2013-08-19

Apple's iPhone Fingerprint Sensor May Use This Unconventional Technology

Even fingerprint sensors aren't spoof-proof, leaving in doubt whether this feature could turn your iPhone into a de facto security device for high-value accounts and services. But Apple is using a new kind of fingerprint technology that might be (almost) immune to subversion.



Fingerprint sensors and the iPhone 5S are two pieces of technology that have been dancing in and out of the headlines for months. Some commenters think the pairing is likely, others say it's silly.

But fresh fuel was thrown on the rumor fire late last week by leaked photos of a purported iPhone 5S front glass cover that seemed to have space in it for new components next to the home button...which is where Apple's own code suggested a user may scan their print on a future iPhone. And then there's news of another fingerprint patent that Apple gained when it bought fingerprint firm Authentec last year, via PatentlyApple.com. Where other fingerprint scanners have proven unreliable in terms of accuracy or spoofability, leading to doubts Apple would adopt the tech, this new system is quite crazily clever. In fact, it's clever enough to image the tiny ridges and furrows of flesh that make up a finger even through a "cellphone case" or an "LCD display cover plate."

Many fingerprint scanners use an optical technique that either images a whole fingertip at once or in slices as you slide your finger over a small sensor gap. These do work, pretty reliably...though it has been noted that variability in the sensor production can seriously affect the final device accuracy, and that a clever enough criminal could spoof the scanner with an image or a reconstruction of a finger. This is basically because to fool an image-sensitive system you only need the right kind of image--remember the latex fingerprints in the film Gattaca? If you doubt this, MythBusters has already proved the point, and you also need to read this fascinatingly odd story of a Brazilian doctor and her "bag full of fake fingers."

But in the Authentec/Apple patent a fingertip is imaged via a different technique: Radiofrequency scanning. Skin and flesh, thanks to the cocktail of chemicals they contain, have their own electrical signature--meaning a human body can in fact block a radio signal of the right frequency, while other frequencies sail right through us more or less unaffected. The sensor in the new patent makes use of this fact by sending out very precise radio signals over a very short range and detecting the signals that have been affected by the bumps and gaps in a human fingertip. Basically the tiny ridges of flesh in a fingerprint affect the electrical signals coming from the sensor array in a measurable way, allowing the device to calculate the position and alignment of all the whorls and loops.

The advantage of this system is that you couldn't fool it with an image of a fingerprint or a latex cast of a fingerprint because the RF signals from the sensor have to interact with a material that has a flesh-like radio response in order to register the print. It's suggested that the sensor can also detect live tissue beyond the simple skin of a fingerprint, which removes the one scary scenario of fingerprint tech: The idea that a really determined thief would also have to "steal" the finger in question. That's unlikely to be a problem with a simple smartphone, but it does have implications for some of the more secure uses of fingerprint tech.

This sort of tech seems very Apple, don't you think? Novel, unexpected, and something of a lateral approach to the problem. It also seems like it would be both more secure and more easy to use than other types of fingerprint scanners. Does this mean Apple is going to use this tech in the iPhone 5S (iPhone 6, or whatever it's going to be called)? Not necessarily. But it is definitely one in the eye for some fingerprint naysayers who dismiss the idea of a fingerprint-sensing iPhone.

[Image: Flickr user Martin Cathrae]






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1 Comments

  • PacoBell

    "because the RF signals from the sensor have to interact with a material that has a flesh-like radio response in order to register the print."

    Ballistics gel has been proven to have similar electrical characteristics to human flesh. So thieves will just switch from latex to gelatin. Are we supposed to feel safer?