Image of external fingerprints on the left, internal fingerprints on the right and sweat ducts in the middle

Spoof-proof tech for taking 'inside fingerprints'

French researchers have developed a new technique to take the so-called inside fingerprints that cannot be as easily concealed or faked as surface fingerprints. 

The technique, based on the so called optical coherence tomography (OCT), currently used in medical imaging, can look up to a millimetre under the surface of the fingertip at the underlying pattern, which forms the basis for the surface fingerprint.

Unlike the surface fingerprint, which can be damaged by hard work or intentionally flattened to avoid identification, the internal fingerprint is impossible to destroy.

"In the past years, the use of fingerprint sensors has expanded greatly beyond the field of forensics,” said Egidijus Auksorius, postdoctoral researcher at the Langevin Institute in Paris, who has developed the new fingerprint reader together with his colleague Professor Claude Boccara.

“Far from just being used for border security or passport registration, current uses of these sensors allow access to mobile phones, computers and even gym facilities."

OCT analyses the interference pattern created by a beam of light travelling through a biological sample as it meets with a reference beam.

Usually, the technology produces 3D imagery but the two French researchers managed to simplify their system to produce 2D images. The device can also image sweat pores, which can provide an additional source of identification.

In the heart of the shoe-box sized system is a specialised infrared camera, at $40,000 the most expensive component of the device. But the researchers believe they can bring down the cost of the device to as little as $10,000. While the price is still significantly higher than standard fingerprint sensors, Auksorius predicts that the new device could find a market dedicated to imaging problematic fingerprints or in areas where security is a particular concern.

"We showed that the internal fingerprints could be imaged with a relatively simple and inexpensive system," Auksorius said. "Furthermore, recent results with the new camera show that the system can potentially be a commercially viable solution."

Currently prevalent optical fingerprint sensors produce images by reflecting light from areas where the skin of the fingertip does not come in contact with a glass plate. Such techniques, however, only scan the very top layer of the skin.

But researchers have proved in the past that such systems are easy to spoof.

In 2002, the Japanese cryptographer Tsutomu Matsumoto showed that imitation fingerprints made cheaply from gelatin, a main component of gummy sweets, could trick up to 80 per cent of standard fingerprint sensors. The sensors also sometimes fail to recognise legitimate prints when the finger being scanned is dirty, worn, scarred, or too wet or dry.


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