Techniques of Visual Cryptography Schemes: A Review

The effective and secure protections of sensitive information are primary concerns in commercial, medical and military systems. To address the reliability problems for secret images, a visual cryptography scheme is a good alternative to remedy the vulnerabilities. Visual cryptography is a very secure and unique way to protect secrets. Visual cryptography is an encryption technique which is used to hide information which is present in an image. Unliketraditional cryptographic schemes, it uses human eyes to recover the secret without any complex decryption algorithms and the facilitate of computers. It is a secret sharing scheme which uses images distributed as shares such that, when the shares are superimposed, a hidden secret image is revealed.In this paper we represent various cryptography technique and research work done in this field.

Cryptography is study of transforming information in order to make it secure from unintended recipients or use. Visual Cryptography Scheme (VCS) is a cryptography method that encrypts visual information (picture, printed text, handwritten notes) such that decryption can be performed using human visual system. The idea is to convert this visual information into an image and encypher this image into n different shares (known as sheets). The deciphering only requires selecting some shares out of n shares. The intent of this review paper is to contribute the readers an overview of the basic visual cryptography scheme constructions as well as continued work in the area. In inclusion, we also review some applications that take advantage of such secure system.

Allied Journals, 2015

Visual cryptography is an encryption technique which is used to hide information of an image in multiple secret shares. These shares make the secrecy levels. For n level region incrementing visual cryptography scheme, image is divided in n regions. Each region consists of one level information. For implementing visual cryptography in n levels we need to encode(n+1) shares in such a way so that any single share is not able to show the information and by combining any two shares, first level information would be visible. Similarly by superimposing any three shares, information upto second level could be seen. In similar way, for revealing whole information all the (n+1) shares are superimposed. In this paper, we are comparing many visual cryptography algorithms. Traditional visual cryptography Algorithms were based on permutation whereas modern approach are based on random column selection. In Proposed algorithm, problem of pixel expansion and poor contrast has been removed and further it is modified to generate the levels automatically which is named as automatic region incrementing visual cryptography.

International Journal of Computer Applications

In today's world handling and security of information from attacks becomes very important aspect for the individuals. Researchers are innovating new techniques to secure the information from unwanted intrusions. Various cryptography techniques are discovered and many are yet to be revealed. Here in this paper we are going to review an advanced method of information hiding i.e. Visual Cryptography. Visual Cryptography emerged as a special encryption technique for information hiding using images. In way that encrypted image can be decrypted by the human vision if the correct image key is used. By this cryptographic technique we can encrypt visual information (pictures, text, etc.) in a way that human visual system can perform decryption of encrypted information & no aid of computers needed. In visual cryptography a secret image is transformed into several share images. These share images are meaningful but noisy or distorted images. Combination of these share images can reveal the original secret image. This paper reviews two methods for visual cryptography of color images based on Shamir encryption method variants of k-out-of-n i.e.2-out-of-2, 2-out-of-n, n-out-of-n, and k-out-ofn scheme encryption method.

Cryptography is a technique used for secure transformation of information that is secret data in presence of unauthenticated interceptor. Visual Cryptography Scheme is a method that converts secret data like images or written text into binary images and then encodes them into n images, also called as shares of images. For decoding only some of the n shares or all n shares are required which are stacked on each other. The purpose of this review paper is to make clear the idea of visual cryptography schemes and continued work in the area.

Visual Cryptography (VC) is recent technology used to the strengthen security of many applications in various fields. It allows visual information like printed text, handwritten notes, and images to be encrypted by dividing it into shares. The most important characteristic of VCS is that one can visually decrypted the secret image by stacking shares without computation. The current paper aims at introducing a descriptive review for VC, which covering the "state-of-the-art" concept, and classification of schemes. In this paper, we have classified the VC schemes and provide some interpretation on the base of some various measures such as pixel expansion, share generated, format of secret image and number of secret image, which actually deemed as valuable contribution in the field of VC studies.

2015

Image cryptography is emerging field of the research. There are various techniques has been established for cryptography. The many encryption techniques have been used for hide the visual information (pictures, text, etc.) in images. The main idea of encryption is possibility of decryption by the human vision if the correct key image is used is known as visual cryptography. In this paper, different research has been discussed for Visual Cryptography.

Visual cryptography (VC) is a encryption scheme used to share secret image. It encodes image into n shares. These shares are either printed on transparencies or are encoded and stored in a digital form. The shares can look as noise-like pixels or as meaningful images. Decoding does not require all n shares .These shares are printed on transparencies and stacking them top to each other reveal the secret image. In this survey paper, we present the readers a overview of visual cryptography scheme and different approaches of visual cryptography.

2013

Visual cryptography is a cryptographic technique which encrypt a visual information (e.g. text, handwritten notes and pictures) in such a way that the decryption done by the human visual system. It needs neither cryptography knowledge nor complex computation. For security purposs, it also ensures that hacker cannot obtain any clues about a secret image from individual sharess. Naor and Shamir proposed the basic model of visual cryptography in 1994. Visual cryptography scheme eliminates complex computation problem at the decryption the secret images can be restored by stack operation. The important issue of visual cryptography is quality of relevant image. Performance of visual cryptography scheme depends, such a number of image(single, multiple), types of image(binary, gray, color),share generation(meaningful, meaningless), security, accuracy pixel expansion, complexity,) encrypted by the scheme.