Visual cryptography

About: Visual cryptography is a research topic. Over the lifetime, 1724 publications have been published within this topic receiving 25300 citations.

The Comparative Study on Visual Cryptography and Random Grid Cryptography

Abstract: Visual cryptography scheme is a cryptographic technique which allows visual information to be encrypted into several shares in such a way that the decryption can be performed by the human visual system, without the aid of computers. Random grid is a methodology to construct visual secret sharing (vss) scheme without pixel expansion in which an RG scheme takes an input image and transforms it into multiple cipher- grids that provide no information on the original image and the resulting decrypted image retains the size of the original image. Intent of this paper is on comparative study of visual cryptography and Random grid cryptography on the basis of analysis and correctness of simple VC schemes and RG schemes, i mproving contrast of the reconstructed image using various algorithms and multiple-image encryption using rotating angles. Keywords - ideal contrast, random grid scheme, ring shadow technology, rotating random grids, visual cryptography scheme.

A Novel Weighted Visual Cryptography Scheme with High Visual Quality.

Abstract: Visual Cryptography (VC) has been developed to encode a secret image into n shares for n participants in the past decades, in which each share is treated with the same priority. However, the privilege for participants in a group is not always the same. In this paper, a weighted visual cryptography scheme is proposed such that each participant obtains her/his share with different weight according to the different group of predefined privilege. The secret can be disclosed only if stacking predefined k or more shares in which containing predefined some specific shares from the specific groups. Otherwise, no information about the secret can be revealed. It is worthwhile to note that the higher value of total weight of stacking shares; the more information about the secret revealed from the stacked result. The experimental results demonstrate that the proposed scheme does work.

A Multiple Watermarking Scheme for Gray-Level Images using Visual Cryptography and Integer Wavelet Transform

Abstract: A multiple watermarking scheme for gray-level images by using visual cryptography, modified histogram, integer wavelet transform, and the wavelet tree is presented. The process rearranges the share im- age and embeds it in the coefficients of the corresponding IWT middle frequencies, and the owner keeps an- other share image as the key. Under this scheme, all owners will have dual watermark authentication, and through this method, the number of ownerships can be increased. The goal of the proposed scheme for multi- ple watermarking is to satisfy more requirements of the watermarking characteristics. From security point of view, without the personal key share images, even if the hidden share images were retrieved to obtain the original share image, the watermark information remains unavailable. Applying the proposed four points dis- tinguishing law and bitwise right shift operation, and the share image blocks deciphering rule, the owner's dual watermarks can be extracted to verify the ownership.

Trusted display device for visual cryptography

Abstract: A trusted display device (1) for, upon being superimposed on an untrusted display (2), reconstructing a graphical message, said device comprising a display screen (la) having a plurality of independently addressable pixels. A plurality of sensors (l c) are associated with at least a subset of the pixels of said display screen (l a) and arranged such that they, when the displays (1, 2) are superimposed, are able to detect optically encoded information presented by an underlying pixel of the untrusted display (2) and adapt the activation of its pixels based on said information sensed.

(2,n) Visual Threshold Scheme Based on Permutation

Abstract: Two parameters,pixel expansion and contrast,are very important in visual cryptography.It's very difficult to optimize both of them in theory.Based on permutation,a(2,n)scheme,which existence has been proved theoretically,is proposed.The method of construction has been carried out.Simulation results demonstrate that this scheme can balance performance between pixel expansion and contrast,i.e.,when the contrast is close to optimality,the pixel expansion is relatively minor.