Research On Cheater Preventable Visual Cryptography

Visual cryptography is a new secret sharing scheme introduced by Naor and Shamir at Eurocrypt 94.The scheme conceals secret images into several transparencies called�'hares? From the unqualified set of shares,participants can not get any information of the secret image. In the processing of recovering,the participants only need to stack their shares and are able to decrypt the secret by their visual system without any knowledge of cryptography and without performing any cryptographic computation and using any cryptographic equipment.Visual cryptography system is privy,secure,simple and universal.The shares are keys of the others mutually.They are produced independently each time and only used one time.The share is not smaller than the secret image in size,so visual cryptography is similar to搊ne time pad? cryptographic system.There are cheating problems in visual cryptography as same as in other secret sharing schemes.A cheater can use a fake share to spoil the recover of secret or grab the secret by deception.But the participants can not find who the cheater is.By(k,n)-VCS and(k-1,k-1) -VCS,a cheater preventable VCS is designed.There are no fringes in the reconstructed image so that the secret information can be recognized clearly.Based on the scheme,a multi-secret sharing VCS which can share more than one image at a time is constructed.A cheater preventable VCS based on cumulative array was also introduced in this paper.Compared to previous schemes,it is more convenient and can find more cheaters.The two cheater-preventable VCSs proposed in this paper can find the cheater and prevent the cheating without extra information and don抰show any information of the secret image.In this paper,we studied verifiable visual cryptography schemes by adding a verifier to common visual cryptography scheme.We proposed four schemes and analyzed them.We gave the construction of a better scheme.This scheme can be used in any access structures and can check every share in order to prevent cheaters from spoiling and grabbing the secret information.