Random Grid and Deterministic Visual Cryptography with Enhanced color patterns

Abstract

Visual Cryptography Scheme (VCS) is an encryption method used to encode secret written materials. It converts the written material into a binary image and encode this image in to 'n' shadow image. This image is called as share images. The decoding process requires selecting some subset of the n shadow images, and stacking them on top of each other. Each user holds a transparency. The previous research works on visual cryptography focuses on two parameters: large pixel expansion and contrast. Further, the number of sub pixels (m) for encoding each secret pixel, referred to as the pixel expansion, is to be reduced. The pixel expansion and relative contrast are the most critical measurements to evaluate the effectiveness of a VCS[17]. In this paper we develop a novel and efficient construction for Random Grid and DVCS which aims at the minimization of the pixel expansion and maximal contrasts for individual VC. The Experimental result is expected to have better feasibility and flexibility of our construction. The pixel expansions and obtained in our scheme are better than the previous results.