What Is Contactless Fingerprinting, and How Does It Work?

Contactless fingerprinting is the latest step in the evolution of biometrics. Unlike the inkpad and bioscanner methods, the setup for contactless fingerprinting removed the need to press a hand against a device. This technology only requires a hand, a smartphone, and a special app to record and analyze fingerprints.

Basically, you hold your hand about an inch away from your smartphone camera lens. Then, the camera takes a picture of your fingers and produces a fingerprint image, as older tech would. On the surface, the idea—and technology required to do contact fingerprinting—is really simple because all you need to take a picture is an Android smartphone with a 2MP camera. In reality, the underlying technology is intriguing, albeit complex.


Although the technology behind contactless fingerprinting looks simple, there is much more going on in the background to ensure accurate capturing, processing, and recognition. As a matter of fact, most contactless fingerprinting setups use four stages:

  1. Preprocessing
  2. Feature Extraction
  3. Principal Component Analysis
  4. Matching


First, the app converts the image to gray scale from rich color (RGB). This stage accounts for contrasts in skin colors and tones as well as variations or distortions caused by lighting and the image background.

Then, the app scales the resolution and enhances the image using Short-time Fourier Transform (STFT) or similar methods. You can think of it like tuning a keyboard. In the end, preprocessing produces a detailed image ready for feature extraction.

Human fingerprints are morphologically different in shape and pattern. And this is the primary basis for print uniqueness. In this stage, the app uses Gabor filters to extract the unique features of each finger. The app scans for and extracts patterns, especially the arrangement of friction ridges. Friction ridges differ in orientation and frequency, which determines what sections of a fingerprint look like.

To put it into perspective, think of each finger as a piece of farmland. The friction ridges are the corn plants. Corn plants will most likely look different in leaf width, twig size, and even stem height, even if planted around the same time.

Now, to answer the question of the arrangement and orientation of the ridges. Imagine a hippy farmer who chose to plant corn in creative patterns to confuse birds. So, instead of the conventional rows, there are arches, loops, and whorls. You can imagine a bird scanning the terrain and using a mental filter to scan each plant to isolate the ones bearing sweet corns.

Principal Component Analysis (PCA)

In PCA, the app takes the data extracted so far and sorts for the features that contribute most to variation. It then isolates and tags the features identified.

To put it into perspective, you can imagine the features to be how many leaves, stems, and corn ears a bird must examine to isolate the prime ones. (Must be a tough day in the life of that bird.)


Matching involves comparing the features of a fingerprint against other fingerprints in a database. The app uses a complex (but familiar) algorithm to cross-reference possible matches and display those results. Current methods involve calculating the Euclidean distances, the Manhattan distances, and the cosine angles between the features identified from the friction ridges.

Voilà! Contactless fingerprinting.

Law enforcement agencies are likely to adopt this technology, but private companies may also adopt it to bolster security and hygiene. However, there’s no denying that contactless fingerprinting makes it easy and fast to collect and analyze biometric data. The tools are easy enough to create or get. Fingerprint databases largely remain in the custody of the authorities, but one can imagine how motivated cybercriminals can put the technology to malicious use.

There’s no avoiding or taking measures against fingerprinting if you are the subject of a forensic investigation or in custody. However, Vincent in the cyberpunk thriller Gattaca begs to differ.

That said, you can still ensure your safety from cybercriminals on a fingerprint-harvesting spree. Here are three ways:

Enable Additional Security on Your Accounts

Fingerprint scanning is increasingly becoming a login option on many bank apps and online accounts. Indeed, it is convenient. But it could also pose a security risk in the future if the technology behind contactless fingerprinting becomes more accessible for everyday use.

So, consider using the old but reliable method of securing your important accounts with alphanumeric passwords. You don’t have to create new passwords every time or keep passwords in your head. Several free password managers can handle all the nitty-gritty for you.

Scammers scour the internet for pictures of real people and use those pictures to catfish unsuspecting persons. In the case of contactless fingerprinting, consider avoiding posts where the ventral surface of your fingertips is on full display. Doing this wouldn’t stop you from sharing adorable pictures of your engagement ring, though, as you’ll most likely be posting pictures of the dorsal surface of your fingers.

You may also apply blurring effects or filters to pictures showing your fingertips on social media. Best of all, you don’t need advanced photo-editing skills to do this. We’ve shown how easy it is to annotate and blur images on Android.

Meanwhile, you should have taken security measures like removing your phone numbers and house address from social media. Why? Scammers can use this information to impersonate you. When it comes to pictures, there aren’t strict rules of thumb, of course. But you should consider restricting the visibility of your posts or making your account private. The latter makes your media visible to only trusted friends and connections.

Wear Gloves

You’ve taken to safeguard pictures of your fingers and enable additional security on your accounts. However, there’s the matter of someone using high-resolution scanners and cameras to take pictures of your fingertips. Using the prints in cases will skirt legality, of course, but it will likely be fair game if the picture was taken in a public place.

Consider wearing gloves when you’re outside if you’re worried about getting printed without consent. Taking this measure would be impractical (and look neurotic) in the heat of summer, of course.

Contactless fingerprinting is a nifty advancement in biometrics. Indeed, the simplicity of the tools required to scan and analyze fingerprints in contactless fingerprinting belies the complexity of the technology. However, this simplicity also raises privacy and security questions for which there are no ready answers. The tips highlighted in this article can help protect your privacy and improve your digital security in the meantime.

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