FINGERPRINT scanners, increasingly used for everything from improving security at airports to preventing cellphone theft, can be fooled by fake fingers made of silicone, gelatine and even Play-Doh. Biometrics experts are working on ways to beat the fraudsters, and one of the latest takes a sensuous approach: an 鈥渆lectronic nose鈥� that can distinguish the unique aroma of human skin.
Electronic noses are often used to monitor pollution and to determine whether food is spoilt. They contain a metal oxide film the electrical properties of which change when certain gas molecules pass over it. Different metal oxides react to different gases.
Now Davide Maltoni at the University of Bologna in Italy suggests placing noses inside fingerprint scanners, next to the optical device that images the fingerprint, to detect the volatile molecules exuded by human skin. To test the idea, he used an off-the-shelf electronic nose based on a single metal oxide linked to specially designed computer software. He made a variety of fake fingers from different materials including silicone, latex and gelatine and presented them to the nose one at a time. The software recorded the voltage changes in the nose over a few seconds, providing the system with patterns of voltages that would betray impostors made of those materials. He took readings from 32 volunteers to find the average electronic smell of human skin.
Advertisement
He passed each fake finger over the sensor five times and asked all 32 volunteers to scan two of their fingers 10 times each. The software had a 92 per cent success rate in distinguishing between real and fake fingers.
Maltoni says several different detectors could be used in the same scanner. He is to present the device, along with another method for detecting the 鈥渓iveness鈥� of fingers based on skin elasticity, at the International Conference on Biometrics in Hong Kong this week.
鈥淭he 鈥榥ose鈥� could be placed inside fingerprint scanners to detect real human skin鈥�
The need for liveness detection came to light in 2002 when Tsutomu Matsumoto and colleagues from Yokohama National University in Japan tricked commercial scanners by making gelatine mock-ups of fingerprints lifted from glass.
The company TBS in Zurich, Switzerland, is developing an alternative system: scanners that test for liveness by checking that sweat pores on a finger are opening up, releasing sweat and closing. But more liveness detection tools are needed, says Farzin Deravi, a biometrics expert at the University of Kent, UK.
