Thermal

 
 
By Peter-Michael Ziegler  |  Posted 2002-06-03 Print this article Print
 
 
 
 
 
 
 


: Good Sensor, Bad Software"> A lot less frequently than those with capacitive or optical systems are fingerprint scanners with thermal recognition systems deployed. The latter systems measure the minimal temperature differences between the hills (the lines of fingertips) and the valleys (the furrows in between) that the sensor registers on the fingertips surface. IdentAlinks Sweeping Fingerprint Scanner FPS100U works on the basis of Atmels CMOS-Finger-Chip-Sensor FCD4B14, which consists of a total of eight rows, placed one after the other, with 240 sensor pixels each. To trigger the scanning procedure one moves ones finger, applying gentle pressure, slowly across the only about half a centimeter wide thermal sensor. Located right next to it is a small heating unit that raises the temperature of the lines of the finger while they are moving across the sensor. Immediately after it has been switched on the device cannot supply usable images, only after a short heating-up period can high quality images of fingers be generated. If the BioLogon software that goes with the device hadnt repeatedly stymied our attempts at getting to grips with it - on occasion the system crashed five times during enrollment and was only forced back into cooperating with us by our pulling the USB plug - IdentAlinks Sweeping Fingerprint Scanner might have made a comparatively good impression during the tests. Because unlike the case with the capacitive and optical sensors owing to the thermal sensors minute surface area it was not possible to reactivate latent images or make use as before of our otherwise so successful adhesive film technique.
Only on the basis of silicone copies of authentic fingerprints were we able to score some successes: With their aid we repeatedly surmounted the biometric-access protection barrier. With a little bit of practice we were able to use silicon copies to create reference data sets and thereafter to gain access with the original finger as well as with the copy of the same.
In conclusion it must be said, however, that the amount of effort required to trick the sensor mechanism of a thermal fingerprint scanner with artificial data is significantly higher than that required in the other cases described above. Nevertheless, even the FPS100U is still a long way off from guaranteeing secure access.


 
 
 
 
 
 
 
 
 
 
 

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