Visual Cryptography for Multiple Secrets - Visual Cryptography and Secret Image Sharing - page 56

3

Visual Cryp tography for Multiple Secrets

Shyong Jian Shyu
Ming Chuan University, Taiwan

CONTENTS
3.1 Introduction :::::::::::::::::::::::::::::::::::::::::::::::::::::: 57

3.2 Naor and Shamir's Basic Visual Secret Sharing Scheme :::::::: 59

3.3 Visual Two-Secret Sharing Schemes ::::::::::::::::::::::::::::: 61

3.3.1 Wu and Chen's Scheme :::::::::::::::::::::::::::::::::: 62

3.3.2 Wu and Chang's Scheme :::::::::::::::::::::::::::::::: 64

3.4 Visual Multiple-Secret Sharing Schemes ::::::::::::::::::::::::: 68

3.4.1 Shyu et al.'s Scheme ::::::::::::::::::::::::::::::::::::: 68

3.4.1.1 Informal Description ::::::::::::::::::::::::: 68

3.4.1.2 Encoding Circle Share A ::::::::::::::::::::: 69

3.4.1.3 Encoding Circle Share B ::::::::::::::::::::: 71

3.4.1.4 General Algorithm ::::::::::::::::::::::::::: 80

3.4.2 Feng et al.'s Scheme ::::::::::::::::::::::::::::::::::::: 83

3.4.3 Experimental Results :::::::::::::::::::::::::::::::::::: 84

3.4.4 Comparison and Discussions :::::::::::::::::::::::::::: 87

3.5 Concluding Remarks ::::::::::::::::::::::::::::::::::::::::::::: 91

Bibliography :::::::::::::::::::::::::::::::::::::::::::::::::::::::: 92

3.1 Introduction
Visual cryptography proposed by Naor and Shamir [7] discloses the possibility
for using human visual ability to perform the decryption process. Specifically,
one secret image is encoded into two shares that are seemingly random pic-
tures. By xeroxing them onto transparencies, the dealer distributes the two
random transparencies to two participants (one share for each participant).