A (2,2) XOR-based visual cryptography scheme without pixel expansion

摘要

Visual cryptography (VC) is a technique that encodes the content of a secret image into two or more images, which are called shares. These shares are printed on transparencies and superimposed to reveal the original secret image. Frequently, VC techniques require a pixel expansion and a good alignment, which reduces the final spatial resolution. In this paper, we propose a physical VC scheme that only requires two shares and do not demand a pixel expansion. The first share is a colored transparency printed on a Polyvinyl Chloride (PVC) surface of 3 mm, while the second share is a colored image displayed on a smartphone screen. The decoded pixels of the proposed scheme have defined colors and a good resolution. We perform a physical evaluation of the color interference properties of the two shares, to find the most adequate color space, and test the proposed method with practical examples. (C) 2019 Elsevier Inc. All rights reserved.