Construction of a Monochrome Visual Cryptographic Scheme Using Latin Squares
by
Avishek Adhikari
INRIA-Rocquencourt, Projet CODES, BP 105, 78153 Le Chesnay, France
Coauthors: Mausumi Bose, Applied Statistics Unit, Indian Statistical Institute, 203 B. T. Road, Kolkata-700 108, India.

We consider the problem of visual cryptography where printed or handwritten material is encrypted in a secure way which can subsequently be decoded by the human visual system in a simple manner. For such schemes two parameters are very important viz. pixel expansion and relative contrast. Optimizing both is a very hard problem. The schemes having optimal relative contrast tend to use a high pixel expansion. The focus of the paper is to construct schemes for which pixel expansion is modest and the contrast is close to optimality. Here the tool is latin squares. In this paper we show how latin square may be used to obtain good visual cryptographic schemes. We obtain scheme for black and white texts. The scheme is fully secure and easy to implement.

Date received: October 28, 2005