Mask secures personal displays

[R. A. Hettinga]

Sounds like something out of a Gibson novel...

Cheers,
RAH
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<http://optics.org/articles/news/10/4/20/1>

optics.org - News - 

 Mask secures personal displays

26 April 2004

A mask that decodes encrypted pixels ensures that sensitive information can
be viewed securely.

When you view secure information on a screen, there is always the risk that
someone is peering over your shoulder and taking notes. To remove this
worry, scientists in Japan have been experimenting with a technique known
as visual cryptography. The team believes this approach could ensure the
security of information displayed on PDAs, computer screens or bank
terminals. (Optics Express 12 1258)

Secure display

In a visual cryptography system, the image containing the sensitive
information is encrypted and appears as a random pattern. The only way to
view the information is to place a decoding mask over the encrypted image.

 Hirotsugu Yamamoto and colleagues from the University of Tokushima have
developed a decoding mask that has two functions: to decrypt the display
and limit the viewing zone of the decrypted image.

Key to the technique is an algorithm that generates the pixels in both the
encrypted image and the mask. The team's paper describes its algorithm to
encrypt images containing 8 colours.

 To test their algorithm, the researchers printed the mask out on an
overhead transparency and placed it in front of an LCD showing an encrypted
image. Secret images were only perceived when the viewer stood in front of
the LCD. "The viewing zone covers about 10 cm to the right and 10 cm to the
left of the center at the designated viewing distance of 1.5 m," Yamamoto
explained.

Improving both the security of the decoding mask and the image quality are
now Yamamoto's priorities. "In the next version, I'm making the mask
pattern on a plastic plate," he told OLE. "The mask pattern has some layers
and prevents someone from copying it. The number of encrypted colours has
also been increased to 216 and 343." The team is also working on a decoding
goggle similar to the glasses that cinema audiences have to wear to see
movies in 3D.

 Yamamoto is also optimistic that this technique will find commercial
applications. "Display of secret information on PDA and computer screens
are practical applications," he explained. "Other business applications
include: securing the screen of a terminal at a bank; an operator screen
that shows personal information; and a touch panel screen of a safe."

This work was funded by the Japanese Ministry of Education, Culture,
Sports, Science and Technology; the Mazda Foundation; and the Secom Science
and Technology Foundation.

Author
 Jacqueline Hewett is technology editor on Optics.org and Opto & Laser
Europe magazine.



-- 
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R. A. Hettinga <mailto: rah at ibuc.com>
The Internet Bearer Underwriting Corporation <http://www.ibuc.com/>
44 Farquhar Street, Boston, MA 02131 USA
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