[ltp] Fingerprint reader and the Bios

[Shem Multinymous]

On 12/15/05, George Katsitadze <george.katsitadze@gmail.com> wrote:
> On Thu, Dec 15, 2005 at 08:55:50AM +0100, Michele Campeotto wrote:
> >   Not really, the ThinkPad fingerprint reader is a swipe sensor just
> > to prevent that. Imagine what happens when you sweep a ball of
> > Play-Doh on something.
> >   The fooled sensor was just taking pictures of the fingerprint and
> > analyzing those, not that surprising it's so easily confused. With
> > that kind of contact sensor you can get a nice fingerprint by just
> > taking a picture of the sensor surface.
>
> OK then, how does the ThinkPad sensor work? In other words,
> what does it sense?

"CMOS active capacitive pixel-sensing"
(http://www.upek.com/products/sensors.asp).

The fingerprint reader consists of a matrix of cells, each of which
senses local skin proxmity by the induced change in capacitance
between two plates (see
http://www-micro.deis.unibo.it/~tartagni/Finger/FingerSensor.html).
Array sensors ("one touch") are roughly square-shaped and have a large
cell matrix that can sample the whole fingerprint at once. Strip
sensors, as found on the ThinkPad, use a very narrow cell matrix (just
a few cells wide), and relies on finger movement for scanning the
whole fingerprint. This finger movement also wipes out (most of) the
residue fingerprint from the reader's surface, so strip sensors are
considered safer. I don't know which type was analyzed by Schuckers's
group at Clarkson.

  Shem