Visual cryptography

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

An optimization model for visual cryptography schemes with unexpanded shares

Abstract: Visual cryptography schemes encrypt a secret image into n shares so that any qualified set of shares enables one to visually decrypt the hidden secret; whereas any forbidden set of shares cannot leak out any secret information. In the study of visual cryptography, pixel expansion and contrast are two important issues. Since pixel-expansion based methods encode a pixel to many pixels on each share, the size of the share is larger than that of the secret image. Therefore, they result in distortion of shares and consume more storage space. In this paper, we propose a method to reach better contrast without pixel expansion. The concept of probability is used to construct an optimization model for general access structures, and the solution space is searched by genetic algorithms. Experimental result shows that the proposed method can reach better contrast and blackness of black pixels in comparison with Ateniese et al.'s.

Some Extensions on Threshold Visual Cryptography Schemes

Abstract: Droste [CRYPTO’96] proposed a construction of threshold visual cryptography scheme (TVCS) under the visual cryptography model of Naor and Shamir, ie the visual cryptography model with the underlying operation OR In this article, we give three extensions of TVCS First, we prove that the TVCS proposed by Droste which was based on the OR operation is still a valid TVCS under the XOR operation, and then we propose a method to further reduce its pixel expansion We then propose an interesting construction of TVCS with all shares being concolorous Finally, we give a construction of threshold extended visual cryptography scheme (TEVCS) with the underlying operation OR or XOR All of our schemes can be applied to the visual cryptography model introduced by Tuyls et al (First Int Conf Security in Pervasive Computing 2004, International Patent with Application No: PCT/IB2003/000261)

An overview of visual cryptography

Abstract: Security has become an inseparable issue as information technology is ruling the world now. Cryptography is the study of mathematical techniques related aspects of Information Security such as confidentiality, data security, entity authentication and data origin authentication, but it is not the only means of providing information security, rather one of the techniques. Visual cryptography is a new technique which provides information security which uses simple algorithm unlike the complex, computationally intensive algorithms used in other techniques like traditional cryptography. This technique allows Visual information (pictures, text, etc) to be encrypted in such a way that their decryption can be performed by the human visual system, without any complex cryptographic algorithms. This technique encrypts a secret image into shares such that stacking a sufficient number of shares reveals the secret image. Shares are usually presented in transparencies. In this paper we provide an overview of the emerging Visual Cryptography (VC) and related security research work done in this area.

A new visual cryptography with multi-level encoding☆

Abstract: Visual secret sharing (VSS) is a visual cryptography scheme which decodes secret messages into several enlarged shares, and distributes them to different participants The participants can recover the secret messages by stacking their shares, and then secret message can be revealed by human visual sensitivity Afterward some researchers start to research size invariant scheme, and apply to encode grayscale images such as scenic photos or pictures, not only binary messages Owing to the gray values distribution of pictures are different, extreme distribution may cause blurred revealed image In this paper, we proposed a size invariant VSS scheme which is suitable for different distribution of image's gray values Experiment results show that the reconstructed images of our method, for brighter, darker, and normal images, have clearer and higher contrast, and without apparent artifact and unexpected contour

Security enhancement in image steganography using neural networks and visual cryptography

Abstract: Data Security has been an essential area of concern as the communication medium is widely used over internet. Image steganography indicates sending the secret data in the cover image while hiding the very existence of it self. Before embedding the secret data in the cover image, it is encrypted in order to obtain better level of security. Steganalysis is concerned with field of defeating steganographic techniques. Hence continuous research has been under taken in order to enhance data security. Cryptography involves a process called encryption and is not concerned with hiding the secret data in the cover image. Visual cryptography is a renowned technique to protect data which is image based. During encryption, the image is split into ‘n’ number of shares. During decryption, these shares are stacked together to get original image. Hence specific decryption algorithm is not necessary and just human visual system would suffice. In order to enhance security mechanism, visual cryptography and image steganography are used together. Neural networks are concerned with identifying the best locations in host image in order to embed the secret data thus improving the image quality.