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Proceedings Paper

Securing display of grayscale and multicolored images by use of visual cryptography
Author(s): Hirotsugu Yamamoto; Yoshio Hayasaki; Nobuo Nishida
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Paper Abstract

Security has become an important issue as information technology has become increasingly pervasive in our everyday lives. Security risks arise with a display that shows decrypted information. In this paper, we propose a secure information display technique using visual cryptography. Its decryption requires no special computing devices and is implemented using only human vision: the proposed display appears as a random pattern to anyone who looks at it unless the person views the displayed image through a decoding mask. We have constructed code sets to represent grayscale and multicolored images. Each pixel in a secret image is expanded to a group of subpixels. The displayed image consists of black and white subpixels to encrypt a grayscale image. To encrypt a multicolor image, black, red, green, and blue subpixels compose the displayed image. The decoding mask consists of transparent and opaque subpixels. Every pixel is encrypted using a pair that is chosen at random. We have demonstrated the proposed secure display with an LCD panel and a transparency on which a decoding mask was printed. The secret image was visible for a viewer within the viewing zone, although viewers outside the viewing zone perceived it as a random dot pattern.

Paper Details

Date Published: 22 June 2004
PDF: 9 pages
Proc. SPIE 5306, Security, Steganography, and Watermarking of Multimedia Contents VI, (22 June 2004); doi: 10.1117/12.528495
Show Author Affiliations
Hirotsugu Yamamoto, Univ. of Tokushima (Japan)
Yoshio Hayasaki, Univ. of Tokushima (Japan)
Nobuo Nishida, Univ. of Tokushima (Japan)


Published in SPIE Proceedings Vol. 5306:
Security, Steganography, and Watermarking of Multimedia Contents VI
Edward J. Delp; Ping W. Wong, Editor(s)

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