Showing papers on "Visual cryptography published in 2013"

Generalized Random Grid and Its Applications in Visual Cryptography

Abstract: Random grid (RG) is a method to implement visual cryptography (VC) without pixel expansion. However, a reconstructed secret with lower visual quality reveals in RG-based VC due to the fact that average light transmission of a share is fixed at 1/2. In this work, we introduce the concept of generalized RG, where the light transmission of a share becomes adjustable, and adopt generalized RG to implement different VC schemes. First, a basic algorithm, a (2,2) generalized RG-based VC, is devised. Based on the (2,2) scheme, two VC schemes including a (2,n) generalized RG-based VC and a (n,n) xor-based meaningful VC are constructed. The two derived algorithms are designed to solve different problems in VC. In the (2,n) scheme, recovered image quality is further improved. In the (n,n) method, meaningful shares are constructed so that the management of shadows becomes more efficient, and the chance of suspicion on secret image encryption is reduced. Moreover, superior visual quality of both the shares and recovered secret image is achieved. Theoretical analysis and experimental results are provided as well, demonstrating the effectiveness and advantages of the proposed algorithms.

Video watermarking scheme based on visual cryptography and scene change detection

Abstract: There is wide interest in multimedia security and copyright protection due the explosion of data exchange in the Internet and the extensive use of digital media. We propose a novel video watermarking scheme based on visual cryptography and scene change detection in discrete wavelet transform domain. We start with a complete survey of the current image and video watermarking technologies, and have noticed that majority of the existing schemes are not capable of resisting all attacks. We propose the idea to use different parts of a single watermark into different scenes of a video for generation of the owner's share from the original video based on the frame mean in same scene and the binary watermark, and generation of the identification share based on the frame mean of probably attacked video. These two shares after stacking can reveal the copyright ownership. Experiments are conducted to verify the robustness through a series of experiments. The security requirement of the proposed algorithm is achieved with the visual cryptography.

An extended visual cryptography scheme without pixel expansion for halftone images

Abstract: Visual cryptography 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 extended visual cryptography, the share images are constructed to contain meaningful cover images, thereby providing opportunities for integrating visual cryptography and biometric security techniques. In this paper, we propose a method for processing halftone images that improves the quality of the share images and the recovered secret image in an extended visual cryptography scheme for which the size of the share images and the recovered image is the same as for the original halftone secret image. The resulting scheme maintains the perfect security of the original extended visual cryptography approach.

Optimal Contrast Grayscale Visual Cryptography Schemes With Reversing

Abstract: The visual cryptography scheme (VCS) is an encryption technique that utilizes the human visual system in recovering a secret image and it does not require any complex calculation. However, the contrast of the reconstructed image could be quite low. A number of reversing-based VCSs (or VCSs with reversing) (RVCS) have been proposed for binary secret images, allowing participants to perform a reversing operation on shares (or shadows). This reversing operation can be easily implemented by current copy machines. Some existing traditional VCS schemes without reversing (nRVCS) can be extended to RVCS with the same pixel expansion for binary image, and the RVCS can achieve ideal contrast, significantly higher than that of the corresponding nRVCS. In the application of grayscale VCS, the contrast is much lower than that of the binary cases. Therefore, it is more desirable to improve the contrast in the grayscale image reconstruction. However, when grayscale images are involved, one cannot take advantage of this reversing operation so easily. Many existing grayscale nRVCS cannot be directly extended to RVCS. In this paper, we first give a new grayscale nRVCS with minimum pixel expansion and propose an optimal-contrast grayscale RVCS (GRVCS) by using basis matrices of perfect black nRVCS. Also, we propose an optimal GRVCS even though the basis matrices are not perfectly black. Finally, we design an optimal-contrast GRVCS with a minimum number of shares held by each participant. The proposed schemes can satisfy different user requirements; previous RVCSs for binary images can be viewed as special cases in the schemes proposed here.

Image Size Invariant Visual Cryptography for General Access Structures Subject to Display Quality Constraints

Abstract: Conventional visual cryptography (VC) suffers from a pixel-expansion problem, or an uncontrollable display quality problem for recovered images, and lacks a general approach to construct visual secret sharing schemes for general access structures. We propose a general and systematic approach to address these issues without sophisticated codebook design. This approach can be used for binary secret images in non-computer-aided decryption environments. To avoid pixel expansion, we design a set of column vectors to encrypt secret pixels rather than using the conventional VC-based approach. We begin by formulating a mathematic model for the VC construction problem to find the column vectors for the optimal VC construction, after which we develop a simulated-annealing-based algorithm to solve the problem. The experimental results show that the display quality of the recovered image is superior to that of previous papers.

Sensitive Digital Image Watermarking for Copyright Protection

Abstract: In this paper, a watermark hiding scheme for copyright protection of sensitive images is proposed. The concept of visual cryptography is used, so that the original host image is not altered. The proposed scheme aims at improving the security of the related schemes. The scheme also reduces the size of codebook and size of shares, to be used in watermark hiding process. This is achieved by adapting the concept of Pair-Wise Visual Cryptography (PWVC). The simulation results reveal that the proposed scheme has good robustness to a range of image processing attacks.

Visual Cryptography and Random Grids Schemes

Abstract: Visual Cryptography (VC) and Random Grids (RG) are both visual secret sharing (VSS) techniques, which decode the secret by stacking some authorized shares. It is claimed that RG scheme benefits more than VC scheme in terms of removing the problems of pixel expansion, tailor-made codebook design, and aspect ratio change. However, we find that the encryption rules of RGS are actually the matrices sets of probabilistic VCS. The transformation from RGS to PVCS is proved and shown by means of giving theoretical analysis and conducting some specific schemes. The relationship between codebook and computational complexity are analyzed for PVCS and RGS. Furthermore, the contrast of PVCS is no less than the one of RGS under the same access structure, which is shown by experimental results.

Securing Visual Cryptographic shares using Public Key Encryption

Abstract: The Visual Cryptography Scheme is a secure method that encrypts a secret document or image by breaking it into shares. A distinctive property of Visual Cryptography Scheme is that one can visually decode the secret image by superimposing shares without computation. By taking the advantage of this property, third person can easily retrieve the secret image if shares are passing in sequence over the network. The project presents an approach for encrypting visual cryptographically generated image shares using Public Key Encryption. RSA algorithm is used for providing the double security of secret document. Thus secret share are not available in their actual form for any alteration by the adversaries who try to create fake shares. The scheme provides more secure secret shares that are robust against a number of attacks & the system provides a strong security for the handwritten text, images and printed documents over the public network.

Quality-improved threshold visual secret sharing scheme by random grids

Abstract: Random grids (RGs)-based visual secret sharing (VSS) has gained much attention in academia than before to avoid the potential drawbacks in visual cryptography-based VSS. With its still being in infancy, a growing number of researches to RG-based VSS demonstrate a great potential. Although there are some RG-based schemes proposed in the past years for different applications, most of them can still be improved to achieve a better performance. This study proposes a new threshold RG-based VSS scheme with better performance compared with the previous threshold RG-based VSS scheme. The experimental results illustrate the feasibility; the better performance is theoretically analysed.

Steganography using Genetic Algorithm along with Visual Cryptography for wireless network application

Abstract: Image steganography is an emerging field of research for secure data hiding and transmission over networks. The proposed system provides the best approach for Least Significant Bit (LSB) based steganography using Genetic Algorithm (GA) along with Visual Cryptography (VC). Original message is converted into cipher text by using secret key and then hidden into the LSB of original image. Genetic Algorithm and Visual Cryptography has been used for enhancing the security. Genetic Algorithm is used to modify the pixel location of stego image and the detection of this message is complex. Visual Cryptography is used to encrypt the visual information. It is achieved by breaking the image into two shares based on a threshold. The performance of the proposed system is experimented by performing steganalysis and conducting benchmarking test for analysing the parameters like Mean Squared Error (MSE) and Peak Signal to Noise Ratio (PSNR). The main aim of this paper is to design the enhanced secure algorithm which uses both steganography using Genetic Algorithm and Visual Cryptography to ensure improved security and reliability.

Aspect ratio invariant visual cryptography by image filtering and resizing

Abstract: In visual cryptographic scheme (VCS), each secret pixel is expanded to m subpixels in shadow images to encrypt a secret image. Apparently, we should put these m subpixels as a rectangle such that the blocks can be arranged compactly with each other. However, if the aspect ratio is viewed as important information of the secret image, the distortion occurs at the case that m is not a square. An aspect ratio invariant VCS (ARIVCS) was accordingly proposed to address the arrangement of subpixels. However, the existing ARIVCSs relied on adding dummy subpixels to the shadow images. In addition, their method needs a mapping pattern that reduces the number of dummy subpixels, but how to design a mapping pattern is a huge challenge. In this paper, we propose an easy solution to construct ARIVCS by image filtering and resizing.

Robust digital video watermarking using reversible data hiding and visual cryptography

Abstract: Watermarking is a major image processing application used to authenticate user documents by embedding and hiding some authenticated piece of information behind an image, audio or the video file. For example, copyright symbols or signatures are often used. Our proposed work is to develop and implement an improved layered approach to video watermarking. The traditional watermarking approach tends to embed an entire watermark image within each video frame or within random video frames to give the appearance of a hidden watermark to the casual observer. This work proposes a more efficient and secured approach to perform watermarking, by using sub image classification. That is to say, selected frames only will contain a fractional number of total bits from the watermark image. We take k bits from the watermark and store then within a video frame, depending on the size of that watermark image. Our algorithm is capable of hiding high capacity information over video frames. The novel approach is to partially distribute the watermarking data over a set of frames until the entire watermark is eventually distributed throughout the entire video. The originality our technique is that it is a histogram inspired and reversible watermarking approach as defined with visual cryptography. Our approach hides similar watermarking bits of information with frames of a similar appearance. Differing sets of watermark bits are thus embedded within dissimilar frames, thus making the system more robust. It will provide a high degree of authentication, as the extraction of information from a single frame only will not reveal the entire watermarking data, or even give any obvious indication that it contains a fraction of the watermark bits. The robustness of our technique will be tested by calculating MSE, PSNR values and by performing some common

Optical security enhancement device

Abstract: An optical security device can be used to view sensitive information provided in an obscured format via a potentially untrusted and/or compromised computer. The techniques described herein enable use of untrusted computers for access to sensitive information. The optical security device employs one or more forms of visual cryptography such as spatial cryptography and/or temporal cryptography in some instances via a programmable mask and/or a programmable color filter to reveal sensitive information that is provided in an obscured form by a potentially untrusted computer.

A(3,3) visual cryptography scheme for authentication

Abstract: The visual cryptography is a secret sharing technique,for which the secret can be decoded directly by human visual system without any cryptography knowledgeThis technique splits a secret image into n shares in such a way that the stacking of any k shares can reveal the secret image but any less than k shares should provide no informationIn this paper,a(3,3) visual cryptography scheme has been proposed which may be used for the trusted third party to verify the two other participantsThis scheme involves two validation images and a secret imageThe validation images are used to verify the participantsThe secret image is split into three sharesOne of the shares is hold by the trusted third party and the other by the two participantsThe trusted third party stacks his/her share with the share of the two other participants respectively and the two different images for participant authentication will be revealedExperiments show the effectiveness of the proposed(3,3) visual cryptography scheme

Secure Two-Party Computation: A Visual Way

Abstract: In this paper we propose a novel method for performing secure two-party computation. By merging together in a suitable way two beautiful ideas of the 80’s and the 90’s, Yao’s garbled circuit construction and Naor and Shamir’s visual cryptography, respectively, we enable Alice and Bob to securely evaluate a function \(f(\cdot ,\cdot )\) of their inputs, \(x\) and \(y\), through a pure physical process. Indeed, once Alice has prepared a set of properly constructed transparencies, Bob computes the function value \(f(x,y)\) by applying a sequence of simple steps which require the use of a pair of scissors, superposing transparencies, and the human visual system. A crypto-device for the function evaluation process is not needed any more.

Information hiding in gray scale images using pseudo-randomized visual cryptography algorithm for visual information security

Abstract: Security has gained a lot of importance as information technology is widely used. Cryptography refers to the study of mathematical techniques and related aspects of Information Security like data confidentiality, data Integrity, and of data authentication. Visual cryptography (VC) is a process where a secret image is encrypted into shares which refuse to divulge information about the original secret image. Its strength is a fact that the decryption of the secret image is through human visual system without computation. A basic model for visual cryptography for natural images was proposed by Naor and Shamir. In this paper, a novel method of VC is presented for halftone images which represent the resultant image in the same size as the original secret image. Hiding of the visual information based on pseudo randomization and pixel reversal is also proposed.

XOR-based meaningful visual secret sharing by generalized random grids

Abstract: In recent years, random grid (RG) received much attention for constructing visual secret sharing (VSS) scheme without pixel expansion. But recovered secret image with low visual quality reveals due to the stacking operation. To improve the recovered image quality, XOR-based VSS is adopted. However, shares constructed from XOR-based VSS are random-looking. The noise-like appearance further increases the chance of suspicion on secret image communication and imposes difficulty for managing the shares. In this work, a novel (2,2) generalized RG-based VSS is introduced. By adopting the (2,2) VSS, we propose a XOR-based meaningful VSS where shares with meaningful contents are constructed. Moreover, superior visual quality is provided by this method as well.

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.

Securing Biometric Data with Visual Cryptography and Steganography

Abstract: Visual cryptography is the technique used to encrypt the data which is in the form of visual information such as images. Since the biometric templates stored in the database is usually in the form of images, the visual cryptography can be efficiently employed to encrypt the templates from attacks. The technique of steganography is used in combination to the visual cryptography for imparting additional security to biometric data. The biometric information such as the private face image is decomposed into two shares and stored in separate database tables such that the private image can be revealed only when both shares are simultaneously available. Each individual share is covered with a different image which is selected from a public host image database. The LSB steganography is applied to keep the user name and password hidden inside the final shares of visual cryptographic phase there by provides a mutually interconnected security mechanism.

A new color visual cryptography scheme with perfect contrast

Abstract: In this paper, we propose a new color visual cryptography scheme based on the modified visual cryptography This scheme can share a color secret image over n-1 arbitrary natural images and one noise-like share image Instead of altering the contents of natural images, the encryption process extracts feature images from each natural image In such a way, the proposed approach can effectively reduce the transmission risk and solve the management problems Moreover, this approach avoids the pixel expansion problem and makes it possible to recover secret images without any distortion Thus, the proposed scheme can share b&w, gray-level or color images in a secret way and is easy to implement

Visual Cryptography Schemes using Compressed Random Shares

Abstract: Visual cryptography is one of the most secure techniques the allows the user to encrypt the secret images by transforming them into printable transparent sheets and these sheets can be distributed to different intended person through various mediums (physically, internet). On receiving the intended person may regenerate the original image by stacking all transparent sheets on each other. There are many visual cryptography schemes available that facilitates user to encrypt any various types and formats of images to encrypt and. This paper presents a visual cryptography scheme that can generate n number of transparent shares with reduced size and supports a variety of image formats and presents an integrated approach for binary, Gray and color image visual cryptography by maintaining the visual quality and pixel expansion.

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.

Secure Visual Cryptography Technique for Color Images Using RSA Algorithm

Abstract: Visual Cryptography is a special technique which is used to send the images securely over the network. Visual cryptography is a cryptographic technique which allows visual information to be encrypted in such a way that decryption becomes a mechanical operation that does not require a computer. Simple Visual Cryptographic technique is insecure. This cryptographic technique involves dividing the secret image into n shares and a certain number of shares (m) are sent over the network. The decryption process involves stacking of the shares to get the secret image. In the current work, we have proposed a cryptographic technique for color images where we are using color error diffusion with XOR operation. The shares are developed using Random number. The key generated for decryption process is sent securely over the network using RSA algorithm. This approach produces less distorted image and the size of the decrypted images is same as the original image.