1. General description
Fingerprint identification is the most mature biometric method
being implemented at an early level since 1960. The recognition of
a fingerprint can be done with two methods: “one-to-one” (verifi-
cation) and “one-to-many” (1 : N identification). The first method
is applied when we have two fingerprints and we want to verify if
they belong to the same person. The second one is used when we
have one fingerprint and we search itin a data base. The verification
is much easier and faster because we have the two fingerprints and
we just need to compare them. On the other hand, the identification
implies more time for extracting the fingerprint because there
are needed much more details.
The fingerprints are not compared with images, they use a
method based on characteristic points named “minutiae”. These
points are characterized by ridge ending (the abrupt end of a ridge),
ridge bifurcation (a single ridge that divides in two ridges), delta (a Yshaped
ridge meeting), core (a U-turn in ridge pattern), etc.Allthese
features are grouped in three types of lines: line ending, line bifurcation
and short line. After the minutiae points are localized, a map
with alltheir locations on the finger is created. Every minutiae point
has associated two coordinates (x, y), an angle for orientation and
a measure for the fingerprint quality. The matching of two fingerprints
depends on the position and on the rotation. For this reason,
every fingerprint is represented, not only, as a group of points with
two coordinates, but also, as a group of points with coordinates