Fingerprint scanner as a USB device

September 4, 2013 11:47 AM

Hmm. You know how barcode scanners are sort of like a keyboard when connected via USB - if you scan a barcode it will just "type" that string of text into whatever you're doing just as if you'd used the keyboard?

Do USB fingerprint scanners work in a similar way? I've just bought this one on the advice of my ePOS vendor who assure me I can use one in conjunction with their till software to login.

Only I can't see how the device can take my fingerprint, scan it, and return a string of data that will always be the same? Surely there is software needed on the computer to DO something with the returned data?

Or have I misunderstood a way in which these devices can work?

Thanks

posted by dance to Computers & Internet (8 answers total)

Windows 7 and newer has built in support for biometric devices. So it's not emulating a keyboard. Windows is providing the software for figuring out if two reads of a fingerprint are the same, and using that for authentication. If your vendor isn't using windows 7 or newer then they may have included their own drivers for that device.
posted by aubilenon at 11:58 AM on September 4, 2013

Response by poster: Interesting. Can I clarify?

The till software has a text field for recording a string in. So I can scan a barcode into that field and if I scan the same barcode at the login field it'll match the string against the recorded one and log me in.

Are you saying that because Win7 understands biometric devices when I scan my fingerprint it'll insert into this text field a string which represents the data in my fingerprint? Because I can't see how that would work! :-) a barcode is going to be the same each time you scan it, a fingerprint not?? Thanks
posted by dance at 12:55 PM on September 4, 2013

Some (cheap) fingerprint readers on Windows will store your password with your fingerprint data. And then when the scanner sees your fingerprint it just outputs the password into the field.

Not really secure.
posted by sbutler at 1:09 PM on September 4, 2013

I have done some work with fingerprint scanners in a different environment, so I can tell you something about how they work, although I don't know exactly how the lower end personal scanners handle things. There are two main types of scanners, optical and capacitance. Optical scanners essentially take a photo of your fingerprint and capacitance scanners identify the ridges via electrical resistance. In both cases the scanners create something akin to a standard photo image file. In my application, this is what the scanner transmits to the processor, a kind of photograph. The next layer is the extraction of what we call minutiae, which identifies places where ridges end or split into two segments. There are a variety of other indicators (islands, enclosures, spurs, bridges, deltas, cores, etc). These minutiae are the important bits and we create a kind of map of these key features. Once you have extracted a map of these features, you can compare any new image to your existing maps. I'd assume that Windows or your POS system just uses the scanner to send an image file and does all the processing on the back end.
posted by Lame_username at 1:12 PM on September 4, 2013 [1 favorite]

Bar codes were designed from the beginning to encode a bit of text. Fingerprints weren't.

There is no obvious way to encode a fingerprint as a piece of text. You could come up with something, but it would be hard to get repeatable results. Skin is stretchy, people get cuts and injuries. The process of identifying a fingerprint is probably more like "these fingerprints are more than 98% similar, that's good enough" rather than "these fingerprints are the same."

You start with image of the fingerprint from the scanner. Then you process the image and compare it to a database of known fingerprints on the computer. This is a difficult and (probably) computationally heavy task, and it probably takes a lot of engineering expertise to get right. It wouldn't make sense for every single fingerprint reader to take on the job.

In contrast, converting the brightness readout from a laser on a barcode is easy. There are only a few different widths of bars to deal with, and they are always printed in crisp black on white in a very regular configuration.

[I know nothing about fingerprint recognition software, but I am a programmer.]
posted by scose at 1:13 PM on September 4, 2013

Surely there is software needed on the computer to DO something with the returned data?

Surely, yes. Is your question whether your POS vendor actually includes this software? Their recommendation of the device you have tells me it does.
posted by rhizome at 2:05 PM on September 4, 2013

I think what will happen is you'll scan your fingerprint and it will log you in, without using the password field.
posted by aubilenon at 2:35 PM on September 4, 2013

When USB devices are first plugged in, the computer and the device talk to one another to find out what the device does. It is the equivalent of the computer saying "hi! I'm a computer!" and the device saying "hi! I'm a keyboard!" or "hi! I'm a fingerprint scanner!" or "hi! I'm a mouse!" Based on that, the computer decides where to send the data that comes in from the device.

So a fingerprint scanner doesn't act like a keyboard any more than a mouse does. If that makes any sense.
posted by gjc at 12:58 AM on September 5, 2013