Proceedings Article•
Extended visual cryptography for natural images
01 Jan 2002-pp 303-310
TL;DR: This paper presents a system which takes three pictures as an input and generates two images which correspond to two of the three input pictures, which are reconstructed by printing the two output images onto transparencies and stacking them together.
Abstract: Extended Visual Cryptography[Ateni01] is a type of cryptography which encodes a number of images in the way that when the images on transparencies are stacked together, the hidden message appears without a trace of original images The decryption is done directly by the human visual system with no special cryptographic calculations This paper presents a system which takes three pictures as an input and generates two images which correspond to two of the three input pictures The third picture is reconstructed by printing the two output images onto transparencies and stacking them together While the previous researches basically handle only binary images, this paper establishes the extended visual cryptography scheme suitable for natural images Generally, visual cryptography suffers from the deterioration of the image quality This paper also describes the method to improve the quality of the output images The trade-off between the image quality and the security are discussed and assessed by observing the actual results of this method Furthermore, the optimization of the image quality is discussed
Citations
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TL;DR: HVC construction methods based on error diffusion are proposed, where the secret image is concurrently embedded into binary valued shares while these shares are halftoned by error diffusion-the workhorse standard of halftoning algorithms.
Abstract: Halftone visual cryptography (HVC) enlarges the area of visual cryptography by the addition of digital halftoning techniques. In particular, in visual secret sharing schemes, a secret image can be encoded into halftone shares taking meaningful visual information. In this paper, HVC construction methods based on error diffusion are proposed. The secret image is concurrently embedded into binary valued shares while these shares are halftoned by error diffusion-the workhorse standard of halftoning algorithms. Error diffusion has low complexity and provides halftone shares with good image quality. A reconstructed secret image, obtained by stacking qualified shares together, does not suffer from cross interference of share images. Factors affecting the share image quality and the contrast of the reconstructed image are discussed. Simulation results show several illustrative examples.
257 citations
Cites methods from "Extended visual cryptography for na..."
...As an example, the and in a 2-out-of-2 scheme are shown as follows: (1) corresponds to the encoding of a white secret pixel and corresponds to the encoding of a black secret pixel....
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TL;DR: This work explores the possibility of using visual cryptography for imparting privacy to biometric data such as fingerprint images, iris codes, and face images, and the difficulty of cross-database matching for determining identities.
Abstract: Preserving the privacy of digital biometric data (e.g., face images) stored in a central database has become of paramount importance. This work explores the possibility of using visual cryptography for imparting privacy to biometric data such as fingerprint images, iris codes, and face images. In the case of faces, a private face image is dithered into two host face images (known as sheets) that are stored in two separate database servers such that the private image can be revealed only when both sheets are simultaneously available; at the same time, the individual sheet images do not reveal the identity of the private image. A series of experiments on the XM2VTS and IMM face databases confirm the following: 1) the possibility of hiding a private face image in two host face images; 2) the successful matching of face images reconstructed from the sheets; 3) the inability of sheets to reveal the identity of the private face image; 4) using different pairs of host images to encrypt different samples of the same private face; and 5) the difficulty of cross-database matching for determining identities. A similar process is used to de-identify fingerprint images and iris codes prior to storing them in a central database.
167 citations
Cites background from "Extended visual cryptography for na..."
...Thus, more work is necessary to handle this problem....
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...These steps will be explained in more detail in the following subsections....
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TL;DR: The proposed scheme makes the number of secret images not restricted and further extends it to be general as a result, the proposed scheme enhances visual secret sharing schemes' ability for multiple secrets.
148 citations
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TL;DR: In this paper, the authors proposed an extended visual cryptography (EVCS) which consists of meaningful shares (compared to the random shares of traditional VCS), which is realized by embedding random shares into meaningful covering shares.
Abstract: A visual cryptography scheme (VCS) is a kind of secret sharing scheme which allows the encoding of a secret image into n shares distributed to n participants. The beauty of such a scheme is that a set of qualified participants is able to recover the secret image without any cryptographic knowledge and computation devices. An extended visual cryptography scheme (EVCS) is a kind of VCS which consists of meaningful shares (compared to the random shares of traditional VCS). In this paper, we propose a construction of EVCS which is realized by embedding random shares into meaningful covering shares, and we call it the embedded EVCS. Experimental results compare some of the well-known EVCSs proposed in recent years systematically, and show that the proposed embedded EVCS has competitive visual quality compared with many of the well-known EVCSs in the literature. In addition, it has many specific advantages against these well-known EVCSs, respectively.
135 citations
TL;DR: An efficient (n+1, n+1) multi-secret image sharing scheme based on Boolean-based VSS is proposed to not only keep the secret images confidential but also increase the capacity of sharing multiple secrets.
134 citations
References
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TL;DR: This paper examines graph-based access structures, i.e., access structures in which any qualified set of participants contains at least an edge of a given graph whose vertices represent the participants of the scheme, and provides a novel technique for realizing threshold visual cryptography schemes.
Abstract: A visual cryptography scheme for a set P ofnparticipants is a method of encoding a secret imageSIintonshadow images called shares, where each participant in P receives one share. Certain qualified subsets of participants can “visually” recover the secret image, but other, forbidden, sets of participants have no information (in an information-theoretic sense) onSI. A “visual” recovery for a setX?P consists of xeroxing the shares given to the participants inXonto transparencies, and then stacking them. The participants in a qualified setXwill be able to see the secret image without any knowledge of cryptography and without performing any cryptographic computation. In this paper we propose two techniques for constructing visual cryptography schemes for general access structures. We analyze the structure of visual cryptography schemes and we prove bounds on the size of the shares distributed to the participants in the scheme. We provide a novel technique for realizingkout ofnthreshold visual cryptography schemes. Our construction forkout ofnvisual cryptography schemes is better with respect to pixel expansion than the one proposed by M. Naor and A. Shamir (Visual cryptography,in“Advances in Cryptology?Eurocrypt '94” CA. De Santis, Ed.), Lecture Notes in Computer Science, Vol. 950, pp. 1?12, Springer-Verlag, Berlin, 1995) and for the case of 2 out ofnis the best possible. Finally, we consider graph-based access structures, i.e., access structures in which any qualified set of participants contains at least an edge of a given graph whose vertices represent the participants of the scheme.
639 citations
TL;DR: An extended visual cryptography scheme, for an access structure (ΓQual,ΓForb) on a set of n participants, is a technique to encode n images in such a way that when the authors stack together the transparencies associated to participants in any set X∈�Qual they get the secret message with no trace of the original images, but any X∈Γ forb has no information on the shared image.
423 citations
TL;DR: Two general k out of n constructions that are related to those of maximum size arcs or MDS codes and the notion of coloured visual secret sharing schemes is introduced and a general construction is given.
Abstract: The idea of visual k out of n secret sharing schemes was introduced in Naor. Explicit constructions for k = 2 and k = n can be found there. For general k out of n schemes bounds have been described.
Here, two general k out of n constructions are presented. Their parameters are related to those of maximum size arcs or MDS codes. Further, results on the structure of k out of n schemes, such as bounds on their parameters, are obtained. Finally, the notion of coloured visual secret sharing schemes is introduced and a general construction is given.
349 citations
TL;DR: Visual cryptography and (k, n)-visual secret sharing schemes were introduced by Naor and Shamir in [NaSh1].
163 citations
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TL;DR: In this paper, the authors proposed an alternative model for reconstruction with a different set of operation (which they call the "Cover" semi-group), which is able to obtain a better contrast than is possible in the previous one.
Abstract: In Eurocrypt 1994 we proposed a a new type of cryptographic scheme, which can decode concealed images without any cryptographic computations, by placing two transparencies on top of each other and using the decoder's (human) visual systems. One of the drawback of that proposal was a loss in contrast: a black pixel is translated in the reconstruction into a black region, but a white pixel is translated into a grey region (half black and half white). In this paper we propose am alternative model for reconstruction with a different set of operation (which we call the “Cover” semi-group) is proposed. In this model we are able to obtain a better contrast than is possible in the previous one.
149 citations