How to zombie-proof a fingerprint scanner

Scientists are working on ways to make a fingerprint scanner differentiate between a living or dead finger, limiting the chance security will be breached by using an amputated digit. Or a zombie. Flickr/theogeo

High-tech fingerprint scanners may stop most thieves accessing a restricted area, but they have one fatal flaw: scanners can’t tell the difference between a finger that’s living or dead. Or undead.

Cases of robbers amputating a kidnap victim’s finger to get past biometric security systems (and perhaps a very natural fear of a zombie attack) have inspired scientists to examine how to make scanners smarter.

In a paper published in the journal Forensic Science International, German scientists report a breakthrough in what they describe as “liveness detection”.

“Differentiation of living fingers, fake fingers and fingers from dead bodies was investigated using spectral analysis,” the authors write.

The scientists investigated how light was absorbed by a living finger when it “blanches” or turns whitish as blood drains away when pressure is applied. Dead digits were also put to the test.

“For this purpose, reflection and transmission spectra in the wavelength region from 400 to 1650 nm were recorded from living volunteers and corpses,” the paper said.

“The dynamic differences in the curves (including the absorption changes caused by the blanching effect and the pulse) provide initial approaches for the realisation of systems for liveness detection. Significant differences that would be useful for the integration into fingerprint recording systems of methods to defend against forgeries are discussed.”