursive construction • A reversible data hiding method for binary cover • Future work: Integer-domain reversible data hiding

  30. Thank you for your attention!

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