Visual cryptography

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

Traceable visual cryptography

Abstract: In this paper we present a new k out of n visual cryptography scheme which does not only meet the requirements of a basic visual cryptography scheme defined by Naor and Shamir [5] but is also traceable. A k out of n visual cryptography scheme is a special instance of a k out of n threshold secret sharing scheme [6]. Thus, no information about the original secret can be revealed if less than k share-holders combine their shares. In those systems it is inherently assumed that even if there are k or more share-holders with an interest in the abuse of the secret, then it is almost impossible that they can meet up as an entirety (e.g. because they are to cautious to inform too many others about their intentions) and combine their shares to misuse the secret. But in real scenarios it might not be too unlikely that the betrayers find together in small groups. Even though each one of these groups is too small to compute the original secret, the betrayers of such a group can impose a major security risk on the system by publishing the information about their shares. Suppose for example that k − 1 betrayers find each other and do the publishing. Then all the other n − k + 1 share-holders can potentially reveal the secret without ever meeting up with at least k − 1 other share-holders as is intended by the system. In order to cope with this lack of security, we present in this paper the idea of traceable visual cryptography schemes which allows to track down the publishing saboteurs.

Visual Cryptography Scheme Using Pi-sigma Neural Networks

Abstract: A visual cryptography scheme (VCS) for general access structures is a method to encode a secret image into n shares for n participants. Only qualified subsets of participants can recover the secret image. The yet known schemes omitted the deference between primary information and secondary one in secret image, and its best known upper bound on the share size is exponential. Besides its information communication rate is high. This paper proposes a new VCS for general access structures using pi-sigma neural networks (VCSPSN). A pi-sigma neural network (PSN) is a class of two-layer feedforward net-work. Compared to other high-order networks, a PSN has a highly regular structure, needs a much smaller number of weights and less training time. Using PSN's capability of large-scale parallel classification, VCSPSN reduces the information communication rate greatly, makes best known upper bound polynomial, and distinguishes the deferent information in secret image. This paper firstly introduces the structure of PSN, and then constructs the VCSPSN and analysis its security and capability.

An overview of visual cryptography techniques

Abstract: Visual cryptography is an encryption technique that decomposes secret images into multiple shares. These shares are digitally or physically overlapped to recover the original image, negating the need for complex mathematical operations or additional hardware. There have been many variations of visual cryptography proposed over the years, each addressing different problems or to fulfill different security requirements. Existing review papers on the area only cover certain types of visual cryptography or lack comparisons between the various schemes. To address this gap, this paper provides broad overview of the area to aid new researchers in identifying research problems or to select suitable visual cryptography methods for their desired applications. For more veteran researchers in the area, our paper provides the most up-to-date coverage of the state-of-the-art. We first provide an introduction to the various categories of visual cryptography techniques, including a discussion on recently proposed schemes. These schemes are then compared in terms of their features, performance metrics, advantages and disadvantages. Compared to prior work, we extend the number of comparison metrics to include signal-to-noise ratio and the type of shares. Over 40 visual cryptography schemes that have been proposed in the past two decades were analyzed and compared. Our findings indicate that existing problems such as pixel expansion, poor quality of recovered image quality, computational and memory complexities still exist, and a optimizing the trade-off between these requirements still requires further investigation. We conclude the paper with a discussion of these open problems and future research directions.

Content based authentication of visual cryptography

Abstract: Visual Cryptography (VC) has been developed as a significant research arena in media security. Despite of its obvious strengths, recent investigations have debated this scheme from adverse aspects, its problem is lack of authentication of VC shares, VC authentication related to digital image processing and cryptography has not been fully integrated together in the past years. In this paper, we analyze both visual features and cryptographic features of VC shares and take use of them for VC authentication. Compared to those existing methods, our contribution is the first one to integrate visual features and cryptographic features of VC shares into Hash code for the purpose of VC authentication.

Usability of Augmented Reality for Revealing Secret Messages to Users but Not Their Devices

Abstract: We evaluate the possibility of a human receiving a secret message while trusting no device with the contents of that message, by using visual cryptography (VC) implemented with augmented-reality displays (ARDs). In a pilot user study using Google Glass and an improved study using the Epson Moverio, users were successfully able to decode VC messages using ARDs. In particular, 26 out of 30 participants in the Epson Moverio study decoded numbers and letters with 100% accuracy. Our studies also tested assumptions made in previous VC research about users’ abilities to detect active modification of a ciphertext. While a majority of the participants could identify that the images were modified, fewer participants could detect all of the modifications in the ciphertext or the decoded plaintext.