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Progressive Visual Cryptography with Unexpanded Shares

Progressive Visual Cryptography with Unexpanded Shares. Source: IEEE Transactions on Circuits and Systems for Video Technology, Volume PP, Issue 99, January 2011 Authors: Young-Chang Hou and Zen-Yu Quan Speaker: Marcos Date: 2011/03/24. Outline. Introduction Related Work Proposed Method

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Progressive Visual Cryptography with Unexpanded Shares

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  1. Progressive Visual Cryptography with Unexpanded Shares Source: IEEE Transactions on Circuits and Systems for Video Technology, Volume PP, Issue 99, January 2011 Authors: Young-Chang Hou and Zen-Yu Quan Speaker: Marcos Date: 2011/03/24

  2. Outline • Introduction • Related Work • Proposed Method • Experimental Results • Conclusions

  3. Introduction • Proposed Method • Progressive VSS (halftone images) • No pixel expansion • More than 50% contrast

  4. Related WorkFang and Lin’s Progressive Visual Sharing Scheme • Disadvantages: • Black block darker than white one - > security problem • Candidate blocks randomly choose -> poor quality of the recovered image • Pixel expansion -> shares 4x more than secret image

  5. Proposed Scheme (1/2) • Input: W x H halftone secret image P (3x3) • Output: n (4) shares Sm, m = 1 , … , n (4) (S1, S2,S3, S4) Step 1: Generate sharing matrices C0 (white pixels) and C1 (black pixels) (n x n - 4x4) Row: sharing method Column: value assigned to every participant Probability of each pixel on the shares to be black: 1/n (1/4)

  6. Proposed Scheme (2/2) • Input: W x H halftone secret image P (3x3) • Output: n (4) shares Sm, m = 1 , … , n (4) (S1, S2,S3, S4) Step 2: Generate n (4) shares (S1, S2,S3, S4) 0 0 1 1 0 0 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0 1 0 0 l = 3 l = 4 1 1 1 0 0 0 0 0 0 0 0 0

  7. Experimental Results (1/3)

  8. Experimental Results (2/3)

  9. Experimental Results (3/3)

  10. Conclusions • Fang and Lin Scheme • Pixel expansion (4) • Poor quality of the recovered image • Security problem (shares with secret information) • Proposed Scheme • No pixel expansion • Better image quality => (n-1)/n • Shares noise-like

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