Showing papers on "Visual cryptography published in 2000"

New Colored Visual Secret Sharing Schemes

Abstract: Visual secret sharing (VSS) schemes are used to protect the visual secret by sending n transparencies to different participants so that k-1 or fewer of them have no information about the original image, but the image can be seen by stacking k or more transparencies. However, the revealed secret image of a conventional VSS scheme is just black and white. The colored k out of n VSS scheme sharing a colored image is first introduced by Verheul and Van Tilborg [1]. In this paper, a new construction for the colored VSS scheme is proposed. This scheme can be easily implemented on basis of a black & white VSS scheme and get much better block length than the Verheul-Van Tilborg scheme.

A Digital Image Copyright Protection Scheme Based on Visual Cryptography

Abstract: A simple and efficient watermark method is proposed in this paper. The watermark method is an excellent technique to protect the copyright ownership of a digital image. The proposed watermark method is built up on the concept of visual cryptography. According to the proposed method, the watermark pattern does not have to be embedded into the original image directly, which makes it harder to detect or recover from the marked image in an illegal way. It can be retrieved from the marked image without making comparison with the original image. The notary also can off-line adjudge the ownership of the suspect image by this method. The watermark pattern can be any significant black/white image that can be used to typify the owner. Experimental results show that the watermark pattern in the marked image has good transparency and robustness. By the proposed method, all the pixels of the marked image are equal to the original image.

Repeating Image Watermarking Technique by the Visual Cryptography

Abstract: A repeating watermarking technique based on visual secret sharing (VSS) scheme provides the watermark repeated throughout the image for avoiding the image cropping. In this paper, the watermark is divided into public watermark and secret watermark by using the VSS scheme to improve the security of the proposed watermarking technique. Unlike the traditional methods, the original watermark does not have to be embedded into the host image directly and, thus, it is hard to be detected or removed by the pirates or hackers. The retrieved watermark extracted from the watermarked image does not require the complete original image, but requires a secret watermark. Furthermore, the watermarking technique suits the watermark with an adaptive size of binary image for designing the watermarking system. The experimental results show that the proposed method can withstand the common image processing operations, such as filtering, lossy compression and the cropping attacking etc. The embedded watermark is imperceptible, and that the extracted watermark identifies clearly the owner’s copyright. key words: watermarking, visual secret sharing, common image

A new scheme for sharing secret color images in computer network

Abstract: Based on a visual cryptography scheme, an effective and generalized scheme of color image hiding is proposed. By means of little additional computations, it goes through a color index table to hide and recover a secret image. In this scheme, a secret color image hides itself in two arbitrary color images, which can be constructed and then are kept by two participants, separately. Note that the processed images are significant. It is a kind of camouflage. Later, the secret image can be recovered through the same simple algorithms on two camouflage color images. The paper proves that only one of the two camouflage color images cannot reveal the secret image. Thus, the hidden information is secured.

An asymmetric watermarking scheme based on visual cryptography

Abstract: Digital watermarking is a very active research area for copyright protection of electronic documents and media. A visual cryptographic approach is used to generate two random shares of a watermark: one is embedded into the cover-image and another is kept as a secret key for the later watermark extraction. The watermark can be extracted by simply superimposing the key share over the stego-image. This asymmetric digital watermark is specially designed and is not easily changed or removed. But, it is very convenient to be extracted. The embedded digital watermark by this approach seems robust after several attacks are performed on the stego-image.

A neural network approach for visual cryptography

Abstract: Visual cryptography finds many applications in the cryptographic field such as key management, message concealment, authorization, authentication, identification, and entertainment. The authors propose a novel approach for visual cryptography using neural networks (NNs). To perform encrypting, the input to the NN is a set of gray level images, and the output is a set of binary images (shares) that fulfils the desirable access scheme. This approach is considerably different from the traditional one, and can be applied to cope with very complex access schemes.

Randomness in Visual Cryptography

Abstract: A visual cryptography scheme for a set P of n participants is a method to encode a secret image into n shadow images called shares each of which is given to a distinct participant. Certain qualified subsets of participants can recover the secret image, whereas forbidden subsets of participants have no information on the secret image. The shares given to participants in X ⊆ P are xeroxed onto transparencies. If X is qualified then the participants in X can visually recover the secret image by stacking their transparencies without any cryptography knowledge and without performing any cryptographic computation. This is the first paper which analyzes the amount of randomness needed to visually share a secret image. It provides lower and upper bounds to the randomness of visual cryptography schemes. Our schemes represent a dramatic improvement on the randomness of all previously known schemes.

Visual Hiding Scheme Using One Secret Image

Abstract: A new scheme is introduced to encode a secret image into single shadow image called visual hiding in the paper, where decode uses the shadow image stack itself and shows the original image in certain orientation. The shadow image acts both encoder and decoder function, which can visually recover the original image without any knowledge of cryptography and without performing of any cryptographic computation. The definition of visual hiding image, general construction and threshold scheme are to given in this paper. The correctness and uniqueness of recovering the original image using visual matrix is to be approved in this paper. The visual hiding has the property of anti compression and anti distortion, while visual cryptography has not. The scheme of visual hiding has various models and random characteristics, while visual cryptography has not.

Randomness in visual cryptography

Abstract: A visual cryptography scheme for a set P of n participants is a method to encode a secret image into n shadow images called shares each of which is given to a distinct participant. Certain qualified subsets of participants can recover the secret image, whereas forbidden subsets of participants have no information on the secret image. The shares given to participants in X C P are xeroxed onto transparencies. If X is qualified then the participants in X can visually recover the secret image by stacking their transparencies without any cryptography knowledge and without performing any cryptographic computation. This is the first paper which analyzes the amount of randomness needed to visually share a secret image. It provides lower and upper bounds to the randomness of visual cryptography schemes. Our schemes represent a dramatic improvement on the randomness of all previously known schemes.