Non-expansible XOR-based visual cryptography scheme with meaningful shares

A (n, n) threshold non-expansible XOR based visual cryptography with unique meaningful shares

In the past decade, the researchers paid more attention to the cheating problem in visual cryptography (VC) so that many cheating prevention visual cryptography schemes (CPVCS) have been proposed. In this paper, the authors propose a novel method, which first makes use of Latin square to prevent cheating in VC. Latin squares are utilised to guide the choosing of authentication regions in different rows and columns of each divided block of the shares, which ensures that the choosing of authentication regions is both random and uniform. Without pixel expansion, the new method provides random regions authentication in each divided block of all shares. What is important is that the proposed method is applicable to both (
 k
, n
)-deterministic visual cryptography scheme ((
 k
, n
)-DVCS) and (
 k
, n
)-probabilistic visual cryptography scheme ((
 k
, n
)-PVCS). Experimental results and properties analysis are given to show the effectiveness of the proposed method.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-ifs.2016.0126

Cheating prevention visual cryptography scheme using Latin square

To evaluate the visual quality in visual secret sharing schemes, most of the existing metrics fail to generate fair and uniform quality scores for tested reconstructed images. We propose a new approach to measure the visual quality of the reconstructed image for visual secret sharing schemes. We developed an object detection method in the context of secret sharing, detecting outstanding local features and global object contour. The quality metric is constructed based on the object detection-weight map. The effectiveness of the proposed quality metric is demonstrated by a series of experiments. The experimental results show that our quality metric based on secret object detection outperforms existing metrics. Furthermore, it is straightforward to implement and can be applied to various applications such as performing the security test of the visual secret sharing process.

/pdf/a-novel-quality-assessment-for-visual-secret-sharing-schemes-4fh631ne7m.pdf

A novel quality assessment for visual secret sharing schemes

Visual secret sharing (VSS) is a new technique for sharing a binary image into multiple shadows. For VSS, the original image can be reconstructed from the shadows in any qualified set, but cannot be reconstructed from those in any forbidden set. In most traditional VSS schemes, the shadows held by participants have the same importance. However, in practice, a certain number of shadows are given a higher importance due to the privileges of their owners. In this article, a novel (t, s, k, n)-threshold VSS scheme is proposed based on access structure partition. First, we construct the basis matrix of the proposed (t, s, k, n)-threshold VSS scheme by utilizing a new access structure partition method and sub-access structure merging method. Then, the secret image is shared by the basis matrix as n shadows, which are divided into s essential shadows and n-s non-essential shadows. To reconstruct the secret image, k or more shadows should be collected, which include at least t essential shadows; otherwise, no information about the secret image can be obtained. Compared with related schemes, our scheme achieves a smaller shadow size and a higher visual quality of the reconstructed image. Theoretical analysis and experiments indicate the effectiveness of the proposed scheme.

A Novel (t, s, k, n)-Threshold Visual Secret Sharing Scheme Based on Access Structure Partition

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.

XOR-based meaningful visual secret sharing by generalized random grids

Tagged visual cryptography (TVC) is a brand new type of visual cryptography (VC) in which additional tags are concealed into each generated share. By folding up each single share, the associated tagged pattern is visually revealed. Such additional tag patterns greatly enrich extra abilities of VC, such as augmented message carried in a single share, user-friendly interface to manage the shares, and/or evidence for verifying consistency among those shares cooperating in a decryption instance. However, reported \((k,n)\) TVC proposed by Wang and Hsu still suffers from the defects such as pixel expansion, code book required in the encoding phase and low image quality. In this work, a \((k,n)\) TVC by adopting the concept of random grid (RG) is introduced. The proposed method can solve the pixel expansion and code book needed problems. Further, better visual quality of both the recovered secret image and reconstructed tag image is provided according to the theoretical analysis and demonstrated experiments.

Improved Tagged Visual Cryptograms by Using Random Grids

This paper presents a novel \((n,n)\)–threshold secret sharing in images by using error-diffused block truncation coding (EDBTC) and error diffusion. The proposed scheme is designed to share a secret binary image, such as text image or natural image, into \(n\) EDBTC-compressed images including meaningful contents. The compressed shadows generated by our proposed scheme have good visual quality and no pixel expansion, which are beneficial to reduce suspicions from the invaders. Each value in the secret image is reconstructed by using boolean XOR operations which are considered as light-weight devices, thus the recovering process is simple and fast. In addition, EDBTC-compressed images instead of the original format images are selected as shadows, which can improve the efficiency for data transmission and storing. The experimental results demonstrate that the proposed scheme offers a high secure and effective mechanism for secret image sharing.

Lu Dai

Papers

XOR-based meaningful visual secret sharing by generalized random grids

Improved Tagged Visual Cryptograms by Using Random Grids

Secret Sharing in Images Based on Error-Diffused Block Truncation Coding and Error Diffusion