User-Friendly Random-Grid-Based Visual Secret Sharing

Recently, the visual secret sharing (VSS) technique based on a random-grid algorithm (RGVSS), proposed by Kafri and Keren in 1987, has drawn attention in academia again. However, Kafri and Keren´s scheme is not participant-friendly; that is to say, the generated shared images are meaningless, so users feel that this huge amount of data is hard to manage. The literature has illustrated the concept of creating meaningful shared images, in which some shape or information appears for easing management, for VSS technique by visual cryptography (VCVSS). Those friendly VCVSS schemes are not directly suitable for RGVSS. Instead, a new friendly RGVSS must be designed. Most friendly VCVSS schemes worsen the pixel expansion problem, in which the size of shared images is larger than that of the original secret image, to achieve the goal of generic meaningful shares. As a result, in this paper we have focused on proposing a novel RGVSS scheme by skillfully designing a procedure of distinguishing different light transmissions on shared images based on the pixel values of the logo image with two primary advantages: no pixel expansion, and being user-friendly. In order to illustrate the correctness, the formal analysis is demonstrated while the experimental results show the proposed schemes do work.