A new 3D printed hand simultaneously makes fingerprint scanners more secure and vulnerable

Fake hands can fool the best of scanners.
Fake hands can fool the best of scanners.
Image: G.L Kohuth, Michigan State University
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Replicating a whole hand to crack open biometrically sealed vaults is the stuff movies are made of.

But in September, that break-in tactic became more than make-believe. Researchers at Michigan State University say they’re able to 3D print a full hand, complete with fingerprints on all ten fingers. Their goal is more juridicial than nefarious: to standardize the calibration of fingerprint scanners in airport immigration, police departments, banks and more, using a realistic model of a hand in place of the 2D representations currently in use that are not as consistent or repeatable. “While useful for evaluating fingerprint readers, 2D targets are not adequate to simulate how users interact with the reader during the fingerprint capture process,” the researchers wrote in their paper. In other words, the 2D models are not able to produce human-like finger or hand orientations on the reader plate for contact-based capture or above the surface for contactless capture.

In July, the same researchers were able to unlock a murder victim’s phone by cloning one finger. They digitally enhanced the prints by filling in the broken ridges and valleys. Then, they printed 2D replicas using a special conductive ink that would create an electrical circuit needed to spoof the phone sensor, and one of them worked. At that time, they had failed to create a functional 3D version.

Using a high-resolution 3D printer that can produce the same ridges and valleys as a real finger and print material with the same thickness and elasticity as human skin, the team has now successfully created a glove-like wearable that transforms your hand into someone else’s, at least on a surface level. It can be used with slap scanners where you need to press all your fingers to the surface or contactless scanners that capture fingerprints when you wave your hand. While testing their innovation, the team found that light-colored material works better than darker shades. In addition, to work with mobile phone scanners that sense conductivity, the fingertips have to be coated with conductive ink like silver or gold.

3D-printed hand
MSU’s 3D printed hand.
Image: G.L Kohuth, Michigan State University

Materials for one hand cost almost $500, says MSU’s Anil Jain, the lead researcher on the project. And that’s not the expensive part—the Stratasys Objet350 Connex printer used to create it retails for about $250,000. To bring the price down, the team is working on 3D printing a mold for the hand, instead of printing the hand itself every time. “When I pour gelatin and pull it out, I’ll have pattern on the outside,” Jain says. Multiple hands can be used with a number of machines at once, and distributed to different vendors faster. Not only will that cut out 3D printing from the procedure each time, but the materials that can be used with molding are much cheaper than 3D printing materials.

Even though Jain and his team don’t dream of heists and fake identities, it doesn’t mean no one else will. The project, funded by the National Institute of Standards and Technology (NIST), signals the vulnerability of commercial fingerprint scanners. In response, Jain encourages vendors and agencies to work on closing current loopholes. One suggestion is to introduce some sort of “anti-spoofing technology,” he says, that can tell a real human skin from a fake hand. Ideally, the feature should be able to be turned off during calibration and turned back on when it’s in use.