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Step Construction of Visual Cryptography Schemes. IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY, VOL. 5, NO. 1, MARCH 2010 Feng Liu, Chuankun Wu , Senior Member, IEEE, and Xijun Lin. Reporter:Bibitana. Introduction.
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Step Construction of Visual Cryptography Schemes IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY, VOL. 5, NO. 1, MARCH 2010 Feng Liu, Chuankun Wu, Senior Member, IEEE, and Xijun Lin Reporter:Bibitana
Introduction • propose a step construction to constructGeneral access structure • VCSOR • VCSXOR • their scheme applies a technique to simplify the access structure • multiple share images • reduce the average pixel expansion (APE) • Applying a (2, 2) VCS recursively
Preliminaries (1/2) • V={1, 2, …,n}, Qual Forb= and Qual Forb=2V
Preliminaries (2/2) • (2, 2)-VCSOR (2, 2)-VCSXOR
STEP CONSTRUCTION OF VCS FOR GENERAL ACCESS STRUCTURE (1/4) • They propose 3 constructions of the step construction of general access structure VCS. • Each of the participants may take multiple share images with different pixel expansions.
STEP CONSTRUCTION OF VCS FOR GENERAL ACCESS STRUCTURE (2/4) • Example (3, 3)OR: APEOR=(2+4+4)/3=10/3, OR=1/4
STEP CONSTRUCTION OF VCS FOR GENERAL ACCESS STRUCTURE (3/4) • Example (3, 3)XOR: APEXOR=1, XOR=1
STEP CONSTRUCTION OF VCS FOR GENERAL ACCESS STRUCTURE (4/4) • (n, n)-VCS can achieve by applying (2, 2)-VCS for n-1 times • APEOR=(3*2n-1-2)/n • OR=2-(n-1) • optimal pixel expansion and contrast
Simplifying the Access Structure by Using Equivalent Participants (1/3) • Participant i is equivalent to j • they can be assigned to identical shares without affecting the access structure
Simplifying the Access Structure by Using Equivalent Participants (2/3)
Simplifying the Access Structure by Using Equivalent Participants (3/3) • Example of construction 1: • (2, 2)-VCS, first share assing {1, 4} and another assing to {2, 3}
Thank You!! • Next Week will present: • Construction 2, • Construction 3 • The rest session of the paper.