A person’s fingerprints begin forming early in fetal development, around the 10th week of gestation, and they reach their mature pattern by around 24 weeks (roughly six months into pregnancy). The friction ridges—the unique loops, whorls, and arches—develop as a result of the interaction between genetic factors and the local environment in the womb, including pressure, position, and movement. Once formed, these patterns are considered mature and largely remain unchanged throughout a person’s life, barring injuries or significant wear and tear.

By the time a baby is born, their fingerprints are essentially in equilibrium, meaning the pattern is fully established. However, the ridges may continue to thicken and develop as the child grows. The size of the fingerprint area increases with age, but the relative pattern—the ridges and valleys—remains the same. In short, fingerprints reach their ”mature” form during fetal development and maintain this form throughout life.

Fingerprints are influenced by genetic factors, but they do not uniquely map to DNA. While identical twins share the same DNA, they still have different fingerprints. This distinction occurs because fingerprints are not solely determined by genetics but also by epigenetic factors—namely, environmental influences in the womb, such as pressure from amniotic fluid and the positioning of the fetus. These external forces shape the fine details of the ridge patterns, creating variations even among individuals with identical genetic material.

In other words, while certain broad features of fingerprints, like ridge density or basic pattern type, are heritable, the exact ridge formation is randomized due to the microenvironment in the womb. This means that two people, even with closely related DNA, will have different fingerprints. Fingerprints, therefore, cannot be reverse-engineered from DNA.

The relationship between fingerprints and DNA is complex: DNA provides the blueprint for the general structure and formation of skin and its ridges, but it does not uniquely encode the specific fingerprint pattern. Each fingerprint is the result of both nature (genetics) and nurture (environment) during fetal development.

Fingerprint authentication has become a widely used biometric method for securing devices, applications, and even digital assets. But how does it actually work, what are its limitations, and how can it be applied securely in the realm of self-custody?

How Does a Fingerprint Scanner Work?

Fingerprint scanners function by capturing an image of the ridges and valleys that make up a fingerprint pattern. This image is processed and converted into a digital template, which maps unique features, such as ridge bifurcations and ridge endings. The two most common types of fingerprint scanners are optical and capacitive:

Optical Scanners: These scanners use light to create an image of the fingerprint. The scanner shines light onto the finger and records the reflected light through a sensor to capture the pattern.

Capacitive Scanners: These scanners measure electrical currents that differ between ridges and valleys on the finger. Capacitive sensors tend to be more secure because they require the finger to be physically present and don’t rely solely on an optical image, making them harder to spoof with a photograph.

Once the fingerprint is scanned, the system doesn’t store the image itself but creates a unique digital template based on the fingerprint’s features. This template is used for future comparison to authenticate the user.

Do Your Fingerprints Change Over Time?

For most individuals, fingerprints remain largely unchanged throughout their lives. The patterns are formed before birth and remain consistent even as the body ages. However, factors like injuries, cuts, and burns can alter the surface of the skin temporarily or, in some cases, permanently. Over time, wear and tear from manual labor or certain health conditions (such as diabetes or arthritis) can cause the fingerprint patterns to become less pronounced, affecting the accuracy of fingerprint recognition systems.

Although changes may occur on the surface, the core fingerprint patterns tend to remain intact. As a result, modern fingerprint systems account for slight variations, ensuring that minor changes don’t affect the overall authentication process.

In Practice, Do Third Parties Store Your Fingerprint?

In most cases, third parties do not store the actual fingerprint image. Instead, they store a hashed or encrypted version of the digital template derived from your fingerprint. This template contains information about the unique characteristics of your fingerprint but is not reversible into the original fingerprint image. However, this doesn’t entirely eliminate privacy concerns.

There are situations where fingerprint data might be improperly handled. For example, some companies may store fingerprint templates insecurely or fail to implement strong encryption. Additionally, third-party systems that handle biometric authentication often maintain centralized databases of user information, which could become targets for cyberattacks. While these databases don’t contain raw fingerprint images, a breach could expose hashed biometric data that could, in theory, be used in sophisticated spoofing attacks if decrypted.

How Can a Fingerprint Be Used to Secure Digital Assets?

In the context of self-custody, fingerprint authentication offers a convenient yet potentially vulnerable way to secure digital assets. When integrated with digital wallets or devices holding cryptographic keys, a fingerprint can serve as the authentication factor to unlock access.

However, fingerprints differ from passwords or private keys in one crucial way: they are immutable and public. Your fingerprint is left behind on every surface you touch, making it relatively easy to capture. This introduces the risk that, if compromised, your fingerprint cannot be changed, unlike a password or private key.

To address this, modern self-custody systems combine biometric authentication with additional factors, such as passwords (multi-factor authentication) or hardware wallets. The idea is that the fingerprint alone never directly controls access to the private key or assets, but rather, it triggers a second layer of security—like unlocking a device that stores a private key.

For example, in a hardware wallet setup, your fingerprint could be used to unlock the device, but actual transaction signing would still require a separate, secure action, like pressing a button or entering a passphrase. This layered approach ensures that even if the fingerprint data is stolen, it cannot be used in isolation to compromise the system.