Cheating in Visual Cryptography

  • Authors:

  • Gwoboa Horng;Tzungher Chen;Du-Shiau Tsai

  • Affiliations:

  • Department of Computer Science, National Chung Hsing University, Taichung, R. O. C 40227;Department of Computer Science, National Chung Hsing University, Taichung, R. O. C 40227;Department of Information Management, Hsiuping Institute of Technology, Dali City,Taichung County 412, Taiwan R. O. C.

  • Venue:
  • Designs, Codes and Cryptography
  • Year:
  • 2006

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Abstract

A secret sharing scheme allows a secret to be shared among a set of participants, P, such that only authorized subsets of P can recover the secret, but any unauthorized subset cannot recover the secret. In 1995, Naor and Shamir proposed a variant of secret sharing, called visual cryptography, where the shares given to participants are xeroxed onto transparencies. If X is an authorized subset of P, then the participants in X can visually recover the secret image by stacking their transparencies together without performing any computation. In this paper, we address the issue of cheating by dishonest participants, called cheaters, in visual cryptography. The experimental results demonstrate that cheating is possible when the cheaters form a coalition in order to deceive honest participants. We also propose two simple cheating prevention visual cryptographic schemes.