From National Public
Radio, July 27, 2016
http://www.npr.org/sections/alltechconsidered/2016/07/27/487605182/police-use-fingertip-replicas-to-unlock-a-murder-victims-phone?utm_medium=RSS&utm_campaign=law
Michigan State University
researchers Sunpreet Arora (left), Anil Jain (center) and Kai Cao (right) tried
3-D printed fingertips and 2-D fingerprint replicas on conductive paper to
unlock a murder victim's phone, similar to one in the photo.
Michigan State University
researchers Sunpreet Arora (left), Anil Jain (center) and Kai Cao (right) tried
3-D printed fingertips and 2-D fingerprint replicas on conductive paper to
unlock a murder victim's phone, similar to one in the photo.
Derrick Turner/Michigan
State University
Dead men tell no tales,
but their phones might.
Early last month, two
detectives walked into the lab of Anil Jain, a professor of computer science and engineering at
Michigan State University. They had heard of Jain's cutting-edge work in fingerprint recognition and wanted his help in a
murder investigation.
The detectives brought the
victim's locked Samsung Galaxy S6 phone and a copy of his fingerprints, as he
had been previously arrested. The investigators said they believed his phone
might hold clues to who killed him and asked Jain to help them get inside the
phone by overcoming the fingerprint scanner lock.
Jain and his team —
doctoral student Sunpreet Arora and postdoctoral student Kai Cao — spent the
following several weeks tinkering with a solution. This week, they found one
that worked.
Plans A,
B and C
Setting off to create a
successful fingerprint key, Jain knew that the models would have to be able to
conduct electricity. Real human skin is conductive, similar to copper or
silver.
Anil Jain and his team
have created a computer program to digitally enhance fingerprints for use with
fingerprint detection technology.
Jain says that the
differences in the ridges and valleys in our fingerprints create different
electrical currents, which can be converted into unique images on the sensors of
our phones — this is what powers the new biometric phone locks.
"The fingerprints
they provided us were just ink on paper, which doesn't have a conductive
property," Jain says. "So the first thing we tried was to print the
fingerprints on a special conductive paper, just like a photographic
paper."
The conductive paper
prints didn't work, so the researchers moved to Plan B: create 10 3-D printed
replicas of the victim's fingertips, complete with copies of his fingerprints
embedded onto them. To make them conductive, another machine was used to apply
a micron-level coating of silver or copper to test which would work the best.
This method was much more
expensive and time-consuming than the 2-D alternative. It took 40 minutes per
finger on a $250,000 machine to print each fingertip, Jain says. From there,
the fingertips went into a $600,000 machine to get the metallic coating.
Despite the high price
tag, the 3-D fingertips didn't work either. Jain says the simple, conductive
paper prints were still on his mind.
"That idea appealed
to us, so we said let's try to see how we can improve the quality of the
fingerprints that the police gave us," Jain says.
For their third attempt,
the researchers used an image-enhancement algorithm specific to the unique flow
pattern of fingerprints and created more precise representations of each print.
They printed the high-quality fingerprints on the same conductive paper and
called the detectives in for a test.
On Monday afternoon, the
detectives and the researchers stood over the replica fingerprints laid out on
a table and tested the final copies on the victim's phone. Jain and his team
had printed all 10 digits just in case, but the phone unlocked after they tried
the first, most common one, the right thumb.
There was a moment of awed
silence before the detectives broke into cheers.
Concerns
for the future
Jain says he was happy to
help the police, but he also hopes this achievement will show the limits of
fingerprint locks on mobile phones. He says this may prompt improvements in
biometric security.
"Hopefully the phone
companies are watching this and they will make fingerprint devices more robust
against such simple attacks," Jain says. "Unless you first show the
weakness, you cannot strengthen it."
Of course, with this
technology, there are also legal considerations.
Because this particular
phone belonged to a victim rather than a suspect — and one who is no longer
alive — accessing the information on the phone wouldn't trigger the Fifth
Amendment's protection against self-incrimination.
But the method could have
implications for future criminal cases.
In 2014, the Supreme Court unanimously agreed
that police need to get a warrant before they can search a suspect's cellphone.
The same year, a Virginia Circuit Court ruled that a suspect in that state
"cannot be compelled [by the police] to produce his passcode to access his
smartphone, but he can be compelled to produce his fingerprint to do the
same."
The distinction lies in
the nature of the key. A passcode is an intangible thought in someone's mind,
whereas a fingerprint is considered physical evidence, like blood and DNA.
Did Jain and his team
crack both the phone and the case? He says he'll leave that to the detectives;
he doesn't know whether the phone contained anything helpful — and he doesn't
want to know.
"I think that's the
best way to deal with it," Jain says. "They brought us the phone and
requested us to unlock it. In a sense, our job ends now."
