Weighted Visual Cryptography with Non-Expansible Shares

In this paper, a non-expansible visual cryptography (VC) scheme with weighted-style is designed in this paper. The n weighted transparencies {t_1, t_2,…, t_n}, called shares, are generated to share a secret image. No single share can reveal any information about the secret image. However, when we stack at least two shares, the secret image is revealed to an extent; and the revealed contrast level is (SUM{weights} - MAX{weights})/(p×q). (Here, both SUM and MAX operators are evaluated using the set of the shares being stacked, which is a subset of {t_1, t_2,…, t_n}, and p×q means encoded block size.) The proposed VC scheme is fault-tolerant and with progressive contrast; furthermore, if weights are suitably chosen, then our best contrast is often higher than that of every reported design.