Visual cryptography

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

Clarity Corresponding to Contrast in Visual Cryptography

Abstract: The visual quality of the recovered secret image is usually evaluated by contrast in visual cryptography (VC). Precisely, the reconstructed secret image can be recognized as the original secret image when contrast is greater than zero. It is important for the user to know the clarity of the revealed secret image corresponding to different contrast values. In this paper, the clarity corresponding to contrast is investigated through conducting subjective evaluation scores and objective evaluation indexes, which can be extended to general applications.

Multi secret image color visual cryptography schemes for general access structures

Abstract: In the proposed visual cryptography schemes for general access structures, the single secret image black-and-white visual cryptography schemes with meaningful shares have been constructed, in which the shares are innocent looking images. The meaningful shares have not been realized in single secret image color schemes; neither have the multi secret images color schemes. In this paper, the multi secret images color visual cryptography schemes for general access structures with meaningful shares are constructed by the method of matrix concatenation, the pixel expansion is obtained, and the validity of the scheme is proven. In our scheme, the different combination of meaningful color shares can be used to recover distinct color secret images. The multi secret images black-and-white visual cryptography scheme is a special case of our color scheme. *Supported by National Natural Science Foundation of China (Grant No. 90304014) and the Major State Basic Research Development Program of China (Grant No. ...

Multi-secret visual cryptography with deterministic contrast

Abstract: The multi-secret visual cryptography scheme (MVCS) allows for the encryption of multiple secret images into a given image area. The previous works on MVCS with probabilistic contrast can not guarantee that every original pixel will be reconstructed correctly. However, MVCS with deterministic contrast can reconstruct every original pixel with simple computation for high-end applications, but they are all simple 2-out-of-2 cases. These drawbacks limit the applicability of MVCSs existed. Based on ringed shares, MVCS with deterministic contrast has been defined in this paper. Furthermore, an (k, n)-MVCS with deterministic contrast, which makes the number of secret images not restricted, is proposed on the basis of the share rotation algorithm and the basis matrices of single secret sharing visual cryptography. Experimental results show that our scheme is the first (k, n)-MVCS with deterministic contrast, which can be applied on any k and n.

Structure Aware Visual Cryptography

Abstract: Visual cryptography is an encryption technique that hides a secret image by distributing it between some shared images made up of seemingly random black-and-white pixels. Extended visual cryptography EVC goes further in that the shared images instead represent meaningful binary pictures. The original approach to EVC suffered from low contrast, so later papers considered how to improve the visual quality of the results by enhancing contrast of the shared images. This work further improves the appearance of the shared images by preserving edge structures within them using a framework of dithering followed by a detail recovery operation. We are also careful to suppress noise in smooth areas.