Topic
Visual cryptography
About: Visual cryptography is a research topic. Over the lifetime, 1724 publications have been published within this topic receiving 25300 citations.
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TL;DR: This paper analyzes visual cryptography schemes in which the reconstruction of black pixels is perfect, that is, all the subpixels associated to a black pixel are black, and shows that the minimum pixel expansion of such schemes can be simply computed by solving a suitable linear programming problem.
72 citations
TL;DR: Two multi-pixel encryption size invariant visual cryptography schemes (ME-SIVCS's) are proposed which improve the visual quality of the recovered secret image by reducing the variance of the darkness levels.
71 citations
TL;DR: The concept of generalized RG, where the light transmission of a share becomes adjustable, is introduced, and generalized RG is adopted to implement different VC schemes to solve different problems in VC.
Abstract: Random grid (RG) is a method to implement visual cryptography (VC) without pixel expansion. However, a reconstructed secret with lower visual quality reveals in RG-based VC due to the fact that average light transmission of a share is fixed at 1/2. In this work, we introduce the concept of generalized RG, where the light transmission of a share becomes adjustable, and adopt generalized RG to implement different VC schemes. First, a basic algorithm, a (2,2) generalized RG-based VC, is devised. Based on the (2,2) scheme, two VC schemes including a (2,n) generalized RG-based VC and a (n,n) xor-based meaningful VC are constructed. The two derived algorithms are designed to solve different problems in VC. In the (2,n) scheme, recovered image quality is further improved. In the (n,n) method, meaningful shares are constructed so that the management of shadows becomes more efficient, and the chance of suspicion on secret image encryption is reduced. Moreover, superior visual quality of both the shares and recovered secret image is achieved. Theoretical analysis and experimental results are provided as well, demonstrating the effectiveness and advantages of the proposed algorithms.
71 citations
TL;DR: A progressive viewing method useful in sharing a sensitive image that characterizes its ability to recover the image by stacking transparencies without any computation by balancing the sensitivity and the daily-processing convenience of the image.
Abstract: The paper proposes a progressive viewing method useful in sharing a sensitive image. As in visual cryptography, this method characterizes its ability to recover the image by stacking transparencies without any computation. However, the method balances the sensitivity and the daily-processing convenience of the image.
71 citations
TL;DR: A novel copyright protection scheme that combines the discrete wavelet transform (DWT) and the singular value decomposition (SVD) is proposed and can effectively resist several common attacks.
71 citations