Article: Embedding Identities

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>From http://www.israel21c.com/channels/technology/articles/tech_0014.htm:

Researchers at Ben-Gurion University of the Negev and the University of
Connecticut have designed a novel method for improving the security of
identification cards or passports.

In the sophisticated approach, a block of encrypted information - such as
the bearer's fingerprint pattern or other unique personal facts - can be
concealed within a picture on a document. Because this information is
relevant to the bearer alone, use of the ID by a person resembling the
cardholder is easily unmasked. Moreover, since only the issuer knows the
complex keys used to encrypt the hidden information, it would be nearly
impossible to forge an ID that would pass through the system.

According to Prof. Joseph Rosen at BGU's Department of Electrical and
Computer Engineering, the new development combines two well-known methods of
representing data. One is the half-tone image, a two-dimensional pattern of
larger and smaller dots used in reproducing pictures. The other is a 2D
barcode, in which a checkerboard of tiny dots and spaces represents digital
information.

Barcodes are familiar to all of us: They are the long string of lines
printed on packaging labels for product identification. But a 2D barcode
comprised of small dots can record much more information than the string of
lines and is an inexpensive way to provide extensive data about a person or
a manufactured product.

In this new development, Rosen and his colleague Prof. Bahram Javidi of the
University of Connecticut have combined the 2D halftone image and barcode by
slightly shifting the positions of the arrangement of halftone dots. The
concealed barcode information can be retrieved using what is known as a 2-D
spatial correlator, which contains a confidential filter function that
deciphers the concealed image.

The new technology, Rosen said, is very robust as even a damaged ID picture
or a half-covered picture contains sufficient hidden data to retrieve the
encrypted information. This is because the entirety of secret data is
distributed throughout the picture. However, if the original picture is not
whole, the hidden picture will be reproduced with lower quality. Another
advantage of this development is that both optical and computational
approaches can be used to reveal the hidden data. A patent has been
submitted for the approach to conceal an image within an image.
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