ISO/IEC TR 24722:2015
(Main)Information technology — Biometrics — Multimodal and other multibiometric fusion
Information technology — Biometrics — Multimodal and other multibiometric fusion
ISO/IEC TR 24722:2015 contains descriptions of and analyses of current practices on multimodal and other multibiometric fusion, including (as appropriate) references to more detailed descriptions. ISO/IEC TR 24722:2015 contains descriptions and explanations of high-level multibiometric concepts to aid in the explanation of multibiometric fusion approaches including multi-characteristic-type, multiinstance, multisensorial, multialgorithmic, decision-level and score-level logic.
Technologies de l'information — Biométrie — Fusion multimodale et autre fusion multibiométrique
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TECHNICAL ISO/IEC TR
REPORT 24722
Second edition
2015-12-15
Information technology —
Biometrics — Multimodal and other
multibiometric fusion
Technologies de l’information — Biométrie — Fusion multimodale et
autre fusion multibiométrique
Reference number
©
ISO/IEC 2015
© ISO/IEC 2015, Published in Switzerland
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ii © ISO/IEC 2015 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Overview of multimodal and other multibiometric systems . 3
3.1 General . 3
3.2 Simultaneous and sequential presentation . 5
3.2.1 General multibiometric system model. 5
3.2.2 Simultaneous presentation . 5
3.2.3 Sequential presentation. 6
3.3 Correlation . 6
4 Levels of combination . 7
4.1 Overview . 7
4.2 Decision-level fusion . 9
4.2.1 Simple decision-level fusion . 9
4.2.2 Advanced decision-level fusion . 9
4.3 Score-level fusion .11
4.3.1 Overview .11
4.3.2 Score normalization .11
4.3.3 Score fusion methods.14
4.4 Feature-level fusion .17
5 Characterisation data for multibiometric systems .17
5.1 Overview .17
5.2 Use of characterisation data in normalisation and fusion .17
Bibliography .19
© ISO/IEC 2015 – 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
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.
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).
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. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/IEC JTC 1, Information technology, Subcommittee
SC 37, Biometrics.
This second edition cancels and replaces the first edition (ISO/IEC/TR 24722:2007), which has been
technically revised with the following changes:
— the original Clause 2 (Terminology issues) and Clause 7 (Scope and options for standardisation) are
removed in this edition;
— Clause 2 (Terms and definitions) is aligned with ISO/IEC 2382-37;
— the current Clause 3, Clause 4, and Clause 5 have been technically revised in terminology, the state
of arts updates, and other aspects. Such modifications have also been reflected in the bibliography.
iv © ISO/IEC 2015 – All rights reserved
Introduction
Some applications of biometrics require a level of technical performance that is difficult to obtain with
a single biometric measure. Such applications include prevention of multiple applications for national
identity cards and security checks for air travel. In addition, provision is needed for people 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
[22][45]
using an independent measure, has been discussed in the technical literature since at least 1974.
Advanced methods for combining measures at the score level have been discussed in Reference [15]
and Reference [16]. At the current level of understanding, combining results at the score level typically
requires knowledge of both genuine and impostor 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 those 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 Technical Report is not issued
as an International Standard, in order not to force industrial solutions to conform to the methodology
described herein. However, this Technical Report revision provides a mature technical description for
developments of multibiometric systems. It will also provide a reference on multibiometric fusion for
developers of other biometric standards and implementers.
© ISO/IEC 2015 – All rights reserved v
TECHNICAL REPORT ISO/IEC TR 24722:2015(E)
Information technology — Biometrics — Multimodal and
other multibiometric fusion
1 Scope
This Technical Report contains descriptions of and analyses of current practices on multimodal and
other multibiometric fusion, including (as appropriate) references to more detailed descriptions.
This Technical Report contains descriptions and explanations of high-level multibiometric concepts
to aid in the explanation of multibiometric fusion approaches including multi-characteristic-type,
multiinstance, multisensorial, multialgorithmic, decision-level and score-level logic.
2 Terms and definitions
The following two categories of terms are defined here:
— terms that are specific to multimodal and multibiometric systems;
— terms that are not specific to multimodal and multibiometric systems, but are required to define the
terms in the first category and not defined in the latest revision of ISO/IEC 2382-37.
For definitions of other terms in the subject field of biometrics, refer to ISO/IEC 2382-37. For the
purposes of this document, the terms and definitions given in ISO/IEC 2382-37 and the following apply.
2.1
biometric data source
information channel (e.g. sensors, characteristic types, algorithms, instances or presentations) that
is the origin of data (e.g. captured biometric sample, extracted features, comparison score, rank or
decision) treated in fusion algorithms
2.2
biometric process
automated process using one or more biometric characteristics of a single individual for the purpose of
enrolment, verification, or identification
2.3
biometric fusion
combination of information from multiple sources, i.e., sensors, characteristic types, algorithms,
instances or presentations
2.4
cascaded system
system where pass/fail thresholds of biometric samples are used to determine if additional biometric
samples are required to reach an overall system decision
2.5
layered system
system where individual biometric scores are used to determine the pass/fail thresholds of other
biometric data processing
2.6
multialgorithmic
using multiple algorithms for processing the same biometric sample
© ISO/IEC 2015 – All rights reserved 1
2.7
multibiometric
uses multiple biometrics that can be combined at image, feature, score and/or decision level
Note 1 to entry: Multibiometric has five distinct subcategories: multi-characteristic-type (2.10), multiinstance
(2.11), multisensorial (2.13), multialgorithmic (2.6) and multipresentation (2.12).
2.8
multibiometric process
biometric process (2.2) involving the use of biometric fusion (2.3)
2.9
multibiometrics
automated recognition of individuals based on their biological or behavioral characteristics and
involving the use of biometric fusion (2.3)
2.10
multi-characteristic-type
multi-type
using information from multiple types of biometric characteristics
EXAMPLE Biometric characteristics types include: face, voice, finger, iris, retina, hand geometry,
signature/sign, keystroke, lip movement, gait, vein, DNA, ear, foot, scent, etc.
2.11
multiinstance
using multiple biometric instances within one biometric characteristic type
EXAMPLE Iris (left) + Iris (right), Fingerprint (left index) + Fingerprint (right index).
2.12
multipresentation
using either multiple presentation samples of one instance of a biometric characteristic or a single
presentation that results in the capture of multiple samples
EXAMPLE Several frames from video camera capture of a face image (possibly but not necessarily
consecutive).
Note 1 to entry: Multipresentation biometrics is considered a form of multibiometrics (2.9), if fusion techniques
are employed. Many fusion and normalisation techniques are appropriate to the integration of information from
multiple
...
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