fingerprint: one construct, many systems

In forensic identification a fingerprint is the pattern of friction-ridge skin on a fingertip, whose loops, whorls, arches, and tiny ridge endings and bifurcations are taken to be unique to each person and stable across a lifetime, so that a latent mark left at a scene can be matched to the finger that made it. Faulds's 1880 note On the skin-furrows of the hand in Nature proposed using these impressions to identify individuals, the idea that grew into the whole discipline of dactyloscopy. The referent is a physical biometric trace on skin, and it is the literal source from which every later 'fingerprint' takes its meaning of a uniquely identifying pattern.[1]

Unit

The configuration of friction ridges and minutiae on a fingertip

Recovery means

Not applicable

Measured by

Compared by minutiae matching: the type, position, and relation of ridge endings and bifurcations between a latent mark and a reference print

In genetics a DNA fingerprint is an individual-specific pattern read from highly variable repeated regions of the genome: minisatellites whose repeat counts differ so widely between people that the resulting band pattern is, in practice, unique to one person and shared partly with blood relatives. Jeffreys, Wilson, and Thein's 1985 Individual-specific 'fingerprints' of human DNA in Nature introduced the method and the name, deliberately borrowing the forensic word because the output plays the same identifying role. It is the same construct as a skin fingerprint (a uniquely identifying pattern) realised in the genome rather than on the fingertip, and read by electrophoresis rather than by eye.[2]

Unit

The multi-locus band pattern from hypervariable repeat regions of DNA

Recovery means

Not applicable

Measured by

Resolved by gel electrophoresis of amplified repeat loci (and later PCR-based STR profiling), compared band for band or allele for allele

In information security a device or browser fingerprint is a near-unique identifier assembled from the many configuration details a system reveals (user-agent string, installed fonts and plugins, screen and timezone settings, rendering quirks) whose particular combination distinguishes one machine from almost all others without any cookie or stored tag. Eckersley's 2010 How unique is your web browser? measured how much identifying entropy these attributes carry and showed most browsers are individually recognisable. It is again the same construct, a uniquely identifying pattern, here emergent from a configuration rather than printed on skin or coded in DNA, and it powers stateless tracking as well as fraud and bot detection.[3]

Unit

The joint entropy of a device's observable configuration attributes

Recovery means

Not applicable

Measured by

Quantified by the identifying information (bits of entropy) in the attribute combination and the stability of that combination over time