### Visual Cryptography Schemes with Optimal Pixel Expansion

Carlo Blundo, Stelvio Cimato, and Alfredo De Santis

##### Abstract

A visual cryptography scheme encodes a black&white secret image into n shadow images called shares which are distributed to the n participants. Such shares are such that only qualified subsets of participants can visually'' recover the secret image. Usually, the reconstructed image will be darker than the background of the image itself. In this paper we consider visual cryptography schemes satisfying the model introduced by Tzeng and Hu (Designs, Codes and Cryptography, Vol. 27, No. 3, pp. 207-227, 2002). In such a model the recovered secret image can be darker or lighter than the background. We prove a lower bound on the pixel expansion of the scheme and, for (2,n)-threshold visual cryptography schemes, we provide schemes achieving the bound. Our schemes improve on the ones proposed by Tzeng and Hu.

Available format(s)
Publication info
Published elsewhere. Unknown where it was published
Keywords
Visual cryptographyPixel expansion.
Contact author(s)
carblu @ dia unisa it
History
Short URL
https://ia.cr/2006/170

CC BY

BibTeX

@misc{cryptoeprint:2006/170,
author = {Carlo Blundo and Stelvio Cimato and Alfredo De Santis},
title = {Visual Cryptography Schemes with Optimal Pixel Expansion},
howpublished = {Cryptology ePrint Archive, Paper 2006/170},
year = {2006},
note = {\url{https://eprint.iacr.org/2006/170}},
url = {https://eprint.iacr.org/2006/170}
}

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