At Umanick, we continue with our series of articles dedicated to analyzing the fingerprint and its use as a method of biometric identification of people. In this second installment, we will explain the reasons that differentiate one fingerprint from another, how it is processed electronically in order to make the identification and we will expose some advantages and disadvantages that the fingerprint recognition systems present.

Let’s start by answering the first big question: Why is one fingerprint different from another? The answer lies in the fact that every fingerprint has a set of particularities – convergences, deviations, unions, interruptions, fragments, among others – that draw the crests that compose it. In each fingerprint we have a series of ridges, and valleys, that create a drawing where we can recognize certain points of interest for their use in identification. These points are called minutiae.

01 Jack Spader

Fingerprint, from Jack Spader with CC license.

Of all these minutiae are interesting for the identification of terminations and the bifurcations of the crests. The reason that makes these two fundamental is that, between them, they account for almost 80% of the points of the fingerprint. In addition, there are also other points of interest, such as the core of the pattern of the fingerprint, islands, deltas and discontinuities.

At each minutia are attributed two characteristics: the position, which we will indicate with two coordinates (x, y), and the orientation, which we will quantify as the angle between the horizontal to the right (all three in a clock) and the prolongation of the line with positive direction against the clock.

The fingerprint formed by ridges and valleys is unique in each person, due to the infinite number of variants they present. That is, there are no two people with the same fingerprints. And, in addition, we have a method to classify them through the coordinates and orientation of these minutiae. Now we must take the next step: efficient processing so that the method is really effective and safe to identify people safely.

How is a fingerprint processed electronically?

For a fingerprint identification system to be efficient, the use of electronic fingerprint processing is absolutely necessary. To perform this processing, the algorithm in charge of comparing the fingerprint must receive as parameters the characteristics of the minutiae present in the sample.

But obtaining such information is not a trivial problem. This procedure is called filtering and is responsible for removing unnecessary information to stay only with the interesting: the minutiae and their position and address pair, that is, coordinates and orientation.

For a device based on fingerprint identification to guarantee access to a service only to the desired users, there is a pre-identification process, called enrolment. The enrolment consists of the insertion, within the system, of the fingerprint of a user so that he can be recognized in future operations, as well as the rights linked to this fingerprint.

The user can be enrolled by placing his finger on a fingerprint recognition device, a fingerprint sensor / scanner, such as a desktop device or the same access control device. The sensor digitizes the user’s finger and captures the image of the fingerprint.

A specific algorithm extracts particular points from the image and converts the information into a single mathematical model, comparable to a password with 60 digits. This unique model is encrypted and archived to represent the user. No specific image of the fingerprint is saved, so it can’t be used for the physical reconstruction of the fingerprint.

 Verification and identification

Once the user is included in the system, he can already be recognized. How this recognition is made will depend on the mode of operation of the system: verification or identification.

In the verification, the identity of a previously enrolled user is confirmed. The user provides fingerprint (positioning the finger on the sensor) along with identity information, such as ID number. The fingerprint check system retrieves the fingerprint template according to the ID number and compares it with the fingerprint of the user acquired in real time. If both are the same, the previously recorded sample and the current sample, the user is positively verified.

04 Exercise Tradewinds 2009

Fingerprinting, by Exercise Tradewinds 2009 with CC license

Instead, in case of identification, the identity of an individual is established by comparing his live captured fingerprint against a database of known individuals. Without prior knowledge of the identity of the person, the fingerprint identification system compares this fingerprint with those in the database. If it finds a very similar fingerprint, the subject is successfully identified.

Advantages and disadvantages

Among the advantages of fingerprint recognition systems, we can mention the extremely low failure rate compared to other biometric techniques, the equipment is relatively inexpensive, it is easy to use since a sample is easy to take and maintain, and is a very developed and used method.

On the other hand, a fingerprint identification system presents a drawback in some kind of work environments. In some users, for example those who work very intensely with their hands, the sensor may have it difficult to capture a complete and correct fingerprint. Another drawback is, although less and less, that users relate this technique to police investigations and criminal-activities and cause them some rejection.

In the near future, in our blog we will continue explaining in detail all the aspects related to the identification of people by fingerprint. If you do not want to miss it, you can subscribe to our newsletter with the form that you have at the top of this page.