IP: Fingerprint Readers Fooled with Gelatin Molds of *Latent* Prints

[Dave Farber <dave () farber net>]

------ Forwarded Message
From: Chris Hoofnagle <hoofnagle () epic org>
Date: Thu, 16 May 2002 08:30:49 -0400
To: dave () farber net
Subject: Fingerprint Readers Fooled with Gelatin Molds of *Latent* Prints

Dear Dave,

This is from Bruce Schneier's Crypto-Gram.
(http://www.counterpane.com/crypto-gram.html) Thought it would be of
interest.

Regards,
Chris

http://www.counterpane.com/crypto-gram-0205.html#5

Fun with Fingerprint Readers

Tsutomu Matsumoto, a Japanese cryptographer, recently decided to look at
biometric fingerprint devices. These are security systems that attempt to
identify people based on their fingerprint. For years the companies selling
these devices have claimed that they are very secure, and that it is almost
impossible to fool them into accepting a fake finger as genuine. Matsumoto,
along with his students at the Yokohama National University, showed that
they can be reliably fooled with a little ingenuity and $10 worth of
household supplies.

Matsumoto uses gelatin, the stuff that Gummi Bears are made out of. First he
takes a live finger and makes a plastic mold. (He uses a free-molding
plastic used to make plastic molds, and is sold at hobby shops.) Then he
pours liquid gelatin into the mold and lets it harden. (The gelatin comes in
solid sheets, and is used to make jellied meats, soups, and candies, and is
sold in grocery stores.) This gelatin fake finger fools fingerprint
detectors about 80% of the time.

His more interesting experiment involves latent fingerprints. He takes a
fingerprint left on a piece of glass, enhances it with a cyanoacrylate
adhesive, and then photographs it with a digital camera. Using PhotoShop, he
improves the contrast and prints the fingerprint onto a transparency sheet.
Then, he takes a photo-sensitive printed-circuit board (PCB) and uses the
fingerprint transparency to etch the fingerprint into the copper, making it
three-dimensional. (You can find photo-sensitive PCBs, along with
instructions for use, in most electronics hobby shops.) Finally, he makes a
gelatin finger using the print on the PCB. This also fools fingerprint
detectors about 80% of the time.

Gummy fingers can even fool sensors being watched by guards. Simply form the
clear gelatin finger over your own. This lets you hide it as you press your
own finger onto the sensor. After it lets you in, eat the evidence.

Matsumoto tried these attacks against eleven commercially available
fingerprint biometric systems, and was able to reliably fool all of them.
The results are enough to scrap the systems completely, and to send the
various fingerprint biometric companies packing. Impressive is an
understatement.

There's both a specific and a general moral to take away from this result.
Matsumoto is not a professional fake-finger scientist; he's a mathematician.
He didn't use expensive equipment or a specialized laboratory. He used $10
of ingredients you could buy, and whipped up his gummy fingers in the
equivalent of a home kitchen. And he defeated eleven different commercial
fingerprint readers, with both optical and capacitive sensors, and some with
"live finger detection" features. (Moistening the gummy finger helps defeat
sensors that measure moisture or electrical resistance; it takes some
practice to get it right.) If he could do this, then any semi-professional
can almost certainly do much much more.

More generally, be very careful before believing claims from security
companies. All the fingerprint companies have claimed for years that this
kind of thing is impossible. When they read Matsumoto's results, they're
going to claim that they don't really work, or that they don't apply to
them, or that they've fixed the problem. Think twice before believing them.

Matsumoto's paper is not on the Web. You can get a copy by asking:
Tsutomu Matsumoto <tsutomu () mlab jks ynu ac jp>

Here's the reference:
T. Matsumoto, H. Matsumoto, K. Yamada, S. Hoshino, "Impact of Artificial
Gummy Fingers on Fingerprint Systems," Proceedings of SPIE Vol. #4677,
Optical Security and Counterfeit Deterrence Techniques IV, 2002.

Some slides from the presentation are here:
<http://www.itu.int/itudoc/itu-t/workshop/security/present/s5p4.pdf>

My previous essay on the uses and abuses of biometrics:
<http://www.counterpane.com/crypto-gram-9808.html#biometrics>

Biometrics at the shopping center: pay for your groceries with your
thumbprint.
<http://seattlepi.nwsource.com/local/68217_thumb27.shtml>

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