Visual cryptography

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

Key based Visual Cryptography Scheme using Novel Secret Sharing Technique with Steganography

Abstract: With rapidly growing network, Internet has become a primary source of transmitting confidential or secret data such as military information, financial documents, etc. In such cases, techniques devoted to protect such kind of information are needed and they play an important role in providing confidential and secure transmission over network. Visual Cryptography is also one of them which is used to hide secret visual information (such as image, text, etc) in which secret sharing scheme is used. Secret sharing is used to encrypt a secret image into customized versions of the original image. There are many secret sharing algorithms in literature including Shamir, Blakley, and Asmuth-Bloom to divide the image into no. of shares. These sharing schemes lead to computational complexity and also generate shares like noisy images. Then afterwards Lin & Tsai proposed a scheme which creates meaningful shares but having same computational complexity as like Shamir's scheme. Along with this, in these schemes, as decryption is done using Human Visual system, the secret can be retrieved by anyone if person get at least k no. of shares. To overcome all above problems, we are suggesting one new method in which a symmetric secret key is used to encrypt the image and then secret shares are generated from this image using Novel secret sharing technique with steganography. So, finally this method will produce meaningful shares and use of secret key will ensure the security of scheme. This scheme can become a reliable solution suitable for today's authentication challenges. Index Terms: Visual cryptography, Secret sharing, steganography.

Hiding information using a checkered pattern

Abstract: Visual cryptography is expected to have various applications since it has potential for visual decoding. However, there are still few practical applications. One reason for this is the difficulty of superposition to decode. To solve the alignment difficulty, we propose an information hiding method which can be physically decode by superimposing a checkered pattern. Superimposing a checkered pattern can also be considered as a kind of image sampling process, and a decoding experiment using an ordinary compact digital camera is presented.

A master share (2, n) XOR based visual cryptography scheme by random grids

Abstract: The rapid growth of internet applications and network users has made the processing of digital images via internet highly vulnerable. Existing random grid based visual cryptography schemes (RG-VCS) like any other visual cryptography schemes aim at imparting perfect secrecy and fast decryption without any complex computation. One among the several techniques in visual cryptography is the (2,n) RG-VCS which creates n shares with equal weightage and any of two shares out of n can be combined to recover the original image. The drawback of the existing system is that an attacker can recover the original image if he /she obtain any of the two shares created. The proposed system improves the security of (2, n) RG-VCS by incorporating the concept of a master share. The concept of a master share is introduced in such a way that recovery of the original image is possible if and only if one among the two shares combined is the master share. Decryption using any two shares from the remaining n-1 shares other than the master (i.e. client shares) reveals nothing. XOR-based decryption is implemented here as it seems to be a perfect candidate for (2, n) schemes which enhance the image quality of the recovered secret and solving alignment problems in visual cryptographic systems. There by the proposed work implemented a two-tier priority share model enhancing the confidentiality of visual cryptographic applications. Further, sufficient theoretical proofs are provided for the correctness of the implementation.

Visual Secret Sharing Using Cryptography

Abstract: The Visual Cryptography Scheme (VCS) is a kind of secret sharing scheme that focuses on sharing secret im- ages. The basic idea of the visual cryptography scheme is to split a secret image into number of random shares (printed on transparencies) which separately reveals no information about the secret image other than the size of the secret image. The secret image can be reconstructed by stacking the shares. The underlying operation of this scheme is logical OR operation. The Embedded Extended Visual Cryptography Scheme (EEVCS) uses meaningful covering shares. The scheme EEVCS can be implemented by embedding random shares of secret image into meaningful cover images.The halftoning method is used to convert the gray scale image into binary im- age. After Studying existing Dithering technique of half ton- ing, Otsus Thresholding method is proposed. Least Significant Bit (LSB) matching steganography technique is used to hide the secret pixel information into the covering images.Related works on visual cryptography scheme are also investigated and it was observed that visual quality of recovered secret images are low by using existing dithering halftone based EEVCS techniques.Including Otsus Thresholding method for halfton- ing of an image can produce bright image in a better way. LSB matching steganography is a useful method to hide the secret image. This research aims at employing LSB matching stega- nography with Otsu's method to develop an efficient EEVCS system. Index Terms - Embedded extended visual cryptogra- phy scheme, Otsu's Method, Dithering technique, Least Sig- nificant bit, Visual cryptography Scheme. IntroductionTHE basic principle of the visual cryptography scheme (VCS) was first introduced by Naor and Shamir. VCS is a kind of secret sharing scheme (1), (2) that focuses on sharing secret images. The idea of the visual cryptography model proposed in (3) is to split a secret image into two random shares (printed on transpa- rencies) which separately reveals no information about the secret image other than the size of the secret image. The secret image can be reconstructed by stacking the two shares. The underlying operation of this scheme is logical operation OR. In this paper, we call a VCS with random shares the traditional VCS or simply the VCS. In general, a traditional VCS takes a secret image as input, and outputs shares that satisfy two conditions: 1) any qual- ified subset of shares can recover the secret image; 2) any for- bidden subset of shares cannot obtain any information of the secret image other than the size of the secret image. An example of traditional (2,2)-VCS is shown in Fig. 1.In the scheme of Fig. 1, shares (a) and (b) are distributed to two participants secretly, and each participant cannot get any information about the secret image, but after stacking shares (a) and (b), the secret image can be observed visually by the par- ticipants. VCS has many special applications, for example,

Watermark Embedding for Direct Binary Searched Halftone Images by Adopting Visual Cryptography

Abstract: In this paper, two methods are proposed to embed visual watermark into direct binary search (DBS) halftone images, which are called Adjusted Direct Binary Search (ADBS) and Dual Adjusted Direct Binary Search (DADBS). DADBS is an improved version of ADBS. By using the proposed methods, the visual watermark will be embedded into two halftone images separately, thus, the watermark can be revealed when these two halftone images are overlaid. Experimental results show that both methods can achieve excellent image visual quality and decoded visual patterns.