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High-Payload Image Steganography Using Two-Way Block Matching

High-Payload Image Steganography Using Two-Way Block Matching. IEEE Signal Processing Letters, vol. 13 no.3, March 2006 Ran-Zan Wang and Yeh-Shun Chen speaker: 李惠龍. Outline. Introduction Proposed scheme Experimental results Conclusion. Introduction. MSB. LSB. 8. 7. 6. 5. 4. 3. 2.

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High-Payload Image Steganography Using Two-Way Block Matching

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  1. High-Payload Image Steganography Using Two-Way Block Matching IEEE Signal Processing Letters, vol. 13 no.3, March 2006 Ran-Zan Wang and Yeh-Shun Chen speaker:李惠龍

  2. Outline • Introduction • Proposed scheme • Experimental results • Conclusion

  3. Introduction

  4. MSB LSB 8 7 6 5 4 3 2 1 Introduction • Substitution system • Least-significant-bit (LSB): utilize some mapping rules to embed the message in certain LSB planes of the cover image

  5. Proposed scheme Embed EB/OB, eind/oind, parameters and not-well-match blocks

  6. Proposed scheme • OCand and ECand blocks (amount 2t-1,respectively): • Generate Cand images by replacing the q LSB of CO with its (q+1) to 2q LSB. • Divide Cand image into blocks of size mxn • Two difference blocks PD(D) and ND(D), D={dij} • Use a threshold z and φ to choose OCand and ECand blocks (assign PD(D) to OCand and ND(D) to ECand) c Dist(Dc, Dj)< φ, c-z≤j <c

  7. Proposed scheme • IM blocks • OBr or EBr is defined to be the corresponding odd/even integer closest to μr.

  8. Proposed scheme • IM blocks EX: OBr ODIFFr Br μr=99 + EBr EDIFFr Br μr=99 +

  9. Proposed scheme • Find indices (oind and eind) Embed OBr and oindr or EBr and eindr

  10. Proposed scheme • Sufficiently large error • Dist(ODIFF, OCand) or Dist(EDIFF, ECand) contain large errors. • Directly embed these block in the CO. • The number of not-well-matched blocks:

  11. Proposed scheme • Embedding scheme • Hop method • Key: embedding location • encode by Huffman coding scheme • Embedded data: • Bases, indices, and not-well matched blocks (stego-image) • Parameters: him, wim, k, q, t, z, m, n, and φ • Huffman table

  12. Proposed scheme • Extraction scheme • Extract parameters, Huffman table, and stego-image • Decode stego-image to obtain the bases, indeius and not-well-matched blocks • Generate odd candidate blocks and even candidate blocks from stego-image • Construct IM.

  13. Proposed scheme • Construct IM. • If indi≠2t-1 • Base is odd: Baseindi+ the indith odd candidate block • Base is even: Baseindi+ the indith even candidate block • If indi=2t-1 • Take not-well-matched block

  14. Experimental Results • Parameters: q=2, t=16, z=3, φ=32, and a block size: 4x4

  15. 37.93dB (Stego and Cover) 32.41dB (extract and origin)

  16. Conclusion • Propose a high-payload image steganography method • High quality by two-way block-matching and hop scheme

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