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Cheating immune threshold visual secret sharing

Cheating immune threshold visual secret sharing. Author: R. De Prisco and A. De Santis Source: The Computer Journal, 2009 Presenter: Yu-Chi Chen. Outline. Introduction Model of VC Definition of cheating A better (2, n )-threshold scheme Conclusions. Introduction.

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Cheating immune threshold visual secret sharing

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  1. Cheating immune threshold visual secret sharing Author: R. De Prisco and A. De Santis Source: The Computer Journal, 2009 Presenter: Yu-Chi Chen

  2. Outline • Introduction • Model of VC • Definition of cheating • A better (2,n)-threshold scheme • Conclusions

  3. Introduction • Visual Cryptography (visual secret sharing) • Naor and Shamir, 1994 • Cheating in VC • Horng et al., 2006 • A speech in our seminar, 1/14, by C.C. Chang.

  4. Introduction • Two types of cheating prevention in VC • Share authentication • Blind authentication • De Prisco and De Santis presented a formal definition for cheating, and described deterministic cheating.

  5. Introduction • De Prisco and De Santis proposed a better (2,n) scheme that is blind authentication and immune to deterministic cheating without relying on a complementary image. • The previous schemes have to use a complementary image to protect both black and white pixels.

  6. Outline • Introduction • Model of VC • Definition of cheating • A better (2,n)-threshold scheme • Conclusions

  7. Model of VC - (k,n) • Encoding: Given a secret image, the dealer generates n transparencies, where k transparencies can stack to recover the secret image. • Distributing: The dealer gives each transparencies to each participant. • Decoding: k participants can recover the secret image by stacking their transparencies.

  8. Definition of cheating • Deterministic cheating • pr(0→1)=1 and pr(1→0)=1 for all pixels • Cheating immune • pr(0→1)<1 and pr(1→0)<1 for all pixels

  9. Outline • Introduction • Model of VC • Definition of cheating • A better (2,n)-threshold scheme • Conclusions

  10. A better (2,n)-threshold scheme • A pixel becomes 2n+1+n subpixels. The base matrix is n × (2n+1+n). • 2n: binary coding • 1: all 0 column • n: Naor-Shamir’s VC

  11. Base matrices of (2,3)

  12. Security analysis • They have proven this scheme is immune to deterministic cheating. • The cheaters are impossible to make sure the subpixel is 1 or 0 in victim’s. • The formal proof is given in the paper by De Prisco and De Santis.

  13. Conclusions • The better scheme is the most secure scheme against deterministic cheating without relying on a complementary image.

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