ISO/IEC TR 24722:2024
(Main)Information technology — Biometrics — Multimodal and other multibiometric fusion
Information technology — Biometrics — Multimodal and other multibiometric fusion
This document provides descriptions and analyses of current practices on multimodal and other multibiometric fusion, including (as appropriate) references to more detailed descriptions. This document contains descriptions and explanations of high-level multibiometric concepts to aid in the explanation of multibiometric fusion approaches including: multi-characteristic-type, multi-instance, multi-sensorial, multialgorithmic, decision-level and score-level logic.
Technologies de l'information — Biométrie — Fusion multimodale et autre fusion multibiométrique
General Information
Relations
Standards Content (Sample)
Technical
Report
ISO/IEC TR 24722
Third edition
Information technology —
2024-12
Biometrics — Multimodal and other
multibiometric fusion
Technologies de l'information — Biométrie — Fusion
multimodale et autre fusion multibiométrique
Reference number
© ISO/IEC 2024
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© ISO/IEC 2024 – All rights reserved
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Overview of multimodal and other multibiometric systems . 2
4.1 General .2
4.2 Simultaneous and sequential presentation .4
4.2.1 Overview .4
4.2.2 Simultaneous presentation .5
4.2.3 Sequential presentation .5
4.3 Correlation .6
5 Levels of combination . 7
5.1 Overview .7
5.2 Decision-level fusion .9
5.2.1 Simple decision-level fusion .9
5.2.2 Advanced decision-level fusion .10
5.3 Score-level fusion .11
5.3.1 Overview .11
5.3.2 Rank-level fusion .11
5.3.3 Score normalization .11
5.3.4 Score fusion methods . 15
5.4 Feature-level fusion .17
6 Characterisation data for multibiometric systems . 17
6.1 Overview .17
6.2 Use of characterization data in normalization and fusion .18
Bibliography . 19
© ISO/IEC 2024 – All rights reserved
iii
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
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ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations,
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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
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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.
This third edition cancels and replaces the second edition (ISO/IEC TR 24722:2015), which has been
technically revised.
The main changes are as follows:
— the content of Clause 3 has been removed and ISO/IEC 2382-37 has been listed as a normative reference;
— to enhance information accessibility, symbol descriptors have been paired with clear descriptions;
— the structure of the document has been updated, and various editorial modifications have been made, in
order to improve technical accuracy and bring the document in line with the most recent edition of the
ISO/IEC Directives Part 2.
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.
© ISO/IEC 2024 – All rights reserved
iv
Introduction
Some applications of biometrics require a level of biometric performance that is difficult to obtain with a
single biometric measure. Such applications include the prevention of multiple applications for national
identity cards and security checks for air travel. In addition, provisions are needed for data subjects who are
unable to give a reliable biometric sample for some biometric characteristic types.
Use of multiple biometric measurements from substantially independent biometric sensors, algorithms
or characteristic types typically gives improved technical performance and reduces risk. This includes an
improved level of performance where not all biometric measurements are available, such that decisions can
be made from any number of biometric measurements within an overall policy on accept/reject thresholds.
Of the various forms of multibiometric systems, the potential for multimodal biometric systems, each using
[22],[45]
an independent measure, has been discussed in technical literature since at least 1974. Advanced
methods for combining measures at the score level have been discussed in References [15] and [16]. At
the current level of understanding, combining results at the score level typically requires knowledge of
both mated and non-mated score distributions. All of these measures are highly application-dependent
and generally unknown in any real system. Research on the methods not requiring previous knowledge
of the score distributions is continuing and research on fusion at both the image and feature levels is still
progressing.
Given the current state of research into these questions and the highly application-dependent and generally
unavailable data required for proper fusion at the score level, work on multibiometric fusion can in the
meantime be considered mature. By intention, this document is not issued as International Standard, in
order not to force industrial solutions to conform to the methodology described herein. Rather, the present
edition of this document provides a mature technical description for developments of multibiometric
systems. It also provides a reference on multibiometric fusion for developers of other biometric standards
and implementers.
© ISO/IEC 2024 – All rights reserved
v
Technical Report ISO/IEC TR 24722:2024(en)
Information technology — Biometrics — Multimodal and
other multibiometric fusion
1 Scope
This document provides descriptions and analyses of current practices on multimodal and other
multibiometric fusion, including (as appropriate) references to more detailed descriptions.
This document contains descriptions and explanations of high-level multibiometric concepts to aid in the
explanation of multibiometric fusion approaches including: multi-characteristic-type, multi-instance, multi-
sensorial, multialgorithmic, decision-level and score-level logic.
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 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 and the following apply.
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
multialgorithmic
using multiple algorithms for processing the same biometric sample
3.2
multibiometrics
automated recognition of individuals based on their biological or behavioural characteristic and involving
the use of biometric fusion
3.3
multi-characteristic-type
multi-type
using information from multiple types of biometric characteristic
EXAMPLE Biometric characteristic types include: face, voice, finger, iris, retina, hand geometry, signature/sign,
keystroke, lip movement, gait, scent, vein, DNA, ear, foot, etc.
3.4
multi-instance
requiring two or more instances of a biometric characteristic
EXAMPLE Iris (left) + Iris (right), Fingerprint (left index) + Fingerprint (right index).
© ISO/IEC 2024 – All rights reserved
Note 1 to entry: [SOURCE: ISO/IEC 2382-37:2022, 37.03.47, modified — Note 1 to entry has been removed and an
Example has been added.]
3.5
multipresentation
using either multiple presentation samples of one instance of a biometric characteristic or a single
presentation that
...
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