Visual cryptography for general access structures
Information and Computation
Constructions and Properties of k out of nVisual Secret Sharing Schemes
Designs, Codes and Cryptography
New Colored Visual Secret Sharing Schemes
Designs, Codes and Cryptography
Threshold Visual Cryptography Schemes with Specified Whiteness Levels of Reconstructed Pixels
Designs, Codes and Cryptography
Improved Schemes for Visual Cryptography
Designs, Codes and Cryptography
New visual secret sharing schemes using probabilistic method
Pattern Recognition Letters
Optimal colored threshold visual cryptography schemes
Designs, Codes and Cryptography
Probabilistic Visual Cryptography Schemes
The Computer Journal
Efficient visual secret sharing scheme for color images
Pattern Recognition
Colored visual cryptography without color darkening
Theoretical Computer Science
Cheating Immune Threshold Visual Secret Sharing1
The Computer Journal
Using colors to improve visual cryptography for black and white images
ICITS'11 Proceedings of the 5th international conference on Information theoretic security
Visual Cryptography and Secret Image Sharing (Digital Imaging and Computer Vision)
Visual Cryptography and Secret Image Sharing (Digital Imaging and Computer Vision)
Towards Shift Tolerant Visual Secret Sharing Schemes
IEEE Transactions on Information Forensics and Security
Embedded Extended Visual Cryptography Schemes
IEEE Transactions on Information Forensics and Security
Optimum Pixel Expansions for Threshold Visual Secret Sharing Schemes
IEEE Transactions on Information Forensics and Security - Part 2
A Probabilistic Model of $(t,n)$ Visual Cryptography Scheme With Dynamic Group
IEEE Transactions on Information Forensics and Security - Part 2
An Extended Visual Cryptography Algorithm for General Access Structures
IEEE Transactions on Information Forensics and Security - Part 2
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In this paper we propose the use of colors to improve visual cryptography schemes for black-and-white secret images. The resulting model is called colored-black-and-white visual cryptography (cbw-vc) model. Using this new model we exploit colors to obtain schemes to share b&w images using a smaller pixel expansion. In particular we provide (2,n)-threshold schemes with pixel expansion m=@?log"3n@?, improving on the best pixel expansion attainable in the normal b&w model (bw-vc). For the case of schemes with perfect reconstruction of black pixels we provide a general construction that allows us to transform any bw-vc scheme into a cbw-vc scheme whose pixel expansion is 1/3 of the pixel expansion of the starting bw-vc scheme. We prove that, in the cbw-vc model, it is not possible to construct (2,n)-threshold schemes, for n=4, and (k,n)-threshold schemes, for k=3, without pixel expansion. We also prove that there exist schemes with optimal contrast in the subset of schemes that use only full intensity colors; this is a direct consequence of the definition of contrast which distinguishes only black and non-black pixels. We discuss an alternative measure of contrast that takes into account the ''distance'' between colors. We conjecture that also with this definition of contrast there exist schemes that use only full intensity colors and achieve optimal contrast.