The Police in Michigan is evaluating the possibility to reproduce a dead man’s fingerprint from a prerecorded scan. with 3D printing and use it to unlock any mobile device.
According to Rose Eveleth, the Police asked a 3D printing lab at the University of Michigan to recreate a dead man’s fingers to unlock his phone.
In this specific case, the man was killed and investigators believed that his mobile device contains useful information to solve the case.
Contrary to what you think, it isn’t so easy to reproduce such kind of fingers because modern biometric sensors rely on electrical currents that most 3D-printed objects are not able to conduct.
For this reason, the federal authorities requested the help of the professor Anil Jain at the University of Michigan. The professor “coated the 3D printed fingers in a thin layer of metallic particles” in order to overwhelm the limitation related to the electric conduction of that most 3D-printed objects.
“The police already have a scan of the victim’s fingerprints taken while he was alive (apparently he had been arrested previously). They gave those scans to the lab, and using them Arora has created 3D printed replicas of all ten digits.” stated the report published by Eveleth. “A 3D printed finger alone often can’t unlock a phone these days. Most fingerprint readers used on phones are capacitive, which means they rely on the closing of tiny electrical circuits to work. The ridges of your fingers cause some of these circuits to come in contact with each other, generating an image of the fingerprint. Skin is conductive enough to close these circuits, but the normal 3D printing plastic isn’t, so Arora coated the 3D printed fingers in a thin layer of metallic particles so that the fingerprint scanner can read them.”
Arora and his team haven’t yet tested the fingers on the mobile device of the dead man, but the professor is confident that in a few weeks he will be able to unlock the device .
On the other hand, this technique potentially represents a threat to the users’ privacy, there is the concrete risk that someone could abuse it, for example by stealing a fingerprint using a high-resolution photo and recreating it with a 3D-printing process.
At the time I was writing the investigation is still ongoing and there are no details on the research.
If the experiment will be successful, the unique defense for the users will be to disable the biometric sensor on the mobile smartphone. Fortunately many modern smartphones require a passcode if the owner hasn’t used the fingerprint unlock in over 48 hours.
(Security Affairs – 3D printing, fingers)