Fingerprints. We all have them. They’re always there. No matter where we go, our fingerprints will always follow. This quality is just one of the countless others that make fingerprints such an effective method of security. Not only does law enforcement implement vital systems utilizing fingerprints, but also cell phone companies like Apple and Samsung with their touch IDs.
The best part about all of this? That’s not even the half of it.
Our fingerprints can be used for so many different innovations. Whether it’s transferring money using fingerprint verification or gaining access to “top-secret” spy gear (just like in the movies), with the tip of our fingers we can create an entirely new world of security and technology.
But first, let’s start with the basics.
Fingerprints, Biometrics… What Are Those?
Touch ID and fingerprint recognition fall under the broad category of biometrics. Biometrics, hence the name, is basically biological measurements. It uses different systems designed to identify a person, whether it be distinguishing their behavioral characteristics or determining physical features. There are numerous types of biometric systems, including DNA, voice pattern, iris/eye recognition, and — our favorite — fingerprint identification.
These systems have three components: sensors, computers, and software.
Sensors are used to read information and record the data given. With fingerprints, for example, whenever you touch your finger to your phone’s touch identification, sensors will process the pattern of your fingertip and store it for the next time it must be recognized (aka the next time you unlock your phone). Computers will always be there to store said information into a database for future reference. The software connects the computer and sensor so they may work together.
There are two major types of biometrics: physiological/physical and behavioral. Physiologic biometrics focuses on physical measurements of the body, whereas behavioral identifies patterns in human activities. In this case, fingerprints are a branch of physiological biometrics.
No Two Fingerprints Are the Same
As kids, we heard this all the time. It’s a sentence that has been drilled into our brains since childhood. No two fingerprints are alike. Not even the most identical twins have the same fingerprint. Not triplets, quadruplets, or even quintuplets. In fact, the same fingerprint stamped twice consecutively may look slightly different the second time. There has never been a recorded case of two identical fingerprints.
Have you ever gotten a cut on your fingertip? Or perhaps a blister? Notice how although you may wound your fingertip, the same pattern always remains. Once that wound is healed, your fingerprint is restored back to the way it was. Once that blister is popped, your fingerprint will continue in the exact way. Unless you undergo a severe deforming injury, your fingerprint will always come right back. Why does this happen?
Permanence, by definition, is the state of lasting or staying unchanged indefinitely. This also applies to fingerprints, which stay the same throughout your lifetime. Research has shown that over the years, a person’s regular fingerprint will not be altered. Even as your body is growing new skin cells, the exact pattern is cemented into your fingertips. It’s amazing how such a system works.
Types of Fingerprints
So yes, we know that no two fingerprints are the same. What is consistent, however, is the shape of these fingerprints. There are three major categories, which include arches, whorls, and loops.
Arches have an enter-exit pattern that resembles a little mountain (as I like to picture it). This is the rarest fingerprint type, occurring in only 5% of the world population.
Next is the whorl pattern, which can be a series of circular shapes or a mixture of other pattern types. Around 25% - 35% of people have this one.
Finally, there’s the loop pattern. This type of fingerprint is the most common, consisting of — as the name suggests — various loops.
These patterns aid in identifying and matching specific fingerprints. For example, if there were an unknown fingerprint left behind at a crime scene, an analyst would be able to gather all known prints with similar pattern types before taking a closer look to compare specific points and details.
Matching Fingerprints
There are four main methods of representing fingerprint images: grayscale (a), phase (b), skeleton (c), and minutiae (d).
Minutiae-Based Matching
Minutiae-based matching is the most commonly used method of representing fingerprints due to the compactness and distinctiveness. It utilizes major points in a fingerprint image (called minutiae) to identify the unique features of that image. The two main minutiae include ridge bifurcations — where a ridge diverges into a branch of ridges — and ridge endings — where a ridge abruptly ends. This is represented in the image below.
Other types of minutiae points are -
- Ridge dots (small ridges).
- Ridge islands (in between two diverging ridges; a bit longer than ridge dots).
- Lakes (empty space in the middle of diverging ridges).
- Spurs (protrudes from a ridge).
- Bridges (small ridges that connect two longer ridges).
- Crossovers (two ridges crossing).
Types of Fingerprint Scanners
On a phone with touch ID, there’s always a certain button we must press in order to gain access. These buttons are scanning your fingerprint, then processing them in order to figure out if you’re you.
There are different types of scanners used to collect and identify the image of a fingerprint. This includes optical, capacitive, and ultrasonic scanners.
Optical Scanners
Optical scanners use optical images (photos) to detect patterns in the fingerprint based on dark and light areas. Because it is dark when a finger touches the scanner, there must be a light source (i.e. LED) incorporated into the system.
This is the oldest fingerprint-matching system and is used the least today. That’s quite reasonable, considering that these scanners are the easiest to trick. A high-quality picture or prosthetic could easily impersonate a person’s fingerprint, and this would deceive optical scanners since they only use 2D pictures to match.
Capacitive Scanners
Opposite to optical scanners, capacitive scanners are the most secure type and used in most modern-day smartphones. They use capacitors — a device that stores energy and electrical charge — connected to conductive plates in order to track data about a fingerprint.
When a fingerprint is placed on the conductive plates, energy in the capacitator changes a bit (air gaps make the charge mostly stable). The slight changes are monitored by an op-amp integrator circuit, which is used to track these variations and then recorded by an analogue-to-digital conversion mechanism. This data searches for unique patterns in the fingerprint (and stores it for later).
Ultrasonic Scanners
Finally, we have ultrasonic scanners. These scanners use an ultrasonic receiver and transmitter. When a finger is placed on the scanner, it will emit an ultrasonic sound — a frequency high enough that human ears cannot hear it. The sound waves bounce from the finger and back to the sensor. The sensor in this mechanism calculates how intense the returned pulse is and how long it took for the sound waves to arrive (from numerous locations). There tends to be a longer to return period if the waves bounced off a fingerprint valley, rather than a ridge.
A detailed 3-dimensional copy of the fingerprint is then created. This is matched against the 3D map already stored on the phone. If these two files match, then the phone will be unlocked.
Examples of ultrasonic scanners can be seen in newer Samsung phones, specifically the S10 and S10+.
Fingerprint Identification Implementations
Now we understand how fingerprints are identified and the process that they undergo to work with security. So where does this all lead us?
To the future, of course. With this type of technology, we could create an infinite number of possibilities while improving as we go.
- New security systems (houses, cars, personal files, maybe even rooms!)
- Personalized personal items (an item that you own will not function unless your fingerprint has been identified).
- Simplified clocking into work (simply scan your finger and your attendance has been recorded).
- Secure cash registers (the cash register will not open unless an employee’s fingerprint has been identified).
- Many, many more.
There are many places we can go with fingerprint security. And that is why, as sci-fi as it may sound, your finger is our future.
Key Takeaways
- Touch ID and fingerprint recognition fall under the broad category of biometrics (aka biological measurements).
- Biometric systems use sensors, computers, and software.
- No two fingerprints are alike and there has never been a recorded case of two identical fingerprints.
- There are three major types of fingerprints, which include arches, whorls, and loops.
- Minutiae-based matching is the most commonly used method of representing fingerprints and utilizes major points in a fingerprint image (minutiae) to identify unique features.
- Scanners used to identify fingerprints include optical, capacitive, and ultrasonic.
- We can use fingerprint technology for an infinite number of implementations in the future!
