ISO/IEC 39794-2:2023

INTERNATIONAL ISO/IEC
STANDARD 39794-2
First edition
2023-09
Information technology — Extensible
biometric data interchange formats —
Part 2:
Finger minutiae data
Reference number
© ISO/IEC 2023
© ISO/IEC 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
© ISO/IEC 2023 – All rights reserved

Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms.4
5 Conformance . 4
6 Modality-specific information . .5
6.1 Purpose . 5
6.2 Minutia description . 5
6.3 Minutia kind . 5
6.3.1 General . 5
6.3.2 Unique minutia . 5
6.3.3 Encoding trifurcations . 5
6.4 Minutia location . 6
6.4.1 General . 6
6.4.2 Coordinate system . 6
6.4.3 Minutia location of a ridge ending (encoded as valley skeleton bifurcation
point) . 6
6.4.4 Minutia location of a ridge bifurcation . 7
6.4.5 Minutia location of a ridge ending (encoded as ridge skeleton endpoint) . 8
6.4.6 Usage of the minutia placement . 9
6.5 Minutiae direction . 9
6.5.1 Angle conventions . 9
6.5.2 Minutia direction of a ridge ending (encoded as valley skeleton bifurcation
point) . 9
6.5.3 Minutia direction of a ridge bifurcation . 9
6.5.4 Minutia direction of a ridge ending (encoded as ridge skeleton endpoint) . 9
6.6 Core and delta placement . 9
7 Abstract data elements .11
7.1 Purpose . 11
7.2 Finger minutiae data . 12
7.3 Version . 12
7.4 Representation block . 12
7.5 Position .12
7.6 Impression .12
7.7 Minutiae data . 13
7.8 Spatial sampling rate . 14
7.9 Ridge end encoding . 14
7.10 Capture date and time . 14
7.11 Capture device . 14
7.11.1 Capture device model identifier . 14
7.11.2 Certification identifier blocks . 14
7.11.3 Certification schemes for finger images . 14
7.11.4 Capture device technology identifier . 15
7.12 Biometric sample quality blocks . 16
7.13 Generic ridge counts . 16
7.14 Four neighbour ridge counts . 17
7.15 Eight neighbour ridge counts . 17
7.16 Core data . 18
7.17 Delta data . 18
7.18 Zonal quality . 18
iii
© ISO/IEC 2023 – All rights reserved

7.19 PAD data block . 19
7.20 Vendor specific data . 19
8 Encoding .19
8.1 Tagged binary encoding . 19
8.2 XML encoding . 19
8.3 On-card biometric comparison format . 19
8.3.1 Overview . 19
8.3.2 Minutia placement. 21
8.3.3 Encoding . 21
8.3.4 Minutia position . 21
8.3.5 Minutia type . 21
8.3.6 Minutia angle . 21
8.3.7 Number of minutiae and truncation . 22
8.3.8 Usage of extended data for the on-card comparison format .22
8.3.9 Biometric comparison parameters . 31
9 Registered format type identifiers .34
Annex A (normative) Formal specifications .35
Annex B (normative) Conformance test methodology .46
Annex C (informative) Encoding examples .51
Annex D (informative) Detailed description of finger minutiae location, direction, type .54
Bibliography .79
iv
© ISO/IEC 2023 – 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.
The procedures used to develop this document and those intended for its further maintenance
are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria
needed for the different types of document should be noted. This document was drafted in
accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives or
www.iec.ch/members_experts/refdocs).
ISO and IEC draw attention to the possibility that the implementation of this document may involve the
use of (a) patent(s). ISO and IEC take no position concerning the evidence, validity or applicability of
any claimed patent rights in respect thereof. As of the date of publication of this document, ISO and IEC
had not received notice of (a) patent(s) which may be required to implement this document. However,
implementers are cautioned that this may not represent the latest information, which may be obtained
from the patent database available at www.iso.org/patents and https://patents.iec.ch. ISO and IEC shall
not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see
www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 37, Biometrics.
A list of all parts in the ISO/IEC 39794 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards
body. A complete listing of these bodies can be found at www.iso.org/members.html and
www.iec.ch/national-committees.
v
© ISO/IEC 2023 – All rights reserved

Introduction
Biometric data interchange formats enable the interoperability of different biometric systems. The
first generation of biometric data interchange formats was published between 2005 and 2007 in the
first edition of the ISO/IEC 19794 series. From 2011 onwards, the second generation of biometric data
interchange formats was published in the form of second editions of the established parts and the first
editions of a number of new parts of the ISO/IEC 19794 series. In the second generation of biometric
data interchange formats, new useful data elements such as data elements related to biometric sample
quality were added, the header data structures were harmonized across all parts of the ISO/IEC 19794
series, and XML encoding was added in addition to the binary encoding.
In anticipation of the future need for additional data elements and to avoid future compatibility issues,
ISO/IEC JTC 1/SC 37 has developed the ISO/IEC 39794 series as a third generation of biometric data
interchange formats, defining extensible biometric data interchange formats capable of including
future extensions in a defined manner. Extensible specifications in ASN.1 (Abstract Syntax Notation
One) and the distinguished encoding rules of ASN.1 form the basis for encoding biometric data in binary
tag-length-value formats. XML Schema Definitions form the basis for encoding biometric data in XML
(eXtensible Markup Language).
This third generation of finger minutia data interchange formats complements ISO/IEC 19794-2:2005
and ISO/IEC 19794-2:2011. The first generation of biometric data interchange formats, which has been
adopted in mass deployments, will be retained in the standards catalogue as long as required.
This document is intended for those applications requiring the exchange of fingerprint minutiae data.
It will provide implementers with the flexibility to accommodate minutiae captured from dissimilar
devices, varying image sizes, spatial sampling rates and different grey-scale depths. Use of the finger
minutiae will allow each vendor to implement their own algorithms to determine whether two
fingerprint records are from the same finger.
This document supports both binary and XML encoding, to support a spectrum of user requirements.
With XML, this document meets the requirements of modern IT architectures. With binary encoding,
this document is also able to be used in bandwidth- or storage-constrained environments.
1)
For use on integrated circuit cards and other tokens (see ISO/IEC 7816-11 and ISO/IEC 24787-1:— ), this
document also specifies an on-card biometric comparison format and on-card comparison parameters
based on extensible tag-length-value (TLV) encoding. ISO/IEC 24787-1 specifies the encapsulation of
biometric data in on-card biometric comparison format into TLV-structured verification data for on-
card biometric comparison.
This document defines specifics of the extraction of key points (called minutiae) from fingerprint ridge
patterns. These specifics include a description of the types of minutiae identified, the method used for
the placement of minutiae on an image, a definition of the coordinate system used, and the methods
used to calculate the angle associated with each minutia.
1) Under preparation. Stage at the time of publication: ISO/IEC DIS 24787-1:2023.
vi
© ISO/IEC 2023 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 39794-2:2023(E)
Information technology — Extensible biometric data
interchange formats —
Part 2:
Finger minutiae data
1 Scope
This document specifies:
— generic extensible data interchange formats for the representation of finger minutia data:
— a tagged binary data format based on an extensible specification in ASN.1,
— a textual data format based on an XML schema definition that is capable of holding the same
information as the tagged binary format, and
— an on-card biometric comparison format based on extensible TLV encoding;
— on-card biometric comparison parameters based on extensible TLV encoding for constructing valid
probe data in the on-card biometric comparison format;
— examples of data record contents;
— application-specific requirements, recommendations and best practices in determining minutiae
location, direction and type; and
— conformance test assertions and conformance test procedures applicable to this document.
NOTE Whereas ISO/IEC 39794-4 covers finger, palm, toe and foot image data, this document covers only
finger minutiae and is not applicable to palms, toes or feet.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 39794-1, Information technology — Extensible biometric data interchange formats — Part 1:
Framework
ISO/IEC 8825-1, Information technology — ASN.1 encoding rules — Part 1: Specification of Basic Encoding
Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)
ISO/IEC 19785-3, Information technology — Common Biometric Exchange Formats Framework — Part 3:
Patron format specifications
ISO/IEC 2382-37, Information technology — Vocabulary — Part 37: Biometrics
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 2382-37, ISO/IEC 39794-1
and the following apply.
© ISO/IEC 2023 – All rights reserved

ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
image spatial sampling rate
number of pixels per unit distance in the image
Note 1 to entry: This can be the result of processing a captured image. The original captured scanned image can
have been subsampled, scaled, down-sampled or otherwise processed.
3.2
palm
friction ridge skin on the side and underside of the hand
3.3
fingerprint image
representation of an area of friction skin on the fleshy surface of a finger located horizontally between
the two edges of the fingernail and vertically between the first joint and the tip of a finger
Note 1 to entry: It contains a unique pattern of friction ridge and valley information commonly referred to as a
“fingerprint”.
3.4
friction ridge
ridge present on the skin of the fingers and toes, the palms of the hands and the soles of the feet, which
makes contact with an incident surface under normal touch
Note 1 to entry: On the fingers, the unique patterns formed by the friction ridges make up fingerprints.
3.5
minutia
point where a single friction ridge deviates from an uninterrupted flow
Note 1 to entry: Deviation can take the form of ending, bifurcation, or a more complicated “composite” type.
3.6
typeline
one of the two innermost friction ridges that start parallel, diverge, and surround or tend to surround
the pattern area
3.7
delta
point on a ridge at or nearest to the point of divergence of two typelines and located at or directly in
front of the point of divergence
3.8
core
topmost point on the innermost recurving ridgeline of a fingerprint
Note 1 to entry: Generally, the core is placed upon or within the innermost recurve of a loop.
3.9
four-neighbour of pixel p
pixel that is the top, bottom, left, or right neighbour of pixel p
© ISO/IEC 2023 – All rights reserved

EXAMPLE The pixels e, f, g and h in the following table are four-neighbours of pixel p.
3.10
four-path from pixel p to pixel p
0 n
sequence of pixels (p , p , p , …, p ) such that p is a four-neighbour of p
0 1 2 n i i-1
3.11
four-connected set of pixels
set S of pixels such that for any two pixels p, q ∈ S, there exists a four-path from p to q
3.12
eight-neighbour of a pixel p
pixel that is a four-neighbour or a diagonal (top-left, top-right, bottom-left, or bottom-right) neighbour
of pixel p
EXAMPLE The pixels a, b, c, d, e, f, g and h in the table are eight-neighbours of pixel p.
3.13
eight-path from pixel p to pixel p
0 n
sequence of pixels (p , p , p , …, p ) such that p is an eight-neighbour of p −1
0 1 2 n i i
3.14
eight-connected set of pixels
set S of pixels such that for any two pixels p, q ∈ S there exists an eight-path from p to q
3.15
border ∂S of a set of pixels S
subset ∂S = {x ∈ S : x is four-neighbour of q, q ∉ S } of pixels of S that are four-neighbours of pixels outside
S
3.16
loop
type of fingerprint classification pattern where the friction ridges arrange themselves in the form of a
lasso, making a backward turn without a twist
3.17
whorl
type of fingerprint classification pattern where the friction ridges form a revolution around the centre
© ISO/IEC 2023 – All rights reserved

4 Symbols and abbreviated terms
For the purposes of this document, the abbreviations given in ISO/IEC 39794-1 and the following apply.
AC alternating current
AFIS automated fingerprint identification system
BIT biometric information template
DO data object
EL electroluminescent
ICC integrated circuit card
ICS implementation conformance statement
ppcm pixels per centimetre
ppi pixels per inch
ppmm pixels per millimetre
RF radio frequency
TIR total internal reflection
TLV tag-length-value
5 Conformance
A biometric data block conforms to this document if it satisfies all of the normative requirements
related to:
— its data structure, data values and the relationships between its data elements as specified
throughout Clauses 7 and 8 and Annex A of this document; and
— the relationship between its data values and the input biometric data from which the biometric data
block was generated as specified in Clause 6.
NOTE A biometric data block will always conform to only one of the following formats:
— tagged binary encoding as specified in 8.1, or
— XML encoding as specified in 8.2, or
— binary encoding for on-card biometric comparison as specified in 8.3.
A system that produces biometric data blocks is conformant to this document if all biometric data
blocks that it outputs conform to this document (as defined above) as claimed in the Implementation
Conformance Statement (ICS) associated with that system. A system does not need to be capable of
producing biometric data blocks that cover all possible aspects of this document, but only those that are
claimed to be supported by the system in the ICS.
A system that uses biometric data blocks is conformant to this document if it can read, and use for the
purpose intended by that system, all biometric data blocks that conform to this document (as defined
above) as claimed in the ICS associated with that system. A system does not need to be capable of using
biometric data blocks that cover all possible aspects of this document, but only those that are claimed
to be supported by the system in an ICS.
Conformance test methodology shall be in accordance with Annex B.
© ISO/IEC 2023 – All rights reserved

6 Modality-specific information
6.1 Purpose
This clause defines the placement of minutiae on the fingerprint. Compatible minutiae extraction is
required for interoperability between different finger comparators for the purposes of comparing an
individual against previously collected and stored finger biometric data. Interoperability is based on the
definition of the finger minutiae extraction rules, the definition of the ASN.1 format (8.1 and Clause A.1),
the definition of the XML encoding format (8.2 and Clause A.2), and the on-card biometric comparison
format (8.3) that are common to many finger comparators for acceptable comparing accuracy, while
allowing for extended data to be attached for use with equipment with which they are compatible.
6.2 Minutia description
The establishment of a common feature-based representation shall rely on agreement over 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 in the following subclauses
accomplish this. See Figures 2 to 4 for illustrations of the following definitions.
6.3 Minutia kind
6.3.1 General
There are two major kinds of minutiae: a “ridge skeleton end point” and a “ridge skeleton bifurcation
point” or split point. There are also other kinds of “points of interest” in the friction ridges. These occur
much less frequently and are more difficult to define precisely. More complex kinds of minutiae are
usually a combination of the basic kinds defined above. Some points are neither a ridge ending nor a
bifurcation. Therefore, this document defines an additional kind named “other”, which shall be used
for such a case. The “other” minutiae kind shall not be used for minutiae that are ridge endings or ridge
bifurcations.
Therefore, the following kinds of minutiae are distinguished:
— ridge ending,
— ridge bifurcation,
— other.
A ridge ending may alternatively be referred to as a valley bifurcation depending on the method to
determine its position (6.4.3 and 6.4.5).
6.3.2 Unique minutia
A minutia shall be encoded once. A minutia is uniquely identified by the location and angle.
6.3.3 Encoding trifurcations
The location at which a ridge splits into three separate ridges is a trifurcation. If it is encoded, it shall be
encoded as two bifurcations with identical (X,Y) values and different orientation angle values.
© ISO/IEC 2023 – All rights reserved

6.4 Minutia location
6.4.1 General
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.
6.4.2 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. 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.
Key
1 fingerprint image
2 finger
Figure 1 — Coordinate System
For the finger minutiae ASN.1 format (8.1 and Clause A.1) and the XML format (8.2 and Clause A.2), the
X and Y coordinates of the minutiae are stored in the FeatureCoordinateBlock and measured in pixel
units, with the spatial sampling rate given in the SpatialSamplingRateBlock.
For the on-card biometric comparison format (8.3), the X and Y coordinates shall be measured in fixed
−1
metrical units of one bit per one tenth of a millimetre, or 10 mm as described in 8.3.4.
6.4.3 Minutia location of a ridge ending (encoded as valley skeleton bifurcation point)
The location of a ridge ending (encoded as valley skeleton bifurcation point) 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
© ISO/IEC 2023 – All rights reserved

valley area were thinned down to a single-pixel-wide skeleton, the point where the three skeletal lines
intersect is the location of the minutia. In simpler terms, it is the point where the valley bifurcates, or
(equivalently) where the three thinned valley lines intersect (see Figure 2).
Key
1 valley
2 ridge
Figure 2 — Location and direction of a ridge ending (encoded as valley skeleton bifurcation
point)
6.4.4 Minutia location of a ridge bifurcation
The location of 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
skeletal lines intersect is the location of the minutia. In simpler terms, it is the point where the ridge
bifurcates, or (equivalently) where the three skeletal lines of the thinned ridge intersect (see Figure 3).
© ISO/IEC 2023 – All rights reserved

Key
1 valley
2 ridge
Figure 3 — Location and direction of a ridge bifurcation
6.4.5 Minutia location of a ridge ending (encoded as ridge skeleton endpoint)
The location of a ridge ending (encoded as ridge skeleton endpoint) shall be defined as the centre 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
neighbour pixel belonging to the skeleton (see Figure 4).
Key
1 valley
2 ridge
Figure 4 — Location and direction of a ridge ending (encoded as ridge skeleton endpoint)
© ISO/IEC 2023 – All rights reserved

6.4.6 Usage of the minutia placement
Depending on the specific algorithms implemented, for tagged binary encoding, XML encoding and on-
card biometric comparison format, the following are used:
— valley skeleton bifurcations or ridge skeleton endpoints for locating minutiae on ridge endings; and
— ridge skeleton bifurcations for locating minutiae on ridge bifurcations.
For on-card biometric comparison, a card will request from the card usage system biometric probe
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 (BIT; see ISO/IEC 19785-3
and ISO/IEC 7816-11).
6.5 Minutiae direction
6.5.1 Angle conventions
The minutia angle is measured increasing counter-clockwise starting from the horizontal axis to the
right.
In the finger minutiae ASN.1 format (8.1 and Clause A.1) and the XML format (8.2 and Clause A.2), the
angle of a minutia stored in the MinutiaBlock is scaled to fit the granularity of 1,406 25 (360/256)
degrees per least significant bit.
The angle coding for the on-card biometric comparison format (8.3) is scaled to fit the granularity of
5,625 (360/64) degrees per least significant bit as described in 8.3.6.
6.5.2 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 measured as the angle the tangent of the ending ridge forms with the horizontal axis to
the right (see Figure 2).
6.5.3 Minutia direction of a ridge bifurcation
A ridge bifurcation 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 measured as the angle the tangent of
the ending valley forms with the horizontal axis to the right (see Figure 3).
6.5.4 Minutia direction of a ridge ending (encoded as ridge skeleton endpoint)
The direction of a ridge ending (encoded as 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).
6.6 Core and delta placement
Core and delta points are designated points of interest in a fingerprint. A fingerprint may have 0, 1 or
more cores and 0, 1 or more deltas. The location of the core and delta positions 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.
— Delta position: Three points of divergence are each placed between the two ridges at the location
where the ridges begin to diverge, i.e. 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. The position is at the point on a ridge at, or in front of, and nearest the
© ISO/IEC 2023 – All rights reserved

centre of the divergence of the ridges that start parallel, diverge and surround or tend to surround
the pattern area of the fingerprint image.
Core and delta point placement are illustrated in Figure 5.
NOTE Cores and deltas represent singularities in the ordinary direction field of the fingerprint image.
Hence, angle information of cores and deltas cannot fit smoothly into the direction values of all points in the
neighbourhood.
a) Example fingerprint of type loop with core and delta
b) Example fingerprint of type whorl with core and deltas
Key
1 delta
2 core
Figure 5 — Example fingerprints of type loop and whorl with placement of core and delta points
© ISO/IEC 2023 – All rights reserved

7 Abstract data elements
7.1 Purpose
This clause describes the contents of data elements defined in this document. These descriptions
are independent of the encoding of the data elements. The full naming conventions for ASN.1 module
components and component types definitions, naming conventions for XML schema elements and
element types definitions, and ASN.1 and XML schema definition extensions applied as per the
ISO/IEC 39794 series are specified in ISO/IEC 39794-1.
The tagged binary encoding as well as the XML encoding are given in 8.1, 8.2 and Annex A.
The structure of the abstract data elements is described in Figure 6.
Abstract data elements defined in this clause are used by tagged binary encoding (8.1) and XML
encoding (8.2) extensible biometric formats, which are typically used outside the ICC environment.
These abstract elements are not utilized in the same way as in on-card biometric comparison binary
format based on TLV encoding (see 8.3).
Figure 6 — Overall structure of finger minutiae data
© ISO/IEC 2023 – All rights reserved

7.2 Finger minutiae data
Abstract values: See Figure 6.
Contents: This data element is the container for all data associated with finger minutiae.
7.3 Version
Abstract values: See ISO/IEC 39794-1.
Contents: The generation number of this document shall be 3. The year shall be the year of
the publication of this document.
7.4 Representation block
Abstract values: See Figure 6.
Contents: This data element is the container for all data associated with finger minutiae,
except for the version block information.
7.5 Position
Abstract values: See Table 1.
Contents: This data element establishes which finger region is encoded in the image data.
For example, a right index finger image is described with a position of “right-
IndexFinger” in an ASN.1 encoding. The position encodings are specified to
improve interoperability with existing standards, notably the ANSI/NIST ITL
standard family.
Table 1 — Description for finger position values
Abstract value Description
unknownPosition Unknown finger
rightThumbFinger Right thumb
rightIndexFinger Right index finger
rightMiddleFinger Right middle finger
rightRingFinger Right ring finger
rightLittleFinger Right little finger
leftThumbFinger Left thumb
leftIndexFinger Left index finger
leftMiddleFinger Left middle finger
leftRingFinger Left ring finger
leftLittleFinger Left little finger
7.6 Impression
Abstract values: See Table 2.
Contents: This data element establishes how the finger interacted with the capture system
at the time of capture. The impression encodings are specified to improve inter-
operability with existing standards, notably the ANSI/NIST ITL standard family.
© ISO/IEC 2023 – All rights reserved

Table 2 — Description for finger impression values
Abstract value Description
plainContact A stationary subject’s finger in contact with a fixed scanning surface (or platen).
rolledContact A laterally rolled subject’s finger in contact with a fixed scanning surface
(or platen).
latentImage A residue from a subject’s finger left on a surface that has been captured.
swipeContact A moving subject’s finger (typically vertically) in contact with a fixed thin
scanning bar.
stationarySubjectContactlessPlain A subject’s finger captured without contact in such a way that the image is
not representative of a roll or other 3D structure, and in which the subject
is expected to remain mostly motionless.
stationarySubjectContactlessRolled A subject’s finger captured without contact in such a way that the image is
representative of a roll or other 3D structure, and in which the subject is
expected to remain mostly motionless. A multi camera system that captures
many views of a fingerprint and stitches them together to create a rolled
image would fall into this category.
other Unspecified.
unknown Unknown.
movingSubjectContactlessRolled A subject’s finger captured without contact in such a way that the image is
representative of a roll or other 3D structure, and in which the subject is ex-
pected to move to perform an effective capture. A system in which a subject
performs a rolling action above or inside a capture system (without platen
contact) would fall into this category.
movingSubjectContactlessPlain A subject’s finger captured without contact in such a way that the image is
not representative of a roll or other 3D structure, and in which the subject
is expected to move to perform an effective capture. A contactless swipe
sensor in which the subject slides their fingers above a capture system would
fall into this category.
7.7 Minutiae data
Abstract values: See Table 3.
Contents: This data element contains the encoded minutiae data. It is a sequence of minu-
tia blocks
...