A new authentication based cheating prevention scheme in Naor–Shamir’s visual cryptography

Prevention of cheating in visual cryptography by using coherent patterns

“…The pixel expansion m refers to the number of pixels in a share used to encode a pixel of the secret image. According to the properties in Table 1, the proposed method can encode the n base-shares into the n verifiable-shares without deriving the extra shares [6], verification shares [4,5,7,20,22], and pixel expansion [4,5,22]. Moreover, the size of the n verifiable-shares of the proposed method is same as the original base-shares.…”

“…Hence, the contrast of the base-shares is unaltered. The degraded contrasts of the CPVC scheme [4,5,20,22], method 2 of the scheme in [7], and the proposed method are listed in the last column of Table 1. For the overall comparisons, the proposed CPVC method is practical and can endow conventional VC schemes with the ability to prevent cheating without carrying additional verification shares and pixel expansion shares.…”

“…Later, Hu and Tzeng [4] presented three robust methods to improve the weaknesses of the above cheating prevention VC schemes [5,7]; two of the robust methods were for conventional VC schemes, and the other method was for the extended VC scheme. Based on Hu and Tzeng's scheme, the CPVC schemes [20][21][22] generate extra n verification shares to verify the genuineness of shares. Other cheating prevention VC schemes have been proposed using hybrid codebooks or efficient pixel expansion [3,17].…”

“…Other cheating prevention VC schemes have been proposed using hybrid codebooks or efficient pixel expansion [3,17]. However, the previous CPVC schemes require an additional verification share [4,20,22] and/or greater pixel expansion [4,5,22] to make it possible to resist cheating by malicious participants.…”

Cheating Immune Block-Based Progressive Visual Cryptography

“…There are already many cheating immune VCSs by additional information, e.g., using verification shadows or images [10][11][12][13][14][15]. Here, we construct a cheating immune (2, n)-BPVCS without the use of extra information.…”