Watermarking-Based Transparency Authentication in Visual Cryptography

Steganography is the art of hiding secret data in a medium whereas visual-cryptography is a cryptographic technique where a full image is encrypted. The security of image steganography depends on the secret key set which is used for embedding the secret image. If the secret key is exposed, the secret image can be retrieved. To solve this security issue we propose a new type of steganography method using visual cryptography. In this method, text and image are used as a secret message and image for the cover object. 24-bit RGB color images are used as both secret and cover images. In this method, we use a new image namely share1 which converts a secret image to a totally different image called share2 image. Typically, knowing the extraction method, people can retrieve the secret message easily. A pseudorandomly generated image is used as a key for visual encryption and this ensures the extra layer of security. By this proposed method, we ensure more secured image steganography.

Security has gained a lot of importance with the rapid development of communication/storage technology. Protecting the data has become an important issue. In this paper a transmission system with enhanced security is proposed for the image information. Here, the secret image is encrypted and transmitted by using a combined technique that make use of Discrete Wavelet Transform (DWT), Visual Cryptography (VC) and Water marking. DWT is first used for the compression of the secret image. Visual cryptography encodes the compressed image into noise like shadow images known as shares. Shares are made invisible by digital watermarking, which provides additional security. By stacking the shares together, the secret image can be visually decoded. Different image types are used to evaluate the performance of the proposed scheme. Comparison with different values of scaling parameter M, which is used to decrease the size of image in the VC is also done. The results clearly indicate that the proposed scheme can send more data with less bandwidth more secretly.

Related to the growth of data sharing on the Internet and the wide - spread use of digital media, multimedia security and copyright protection have become of broad interest. Visual cryptography () is a method of sharing a secret image between a group of participants, where certain groups of participants are defined as qualified and may combine their share of the image to obtain the original, and certain other groups are defined as prohibited, and even if they combine knowledge of their parts, they can’t obtain any information on the secret image. The visual cryptography is one of the techniques which used to transmit the secrete image under the cover picture. Human vision systems are connected to visual cryptography. The black and white image was originally used as a hidden image. In order to achieve the owner’s copy right security based on visual cryptography, a watermarking algorithm is presented. We suggest an approach in this paper to hide multiple images in video by meaningful shares using one binary share. With a common share, which we refer to as a smart key, we can decrypt several images simultaneously. Depending on a given share, the smart key decrypts several hidden images. The smart key is printed on transparency and the shares are involved in video and decryption is performed by physically superimposing the transparency on the video. Using binary, grayscale, and color images, we test the proposed method.

Traditional k out of n visual cryptography scheme has been proposed to encrypt single secret image into n shares where only k or more shares can decode the secret image. Many existing schemes on visual cryptography are restricted to consider only binary images as secret which are not appropriate for many important applications. Store-and-Forward telemedicine is one such application where medical images are transmitted from one site to another via electronic medium to analyze the patient's clinical health status. The main objective of Store-and-Forward telemedicine is to provide remote clinical services via two-way communication between the patient and the healthcare provider using electronic medical image, audio and video means. In this paper, a new XOR based Continuous-tone Multi Secret Sharing scheme suitable for store-and-forward telemedicine is proposed to securely transmit the medical images. It also eliminates basic security constraints of VC like pixel expansion in shares/recovered secret images, random pattern of shares, explicit codebook requirement, lossy recovery of secret and limitation on number of secret and shares. Proposed approach is n out of n multi secret sharing scheme which is able to transmit n secret images simultaneously. All secrets could be revealed only after some computations with all n shares and one master share. Master share has been created with the secret key at encoding phase and it can be regenerated at the time of decoding using same secret key. Here all shares are meaningful in continuous-tone which may provide confidentiality to medical images during transmission. Proposed approach not only preserves all basic characteristics of traditional VC but also increases the capacity of secret image sharing. From the experiments we found that irrespective of visible contents of the shares, the probability of getting back the pixel values of respective original secret images at the receiver end is very high.

A hybrid approach combining data hiding with visual cryptography for secure extraction of data hiding

Visual cryptography encodes a secret binary image (SI) into n shares of random binary patterns. If the shares are xeroxed onto transparencies, the secret image can be visually decoded by superimposing a qualified subset of transparencies, but no secret information can be obtained from the superposition of a forbidden subset. The binary patterns of the n shares, however, have no visual meaning and hinder the objectives of visual cryptography. Extended visual cryptography [1] was proposed recently to construct meaningful binary images as shares using hypergraph colourings, but the visual quality is poor. In this paper, a novel technique named halftone visual cryptography is proposed to achieve visual cryptography via halftoning. Based on the blue-noise dithering principles, the proposed method utilizes the void and cluster algorithm [2] to encode a secret binary image into n halftone shares (images) carrying significant visual information. The simulation shows that the visual quality of the obtained halftone shares are observably better than that attained by any available visual cryptography method known to date.

This paper proposes a (k,n) visual cryptography based on Shamir's secret sharing (VCSSS). Using Shamir's secret sharing, a binary secret image can be shared into n meaningless shares, in order to make the generated shares more like noise images, adding the randomness within the process of sharing. Picking any k shares from n meaningless shares, the secret image can be revealed by using Lagrange interpolation. The main contribution of this paper is that applying Shamir's secret sharing to realize a (k,n) visual cryptography, and this method neither requires code book nor suffers from pixel expansion. Experimental results show VCSSS can realize a (k,n) visual cryptography, and correct decoding rate (CDR) of revealed secret image can be guaranteed.

ENHANCING home security through visual CRYPTOGRAPHY

Now a days, most of our data is travelled over internet so the security of that data is most important. Visual cryptography plays a very crucial role for security of image based secret. Visual cryptography encrypts the image in to shares and in decryption process all shares are stacked together to reveal the secret image. Here we are proposing a new scheme for color share generation. In this scheme R, G and B component is extracted from color image then apply gray share generation algorithm on R component and make n number of R gray shares then all shares are combine with B and G component to make color shares. At decryption side B and G component is extracted from all shares and then combine all r gray share to make r component and after that all R, G and B is combined to revealed the secret image. Decrypted secret image has same size as original secret image.

Visual Cryptography for General Access Structures

Visual cryptography (VC) is a method of encrypting a secret image into shares such that stacking a sufficient number of shares reveals the secret image. Shares are usually presented in transparencies. Each participant holds a transparency. Most of the previous research work on VC focuses on improving two parameters: pixel expansion and contrast. In this paper, we studied the cheating problem in VC and extended VC. We considered the attacks of malicious adversaries who may deviate from the scheme in any way. We presented three cheating methods and applied them on attacking existent VC or extended VC schemes. We improved one cheat-preventing scheme. We proposed a generic method that converts a VCS to another VCS that has the property of cheating prevention. The overhead of the conversion is near optimal in both contrast degression and pixel expansion.

A reversible extended secret image sharing scheme based on Chinese remainder theorem

Visual cryptography (VC) schemes provide a distinguished image encryption technique to protect image security since it can visually decrypt the secret image by superimposing the encrypted shadows. VC schemes for both threshold access structures and general access structures are generally constructed based on the OR operation to minimize the pixel expansion. However, VC schemes with optimal pixel expansion typically have low contrast. Stacking operation OR frequently produces recovered images with poor visual quality and are never able to deliver flawless recovery for secret images. Therefore, we studied XOR-based VC (XVC) schemes that employ linear programming to maximize their contrast. Three schemes for general access structures and three schemes for threshold access structures are designed to maximize their contrast. The proposed schemes’ construction is reduced to a linear programming to maximize the contrast by determining the ideal combinations of basis matrices in terms of primary column matrices and unit matrices, respectively. The comparison study and experimental results demonstrate that the contrast of the previous VC and XVC schemes can be further improved.

<p>Visual cryptography (VC) has emerged as a pivotal solution for secure information transmission, leveraging its unique capability to encrypt images in a user-friendly and accessible manner. This survey paper provides an in-depth analysis of various VC methods, highlighting their distinct encryption and decryption techniques, applicability, and security levels. The study delves into the technical specifications of each VC type, offering insights into secret image formats, the number of secret images used, types of shares, pixel expansion, and complexity. Significant attention is given to the practical applications of VC, ranging from secure document verification and anti-counterfeiting measures to digital watermarking and online data protection. The paper also identifies key challenges in the field, such as image quality retention post-decryption, computational efficiency, and scalability. Future prospects of VC are explored, particularly its potential integration with emerging technologies like AI and blockchain. This survey aims to provide a comprehensive understanding of VC’s current state, its diverse applications, and the future possibilities, making it a valuable resource for researchers and practitioners in the field of data security and cryptography.</p>

Traditional k out of n threshold visual cryptography scheme is proposed to hide a secret image into n shares, where only k or more shares can visually reveal the secret image. Most of the previous state of art approaches on visual cryptography are almost restricted in processing of binary images as secret, which are inadequate for many applications like securely transmission of medical images(Store and Forward Telemedicine), forensic images etc. In this paper, a new Verifiable Multi-toned Visual Cryptography (VMVC) scheme is proposed to securely transmit the confidential images on web. Proposed approach also provides cheating prevention, since each pixel of shares contains a self embedding verifiable bit for integrity test of that pixel. Many existing approaches are suffering from many unnecessary encryption constraints like random shares, codebook requirement, contrast loss etc, which all are successfully addressed in proposed approach. Some comparisons with previously proposed methods are also made. Experimental results and analysis are used to prove the efficiency of proposed approach.