Fingerprint

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Nov 30, 2013 (3 years and 4 months ago)

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Wikipedia on Biometrics

Biometrics

(ancient Greek:
bios

="life",
metron

="measure") is the
study of methods for uniquely recognizing humans based upon one
or more intrinsic physical or behavioral traits.

In information technology,
biometric authentication

refers to
technologies that measure and analyze human physical and
behavioural characteristics for authentication purposes. Examples of
physical (or physiological or biometric) characteristics include
fingerprints, eye retinas and irises, facial patterns and hand
measurements, while examples of mostly behavioural characteristics
include signature, gait and typing patterns. All behavioral biometric
characteristics have a physiological component, and, to a lesser
degree, physical biometric characteristics have a behavioral element.

Many choices...


Fingerprint


Face


Iris


Height


Voice


Signature


Handwriting


Hand veins


Facial Thermogram


Keystrokes


Retina


DNA


Odor


Gait (Walk pattern)


Eye color


IQ


Hand geometry


Ear shape


...

One is wrong here! Which one?

Why not IQ?


IQ is used for
ranking
persons


different persons can have the
same
IQ


criteria for computing IQ
can vary
over time


a smart person can simulate a lower IQ


the “acquisition time” for getting the IQ is too
large


some of these may be also true for other
biometrics, but never all of them

...and becoming more

An
OTOACOUSTIC EMISSION
(OAE) is a sound which is generated from within the inner ear.
Having been predicted by Thomas Gold in 1948, their existence was first demonstrated
experimentally by David Kemp in 1978 and they have since been shown to arise by a number of
different cellular mechanisms within the inner ear. Numerous studies have shown that OAEs
disappear after the inner ear has been damaged, so OAEs are often used in the laboratory and
the clinic as a measure of inner ear health.

There are two types of
otoacoustic emissions:
Spontaneous Otoacoustic
Emissions
(SOAEs), which can
occur without external
stimulation, and
Evoked
Otoacoustic Emissions
(EOAEs), which require an
evoking stimulus.

Recently, Beeby, Brown and
White from University of
Southhampton, UK, have
studied the use of OAE for
biometric systems (e.g.
included in mobile telephones).


Two application modi


Identification


Given a biometric pattern, identify the person out
of a set of n persons (1:n match)


Verification


Given a biometric pattern, verify the identity of
that person by comparing with a biometric
template of the same person that was given
before (1:1 match).


Detection?


What could it mean in this context?

Several Aspects...


Universality

describes how commonly a biometric is found in
each individual.


Uniqueness

is how well the biometric separates one individual
from another.


Permanence

measures how well a biometric resists aging.


Collectability

explains how easy it is to acquire a biometric for
measurement.


Performance

indicates the accuracy, speed, and robustness of
the system capturing the biometric.


Acceptability

indicates the degree of approval of a technology by
the public in everyday life.


Circumvention

is how hard it is to fool the authentication system.

Fingerprints

Impression of friction ridges of tip
part of the finger.

Known from history as being
unique for every person.

Used in legal issues for more than
100 years (first use reported 1892
by Argentine police to identify a
murder).

Several countries maintain large
collections of fingerprints, so
-
called AFIS (automated fingerprint
identification systems).

Some related questions


Do twins have the same fingerprint?


Are the fingerprints of different fingers of the
same person different?


Do the same left and right finger of the same
person have a mirrored fingerprint?


Are relatives having similar fingerprints?


Are the fingerprints of the same person aged
20 and aged 60 identical?


Can the gender be concluded from a
fingerprint?

Some related questions


Do twins have the same fingerprint?
no


Are the fingerprints of different fingers of the
same person different?
yes


Do the same left and right finger of the same
person have a mirrored fingerprint?
no


Are relatives having similar fingerprints?
no


Are the fingerprints of the same person aged
20 and aged 60 identical?
nearly


Can the gender be concluded from a
fingerprint?
no

Our criteria (L,M,H)

Universality?

Fingerprint: Universality


Medium!


There is so
-
called Naegeli syndrome.
Affected persons have a dimished function of
the sweat glands, therefore, they are not
producing a fingerprint.


Injuries may also affect the fingerprint
pattern.

Our criteria (L,M,H)

Uniqueness?

Fingerprint: Uniqueness


High!


No two fingerprints have ever been found
identical.


However, between features like minutiae
position there might be some similarity
(twins).

Our criteria (L,M,H)

Permanence?

Fingerprint: Permanence


High!


Despite of affections during lifetime (injuries),
the fingerprint pattern is preserved during
skin alterations during lifetime.

Our criteria (L,M,H)

Collectability?

Fingerprint: Collectability


Medium!


Need special devices and procedures to
visualize a fingerprint.


Comparison of two fingerprints is very hard
for the naked eye, and needs training and
expertize.

Our criteria (L,M,H)

Performance?

Fingerprint: Performance


High!


Accuracy: allows for the identification of a
fingerprint among several thousands of
fingerprints (but not millions!)


Speed: Verification is today possible “on
-
board”, needs a few millisecond on modern
computer (acquisition takes longer!)


Robustness: error measures state a FAR at
1% for a FRR of 0.1%. What does this
mean? Later!

Our criteria (L,M,H)

Acceptability?

Fingerprint: Acceptability


Medium!


Usual association of taking a fingerprint is
related to crime cases.


Many countries pose data protection
regulations on the collection of fingerprints
(often only databases of criminals and public
authorities are allowed to be collected).


The fingerprint pattern can be easily “stolen.”

Our criteria (L,M,H)

Circumvention?

Fingerprint: Circumvention


Medium! (some say High)


Gels can be used to produce a copy of the
ridge pattern of a person.


Finger gloves also fake human warmth.

Fingerprint: Bonus


Do other animals
have fingerprints?

More similar to human
than primates: from which
animal is the fingerprint
to the left?

How does it work?

Fingerprint Sensors

optical

capacitive

thermal

Biometric workflow

Minutia and Terminals


Unique features of a fingerprint
pattern are the location of
forkings of ridges (minutiae)
and their endpoints (terminals).


Most persons have between 20
and 80 such positions.

The set of all minutiae and terminals of a given fingerprint
is called a
template
. It is used for comparing two
fingerprints.

Forkings and Endings

Mahadik, S., Narayanan,
K., Bhoir, D. V., and
Shah, D. 2009.
Access
Control System using
fingerprint recognition
. In
Proceedings of the
international Conference
on Advances in
Computing,
Communication and
Control (Mumbai, India,
January 23
-

24, 2009).
ICAC3 '09. ACM, New
York, NY, 306
-
311. DOI=
http://doi.acm.org/10.114
5/1523103.1523166

Fingerprint Scan

Fingerpint image, as received
from sensor. First it needs to
enhance the contrast of the
image. The goal is to
enhance the ridge structures
of the fingerprint.

Image Enhancement

In smaller areas of the image,
the
ridges
appear to be
parallel straight lines


thus
having
frequency
and
orientation
. A method called
Fourier Transformation
can
be used to
filter
only the lines
having the major frequency
and orientation.

orientation

frequency

Binarization

All pixels in the image are either
assigned Black (0) or White (255) by
using a threshold.

Orientation Field

For some points, the direction of the line is
represented by an
arrow
. This also helps to
identify the fingerprint
class
(but not used in
this system).

Region of Interest (ROI)

The further processing has to be
restricted to some part of the image.
Only in this part, the minutia and
terminals can be safely extracted.
Other parts, out of the border, will not
provide a good enough quality.

Thinning

The ridges (lines in the image) are
“eroded,” until only a line of
one pixel
width

remains


but while
preserving
the topological structure

of the
connected parts of the binary image.


There are several algorithms for such
a Thinning, mostly from the so
-
called
Mathematical Morphology
, a
discipline of image processing.

Candidate Points

From the former result, candidates for
minutia and terminal positions can be
found by looking into the
neighborhood of each white point.


However, it can be seen that there
are too many candidates, some only
caused by artefacts of the thinning
process. Using the ROI, and other
information, the wrong candidates
can be removed.

Final Result

Biometric workflow

Affine Matching

Matching

Template to test

Stored Template

Assumed Corresponding Points

Template to test

Stored Template

Testing

Template to test

Stored Template

according to assumed
correspondance, points
should be e.g. about here in
the stored template

one nearly matches,
the other do not

Better assumed corresponding
points

Template to test

Stored Template

Better assumed corresponding
points

Template to test

Stored Template

now, nearly each
estimated position is
about correct

Last but not least...


the pair of points, for which the number of
matching other points is highest, is found
(A,B)


the ratio for these matching points is
determined
(80%)


if it is larger than a
threshold
, than the system
replies that both fingerprints are from the
same person (same finger)
(80% > 70%
-
>
ok)


note that this threshold is important for the
correct decision of the system

Performance


A biometric system can make two kinds of
errors,
false acceptances
and
false rejections


the best trade
-
off between them is called
equal error rate
and an objective measure for
biometric system performance

However, the weighting of these two
errors might be different (forgeries are
not as likely as correct transactions)

False Acceptance


the template to test is from person A, the
stored template from person B


the system replies that the fingerprints are the
same (
and the door opens
...)


this is a False Acceptance


the ratio among a number of test then is
called False Acceptance Rate (FAR)

False Rejection


the template to test is from person A, the
stored template also from person A


the system replies that the fingerprints are
different (
and keeps the door closed
...)


this is a False Rejection


the ratio among a number of test then is
called False Rejection Rate (FRR)


Equal Error Rate


but the reply of the system depends
on the threshold


assume the treshold t varies from
0% to 100%


for 0%, any match is larger, and the
system will always ACCEPT, so
FAR will be 100%, and FRR will be
0%


for 100%, the system will never
ACCEPT, thus FAR is 0%, and
FRR is 100%


if threshold goes from 0% to 100%,
the FAR line will decrease from
100% to 0%, the FRR will increase
from 0% to 100%


thus, both lines will intersect for
some threshold


this is the so
-
called equal error rate
(EER)

State
-
of
-
the
-
Art