Not long ago if you received fingerprints it was probably because you were charged with a crime; Now, however, this is one of the preferred methods to add a layer of security to our devices as it is a very reliable, simple and also inexpensive method.
Why are fingerprints unique?
It’s quite obvious why we have fingerprints: the little ridges of friction on our fingertips make it easier for us to grasp the objects we want to grip with our hand. By making the fingers rougher, these ridges increase the frictional force between our hands and the objects we are holding, making it difficult for objects to fall. You have fingerprints before you are even born, and in fact, the fingerprints are completely formed when you have only been in the womb for 7 months. Unless you have hand accidents, your fingerprints will remain the same throughout life.
What makes fingerprints such a brilliant way to differentiate people is that they are virtually unique: Fingerprints are developed by an essentially random process with your DNA code, and because the environment in the womb it also has its effect, even two twins have different fingerprints. While it is possible to find two people with virtually identical fingerprints, the chances of this happening are negligible.
Therefore, when fingerprints are used to control a person’s access to a computer system such as a laptop or smartphone, the chances of a random person having the correct fingerprint are usually so slim. which are almost ridiculous, much less than a person can guess. password or can break a physical block. Hence, fingerprints are considered to be one of the best security systems.
How does a fingerprint reader work on a laptop?
Taking your fingerprints at a police station involves pressing your fingers on an ink pad and then rolling your fingers across a piece of paper to leave a crisp impression on a sheet. The prints are also stored digitally afterwards so that the police can check if you have committed any known crimes or if you do so in the future (this is called “being booked”).
But when fingerprints are used to control access to computer systems like a laptop, more sophisticated methods must be used: we must have a fingerprint reader that quickly scans the surface of the finger and then converts the representation. digitized into comparable code. with its database, that is to say to allow prior access, the fingerprint must already be processed and stored.
There are three ways to scan fingers. An optical scanner works by casting a bright light on your fingerprint and literally taking a photo of it. If you’ve ever photocopied your hand, you’ll know exactly how it works, but instead of producing a dirty black photocopy, the image is fed into the PC’s scanner, which uses a light-sensitive microchip (be it a CCD , a charge coupled device or CMOS image sensor) to produce a digital image. The PC automatically analyzes the image, selecting only the fingerprint, and then uses sophisticated pattern matching software to convert it into code.
Another type of scanner, called a capacitive, measures your finger electrically. When the finger rests on a surface, the grooves of the indentations touch the surface while the spaces between them are slightly outside of it. In other words, there are different distances between each part of the finger and the surface below, so the capacitive scanner creates an image of the fingerprint by measuring these distances; This type of scanner is much like cell phone touchscreens, although they are faster than optics, they do not perform well when the finger is not clean or is wet.
The third type of fingerprint reader is called an ultrasound scanner because it uses high frequency sound waves (ultrasound) to “map” your finger instead of using light like the previous two. This type of scanner can be integrated under touch screens, which is why it is used in some smartphone models, but its operation is similar to optical scanners for all purposes.
What Happens While Scanning Fingerprints?
Unlike ordinary digital photographs, scans must capture exactly the correct amount of detail (brightness and contrast) so that individual edges and other details in the fingerprint can accurately match previously taken scans. Remember that fingerprints can be used as evidence in criminal trials, where a conviction could result in a long jail term; For this reason, quality control is certainly the most important part of the fingerprint scanning process, and this also applies to a laptop fingerprint reader.
Here’s how the scanning process works with a simple optical scanner (with the other two types it is similar but with the differences we explained in the previous section):
- A row of LEDs scan the bright light on the glass (or plastic) surface you place your finger on (sometimes referred to as a stage).
- Image quality will vary depending on how you press, how clean or greasy your fingers are, how clean the scanning surface is, the level of ambient light, etc.
- The reflected light bounces off the finger through the glass to a CCD or CMOS image sensor.
- The longer this image capture process takes, the brighter the image formed on the sensor will be.
- If the image is too bright, areas of the fingerprint (including important details) may disappear completely, such as a digital photo indoors where the flash is too close or too strong. If it is too dark, the image will appear black and details will be invisible for the opposite reason.
- An algorithm tests whether the image is too light or too dark; if so, an audible beep or LED indicator alerts the operator and the measurement should be repeated.
- If the image is acceptable, another algorithm tests the level of detail, usually by counting the number of peaks and making sure that there are alternating areas of light and dark (as you would expect from ‘a decent footprint image). If the image fails this test, return to step 1.
- As long as the image passes these two tests, the scanner accepts the image, which is stored as an acceptable scan on a laptop’s internal memory chip for this purpose. Typically, images captured in this manner are 512 x 512 pixels (the dimensions used by the FBI) and the standard image is 2.5 cm (1 inch) square, with 500 dots per inch resolution and 256 shades of gray.
- Now the PC can store the image in its database (temporarily or indefinitely) and automatically compare it with the approved fingerprints to unlock the equipment and allow access.
