Visual cryptography

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

Aspect ratio invariant visual cryptography by image filtering and resizing

Abstract: In visual cryptographic scheme (VCS), each secret pixel is expanded to m subpixels in shadow images to encrypt a secret image. Apparently, we should put these m subpixels as a rectangle such that the blocks can be arranged compactly with each other. However, if the aspect ratio is viewed as important information of the secret image, the distortion occurs at the case that m is not a square. An aspect ratio invariant VCS (ARIVCS) was accordingly proposed to address the arrangement of subpixels. However, the existing ARIVCSs relied on adding dummy subpixels to the shadow images. In addition, their method needs a mapping pattern that reduces the number of dummy subpixels, but how to design a mapping pattern is a huge challenge. In this paper, we propose an easy solution to construct ARIVCS by image filtering and resizing.

A new two-level QR code with visual cryptography scheme

Abstract: The Quick Response (QR) code is designed for information storage recognizable by machine vision. With the popularity of QR code applications, the security of QR codes becomes hot issues concerned by many scholars. In this paper, a novel QR code with two-level information storage is designed to protect private messages. In the meantime, the public level can be directly decoded by any standard QR reader. In contrast to other studies, the computational complexity of the proposed scheme is reduced by combining with the theory of visual cryptography scheme (VCS). In addition, an important characteristic of the QR code, error correction capability, is preserved in this paper, guaranteeing the robustness to QR code damage. Experimental results and analysis show that the proposed scheme is both feasible and reasonably secure, further enriching the application fields and outperforming the previous schemes significantly.

Robust digital video watermarking using reversible data hiding and visual cryptography

Abstract: Watermarking is a major image processing application used to authenticate user documents by embedding and hiding some authenticated piece of information behind an image, audio or the video file. For example, copyright symbols or signatures are often used. Our proposed work is to develop and implement an improved layered approach to video watermarking. The traditional watermarking approach tends to embed an entire watermark image within each video frame or within random video frames to give the appearance of a hidden watermark to the casual observer. This work proposes a more efficient and secured approach to perform watermarking, by using sub image classification. That is to say, selected frames only will contain a fractional number of total bits from the watermark image. We take k bits from the watermark and store then within a video frame, depending on the size of that watermark image. Our algorithm is capable of hiding high capacity information over video frames. The novel approach is to partially distribute the watermarking data over a set of frames until the entire watermark is eventually distributed throughout the entire video. The originality our technique is that it is a histogram inspired and reversible watermarking approach as defined with visual cryptography. Our approach hides similar watermarking bits of information with frames of a similar appearance. Differing sets of watermark bits are thus embedded within dissimilar frames, thus making the system more robust. It will provide a high degree of authentication, as the extraction of information from a single frame only will not reveal the entire watermarking data, or even give any obvious indication that it contains a fraction of the watermark bits. The robustness of our technique will be tested by calculating MSE, PSNR values and by performing some common