Cryptography Reference
In-Depth Information
11
Resolving the Alignment Problem in Visual
Cryptograp
hy
Feng Liu
Institute of Software, Chinese Academy of Sciences, China
CONTENTS
11.1
Introduction :::::::::::::::::::::::::::::::::::::::::::::::::::::: 297
11.2
Preliminaries ::::::::::::::::::::::::::::::::::::::::::::::::::::: 299
11.3
Misalignment with Integer Number of Subpixels :::::::::::::::: 302
11.4
Misalignment with Less Than One Subpixel :::::::::::::::::::: 309
11.4.1
Shares with Slightly Misalignment Can Still Recover the
Secret Image ::::::::::::::::::::::::::::::::::::::::::::: 310
11.4.2
Large Subpixels Have Better Misalignment Tolerance :: 316
11.5
A Misalignment Tolerant VCS ::::::::::::::::::::::::::::::::::: 319
11.5.1
The Algorithm ::::::::::::::::::::::::::::::::::::::::::: 319
11.5.2
Simulations :::::::::::::::::::::::::::::::::::::::::::::: 322
11.6
Conclusions and Discussions ::::::::::::::::::::::::::::::::::::: 325
11.7
Acknowledgments :::::::::::::::::::::::::::::::::::::::::::::::: 325
11.1 Introduction
The basic principle of the Visual Cryptography Scheme (VCS) was first for-
mally introduced by Naor and Shamir [10]. The idea of the VCS proposed
in [10] is to split an image into two random shares (printed on transparen-
cies), which separately reveal no information about the original secret image
other than the size of the secret image. The image is composed of black and
white pixels. The original image can be recovered by stacking the two trans-
parencies together.
One important parameter in VCS is pixel expansion, where the pixel ex-
pansion reflects the size of the recovered secret image. Many papers in the
literature are dedicated to proposing VCS with smaller pixel expansion. How-
Search WWH ::
Custom Search