Visual cryptography

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

Measure-Independent Characterization of Contrast Optimal Visual Cryptography Schemes

Abstract: The contrast in visual cryptography has received a lot of attention. It has been studied using three different measures. In this paper we follow a measure-independent approach, which, by using the structural properties of the schemes, enables us to provide a characterization of optimal schemes that is independent of the specific measure used to assess the contrast. In particular we characterize and provide constructions of optimal schemes for the cases of \((2,n)\)-threshold and \((n,n)\)-threshold schemes. Then, we apply the measure-independent results to the three measures that have been used in the literature obtaining both new characterizations and constructions of optimal schemes and alternative proofs of known results.

Lossless Codebook-Based Digital Watermarking Scheme with Authentication

Abstract: Xing et al. proposed a digital watermarking scheme based on visual cryptography and the extended codebook in order to eliminate ambiguity problem. However, there exists still an ambiguity problem such that the watermark can be extracted from other owner's watermarked image. In order to solve this problem, we propose a new digital watermarking scheme with authentication. The proposed scheme is based on a lossless codebook which degrades a contrast of watermarked image and does not exist an ambiguity problem. Also, the proposed scheme provides authentication because of the utilization of characteristics between original and other images. In order to evaluate robustness and ambiguity problem, several watermarking attacks performed. As the results, the proposed scheme provides robustness against several watermarking attacks and eliminates an ambiguity problem.

A Joint Ownership Protection Scheme for Digital Images Based on Visual Cryptography

Abstract: When an image is created by multiple authors, it is reasonable that no single author monopolize the ownership. The ownership should be shared among these authors, and the ownership should be proved by a group of authors. In this paper, we propose a joint ownership protection scheme for co-authored images. Some of the authors or all of the authors can verify ownership. This scheme integrates discrete cosine transforms and visual cryptography to meet robustness and security requirements. The experimental results show this scheme successfully resists some common attacks.

Colour Visual Cryptography (3,3) Scheme

Abstract: Visual Cryptography is an encryption technique which performs only encryption in cryptography, and it is used to encrypt every visual data. And this cryptography is different and unique in all cryptographic techniques, because of not performing decryption process mechanically, and that is done mechanically. In normal visual cryptography only black and white images are encrypted. In this paper we propose a different type of visual cryptography scheme for colour imagesin CMY format. And it protects the secret of the original image and no other techniques does not decrypt it except our decryption technique.

WiP: Security Enhanced Size Invariant Visual Cryptography with Perfect Reconstruction of White Pixels

Abstract: Visual Cryptography is an image encryption technique which reconstructs the image using human visual system. Presently used size invariant visual cryptography schemes (VCS) does not preserves both security and contrast conditions. In this paper we proposed a new method for size invariant block wise encoding VCS based on perfect reconstruction of white pixels which provides perfect security and retains the contrast. Here we have discussed an outline of size invariant VCS based on random basis column pixel expansion, block wise encoding and random basis VCS with perfect reconstruction of white pixels (PRWP) which have been demonstrated based on various research studies. We have also discussed the demerits of the existing models and made an experimental analysis between previous models and the proposed model. From the analysis we proved that the proposed method enhances the security and maintain the contrast.