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>>computer/tech
2002-08-08 19:08
Software Buries
Secrets In Printed Pictures
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| Passports
at the ready | Software that could invisibly hide your
signature and fingerprints in your passport mugshot has
been developed in Israel.
The software can also
be used to authenticate official documents by hiding
information in company logos and making them harder to
fake. The documents can be faxed, scanned and reprinted
without the hidden data disappearing, say the
researchers developing the technique.
Joseph
Rosen and his team at Ben Gurion University in
Beersheba, had previously only been able to hide
information in black and white pictures, but they can
now do the same trick with full colour images. Colour
images are built up from dots of different colours,
distributed at regular intervals. Larger dots create
bolder colours, and vice versa.
To hide the
image of, say, a fingerprint in a picture, the print and
the picture are scanned into a computer. The computer
runs an algorithm that converts the fingerprint into a
series of numbers. These numbers are then used to shift
the position of some of the dots that make up the
picture (see graphic).
Each dot can be displaced
slightly without noticeably altering the final
appearance of the image. The system can conceal several
different images in the picture at once by shifting the
dots of the different colours separately.
Six
pack
Rosen's team has so far shown that six
different icons can be embedded in a colour picture. To
reveal the hidden fingerprint, you have to scan the
picture again. The computer then uses the same algorithm
that encoded the fingerprint to decipher it. By
measuring the displacements of the dots in the picture,
the computer reconstructs the fingerprint.
The
technique could help bolster passport security, with the
algorithm being distributed to passport checkpoints. A
suspect's picture could then be unscrambled to reveal
the hidden fingerprint. If the fingerprint is missing,
or does not match the suspect's, security will know
something fishy is going on.
Rosen says the
technique could also help create invisible product bar
codes as well as product designs that are more difficult
to counterfeit. "By our method they can conceal a lot of
different information in every logo," he says.
Rosen's team is now working on a way to
unscramble the hidden information more simply. They have
designed a hand-held reader that looks like a magnifying
glass set in a small box. The lens is built from tiny
glass plates oriented at different angles. This ensures
the lens only transmits the hidden image, says Rosen,
making checks much faster.
Will Knight
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