Visual cryptography

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

Using colors to improve visual cryptography for black and white images

Abstract: Black-and-white visual cryptography (BW-VC) allows the sharing of b&w secret images transforming a secret image into a number of b&w shares Colored visual cryptography allows the sharing of color images by means of color shares In this paper we propose a new model, called colored-black-and-white (CBW-VC), in which the secret image is b&w and the shares are color images The motivation for the use of this new model is that of constructing schemes to share b&w images using a smaller pixel expansion Using the CBW-VC model, we provide (2, n)-threshold schemes with pixel expansion m = ⌈log3 n⌉, improving on the best pixel expansion attainable in the BW-VC model For the case of schemes with perfect reconstruction of black pixels we provide a general construction that allows to transform any BW-VC scheme into a CBW-VC scheme whose pixel expansion is 1/3 of the pixel expansion of the starting BW-VC scheme When there are very few participants, namely n = 2, 3, the proposed CBW-VC (2, n)-threshold schemes have no pixel expansion! We prove that the above two cases are the only ones where it is possible to provide schemes without pixel expansion That is, we prove that, in the CBW-VC model, it is not possible to construct (2, n)-threshold schemes, for n ≥ 4, and (k, n)-threshold schemes, for k ≥ 3, without pixel expansion

Multifactor authentication system based on color visual cryptography, facial recognition, and dragonfly optimization

Abstract: Facial recognition as an authentication factor requires that facial images and features are tamper-free. Visual cryptography (VC) is commonly used for this purpose but leads to additional computati...

The General Neural-Network Paradigm for Visual Cryptography

Abstract: This paper proposes the general paradigm to build Q'tron neural networks (NNs) for visual cryptography. Given a visual encryption scheme, usually described using an access structure, it was formulated as a optimization problem of integer programming by which the a Q'tron NN with the so-called integer-programming-type energy function is, then, built to fulfill that scheme. Remarkably, this type of energy function has the so-called known-energy property, which allows us to inject bounded noises persistently into Q'trons in the NN to escape local minima. The so-built Q'tron NN, as a result, will settle down onto a solution state if and only if the instance of the given encryption scheme is realizable.

An enhanced audio ownership protection scheme based on visual cryptography

Abstract: Recently, several ownership protection schemes which combine encryption and secret sharing technology have been proposed. To reveal the original message, however, they exploited XOR operation which is similar to a one-time pad. It is fairly losing the reconstruction simplicity due to the human visual system (HVS). It should be noted that it is completely different from the original concept of visual cryptography proposed by Naor and Shamir. To decrypt the secret message, Naor and Shamir’s concept stacked k transparencies together. The operation solely does a visual OR of the shares rather than XOR, the way HVS does. In this paper, we, consequently, adopt Naor and Shamir’s concept to apply correct theory of visual cryptography. Furthermore, audio copyright protection schemes which exploit chaotic modulation or watermark integration into frequency components have been widely proposed. Nevertheless, security issue against intentional distortions has not been addressed yet. In this paper, we aim to construct a resilient audio ownership protection scheme to enhance the security by integrating the discrete wavelet transform and discrete cosine transform, visual cryptography, and digital timestamps. In the proposed scheme, the watermark does not require to be embedded within the original audio but is used to generate a secret image and a public image. The watermark is then acquired by performing OR between the secret and public image. We can alleviate the trade-off expenses between the capacity of data payload and two other important properties such as imperceptibility and robustness without modifying the original audio signals. The experiments against a variety of audio signals processing provided by StirMark confirm superior robustness of the proposed scheme. We also demonstrate the intentional distortion by modifying the original content via experiments, it reveals comparable reliability. The proposed scheme can be widely applied to the area of audio ownership protection.

XOR based continuous-tone multi secret sharing for store-and-forward telemedicine

Abstract: Traditional k out of n visual cryptography scheme has been proposed to encrypt single secret image into n shares where only k or more shares can decode the secret image. Many existing schemes on visual cryptography are restricted to consider only binary images as secret which are not appropriate for many important applications. Store-and-Forward telemedicine is one such application where medical images are transmitted from one site to another via electronic medium to analyze the patient's clinical health status. The main objective of Store-and-Forward telemedicine is to provide remote clinical services via two-way communication between the patient and the healthcare provider using electronic medical image, audio and video means. In this paper, a new XOR based Continuous-tone Multi Secret Sharing scheme suitable for store-and-forward telemedicine is proposed to securely transmit the medical images. It also eliminates basic security constraints of VC like pixel expansion in shares/recovered secret images, random pattern of shares, explicit codebook requirement, lossy recovery of secret and limitation on number of secret and shares. Proposed approach is n out of n multi secret sharing scheme which is able to transmit n secret images simultaneously. All secrets could be revealed only after some computations with all n shares and one master share. Master share has been created with the secret key at encoding phase and it can be regenerated at the time of decoding using same secret key. Here all shares are meaningful in continuous-tone which may provide confidentiality to medical images during transmission. Proposed approach not only preserves all basic characteristics of traditional VC but also increases the capacity of secret image sharing. From the experiments we found that irrespective of visible contents of the shares, the probability of getting back the pixel values of respective original secret images at the receiver end is very high.