What is contactless fingerprint and how does it work?

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

Basically, you’re holding your hand about an inch away from your smartphone’s camera lens. Then the camera takes a picture of your fingers and produces a fingerprint image, much like older technologies would. On the surface, the idea – and the technology required to perform contact fingerprinting – is very simple as all you need to take a picture is an Android smartphone with a 2MP camera. In reality, the underlying technology is intriguing, albeit complex.


While the technology behind contactless fingerprints sounds simple, there’s a lot more behind the scenes to ensure accurate capture, processing and recognition. In fact, most contactless fingerprint setups use four steps:

  1. Pretreatment
  2. Feature extraction
  3. Principal component analysis
  4. Corresponding to


First, the application converts the image to grayscale from rich colors (RGB). This step takes into account contrasts in colors and skin tones as well as variations or distortions caused by lighting and background in the image.

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

Human fingerprints are morphologically different in shape and pattern. And this is the main basis of the uniqueness of printing. At this point, the application uses Gabor filters to extract the unique characteristics of each finger. The app finds 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 at around the same time.

Now to answer the question of ridge layout and orientation. Imagine a hippie farmer who chose to plant corn in creative patterns to confuse the birds. So, instead of the conventional rows, there are arcs, loops and whorls. You can imagine a bird scanning the ground and using a mental filter to scan each plant to isolate those with corn kernels.

Principal component analysis (PCA)

In PCA, the application takes the data extracted so far and sorts out the features that contribute most to the variation. It then isolates and labels the identified features.

To put things into perspective, you can think of features as the number of leaves, stalks, and ears of corn a bird has to examine to isolate the former. (It must be a difficult day in the life of this bird.)

Corresponding to

Matching consists of comparing the characteristics of a fingerprint with 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 Euclidean distances, Manhattan distances, and cosine angles between features identified from friction edges.

So ! Contactless fingerprinting.

Law enforcement is likely to adopt this technology, but private companies can also adopt it to enhance safety and hygiene. However, it is undeniable that contactless fingerprints facilitate and speed up the collection and analysis of biometric data. The tools are quite easy to create or obtain. Fingerprint databases remain largely in the custody of authorities, but one can imagine how motivated cybercriminals can use the technology for malicious purposes.

There is no way to avoid or take action against fingerprinting if you are under forensic investigation or in custody. However, Vincent in the cyberpunk thriller Gattaca beg to differ.

That said, you can still keep yourself safe from cybercriminals on a fingerprinting spree. Here are three ways:

Enable additional security on your accounts

Fingerprint scanning is increasingly becoming a login option on many banking apps and online accounts. Indeed, it is practical. But it could also pose a security risk in the future if the technology behind contactless fingerprints 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 details for you.

Scammers scour the internet for photos of real people and use those photos to capture unsuspecting people. In the case of contactless fingerprinting, remember to avoid positions where the ventral surface of your fingers is full screen. That wouldn’t stop you from sharing adorable photos of your engagement ring, because you’ll most likely be posting photos of the back surface of your fingers.

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

In the meantime, you should have taken security measures like removing your phone numbers and home address from social media. Why? Scammers can use this information to impersonate you. When it comes to images, of course, there are no hard and fast rules. But you should consider restricting the visibility of your posts or making your account private. The latter makes your media visible only to trusted friends and relations.

Wearing gloves

You have taken to protect your finger photos and enable additional security on your accounts. However, there is someone who uses scanners and high-resolution cameras to take pictures with your fingertips. Using the prints in the cases will circumvent the legality, of course, but it’s likely to be fair game if the photo was taken in a public place.

Consider wearing gloves when outdoors if you are worried about getting printed without consent. Taking that step would be impractical (and look neurotic) in the heat of summer, of course.

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