Size-Adjustable Visual Secret Sharing Schemes

Ching-Nung YANG  Tse-Shih CHEN  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E88-A   No.9   pp.2471-2474
Publication Date: 2005/09/01
Online ISSN: 
DOI: 10.1093/ietfec/e88-a.9.2471
Print ISSN: 0916-8508
Type of Manuscript: LETTER
Category: Information Security
visual secret sharing scheme,  visual cryptography,  secret sharing scheme,  

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Visual secret sharing (VSS) scheme is a perfect secure method that protects a secret image by breaking it into shadows. Unlike other secret sharing schemes, the VSS scheme can be easily decoded by the human visual sight when staking the shadows. We replace a pixel in the secret image by m sub pixels in the shadow image and the value m is called as pixel expansion. In general, most papers are dedicated to find the minimum m for a VSS scheme, i.e. a smaller shadow size. However, it seems that no one studies how to trade the shadow size for the contrast. In this paper, we take the lead in studying size-adjustable VSS schemes such that one can choose appropriate shadow size and the recovered image contrast for practical use.