Visual Secret Sharing Scheme for Digital Image Watermarking

In Visual Cryptography Schemes (VCSs), for message n transparencies are generated, such that the original message is visible if any k of them are stacked. VCS especially for large values of k and n, the pixel expansion’s reduction and enhancement of the recovered images’ display quality continue to be critical issues. In addition to this, it is challenging to develop a practical and systematic approach to threshold VCSs. An optimization-based pixel-expansion-free threshold VCSs approach has been proposed for binary secret images’ encryption. Along with contrast, blackness is also treated as a performance metric for assessing the recovered images’ display quality. An ideally secure technique for a secret image’s protection through its partition into shadow images (known as shadows) is the Visual Secret Sharing (VSS) scheme. Acquirement of a smaller shadow size or a higher contrast is the VSS schemes’ latest focus. The white pixels’ frequency has been utilized to demonstrate the recovered image’s contrast in this work. While the Probabilistic VSS (ProbVSS) scheme is non-expansible, it can also be readily deployed depending upon the traditional VSS scheme. Initially, this work has defined the problem as a mathematical optimization model such that, while contingent on blackness and density-balance constraints, there is the maximization of the recovered images’ contrast. Afterward, an algorithm dependent on the Tabu Search (TS) is devised in this work for this problem’s resolution. Multiple complicated combinatorial problems have been successfully resolved with the powerful TS algorithm. Moreover, this work has attempted to bolster the contrast through the density-balance constraint’s slight relaxation. Compared to the older techniques, the proposed optimization-based approach is superior regarding the recovered images’ display quality and the pixel expansion factor from the experimental outcomes.

Visual Secret Sharing (VSS) schemes address the security concerns of digital images. Rotational VSS schemes are unique in that the shares stacked with the specific rotated shares reveal the secret images. However, these schemes iteratively process huge pixels in sequence. We propose a GPGPU based rotational (2, 3) VSS scheme which leverages concurrency inherent in the traditional rotational schemes. The proposed scheme also makes use of contemporary hardware resources efficiently. The reduction in the memory band-width demand and increased data transfer speed further accelerates the speedup of this scheme. A significant improvement in performance with an efficient resource utilization is observed.

With the rapid growth of data transmission and visual encryption technologies, Visual Secret Sharing (VSS) has become an important technique for image-based information protection. However, many existing VSS schemes remain vulnerable to dishonest participants who attempt to recover secret images through unauthorized stacking or manipulation of shares. To address this issue, this paper proposes a dishonest-participant-resistant VSS scheme based on linearly polarized shares and Probability Distribution Trees (PDTs). The proposed method embeds both secret and fake images into polarized shares, such that any unauthorized stacking of ordinary shares produces a visually plausible fake image or random noise, while only stacking that includes the master share under a predefined optical ordering reveals the true secret image. Binary image binarization and probability-guided polarization assignment are employed to improve computational efficiency and increase uncertainty against adaptive attacks. In addition to visual inspection and contrast analysis, peak signal-to-noise ratio (PSNR), structural similarity index (SSIM), and visual information fidelity (VIF) are used as complementary metrics to distinguish authorized reconstructions from unauthorized and partial ones. Experimental results show that authorized reconstructions achieve high visual fidelity and perceptual recognizability, whereas unauthorized and partial reconstructions yield significantly degraded or misleading outputs, demonstrating effective suppression of information leakage and strong resistance against dishonest behavior. Consequently, the proposed scheme enhances security and practical usability compared with existing polarization-based VSS approaches.

Visual secret sharing (VSS), also called visual cryptography, allows a secret image to be divided into several shares and the secret image can only be recovered through the collaboration of the shares. Due to high security and low computational complexity, VSS has been widely used in secure communications. In this paper, we propose the first turtle shell (TS)-based VSS scheme that shares the secret information into two meaningful shares. Firstly, a TS reference matrix is established. Then, secret information is hidden in a cover image to construct two meaningful shares with the help of TS reference matrix. The hidden secret information can be extracted without distortion if both shares are gathered and the cover image can be correctly restored by solving the location conflict problem. Moreover, an invalid share can easily be detected by the proposed scheme. Experimental results indicate that the proposed scheme provides excellent visual quality and is superior to state-of-the-art VSS schemes.

Visual secret sharing (VSS) scheme can share the secret image with several shares. Shares are performed by the decoding operation to restore the secret image. VSS scheme is mainly used for the secure transmission of images. Quick response (QR) code is often used by people on the Internet. It can be encrypted by the VSS scheme to enhance the security of its transmission. The share is meaningless that will arouse the suspicion of the attacker. The security of the VSS scheme is decreased. This paper proposes a novel VSS scheme for the QR code with meaningful images to solve this problem. Two continue tone images are converted to halftone images. The halftone image is modified to generate the share. Every share is meaningful, not meaningless. Two shares are performed the decoding operation to restore the secret QR code. The restored QR code can be correctly decoded by the general decoder. Experimental results prove that the proposed scheme is feasible.

Pixel expansion is a common drawback of traditional (2,2) visual secret sharing (VSS), unexpanded shares can decrease the bandwidth and save storage. In the literature, we introduce a novel (2,2) VSS scheme, that solved the pixel expansion and visual quality is almost equal with traditional (2,2) VSS. Our scheme not only can apply to (2,2) VSS, but also to (k, k) VSS. At last, analyse and experiment are conducted to evaluate the efficiency of the proposed method.

Conventional visual secret sharing (VSS) schemes generate noise-like random pixels on shares to hide secret images. However, these schemes suffer from two problems, one related to security and one related to management. First, the noise-like shares arouse suspicion, which leads to security problems for participants who are involved in a VSS scheme. Second, participants cannot visually identify each share, especially if they hold more than one share simultaneously, which leads to the management problem. To address the management problem previous researchers developed extended visual cryptography schemes that add a meaningful cover image on each share. Generally, however, these approaches introduce a more serious pixel expansion problem than conventional VSS schemes. In addition, there are still many noise-like shares, which do not effectively reduce the security problems. This paper proposes a natural-image-based secret image sharing scheme (NSISS) that can share a color secret image over n - 1 arbitrary natural images and one noise-like share image. Instead of altering the contents of the natural images, the encryption process extracts feature images from each natural image. In such a way, the unaltered natural images are innocuous, thus greatly reducing the security problem. Experimental results indicate that the proposed approach is an excellent solution for solving the management and security problems. Moreover, the proposed approach avoids the pixel expansion problem and makes it possible to totally recover the secret images.

Visual secret sharing (VSS) is one of the cryptographic techniques of Image secret sharing scheme (ISSS) that performs encoding of secret message image (text or picture) into noise like black and white images, which are called as shares. Shares are stacked together and secret message image is decoded using human visual system. One of the major drawbacks of this scheme is its poor contrast of the recovered image, which improves if computational device is available while decoding. In this paper, we propose to improve poor contrast of classical VSS schemes for text or alphanumeric secret messages and low entropy images. Initially, stacked image is binarized using dynamic threshold value. A mathematical morphological operation is applied on the stacked image to enhance contrast of the reconstructed image. Moreover, a method is proposed that allows the size of the structuring element to change according to the contrast and the size of a stacked image. We perform experiments for different types of VSS schemes, different share patterns, different share types (rectangle and circle), and low entropy images. Experimental results demonstrate the efficacy of the proposed scheme.

------------------------------------------------------------ABSTRACT--------------------------------------------------------Information security becomes more and more important while the internet communication grows up. Visual secret sharing (VSS) schemes hide secret images in shares that are either printed on transparencies or are encoded and stored in a digital form. Conventional visual secret sharing schemes suffers from a management problem, so that dealers cannot identify each share visually The approaches involving the EVCS for GAS suffers from a pixel expansion problem and also needs a sophisticated various encryption schemes. This paper presents natural image based visual secret sharing scheme that shares secret images via various carrier media to protect the secret and the participants during the transmission phase. The proposed (n, n) NVSS scheme can share one digital secret image over n -1 arbitrary selected natural images (called natural shares) and one noise-like share . The natural shares can be photos or hand-painted pictures in digital form or in printed form. The noise-like share is generated based on these natural shares and the secret image -------------------------------------------------------------------------------------------------------------------------------------Date of Submission: 03-April-2015 Date of Accepted: 30-April-2015 --------------------------------------------------------------------------------------------------------------------------------------

The visual secret sharing (VSS) approach by random grids (RG-based VSS) has drawn people's attention "again" recently. Nevertheless, the current RG-based VSS approaches suffer from the problem of meaningless share images (cipher-grids) so that it is not user-friendly to manage noise-like share images. This paper presents a novel color RG-based VSS scheme aiming at providing the friendly color cipher-grids with all the advantages of traditional VSS schemes. To our best knowledge, this paper is the first effort to develop the friendly technique. The experimental results show that the scheme does work.

The traditional cheating prevention is usually based on visual cryptography (VC), in which the constructed image is bigger than the secret image because of the pixel expansion. In this paper, we studied the cheating problems in visual secret sharing (VSS) by random grids (RG) which can prevent the cheating activities with no pixel expansion. We considered the attacks of collusive cheaters who may deviate from the scheme in any way. We presented the cheating method and applied it on attacking existent n-out-of-n VSS scheme based on RG. Then we proposed one cheat-preventing scheme that can prevent the cheating activity upon.

Threshold visual secret sharing by random grids

Weighted visual secret sharing for general access structures based on random grids

Security problem is becoming increasingly crucial in many fields. In order to ensure that secret images are not being stolen during information transmission, a preferred way is to encrypt them before transmission. Visual secret sharing scheme (VSSS) is a scheme of secure communication technology in which a secret image is encrypted into some shares and then restored through human vision by stacking shares directly. A fault-tolerant VSSS is a VSSS which is not necessary to align the shares precisely when recovering the secret image. In the other side, encrypting a secret image into two meaningless shares might invite the attacker's attention. Therefore, this paper proposed two fault- tolerant VSSS which encrypt one secret image into two meaningful shares, and with the fault-tolerant mechanism.

Traditional visual secret sharing (VSS) schemes that encrypt secret images into noise-like images have been extended to multiple secret sharing (MSS) schemes to share multiple secret images using meaningful shares. Due to poor visual quality, such schemes are vulnerable to attacks from intruders. In this paper, we propose an efficient (n, n) MSS scheme for sharing n secret images, where n cover images are embedded in n meaningful shares. The proposed scheme provides improved visual quality with higher sharing capacity. Security is enhanced by meaningful share images. Thus, the proposed scheme offers enhanced quality and efficiency while satisfying security criteria.