Visual cryptography

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

HSV Image Watermarking Scheme Based on Visual Cryptography

Abstract: In this paper a simple watermarking method for color images is proposed. The proposed method is based on watermark embedding for the histograms of the HSV planes using visual cryptography watermarking. The method has been proved to be robust for various image processing operations such as filtering, compression, additive noise, and various geometrical attacks such as rotation, scaling, cropping, flipping, and shearing. Keywords— Histogram, HSV image, Visual Cryptography, Watermark.

Bounds for Visual Cryptography Schemes

Abstract: In this paper, we investigate the best pixel expansion of the various models of visual cryptography schemes. In this regard, we consider visual cryptography schemes introduced by Tzeng and Hu [13]. In such a model, only minimal qualified sets can recover the secret image and that the recovered secret image can be darker or lighter than the background. Blundo et al. [4] introduced a lower bound for the best pixel expansion of this scheme in terms of minimal qualified sets. We present another lower bound for the best pixel expansion of the scheme. As a corollary, we introduce a lower bound, based on an induced matching of hypergraph of qualified sets, for the best pixel expansion of the aforementioned model and the traditional model of visual cryptography realized by basis matrices. Finally, we study access structures based on graphs and we present an upper bound for the smallest pixel expansion in terms of strong chromatic index.

Non-expanded visual cryptography scheme with authentication

Abstract: In recent years, a crucial issue is the manner in which to safely transmit the secret information and prevent the detection of information. An extended visual cryptography with authentication technology for the original image was proposed in previous studies. Fang and Lin's scheme [3] combine the principle of traditional visual cryptography with authentication characteristic, when we fix the first share image and shift the other share image for certain unit, we can obtain the extra confidential data. But in traditional visual cryptography, secret pixels are expanded to cause the size of the recovered image is larger than the original one. So this study combined the non-expanded scheme with the extra ability of hiding confidential data to prevent the detection of information.

A Digital Watermarking Algorithm of Color Image based on Visual Cryptography and Discrete Cosine Transform

Abstract: In this paper, we propose a new digital watermarking algorithm of color image. We process the watermark to generate two shares based on visual cryptography. And one of the shares is embedded into a color image and another is protected by the copyright. The scheme is easy to implement and highly feasible. In addition, the embedding capacity of watermarks and robustness are improved to effectively.

Fourier-based automatic alignment for improved visual cryptography schemes

Abstract: In Visual Cryptography, several images, called "shadow images", that separately contain no information, are overlapped to reveal a shared secret message. We develop a method to digitally register one printed shadow image acquired by a camera with a purely digital shadow image, stored in memory. Using Fourier techniques derived from Fourier Optics concepts, the idea is to enhance and exploit the quasi periodicity of the shadow images, composed by a random distribution of black and white patterns on a periodic sampling grid. The advantage is to speed up the security control or the access time to the message, in particular in the cases of a small pixel size or of large numbers of pixels. Furthermore, the interest of visual cryptography can be increased by embedding the initial message in two shadow images that do not have identical mathematical supports, making manual registration impractical. Experimental results demonstrate the successful operation of the method, including the possibility to directly project the result onto the printed shadow image.