ISO/IEC 19794-2:2005
(Main)Information technology — Biometric data interchange formats — Part 2: Finger minutiae data
Information technology — Biometric data interchange formats — Part 2: Finger minutiae data
ISO/IEC 19794-2:2005 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. ISO/IEC 19794-2:2005 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. ISO/IEC 19794-2:2005 specifies the fundamental data elements used for minutiae-based representation of a fingerprint; three data formats for interchange and storage of this data: a record-based format, and normal and compact formats for use on a smart card in a match-on-card application; optional extended data formats for including additional data such as ridge counts and core and delta location. ISO/IEC 19794-2:2005 provides for interchange of finger minutiae data between sensing, storage and matching systems.
Technologies de l'information — Formats d'échange de données biométriques — Partie 2: Données du point caractéristique du doigt
General Information
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Standards Content (Sample)
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 2005
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ii © ISO/IEC 2005 – All rights reserved
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
© ISO/IEC 2005 – All rights reserved iii
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
iv © ISO/IEC 2005 – All rights reserved
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.
© ISO/IEC 2005 – All rights reserved v
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.
vi © ISO/IEC 2005 – All rights reserved
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.
© ISO/IEC 2005 – All rights reserved 1
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.
2 © ISO/IEC 2005 – All rights reserved
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.
© ISO/IEC 2005 – All rights reserved 3
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.
4 © ISO/IEC 2005 – All rights reserved
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 specifications of minutia location and minutia direction described below accomplish this. See Figure 1 for
an illustration of the definitions below.
6.2 Minutia Type
Each minutia has a “type” associated with it. There are two major types of minutiae: a “ridge skeleton end
point” and a “ridge skeleton bifurcation point” or split point. There are other types of “points of interest” in the
friction ridges that occur much less frequently and are more difficult to define precisely. More complex types
of minutiae are usually a combination of the basic types defined above. Some points are neither a ridge
ending nor a bifurcation. This standard therefore defines additionally a type named “other”, which shall be
used in such a way that the matching conditions specified in 6.6 apply. The "other" minutiae type shall not be
used for minutiae that are ridge endings or ridge bifurcations.
Therefore, the following types are distinguished:
- ridge ending (also identifiable as a valley skeleton bifurcation point);
- ridge bifurcation
- other.
© ISO/IEC 2005 – All rights reserved 5
A ridge ending may — alternatively — be regarded as a valley bifurcation depending on the method to
determine its position (see below). The format type of the biometric information template indicates the use of
ridge endings or valley bifurcations.
6.3 Minutia Location
The minutia location is represented by its horizontal and vertical position. The minutiae determination strategy
considered in this document relies on skeletons derived from a digital fingerprint image. The ridge skeleton is
computed by thinning down the ridge area to single pixel wide lines. The valley skeleton is computed by
thinning down the valley area to single pixel wide lines. If other methods are applied, they should approximate
the skeleton method, i.e. location and angle of the minutia should be equivalent to the skeleton method.
6.3.1 Coordinate System
The coordinate system used to express the minutiae of a fingerprint shall be a Cartesian coordinate system.
Points shall be represented by their X and Y coordinates. The origin of the coordinate system shall be the
upper left corner of the original image with X increasing to the right and Y increasing downward. Note that this
is in agreement with most imaging and image processing use. When viewed on the finger, X increases from
right to left as shown in Figure 1. All X and Y values are non-negative.
The X and Y coordinates of the minutiae shall be in pixel units, with the spatial resolution of a pixel given in
the “X Resolution” and “Y Resolution” fields of the format. X and Y resolutions are stated separately.
xx
xx
yy
yy
lalatteentnt p prrinintt
ffiingengerr
Figure 1 - Coordinate system
For the finger minutiae record format, the resolution of the coordinate system is specified in the record header,
see 7.3.8 and 7.3.9. For the finger minutiae card format, the resolution of the X and Y coordinates of the
minutia shall be in metric units. The granularity is one bit per one hundredth of a millimeter in the normal
format and one tenth of a millimeter in the compact format:
-2 -1
1 unit = 10 mm (normal format) or 10 mm (compact format).
6 © ISO/IEC 2005 – All rights reserved
6.3.2 Minutia Placement on a Ridge Ending (encoded as Valley Skeleton Bifurcation Point)
The minutia for a ridge ending shall be defined as the point of forking of the medial skeleton of the valley area
immediately in front of the ridge ending. If the valley area were thinned down to a single-pixel-wide skeleton,
the point where the three legs intersect is the location of the minutia. In simpler terms, the point where the
valley Y’s, or (equivalently) where the three legs of the thinned valley area intersect (see Figure 2).
θ
valley
ridge
Figure 2 - Location and direction of a ridge ending (encoded as valley skeleton bifurcation point)
6.3.3 Minutia Placement on a Ridge Bifurcation (encoded as a Ridge Skeleton Bifurcation Point)
The minutia for a ridge bifurcation shall be defined as the point of forking of the medial skeleton of the ridge. If
the ridges were thinned down to a single-pixel-wide skeleton, the point where the three legs intersect is the
location of the minutia. In simpler terms, the point where the ridge “Y”’s, or (equivalently) where the three legs
of the thinned ridge intersect (see Figure 3).
θ
valley
ridge
Figure 3 - Location and direction of a ridge bifurcation (encoded as ridge skeleton bifurcation point)
6.3.4 Minutia Placement on a Ridge Skeleton Endpoint
The minutia for a ridge skeleton endpoint shall be defined as the center point of the ending ridge. If the ridges
in the digital fingerprint image were thinned down to a single-pixel-wide skeleton, the position of the minutia
would be the coordinates of the skeleton point with only one neighbor pixel belonging to the skeleton (see
Figure 4).
© ISO/IEC 2005 – All rights reserved 7
θ
valley
ridge
Figure 4 - Location and direction of a ridge skeleton endpoint
6.3.5 Minutia Placement on Other Minutia Types
For minutia other than a bifurcation or ridge ending the position and angle calculations shall be done in such a
way that the matching conditions in 6.5 apply.
6.3.6 Usage of the Minutia Placement by the Record Formats and the Card Formats
The record formats use
- ridge ending and ridge bifurcation points.
The card formats use
- ridge ending and ridge bifurcation points, or
- ridge skeleton end points and ridge bifurcation points
depending on the specific algorithms implemented. In case of on-card matching, a card will request from the
card usage system biometric verification data in the format compliant to its algorithm. The requested format is
either implicitly known to the card usage system or can be retrieved in the Biometric Information Template,
which contain the CBEFF data elements format owner and format type – see ISO/IEC 19785-1 and
ISO/IEC 7816-11.
6.4 Minutia Direction
6.4.1 Angle Conventions
The minutia angle is measured increasing counter-clockwise starting from the horizontal axis to the right.
In the record formats, the angle of a minutia is scaled to fit the granularity of 1.40625 (360/256) degrees per
least significant bit.
The angle coding for the card formats differ for the normal size and the compact size formats; refer to 8.1 and
8.2.
8 © ISO/IEC 2005 – All rights reserved
6.4.2 Minutia Direction of a Ridge Ending (encoded as Valley Skeleton Bifurcation Point)
A ridge ending (encoded as valley skeleton bifurcation point) has three arms of valleys meeting in one point.
Two valleys enclosing the ridge ending line encompass an acute angle. The direction of a valley bifurcation is
defined by the mean direction of their tangents and is measured as the angle the tangent forms with the
horizontal axis to the right (see Figure 2).
6.4.3 Minutia Direction of a Ridge Bifurcation (encoded as Ridge Skeleton Bifurcation Point)
A ridge bifurcation (encoded as ridge skeleton bifurcation point) has three arms of ridges meeting in one point.
Two ridges enclosing the ending valley encompass an acute angle. The direction of a ridge bifurcation is
defined by the mean direction of their tangents and is measured as the angle the tangent forms with the
horizontal axis to the right (see Figure 3).
6.4.4 Minutia Direction of a Ridge Skeleton End Point
The direction of a ridge skeleton endpoint is defined as the angle that the tangent to the ending ridge
encompasses with the horizontal axis to the right (see Figure 4). Ridge skeleton end points are only used in
one type of the card formats, whereas in the other type ridge ending and ridge bifurcation is used as in the
record format.
6.5 Core and Delta Placement and Direction
Core and delta points are designated points of interest in a fingerprint. A fingerprint may have 0, 1 or more
than 1 cores and 0, 1 or more than 1 deltas. Core and delta position and direction are defined as follows.
Core position: If there are ridge endings enclosed by the innermost recurving ridgeline, the ending nearest to
the maximal curvature of the recurving ridgeline defines the core position. If the core is a u-turn of a ridgeline
not enclosing ridge endings, the valley end defines the core position.
Core direction: If the core has a discernible angle of direction, it shall be recorded in the core information,
since this characterizes the type of core. The angle of a core is defined by the angle of the tangent to the
ridge lines that are closest to the core position; the direction measured points towards the open side of the
concave ridge.
Delta position: Three points of divergence are each placed between the two ridges at the location where the
ridges begin to diverge; that is, where the ridges that have been parallel or nearly parallel begin to spread
apart as they approach the delta. The position of the delta is defined by the spatial mean of these three points.
Delta direction: For all observable divergences the angle is defined by the direction of the tangent before the
pair of ridges beings to diverge. The angle shall point from divergent towards parallel ridge lines; that is, the
angles shall point outwards from the delta.
Core and delta point placement is illustrated in Figure 5.
© ISO/IEC 2005 – All rights reserved 9
Figure 5 - Example Core and Delta placement
6.6 Minutia Type Matching
In a matching process, the different minutia types shall be matched according to the following Table 1.
Matchers may choose to assign lower weights (or importance) to a match of type 00 to 01 or 10, than to a
match of type 00 to 00, 01 to 01, or 10 to 10.
Table 1 - Minutia Type Matching
Type of verification minutia Match with type of reference minutia
00 00, 01, 10
01 00, 01
10 00, 10
00 = other
01 = ridge ending (encoded as valley skeleton bifurcation point), or ridge skeleton end point, see note
10 = ridge bifurcation (encoded as ridge skeleton bifurcation point)
NOTE - Whether ridge ending or bifurcation is meant depends on the format type.
6.7 Encoding of multibyte quantities
All multibyte quantities are represented in Big-Endian format; that is, the more significant bytes of any multi-
byte quantity are stored at lower addresses in memory than (and are transmitted before) less significant bytes.
All numeric values are fixed-length integer quantities, and are unsigned quantities.
10 © ISO/IEC 2005 – All rights reserved
7 Finger Minutiae Record Format
7.1 Introduction
The minutiae record format shall be used to achieve interoperability between finger matchers providing a one-
to-one verification. The minutia data shall be represented in a common format, containing both basic and
extended data. With the exception of the Format Identifier and the Version number for the standard, which are
null-terminated ASCII character strings, all data is represented in binary format. There are no record sepa-
rators or field tags; fields are parsed by byte count.
7.2 Record Organization
The organization of the record is as follows:
• A fixed-length (24-byte) record header containing information about the overall record, including the
number of fingers represented and the overall record length in bytes;
• A Single Finger record for each finger, consisting of:
• A fixed-length (4-byte) header containing information about the data for a single finger, including the
number of minutiae;
• A series of fixed-length(6-byte) minutia descriptions, including the position, type, angle and quality of
the minutia;
• One or more “extended” data areas for each finger, containing optional or vendor-specific information.
7.3 Record Header
There shall be one and only one record header for the minutiae record, to hold information describing the type
and characteristics of device that generated the minutia data.
7.3.1 Format Identifier
The Finger Minutiae Record shall begin with the three ASCII characters “FMR” followed by a zero byte as a
NULL string terminator.
7.3.2 Version Number
The version number for the version of this standard used in constructing the minutiae record shall be placed in
four bytes. This version number shall consist of three ASCII numerals followed by a zero byte as a NULL
string terminator. The first and second character will represent the major revision number and the third
character will represent the minor revision number.
The version number is “ 20” (an ASCII space followed by an ASCII ‘2’ and an ASCII ‘0’).
7.3.3 Length of Record
The length of the entire record shall be recorded in four bytes.
7.3.4 Capture Equipment Certifications
This field contains four bits used to indicate that the capture equipment used to capture the original fingerprint
image was compliant with a standard certification method for such equipment. Currently, only two bits are
defined. If the most significant bit is ‘1’, the original capture equipment was certified to be compliant with the
specifications in Annex B, copied from the US Federal Bureau of Investigation’s Image Quality Specifications,
Appendix F. The least significant of the four bits is reserved for a future ISO finger image capture equipment
certification. The two additional bits are reserved for future image quality certifications.
© ISO/IEC 2005 – All rights reserved 11
7.3.5 Capture Device Type ID
The capture device type ID shall be recorded in twelve bits. This ID is used to identify the type or model of
capture device used to acquire the original biometric sample. A value of all zeros will be acceptable and will
indicate that the capture device type ID is unreported. The vendor determines the value for this field, if not
regulated otherwise in an application context. Applications developers and users may obtain the values for
these codes, as well as the model(s) corresponding to a particular ID, from the vendor. Reporting the capture
device type ID is optional but recommended. The value “unreported” may not be allowable in some
applications.
7.3.6 Size of Scanned Image in X direction
The size of the original image in pixels in the X direction shall be contained in two bytes.
7.3.7 Size of Scanned Image in Y direction
The size of the original image in pixels in the Y direction shall be contained in two b
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