The Visual Secret Sharing Scheme Based on the Rgb Color System

The visual secret sharing (VSS) scheme is a method to maintain the confidentiality of a se-cret image by sharing it to some number participants. A (k, n) VSS divides the secret images into n parts, that are called shadows ; to recover the secret back, k shadows should be stacked. Some methods have been developed to implement VSS for color images. However, the methods are only suitable for images with limited number of colors. When more colors are used, the resulted stacked shadow image becomes unclear. Besides that, the size of the shadows becomes bigger as more colors are used. We develop a new method implementing the VSS using the RGB color system. Using our method, the problem related to the unclear stacked shadow image can be overcome

THE VISUAL SECRET SHARING SCHEME BASED ON THE RGB COLOR SYSTEM

The visual secret sharing (VSS) scheme is a method to maintain the confidentiality of a se-cret image by sharing it to some number participants. A (k, n) VSS divides the secret images into n parts, that are called shadows ; to recover the secret back, k shadows should be stacked. Some methods have been developed to implement VSS for color images. However, the methods are only suitable for images with limited number of colors. When more colors are used, the resulted stacked shadow image becomes unclear. Besides that, the size of the shadows becomes bigger as more colors are used. We develop a new method implementing the VSS using the RGB color system. Using our method, the problem related to the unclear stacked shadow image can be overcome

Two Step Share Visual Cryptography Algorithm for Secure Visual Sharing

This paper re - examines the problem of visual secret sharing for general access structures by using visual cryptograms of random grids (VCRG). Given a binary or color secret image shared by a set of n participants with a strong access structure, we devise t wo effective algorithms to produce a set of VCRG so that the members in each qualified set can reconstruct the secret image by superimposing their sh ares, while those in any forbidden set cannot. The basic 2 out of 2 visual cryptography model consists of a secret message encoded into two transparencies, one transparency representing the cipher text and the other acting as a secret key. Both transparencies appear to be random dots when inspected individually and provide no information about the original clea r text. However, by carefully aligning the transparencies, the original secret message is reproduced. The actual decoding is accomplished by the human visual system. Our algorithms do not require any extr a pixel expansion, which is indispensable and grows exponentially as n increases in conventional visual cryptographic schemes

A novel quality assessment for visual secret sharing schemes

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

On Real-valued Visual Cryptographic Basis Matrices

Visual cryptography (VC) encodes an image into noise-like shares, which can be stacked to reveal a reduced quality version of the original. The problem with encrypting colour images is that they must undergo heavy pre-processing to reduce them to binary, entailing significant quality loss. This paper proposes VC that works directly on intermediate grayscale values per colour channel and demonstrates real-valued basis matrices for this purpose. The resulting stacked shares produce a clearer reconstruction than in binary VC, and to the best of the authors’ knowledge, is the first method posing no restrictions on colour values while maintaining the ability to decrypt with human vision. Grayscale and colour images of differing entropies are encrypted using fuzzy OR and XOR, and their PSNR and structural similarities are compared with binary VC to demonstrate improved quality. It is compared with previous research and its advantages highlighted, notably in high quality reconstructions with minimal processing

Steganography: a class of secure and robust algorithms

This research work presents a new class of non-blind information hiding algorithms that are stego-secure and robust. They are based on some finite domains iterations having the Devaney's topological chaos property. Thanks to a complete formalization of the approach we prove security against watermark-only attacks of a large class of steganographic algorithms. Finally a complete study of robustness is given in frequency DWT and DCT domains.Comment: Published in The Computer Journal special issue about steganograph