K out of K Extended Visual Cryptography Scheme Based on “XOR”

Abstract

Visual cryptography schemes (VCS) is an encryption technique that utilizes human visual system in recovering secret image and it does not require any complex calculation. Many VCSs without pixel expansion have been proposed. But they recover secret image with low contrast due to the stacking operation. To improve the quality of recovered image, XOR-based VCS has been proposed. However, shares constructed from XOR-based VCS are random-looking. It suffers a management problem which dealers cannot visually identify each share. In this paper, we propose an (k, k) extended visual cryptography scheme (EVCS) by "XOR" operation to solve above mentioned problem. This is implemented by diving the share image into two parts using a parameter and operating the secret pixels and cover pixels respectively. Comparing with previous schemes, the qualities of share images and recovered image are improved, and our scheme also suit the "OR" operation.