Visual cryptography

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

Multiple Image Encryption using Random Circular Grids and Recursive Image Hiding

Abstract: visual secret sharing (VSS) scheme encrypts the secret information into various meaningless shares. These shares are distributed to the authorized participants and the secret information can be retrieved by any k out of n participants by stacking their respective shares on top of each other. This scheme uses HVS (Human Visual System) to decrypt the information, and thus no technical or financial investment is required. Moreover, it is a one-time pad technique, so decrypting the information by an attacker is almost impossible. This paper proposes an improved visual secret sharing technique in which we aim to build upon the random grid approach of visual cryptography and test the feasibility of Recursive Image Hiding to hide multiple secrets at varying levels of the grids generated. Since we are using circular random grids, it is even possible to hide multiple images in the same grids and obtain the secret images for different angles of rotation of the grids. The participants need to be in possession of both the shares, as well as the fixes angle of rotation for which the secret can be obtained, in order to decrypt the image. In case of recursive image hiding, numerous secrets are hidden recursively in the shares of the original images at each level. Shares carry information for the subsequent secrets as well, thus leading to increased capacity. Also, the limitation on the number of secrets that can be hidden can be overcome because for each grid, multiple secrets can be recursively hidden. Thus, not only will we be able to hide multiple images, but multiple grids as well which in turn carry the information for multiple images.

Feed Forward Networks in Color Extended Visual Cryptography to Generate Meaningful Shares

Abstract: Conventional visual secret sharing schemes generate noise-like random pixels on shares to hide secret images. It suffers a management problem, because of which dealers cannot visually identify each share. This problem is solved by the Extended Visual Cryptography Scheme (EVCS), which adds a meaningful cover image in each share. However, the previous approaches involving the EVCS for color images suffer from a pixel expansion problem. In this paper, we propose a general approach to solve the abovementioned problem; the approach can be used for color images in non computer-aided decryption environments. The proposed approach uses Feed Forward Network to construct the shares. The experimental results indicate that a solution to the pixel expansion problem of the EVCS is achieved. Moreover, the display quality of the recovered image is better than that obtained using other VC schemes.

Recent Research Advances in Black and White Visual Cryptography Schemes.

Abstract: Visual Cryptography (VC) is a type of image secret sharing scheme which decrypts an original secret image with Human Visual System (HVS). In this, the original image can be alienated into n shadows or shares and allocated to n participants; stacking any k shares reveals the secret image which ensures the security measures. In this paper, we examined the recent research advances in black and white VCSs. We reviewed the existing techniques and a comparative study of VC for binary images is presented. The study is performed with respect to different parameters and draws the current barriers related to the visual cryptography schemes.

On visual cryptography schemes

Abstract: We consider visual cryptography schemes in which two pixels combine in an arbitrary way. We analyze the pixel expansion and the contrast of (2,n)-threshold visual cryptography schemes, that is schemes in which any pair of n shares can visually reconstruct the secret image, but any single share has no information on the secret image.

Extended visual cryptography for continuous-tone images: effect of the optimum tone mapping

Abstract: Visual cryptography is a kind of cryptography that can be decrypted only by a human visual system when stacking transparencies. Extended visual cryptography allows to print meaningful images on transparencies which can conceal the existence of 'secret' in the transparencies. Many studies have tried to incorporate continuous-tone images into extended visual cryptography. However, most of them failed in preserving the image quality after the encryption. This paper introduces a scheme for extended visual cryptography for continuous-tone images. The scheme is based on parallel error diffusion that can quickly encrypt images with no pixel expansion. The most important feature of this scheme is the optimum tone mapping so that the resulting images may have very high contrast comparing with the conventional schemes. Some experimental results are shown to evaluate the effectiveness of the optimum tone mapping.