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An Introduction to Biometric
RecognitionAnil K. Jain, Fellow, IEEE, Arun Ross, Member, IEEE, and Salil Prabhakar, Member, IEEE,
IEEE Transactions on Circuits and Systems for Video Technologies, vol. 14, no. 1, Jan. 2004
Multimedia Security
2
Outline (1/2)
• Part Ⅰ. Introduction
• Part Ⅱ. Biometric System
• Part Ⅲ. Biometric System Errors
• Part Ⅳ. Comparison of Various Biometrics
• Part Ⅴ. Application of Biometric Systems
3
Outline (2/2)
• Part Ⅵ. Advantage and Disadvantage of
Biometrics
• Part Ⅶ. Limitation of (Unimodal) Biometric
Systems
• Part Ⅷ. Multimodal Biometric Systems
• Part Ⅸ. Social Acceptance and Privacy
Issues
4
Ⅰ. Introduction (1/5)
• The term biometric comes from the Greek
words bios (life) and metrikos (measure).
• Biometrics – individuals’ physiological
and/or behavioral characteristics.
5
Ⅰ. Introduction (2/5)
• Biometric Recognition
– “who she is” vs. “what she possesses”
6
Ⅰ. Introduction (3/5)
• What biological measurements qualify to
be a biometric?
a) Universality
b) Distinctiveness
c) Permanence
d) Collectability
7
Ⅰ. Introduction (4/5)
• In a practical biometric system, there are
a number of other issues that should be
considered…
a) Performance
b) Acceptability
c) Circumvention
8
Ⅰ. Introduction (5/5)
In conclusion, the system should meet…
a) Accuracy
b) Speed
c) Resource requirement
d) Be harmless to the users
e) Be accepted by the intended population
f) Be sufficient robust to various attack
9
Ⅱ. Biometric System (1/10)
• A biometric system is essentially a pattern
recognition system.
10
Ⅱ. Biometric System (2/10)
• A biometric system is designed using the following four main modules.
1) Sensor module(encapsulating a quality checking module)
2) Feature module
3) Matcher module (encapsulating a decision making module)
4) System database module
11
Ⅱ. Biometric System (3/10)
A sample flow chart:
FeatureExtractor
Sensor
Qualifychecker
SystemDatabase
True / False
Matcher
DecisionMaker
template
The templates in the system databasemay be updated over time.
12
Ⅱ. Biometric System (4/10)
• A biometric system may operate either in
verification mode or identification mode.
a) Verification mode:“Does this biometric data belong to Bob? ”
b) Identification mode:“Whose biometric data is this? ”
13
Ⅱ. Biometric System (5/10)
SystemDatabase
LoginInterface
Get Name & Snapshot
QualityChecker
Check Quality
FeatureExtractor
Enrollment
Template
14
Ⅱ. Biometric System (6/10)
SystemDatabase
True / False
LoginInterface
Get Name & SnapshotOne template
FeatureExtractor
Extract Features
Matcher
One match
Verification
Claimed identity
15
Ⅱ. Biometric System (7/10)
SystemDatabase
User’s identity or“user unidentified”
LoginInterface
Get Name & SnapshotN templates
FeatureExtractor
Extract Features
Matcher
N match
Identification
16
Ⅱ. Biometric System (8/10)
• “Recognition” is the generic term of
verification and identification.
• We do not make a distinction between
verification and identification.
17
Ⅱ. Biometric System (9/10)
Describing the verification problem:
a) An input feature vector: XQ
b) A claimed identity: I
c) The biometric template corresponding to I : XI
d) The similarity between XQ and XI: S(XQ, XI)
e) The predefined threshold of similarity: t
f) True (a genuine user): ω1 ; False (an imposter): ω2
otherwise
),(S if
,2
,1),(
tXX
ω
ωXI
IQ
Q
18
Ⅱ. Biometric System (10/10)
The identification problem…a) The identity enrolled in the system: Ik, k=1, 2,…, N
b) The reject case: IN+1
c) The biometric template corresponding to Ik : XIk
otherwise
,,2,1,)},(Sax{ if
,
,
1
NktXXm
I
IX kIQ
N
k
Q
19
Ⅲ. Biometric System Errors (1/9)
• A biometric verification system makes two types of errors:
1) mistaking biometric measurements from two different persons to be from the same person (called false match)
2) mistaking two biometric measurements from the same person to be from two different persons (called false non-match)
20
Ⅲ. Biometric System Errors (2/9)
Hypothesis testing:
1) H0: input XQ does not come from the
same person as the template XI
2) H1: input XQ comes from the same
person as the template XI
21
Ⅲ. Biometric System Errors (3/9)
If S (XQ , XI) ≧ t , then decide D1 , else decide D0 .
Decision:
D0: person is not who she claims to be
D1: person is who she claims to be.
22
Ⅲ. Biometric System Errors (4/9)
• Such a hypothesis testing formulation
contains two type of error:
• Type Ⅰ(α): false match (D1, when H0)
• Type Ⅱ(β): false non-match (D0, when H1)
FMR is the probability of Type I errorFNMR is the probability of Type II error
23
Ⅲ. Biometric System Errors (5/9)
DecisionThreshold (t )
Matching Score (s )
Pro
babili
ty (
p)
∞-∞
ImposterDistribution
p (s|H0)
GenuineDistribution
p (s|H1)
FNMR = P (D0|H1) FMR = P (D1|H0)
24
Ⅲ. Biometric System Errors (6/9)
The errors in identification mode:
FMRN: the identification false match rate
FNMRN: the identification false non-match rate
• FMRN = 1 – (1 – FMR)N ~ N × FMR
• FNMRN ~ FNMR
25
Ⅲ. Biometric System Errors (7/9)
• Some situation may lead to following
formulation of FMRN and FNMRN.
a) FNMRN = RER + (1 - RER) × FNMRRER: retrieval error rate
b) FMRN = 1 – (1 – FMR)N×P
P: the average percentage of database searched
during the identification
26
Ⅲ. Biometric System Errors (8/9)
False Non-match Rate (FNMR)
Fals
e M
atc
h R
ate
(FM
R)
ForensicApplications
High-securityApplications
CivilianApplications
27
Ⅲ. Biometric System Errors (9/9)
• Important specifications in a biometric
system:
1) FMR: false match rate
2) FNMR: false non-match rate
3) FTC: failure to capture (e.g., a faint fingerprint)
4) FTE: failure to enroll
28
Ⅳ. Comparison of Various
Biometrics (1/10)
• Each biometric has its strengths and
weaknesses.
• No biometric is “optimal”.
• A brief introduction of the commonly used
biometrics is given below…
29
Ⅳ. Comparison of Various
Biometrics (2/10)
DNA
– 1-D ultimate unique code
– identical twins have identical DNA patterns
– contamination and sensitivity
– automatic real-time recognition issues
– privacy issues
Ears
– The shape of the ear
– the structure of the cartilaginous tissue of the pinna
30
Ⅳ. Comparison of Various
Biometrics (3/10)
Face - Also used by humans
1) the location and shape of facial attributes
2) the overall analysis of the face image
Requiring a simple background and illumination
In practice, …
– Detect the face
– Locate the face
– Recognize the face
31
Ⅳ. Comparison of Various
Biometrics (4/10)
Facial, hand, and hand vein infrared thermogram
– A thermogram-based system does not require
contact and is non-invasive
– Infrared sensors are prohibitively expensive
手掌靜脈辨識系統資料來源:FUJITSU, Taiwan
32
Ⅳ. Comparison of Various
Biometrics (5/10)
Fingerprint
– A fingerprint scanner costs about US $20
– Single vs. Multiple
33
Ⅳ. Comparison of Various
Biometrics (6/10)
Gait
Hand and finger
Geometry
34
Ⅳ. Comparison of Various
Biometrics (7/10)
Iris– stabilize during the first two years of life
– the irises of identical twins are different
– extremely difficult to surgically tamper the texture of
the iris
35
Ⅳ. Comparison of Various
Biometrics (8/10)
Keystroke
Odor
Palmprint
36
Ⅳ. Comparison of Various
Biometrics (9/10)
Retinal scan
– the most secure biometric
– reveal some medical conditions
Signature
– professional forgers may be able to reproduce signatures that fool the system
Voice
– a combination of physiological and behavioral biometrics
37
Ⅳ. Comparison of Various
Biometrics (10/10)
38
Ⅴ. Application of Biometric
Systems (1/3)
• The application of biometric can be
divided into three main groups:
1) CommercialATM, credit card, cellular phone, distance learning, etc.
2) GovernmentID card, driver’s license, social security, passport control, etc.
3) Forensicterrorist identification, missing children, etc.
39
Ⅴ. Application of Biometric
Systems (2/3)
40
Ⅴ. Application of Biometric
Systems (3/3)
250.9
399.5
523.9
729.1
1049.6
1440.6
1905.4
0
200
400
600
800
1000
1200
1400
1600
1800
2000
1999 2000 2001 2002 2003 2004 2005
SOURCE: The `123' of Biometric Technology
REVEN
UE (
US$m
)
41
Ⅵ. Advantage and Disadvantage of
Biometrics (1/2)
Advantage
• All the users of the system have equal
security level.
• Between 20% and 50% of all help desk
calls are for password resets.
42
Ⅵ. Advantage and Disadvantage of
Biometrics (2/2)
Disadvantage
• Speed is perceived as the biggest problem.
• FMR will increase when scaling up an
identification application.
43
Ⅶ. Limitation of (Unimodal)
Biometric Systems (1/2)
1) Noise in sensed data
2) Intra-class variations
44
Ⅶ. Limitation of (Unimodal)
Biometric Systems (2/2)
3) Distinctivenesse.g. Hand geometry, face, etc.
4) Non-universality
5) Spoof attacks
45
Ⅷ. Multimodal Biometric Systems
(1/19)
Data Fusion Level of Fusion
a) Fusion at Sensor level
b) Fusion at Feature level
c) Fusion at Opinion level
d) Fusion at Decision level
46
Ⅷ. Multimodal Biometric Systems
(2/19)
decision
FeatureExtraction
Biometricsnapshot
MatchingDecisionMaking
FeatureExtraction
Biometricsnapshot
Fusion
SystemDatabase
features
features
47
Ⅷ. Multimodal Biometric Systems
(3/19)
• This combination strategy is usually done
by a concatenation of the feature vectors
extracted by each feature extractors.
• This yields an extended size vector set.
48
Ⅷ. Multimodal Biometric Systems
(4/19)
Two drawbacks:
1) There is little control over the contribution
of each vector component on the result.
2) Both feature extractors should provide
identical vector rates.
49
Ⅷ. Multimodal Biometric Systems
(5/19)
• Although it is a common belief that the
earlier the combination is done, the better
result is achieved, state-of-the-art data
fusion relies mainly on the opinion and
decision level.
50
Ⅷ. Multimodal Biometric Systems
(6/19)
decision
FeatureExtraction
Biometricsnapshot Matching
DecisionMaking
FeatureExtraction
Biometricsnapshot
FusionSystemDatabase
Matching
rank values
rank values
51
Ⅷ. Multimodal Biometric Systems
(7/19)
• The score must be adjusted first:
( Normalization must be done. )
– The similarity measures must be converted
into distance measures.
– The score generated by each classifier must
have same range. [ex. 0-100]
52
Ⅷ. Multimodal Biometric Systems
(8/19)
• The combination strategies can be
classified into three main groups:
– Fixed rules / equal weight
– Trained rules / unequal weight
– Adaptive rules / adaptive weight
53
Ⅷ. Multimodal Biometric Systems
(9/19)
• The most popular schemes are:
– Weight sum
– Weight product
– Decision trees ( base on if-then-else )
54
Ⅷ. Multimodal Biometric Systems
(10/19)
Classifier 1 Classifier 2 Classifier 3
Score1 > t1
Score2 > t2
Score3 > t3 False True
Yes
Yes Yes
No
No No
NoYes
Score2 > t2
False
False True
55
Ⅷ. Multimodal Biometric Systems
(11/19)
decision
FeatureExtraction
Biometricsnapshot Matching
FusionSystemDatabase
Matching
DecisionMaking
DecisionMaking
FeatureExtraction
Biometricsnapshot
decision
decision
56
Ⅷ. Multimodal Biometric Systems
(12/19)
• In this last case, the Borda count method
can be used for combining the classifiers’
outputs.
• This approach overcomes the scores
normalization that was mandatory for the
opinion fusion level.
57
Ⅷ. Multimodal Biometric Systems
(13/19)
Classifier 1
Classifier 2
Classifier 3
class 2
class 1
class 3
class 1
class 2
class 3
class 2
class 3
class 1
class 2=2
class 1=1
class 3=0
class 1=2
class 2=1
class 3=0
class 2=2
class 3=1
class 1=0
class 2=5
class 1=3
class 3=1
58
Ⅷ. Multimodal Biometric Systems
(14/19)
• One problem that appears with decision
level fusion is the possibility of ties.
• For verification applications, at least three
classifiers are needed.
59
Ⅷ. Multimodal Biometric Systems
(15/19)
• An important combination scheme at the
decision level is the serial and parallel
combination, also known as “AND” and
“OR” combination.
System 1 System 2
System 1
System 2
60
Ⅷ. Multimodal Biometric Systems
(16/19)
• The AND combination improves the False
Acceptance Ratio.
• The OR combination improves the False
Rejection Ratio.
61
Ⅷ. Multimodal Biometric Systems
(17/19)
MultimodalBiometrics
Multiplematchers
Multiplesnapshots
Multipleunits
Multiplebiometrics
Multiplesensors
right index &middle fingers
optical &capacitance
sensors
minutiae &non-minutiae
based matchers
face &fingerprint
two attempts ofright index finger
62
Ⅷ. Multimodal Biometric Systems
(18/19)
Example of Multimodal Biometric Systems
“Person Identification Using Multiple Cues” Face, Voice
“Expert Conciliation for Multimodal Person Authentication Systems using Bayesian Statistics” Face, Speech
“Integrating Faces and Fingerprints for Personal Identification” Face, fingerprint
“Personal Verification using Palmprint and Hand Geometry Biometric” Palmprint and Hand Geometry
“Bioid: A Multimodal Biometric Identification System” voice, lip motion, face
63
Ⅷ. Multimodal Biometric Systems
(19/19)
• A combination of uncorrelated modalities
is expected to result in a better
improvement in performance.
• A combination of uncorrelated modalities
can significantly reduce the FTE.
• However, the cost of the system may
increase and the system may cause
inconvenience.
64
Ⅸ. Social Acceptance and Privacy
Issues (1/3)
Social Acceptance
• The ease and comfort in interaction with a
biometric system contribute to its
acceptance.
• Biometric characteristics captured without
the knowledge of the user is perceived as
a threat to privacy by many individuals.
65
Ⅸ. Social Acceptance and Privacy
Issues (2/3)
Privacy Issues
• Biometrics can be used as one of the most
effective means for protecting individual
privacy.
• Biometric characteristics may provide
additional information about the
background of an individual.
66
Ⅸ. Social Acceptance and Privacy
Issues (3/3)
• Legislation is necessary to ensure that
such information remains private and that
its misuse is appropriately punished.
• Most of the commercial biometric systems
available today store a template in an
encrypted format.