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On the Contrast in Visual Cryptography Schemes
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| Abstract: | A visual cryptography scheme is a method to encode a secret image SI into shadow images called shares such that certain qualified subsets of shares enable the ``visual'' recovery of the secret image. The ``visual'' recovery consists of xeroxing the shares onto transparencies, and then stacking them. The shares of a qualified set will reveal the secret image without any cryptographic computation. In this paper we analyze the contrast of the reconstructed image in k out of n visual cryptography schemes. (In such a scheme any k shares will reveal the image, but no set of k-1 shares gives any information about the image.) In the case of 2 out of n threshold schemes we give a complete characterization of schemes having optimal contrast and minimum pixel expansion in terms of certain balanced incomplete block designs. In the case of k out of n threshold schemes with k>2 we obtain upper and lower bounds on the optimal contrast. |
BibTeX
@misc{eprint-1996-11279,
title={On the Contrast in Visual Cryptography Schemes},
booktitle={IACR Eprint archive},
keywords={},
url={http://eprint.iacr.org/1996/013},
note={Appeared in the THEORY OF CRYPTOGRAPHY LIBRARY and has been included in the ePrint Archive. carblu@udsab.dia.unisa.it 10500 received September 25, 1996.},
author={Carlo Blundo and Alfredo De Santis and Douglas R. Stinson},
year=1996
}