標題: Visual cryptography for gray-level images by dithering techniques
作者: Lin, CC
Tsai, WH
資訊工程學系
Department of Computer Science
關鍵字: visual cryptography;secret sharing;watermarking;dithering
公開日期: 1-Jan-2003
摘要: A (k, n)-threshold visual cryptography scheme is proposed to encode a secret image into n shadow images, where any k or more of them can visually recover the secret image, but any k - 1 or fewer of them gain no information about it. The decoding process of a visual cryptography scheme, which differs from traditional secret sharing, does not need complicated cryptographic mechanisms and computations. Instead, it can be decoded directly by the human visual system. Previous efforts in this topic are almost restricted in processing binary images, which are insufficient for many applications. In this paper, a new visual cryptography scheme suitable for gray-level images is proposed. Instead of using gray subpixels directly to construct shares, a dithering technique is used first to convert a gray-level image into an approximate binary image. Then existing visual cryptography schemes for binary images are applied to accomplish the work of creating shares. The overall effect of the proposed method is the achievement of visual encryption and decryption functions for gray-level images. Some comparisons with a previously proposed method are also made. Some experimental results are shown to prove the feasibility of the proposed method. Finally, an application is mentioned to show its practicability. (C) 2002 Elsevier Science B.V. All rights reserved.
URI: http://dx.doi.org/10.1016/S0167-8655(02)00259-3
http://hdl.handle.net/11536/28230
ISSN: 0167-8655
DOI: 10.1016/S0167-8655(02)00259-3
期刊: PATTERN RECOGNITION LETTERS
Volume: 24
Issue: 1-3
起始頁: 349
結束頁: 358
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