Visual cryptography

About: Visual cryptography is a research topic. Over the lifetime, 1724 publications have been published within this topic receiving 25300 citations.

Secret image sharing with capability of share data reduction

Abstract: A novel approach to secret image sharing based on a (k,n)-threshold scheme with the additional capability of share data re- duction is proposed. A secret image is first transformed into the fre- quency domain using the discrete cosine transform (DCT), which is ap- plied in most compression schemes. Then all the DCT coefficients except the first 10 lower frequency ones are discarded. And the values of the 2nd through the 10th coefficients are disarranged in such a way that they cannot be recovered without the first coefficient and that the inverse DCT of them cannot reveal the details of the original image. Finally, the first coefficient is encoded into a number of shares for a group of secret- sharing participants and the remaining nine manipulated coefficients are allowed to be accessible to the public. The overall effect of this scheme is achievement of effective secret sharing with good reduction of share data. The scheme is thus suitable for certain application environments, such as the uses of mobile or handheld devices, where only a small amount of network traffic for shared transmission and a small amount of space for data storage are allowed. Good experimental results proving the feasibility of the proposed approach are also included. © 2003 Society

Visual cryptography in single-pixel imaging.

Abstract: Two novel visual cryptography (VC) schemes are proposed by combining VC with single-pixel imaging (SPI) for the first time. It is pointed out that the overlapping of visual key images in VC is similar to the superposition of pixel intensities by a single-pixel detector in SPI. In the first scheme, QR-code VC is designed by using opaque sheets instead of transparent sheets. The secret image can be recovered when identical illumination patterns are projected onto multiple visual key images and a single detector is used to record the total light intensities. In the second scheme, the secret image is shared by multiple illumination pattern sequences and it can be recovered when the visual key patterns are projected onto identical items. The application of VC can be extended to more diversified scenarios by our proposed schemes.

Perfect contrast XOR-based visual cryptography schemes via linear algebra

Abstract: XOR-based visual cryptography scheme (XVCS) was proposed to solve the poor visual quality problem without darkening the background in the reconstructed secret image. However, investigations on XVCS are not sufficient. In this paper, we focus on the traditional model of VCS for general access structures and exploit some extended capabilities for XVCS. Our main contributions are: (1) we put forward constructions of perfect contrast XVCS using the linear algebraic technique without any assumptions such as participants may carry multiple shares or prior information about the shares are to be submitted during the secret reconstruction phase; (2) for some restricted access structures, we achieve perfect contrast and perfect pixel expansion, namely both 1, which is impossible for any OR-based visual cryptography scheme (OVCS); (3) for general access structures, we achieve perfect contrast with smaller pixel expansion compared with many of the results in the literature; (4) Theoretical analysis on the proposed constructions are provided, as well as extensive experimental results and comparisons for demonstrating the effectiveness and advantages of our constructions.

Joint visual cryptography and watermarking

Abstract: In this paper, we discuss how to use the watermarking technique for visual cryptography. Both halftone watermarking and visual cryptography involve a hidden secret image. However, their concepts are different. For visual cryptography, a set of shared binary images is used to protect the content of the hidden image. The hidden image can only be revealed when enough shared images are obtained. For watermarking, the hidden image is usually embedded in a single halftone image while preserving the quality of the watermarked halftone image. In this paper, we propose a joint visual-cryptography and watermarking (JVW) algorithm that has the merits of both visual cryptography and watermarking

Secure information display with limited viewing zone by use of multi-color visual cryptography.

Abstract: We propose a display technique that ensures security of visual information by use of visual cryptography. A displayed image appears as a completely random pattern unless viewed through a decoding mask. The display has a limited viewing zone with the decoding mask. We have developed a multi-color encryption code set. Eight colors are represented in combinations of a displayed image composed of red, green, blue, and black subpixels and a decoding mask composed of transparent and opaque subpixels. Furthermore, we have demonstrated secure information display by use of an LCD panel.