How Biometric Authentication Works

How Biometric Authentication Works

Biometrics are the ultimate security protocol. Using security coding that is unique to each individual, you can be confident in the authenticator’s identity. We’ve seen biometric securities in science fiction movies, and we use fingerprint authentication daily on our smartphones. Now, let’s break down all of the different kinds of biometric authentication and discover how they work.


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It’s the most reliable identifier. DNA stays constant throughout a person’s life, making it a long-term identifier. And the data is easily digitized.

In 1985, a professor and geneticist in the UK pioneered DNA-based identity testing. Nearly a decade later in 1994, the FBI launched a national DNA database with two main components: DNA from crime scenes and DNA from convicted felons. By 2009, the FBI’s DNA database had 6.7 million profiles. This grew to 12.6 million profiles in 2016.

Hands and Fingers

Fingerprint: A fingerprint maps the ridgelines in the skin of one’s fingertips. Individuality is based on the location and direction of the ridge ending points as well as the splits along a ridge path. Fingerprint technology is popular — 52% of consumers want banks to add fingerprint scans to banking apps. Fingerprinting concepts have been around for a long while. In the late 1800s, Sir Francis Galton identified how fingerprint characteristics are individualized. In a 1903 short story, Sherlock Holmes found a fingerprint. Then in 1969, there was a major push from the FBI to develop a fingerprint identification system. By 1975, the FBI developed automated fingerprint scanners. In the late 1990s, we saw the emergence of commercial fingerprint verification products. By 2006, fingerprint readers were added to many laptops, and in 2013, the iPhone 5S released with Touch ID.

Fingernail: Research is ongoing about fingernail-based biometrics. There are two main categories. In fingernail bed scans, identification is based on the dermal structure underneath the fingernail. Surprisingly, even identical twins have different fingernail beds. To read the nailbed, electromagnetic waves are used. The second category is fingernail plate surfaces. This is currently being explored as a transient biometric that has a lifespan of about two months. For identification, three nail plates are used (ring, middle, and index).

Palm: Similar to fingerprint ID, palm recognition looks at the palm’s ridges, texture, spatial attributes, and geometric characteristics, such as the length of fingers and width of the hand. Using palmprints dates back more than 150 years. In 1858, handprints were used on worker contracts as an identifying mark. More recently in 2003, 30% of the prints lifted from crime scenes were of palms, not fingers. In 2004, state law enforcement agencies began to use palm print databases. Australia has a database of 4.8 million palm prints.

Vascular: A person’s vascular patterns are unique, do not change with age, and are difficult to forge. In this biometric, near-infrared light reveals a hand’s or finger’s blood vessel patterns. In 1992, technology of optical trans-body imaging was developed. The first reference to using blood vessel patterns as identifiers was in 2000.

Knuckle: This is an emerging biometric. The knuckles have stable and unique inherent patterns of geometry and creases. The middle and ring fingers have better distinguishing characteristics than the thumb, index, or little finger.

Eyes and Face

Retina: In this biometric, a person is identified by the unique pattern of blood vessels at the back of their eye. Retinal scans are second only to DNA in their precision capabilities. To scan the retina, a beam of low-energy infrared light is shined into the eye. Retinal blood vessels absorb light easier than surrounding tissue, creating a reflective imprint of the retina’s patterns.
In 1935, the New York State Journal of Medicine published the concept of retinal identification. Forty years later in 1975, technology caught up to the concept, and a device began development. In 1981, the first commercial retinal scanner was released.

Iris: In biometric identification via iris, the intricate structures of the iris are revealed with near-infrared illumination. An iris’ texture is developed during embryonic gestation. Identical twins have different iris patterns, and even the left and right eyes of the same person have different iris patterns. A scan can be captured through clear contact lenses, eyeglasses, and non-mirrored sunglasses.

Divination based on iris patterns dates back to ancient Egypt and ancient Greece. In 1949, a British ophthalmologist likened an iris’ architecture to a person’s fingerprint. By the 1980s, the iris identification concept was patented. In 1994, a patent was issued for iris identification computer algorithms with image processing, feature extraction, and matching. Then in 2006, iris scans became an internationally standardized biometric for e-passport. A decade later in 2016, 1 billion people were enrolled in India’s government iris scan database. The same year, the U.S. had 434,000 iris scans on file since the FBI launched the pilot program in 2013.

Face: There are several techniques for facial recognition. Traditional methods extract facial landmarks. 3D recognition looks at features and is unaffected by lighting changes or viewing angles. Skin texture analysis is a secondary metric that enhances recognition capabilities. Thermal face recognition identifies facial features even when they’re covered with hats, glasses, or makeup.

In the 1960s, the first facial recognition system was deployed, but the administrator had to manually locate features like eyes, nose, and mouth. By the 1970s, technology advanced to automated feature recognition. Over the next two decades, there were advancements in calculation methods and approaches. In 2001, Super Bowl surveillance images were compared to a database of digital mugshots, resulting in a public dialogue about privacy. As of 2015, the FBI database included 52 million faces, about ⅓ of Americans.


This metric is captured dynamically over a period of time, such as a few seconds.

Voice: This is a popular biometric for remote authentication because of the wide availability and data transmission capabilities of telephones and computer microphones. The physical structure of the vocal tract determines acoustic patterns, and individualized behaviors include motion of the mouth, voice pitch, and pronunciations.

In 1960, a Swedish professor identified the connections between physiology and specific sounds. Then in 1976, the U.S. Air Force used a voice authentication prototype built by Texas Instruments. Verification technologies have co-evolved with speech recognition.

Signature: Static signature recognition is a visual comparison of the authenticating signature against a stored signature. But dynamic signature recognition adds spacial coordinate measurements, pressure sensitivity, and pen inclination to the data points.

Keystroke: This method of identification analyzes the unique patterns in a person’s manner and rhythm of typing. It dates back to the 1960s when telegraph operators were able to be identified by their tapping rhythm. This is not a pass/fail authentication but a confidence measurement.

Gait: In this behavioral biometric, the cyclical movement of walking is an unobtrusive identifier. The emerging technology is still affected by footwear, terrain, fatigue, injury, and passage of time.

Even More Authentication Metrics

Earlobe: Geometric identification characteristics include an ear’s height, corresponding angles, and inner ear curve. It’s a stable biometric that does not change as people age. One of the advantages is that identification can take place at a distance.

Odor: Bloodhound dogs are historically used to track a person by scent. A person’s primary odor is stable over time. Secondary odors contain constituents that change with diet and environmental factors. Tertiary odors are externally sourced (lotions, soaps, perfumes, etc.). A canine alert-type system still requires research on the target vapor signature and mechanism for transport detection.

Sweat Pores: This emerging biometric has been used as a secondary factor in fingerprint identification to distinguish between a live finger and a dummy finger.
Lips: Used in conjunction with facial authentication, identification involves targeting unique characteristics like the size of the upper and lower lips, furrows, grooves, and the distance between the lines and the edges.

Tongue: This biometric is difficult to forge. Identification is based on color, geometric shape, and the physiological texture of the tongue.


Written by Rowena Bonnette