Visual cryptography

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

Visualcryptography basedon void-and-clusterhalftoningtechnique

Abstract: Inthis paper, visual cryptography forhalftone images is proposed, whichusesthreshold arrays generated byavoidand-cluster method.The proposedhalftone visual cryptography (HVC)usingthreshold arrays showsgreat flexibility fora combination ofshareimages inorder to decode a secret image. Moreover, italsoachieves high quality shareimages,highspeedprocessing and extensibility to(k,n) thevisual cryptography ofthree share imagecategories, suchas(2,3) or(3,3). Simulation results showthat alltheabove features areachieved, while asecret imageisclearly decoded, andthesecret imagecannot be seenoneachshare image. IndexTerms-Imageprocessing

Application of visual cryptography for learning in optics and photonics

Abstract: In the age data digitalization, important applications of optics and photonics based sensors and technology lie in the field of biometrics and image processing. Protecting user data in a safe and secure way is an essential task in this area. However, traditional cryptographic protocols rely heavily on computer aided computation. Secure protocols which rely only on human interactions are usually simpler to understand. In many scenarios development of such protocols are also important for ease of implementation and deployment. Visual cryptography (VC) is an encryption technique on images (or text) in which decryption is done by human visual system. In this technique, an image is encrypted into number of pieces (known as shares). When the printed shares are physically superimposed together, the image can be decrypted with human vision. Modern digital watermarking technologies can be combined with VC for image copyright protection where the shares can be watermarks (small identification) embedded in the image. Similarly, VC can be used for improving security of biometric authentication. This paper presents about design and implementation of a practical laboratory experiment based on the concept of VC for a course in media engineering. Specifically, our contribution deals with integration of VC in different schemes for applications like digital watermarking and biometric authentication in the field of optics and photonics. We describe theoretical concepts and propose our infrastructure for the experiment. Finally, we will evaluate the learning outcome of the experiment, performed by the students.

An Improved Aspect Ratio Invariant Visual Cryptography Scheme with Flexible Pixel Expansion

Abstract: In traditional visual cryptography scheme (VCS), each pixel of secret image is encrypted into m(\( \geqslant 1 \)) subpixels in the share images. Unfortunately, recovered image will be distorted when the pixel expansion is not a square number. In order to reveal the information of the secret image faithfully, aspect ratio of the recovered image should be kept invariant in VCS. In this paper, we investigate the encryption process of traditional VCS and find that it is able to be divided into mapping stage and size invariant VCS (SIVCS) stage. By improving algorithms of these two stages respectively, we propose a novel construction of aspect ratio invariant VCS (ARIVCS) with flexible pixel expansion. Experimental results show the effectiveness of our scheme that it avoids the defects found in previous research works such as the details distortion problem, thin line problems and blurry edge problem. Meanwhile, our scheme eliminates the jaggy phenomenon to a certain extent when the pixel expansion is large which contributes to improving the visual quality of ARIVCS significantly.

Sharing More Information in Visual Cryptography Scheme with Block Expansion

Abstract: Visual cryptography scheme (VCS) shares secret image into shadows. Without computing, stacking shadows can reveal the secret image. In this paper, we propose a VCS with block expansion. Each shadow pixel is expanded into a 4-pixel block with extra secret information embedded in. In the revealing process, the secret image can be revealed by stacking shadows. In the meanwhile, we can reveal the extra shared secret information by computation.

Secure visual cryptography scheme with meaningful shares

Abstract: Visual cryptography is an outstanding design, which is also known as visual secret sharing. It used to encode a secret portrait into various pointless share images. Normally, item bossed on transparencies and decrypts as loading one or two or the entire share images by means of the human visual system. Suppose, if we encompass great sets of secret shares then the pointless shares are complicated to handle. In this paper, a meaningful secret sharing algorithm and a modified Signcryption algorithm is used to enhance the security of the Visual Cryptography encryption schemes. The foremost intend of the anticipated format is to extend consequential shares and similarly make sure the isolation on conveying the secret data. The anticipated process is executed in the functioning platform of MATLAB and the presentation results are investigated.