To counter counterfeiters, researchers at Télécom Sud in Paris (France) have developed a technology to take our internal fingerprint. Their prototype, called BioDigital, is based on optical coherence tomography.
Whether it is to secure your computer or smartphone or to improve flow management in airports, biometric tools using fingerprints are becoming increasingly popular. But they’re not flawless. And fraud techniques are multiplying with technological innovations. 3D printing facilitates the reproduction of impressions on silicone lures for example. To combat identity theft, a Télécom SudParis research team has been developing a special kind of biometric reader for five years.
Unlike contact sensors sold on the market, which only photograph the external surface of the skin, their prototype, called Biodigital, also collects biological information in depth. That is the matrix of our external imprint, located 300 to 500 microns below the surface of the skin, which allows us to regenerate the pattern if we damage our fingers. The structures of these two footprints, internal and external, are very similar. Once you’ve identified them, you have to compare them to make sure they belong to the same person and that we’re not facing a decoy,” Gottesman says.
A high-resolution 3D image
To capture this impression in depth, researchers rely on optical coherence tomography. Based on a principle similar to that used in ultrasound imaging, these technology projects light waves onto the fingertip via a laser. It is the way in which the photons diffuse, layer by layer, that brings out raw signals that will then be used to reconstruct a high-resolution 3D image of the internal impression. Today, we penetrate to 2 mm under the skin. But the challenge is to get a good quality image. Because the deeper you go, the worse it gets. However, the lure, by adding an extra layer, can decrease the performance of the sensor…”, stresses Yaneck Gottesman.
Is the technology reliable?” We don’t have enough hindsight yet, but synthetically reproducing a lure of such minimal thickness and with such details, it seems impossible today, even with advanced technologies. So we are already significantly increasing the level of difficulty for a forger to reproduce our fingerprints,” notes the researcher. In order to further enhance the safety of the process, the Biodigital reader can also record, in addition to internal and external fingerprints, the position of sweat ducts located between them. The goal is, with the reader, to identify biological structures difficult to reproduce humanly. But to reconstruct these channels, which have a particular structure, in the expected positions, would be a real tour de force,” explains Yaneck Gottesman. The device, now developed with Idemia, is currently the subject of a patent.