ISO/IEC 19794-2:2005

INTERNATIONAL ISO/IEC
STANDARD 19794-2
First edition
2005-09-15


Information technology — Biometric data
interchange formats —
Part 2:
Finger minutiae data
Technologies de l'information — Formats d'échange de données
biométriques —
Partie 2: Données du point caractéristique du doigt





Reference number
ISO/IEC 19794-2:2005(E)
©
ISO/IEC 2005

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ISO/IEC 19794-2:2005(E)
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ISO/IEC 19794-2:2005(E)

Contents Page
Foreword.v
Introduction.vi
1 Scope .1
2 Conformance.1
3 Normative references .1
4 Terms and definitions.1
5 Symbols and abbreviated terms .5
6 Minutiae Extraction .5
6.1 Principle .5
6.2 Minutia Type .5
6.3 Minutia Location .6
6.3.1 Coordinate System .6
6.3.2 Minutia Placement on a Ridge Ending (encoded as Valley Skeleton Bifurcation Point) .7
6.3.3 Minutia Placement on a Ridge Bifurcation (encoded as a Ridge Skeleton Bifurcation
Point) .7
6.3.4 Minutia Placement on a Ridge Skeleton Endpoint .7
6.3.5 Minutia Placement on Other Minutia Types  .8
6.4 Minutia Direction .8
6.4.1 Angle Conventions .8
6.4.2 Minutia Direction of a Ridge Ending (encoded as Valley Skeleton Bifurcation Point) .9
6.4.3 Minutia Direction of a Ridge Bifurcation (encoded as Ridge Skeleton Bifurcation Point) .9
6.4.4 Minutia Direction of a Ridge Skeleton End Point .9
6.5 Core and Delta Placement and Direction .9
6.6 Minutia Type Matching .10
6.7 Encoding of multibyte quantities.10
7 Finger Minutiae Record Format .11
7.1 Introduction.11
7.2 Record Organization.11
7.3 Record Header .11
7.3.1 Format Identifier.11
7.3.2 Version Number .11
7.3.3 Length of Record .11
7.3.4 Capture Equipment Certifications .11
7.3.5 Capture Device Type ID .12
7.3.6 Size of Scanned Image in X direction .12
7.3.7 Size of Scanned Image in Y direction .12
7.3.8 X (horizontal) resolution .12
7.3.9 Y (vertical) resolution .12
7.3.10 Number Of Finger Views .12
7.3.11 Reserved Byte .12
7.4 Single Finger Record Format.12
7.4.1 Finger Header.12
7.4.2 Finger Minutiae Data.14
7.5 Extended Data .14
7.5.1 Common Extended Data Fields .15
7.5.2 Ridge Count Data Format.15
7.5.3 Core and Delta Data Format.17
7.5.4   Zonal Quality Data .19
7.6 Minutia Record Format Summary.21
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ISO/IEC 19794-2:2005(E)

8 Finger Minutiae Card Format .22
8.1 Normal Size Finger Minutiae Format .22
8.2 Compact Size Finger Minutiae Format .22
8.3 Number of Minutiae, Minutiae Ordering Sequence and Truncation.23
8.3.1 General Aspects.23
8.3.2 Biometric matching algorithm parameters .23
8.3.3 Number of Minutiae.23
8.3.4 Minutiae Order.24
8.4 Usage of additional features for the card format.26

8.4.1 Data objects for additional features .26
8.4.2 Indication of card capabilities .26
9 CBEFF Format Owner and Format Types .27
Annex A (normative) Record Format Diagrams .28
A.1 Overall Record Format .28
A.2 Record Header .28
A.3 Single Finger View Minutiae Record.28
A.4 Finger Minutiae Data.29
A.5 Extended Data.29
Annex B (normative) Fingerprint Image Quality Specifications. .30
B.1 SCOPE AND PURPOSE .30
B.2 FINGERPRINT SCANNERS.30
B.2.1 Geometric Image Accuracy.30
B.2.2 Modulation Transfer Function.30
B.2.3 Signal-to-Noise Ratio.31
B.2.4 Gray-Scale Range of Image Data .31
B.2.5 Gray-scale Linearity.32
B.2.6 Output Gray Level Uniformity .32
B.3 LATENT PRINT SCANNERS .32
B.3.1 Geometric Image Accuracy.33
B.3.2 Modulation Transfer Function.33
Annex C (informative) Example Data Record .34
C.1 Data.34
C.2 Example Data Format Diagrams .35
C.3 Raw Data for the Resulting Minutiae Record.36
Annex D (informative) Handling of Finger Minutiae Card Formats. .37
D.1 Enrollment .37
D.1.1 Number of minutiae .37
D.1.2 Number of required finger presentations.37
D.2 Matching .37
D.2.1 Matching conditions .38
D.2.2 Threshold Value .38
D.2.3 Retry Counter.39
D.3 Security Aspects of Finger Minutiae Presentation to the Card .39
Bibliography.40

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ISO/IEC 19794-2:2005(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC 19794-2 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 37, Biometrics.
ISO/IEC 19794 consists of the following parts, under the general title Information technology — Biometric data
interchange formats:
 Part 1: Framework
 Part 2: Finger minutiae data
 Part 3: Finger pattern spectral data
 Part 4: Finger image data
 Part 5: Face image data
 Part 6: Iris image data
The following parts are under preparation:
 Part 7: Signature/sign behavioral data
 Part 8: Finger pattern skeletal data
Vascular image data, hand geometry silhouette data, and signature/sign processed dynamic data will from the
subjects of future Parts 9, 10 and 11, respectively.
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ISO/IEC 19794-2:2005(E)

Introduction
In the interest of implementing interoperable biometric recognition systems, this part of ISO/IEC 19794

establishes a data interchange format for minutiae-based fingerprint capture and recognition equipment.
Representation of fingerprint data using minutiae is a widely used technique in many application areas.
This part of ISO/IEC 19794 defines specifics of the extraction of key points (called minutiae) from fingerprint
ridge patterns. Two types of data formats are then defined: one for general storage and transport, one for use
in card-based systems; the card format has a standard and a compact expression.

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INTERNATIONAL STANDARD                 ISO/IEC 19794-2:2005(E)

Information technology — Biometric data interchange
formats —
Part 2:
Finger minutiae data
1 Scope
This part of ISO/IEC 19794 specifies a concept and data formats for representation of fingerprints using the

fundamental notion of minutiae. It is generic, in that it may be applied and used in a wide range of application
areas where automated fingerprint recognition is involved. This part of ISO/IEC 19794 contains definitions of
relevant terms, a description of how minutiae shall be determined, data formats for containing the data for both
general use and for use with cards, and conformance information. Guidelines and values for matching and
decision parameters are provided in an informative annex.
2 Conformance
A system conforms to this part of ISO/IEC 19794 if it satisfies the mandatory requirements herein for extraction
of minutiae from a fingerprint image as described in Clause 6 and the generation of a minutiae data format as
described in Clause 7 (for general data interchange use) or Clause 8 (for use with cards). Since any finger
minutiae extraction and matching algorithm supporting the described finger minutiae data interchange formats
may be used, interoperability testing is of extreme importance, especially for environments in which components
of different manufacturers interact. In ISO/IEC 19795 "Information technology - Biometric performance testing
and reporting," test methodologies and performance testing of biometric data interchange formats are outlined.
The application specific policies and relevant standards will determine the requirements for conformance
testing and evaluation affecting levels of interoperability.
3 Normative references
The following referenced documents are indispensable for the application of this document. For dated refe-
rences, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ISO/IEC 7816-11:2004, Identification cards — Integrated circuit cards — Part 11: Personal verification through
biometric methods
1)
ISO/IEC 19784-1:— , Information technology — Biometric application programme interface — Part 1: BioAPI
specification
1)
ISO/IEC 19785-1:— , Information technology — Common Biometric Exchange Formats Framework — Part 1:
Data element specification
1)
ISO/IEC 19785-2:— , Information technology — Common Biometric Exchange Formats Framework — Part 2:
Procedures of the operation of the Biometric Registration Authority
4 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
4.1
algorithm
a sequence of instructions that tell a biometric system how to solve a particular problem. An algorithm will
have a finite number of steps and is typically used by the biometric engine (i.e., the biometric system software)
to compute whether a biometric sample and template are a match.
—
1)  To be published.
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ISO/IEC 19794-2:2005(E)

4.2
biometrics
[automated] recognition of [living] persons based on observation of behavioral and biological (anatomical and
physiological) characteristics.

4.3
biometric
pertaining to the field of biometrics.
4.4
biometric data
data encoding a feature or features used in biometric verification.
4.5
biometric Information template
a constructed data object in a card containing information needed by the outside world for a verification
process, see ISO/IEC 7816-11
4.6
biometric sample
information obtained from a biometric device, either directly or after further processing.

4.7
biometric system
an automated system capable of:
1. capturing a biometric sample from an end user;
2. extracting biometric data from that sample;
3. comparing the biometric data with that contained in one or more reference templates;
4. deciding how well they match; and
5. indicating whether or not an identification or verification of identity has been achieved.
4.8
capture
the process of taking a biometric sample from an end user.
4.9
cell
a rectangular region defined by a uniform and non-overlapping division of the image.
4.10
comparison
the process of comparing a biometric sample with a previously stored reference template or templates.
4.11
claimant
a person submitting a biometric sample for verification or identification while claiming a legitimate or false
identity.
4.12
core
a core is the topmost point on the innermost recurving ridgeline of a fingerprint. Generally, the core is placed
upon or within the innermost recurve of a loop.
4.13
database
any storage of biometric templates and related end user information.
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4.14
delta
a delta is that point on a ridge at or nearest to the point of divergence of two type lines, and located at or
directly in front of the point of divergence.
4.15
end user
a person who interacts with a biometric system to enroll or have his/her identity checked. Contrast with “User”.
4.16
enrollment
the process of collecting biometric samples from a person and the subsequent preparation and storage of
biometric reference templates representing that person's identity.
4.17
extraction
the process of converting a captured biometric sample into biometric data so that it can be compared to a
reference template; sometimes called "characterization".
4.18
friction ridge
the ridges present on the skin of the fingers and toes, the palms and soles of the feet, which makes contact
with an incident surface under normal touch. On the fingers, the unique patterns formed by the friction ridges
make up fingerprints.
4.19
identification / identify
the one-to-many process of comparing a submitted biometric sample against all of the biometric reference
templates on file to determine whether it matches any of the templates and, if so, the identity of the enrollee
whose template was matched. The biometric system using the one-to-many approach is seeking to find an
identity amongst a database rather than verify a claimed identity. Contrast with ‘Verification’.
4.20
latent
a fingerprint collected from an intermediate surface, rather than directly via a live capture from the finger itself.
4.21
live capture
The process of capturing a biometric sample by an interaction between an end user and a biometric system.
4.22
live-scan print
a fingerprint image that is produced by scanning or imaging a live finger to generate an image of the friction
ridges.
4.23
match / matching
the process of comparing a biometric sample against a previously stored template and scoring the level of
similarity.
4.24
minutia (single) minutiae (pl)
friction ridge characteristics that are used to individualize a fingerprint. Minutiae occur at points where a single
friction ridge deviates from an uninterrupted flow. Deviation may take the form of ending, bifurcation, or a more
complicated “composite” type.
4.25
population
The set of end-users for the application.
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4.26
record
the template and other information about the end-user (e.g. access permissions).
4.27
resolution
the number of pixels (picture elements) per unit distance in the image of the fingerprint.
4.28
ridge bifurcation
the minutia assigned to the location at which a friction ridge splits into two ridges or, alternatively, where two
separate friction ridges combine into one.
4.29
ridge ending
the minutia assigned to the location at which a friction ridge terminates or, alternatively, begins. A ridge
ending is defined as the bifurcation of the adjacent valley - the location at which a valley splits into two valleys
or, alternatively, at which two separate valleys combine into one.
4.30
ridge skeleton endpoint
the minutia assigned to the location at which a ridge skeleton ends. A ridge skeleton endpoint is defined as
the ending of the skeleton of a ridge.
4.31
skeleton
the single-pixel-wide representation of a ridge or valley obtained by successive symmetric thinning operations.
The skeleton is also known as the medial axis.
4.32
swipe
a method of fingerprint collection where the finger is manually moved across a one-dimensional sensor to
produce the two-dimensional image.
4.33
template / reference template
data, which represents the biometric measurement of an enrollee, used by a biometric system for comparison
against subsequently submitted biometric samples. NOTE - this term is not restricted to mean only data used
in any particular recognition method, such as template matching.
4.34
typeline
the two innermost ridges that start parallel, diverge, and surround or tend to surround the pattern area.
4.35
user
the client to any biometric vendor. The user must be differentiated from the end user and is responsible for
managing and implementing the biometric application rather than actually interacting with the biometric
system.
4.36
valley
the area surrounding a friction ridge, which does not make contact with an incident surface under normal
touch; the area of the finger between two friction ridges.
4.37
valley bifurcation
the point at which a valley splits into two valleys or, alternatively, where two separate valleys combine into one.
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4.38
verification / verify
the process of comparing a submitted biometric sample against the biometric reference template of a single
enrollee whose identity is being claimed, to determine whether it matches the enrollee’s template. Contrast
with ‘Identification’.

5 Symbols and abbreviated terms
BIT Biometric Information Template
CBEFF Common Biometric Exchange Formats Framework
DO Data Object
FAR False Acceptance Rate
FRR False Rejection Rate
RCE Ridge Count Extraction
RFU Reserved for Future Use
6 Minutiae Extraction
6.1 to 6.7 define the placement of minutiae on the fingerprint. Compatible minutiae extraction is required
for interoperability between different finger matchers for the purposes of matching an individual against a
previously collected and stored finger record. The interoperability is based on defining the finger minutiae
extraction rules, record formats and card formats that are common to many finger matchers for acceptable
matching accuracy, while allowing for extended data to be attached for use with equipment that is compatible
with it.
6.1 Principle
Establishment of a common feature-based representation must rest on agreement on the fundamental notion
for representing a fingerprint. Minutiae are points located at the places in the fingerprint image where friction
ridges end or split into two ridges. Describing a fingerprint in terms of the location and direction of these ridge
endings and bifurcations provides sufficient information to reliably determine whether two fingerprint records
are from the same finger.
The specifica
...