On Cheating in Visual Cryptography

• Main Authors: Dushiau Tsai, 蔡篤校
• Other Authors: Gwoboa Horng
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/73127035023480845097

碩士 === 國立中興大學 === 資訊科學研究所 === 91 === 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 can not recover the secret. In 1994, Noar and Shamir proposed a variant of secret sharing scheme called k-out-of-n threshold visual cryptography where the shares given to participants are xeroxed onto transparencies. If more then k transparencies are stacked together, the secret message can visually recovered by anyone without any cryptographic knowledge and without performing any cryptographic computation. In this thesis, we consider the cheating problem in visual cryptography. We show that cheating is possible when the cheaters form a coalition to deceive honest participants. For preventing cheating, an explicit definition of cheating is given; moreover, two cheating protection schemes are proposed to safeguard the honest participants in visual cryptography.