Research & Publication
Abstract:Visual cryptography (VC) is a paradigm of cryptography which prevents a secret from being modified or destructed by using the notions of perfect cipher and can be easily decoded by the human visual system. It doesn’t require any complex cryptographic computations. This visual secret sharing scheme is developed by Moni Naor and Adi Shamir in 1994. In this scheme an image is divided into n shares, so that only someone with all k (k<n) shares can decode the secret, while k-1 shares will not reveal any information about the original secret image. But these initial schemes of visual cryptography suffer from many drawbacks such as: pixel expansion, share management difficulty, etc. So this paper discusses three visual cryptography schemes: OR-based (n, n) VCS, XOR-based (n, n) VCS and extended (n, n) VCS; using random grids. Since RG is used here all the three schemes were designed without pixel expansion. (n, n) extended VCS offers better share management without pixel expansion. This method also removes the restriction of using one cover images for all generated shares. The proposed (n, n) extended VCS provide meaningful share images with improved security and visual quality.