IEC TR 62541-2:2016

OPC unified architecture - Part 2: Security Model

IEC TR 62541-2:2016(E) is a Technical Report and describes the OPC unified architecture (OPC UA) security model. It describes the security threats of the physical, hardware, and software environments in which OPC UA is expected to run. It describes how OPC UA relies upon other standards for security. It provides definition of common security terms that are used in this and other parts of the OPC UA specification. It gives an overview of the security features that are specified in other parts of the OPC UA specification. It references services, mappings, and Profiles that are specified normatively in other parts of this multi-part specification. It provides suggestions or best practice guidelines on implementing security. Any seeming ambiguity between this part of IEC 62541 and one of the normative parts of IEC 62541 does not remove or reduce the requirement specified in the normative part. This second edition cancels and replaces the first edition of IEC TR 62541-2, published in 2010. This second edition includes no technical changes with respect to the first edition but a number of clarifications and additional text for completeness.

General Information

• Status: Published
• Publication Date: 04-Oct-2016
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.100.01 - Open systems interconnection in general
• Technical Committee: SC 65E - Devices and integration in enterprise systems
• Drafting Committee: WG 8 - TC 65/SC 65E/WG 8
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 17-Nov-2020

Relations

• Revised: IEC TR 62541-2:2020 - OPC Unified Architecture - Part 2: Security Model
• Effective Date: 05-Sep-2023
• Revises: IEC TR 62541-2:2010 - OPC Unified Architecture - Part 2: Security Model
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC TR 62541-2 ®
Edition 2.0 2016-10
TECHNICAL
REPORT
colour
inside
OPC unified architecture –
Part 2: Security Model
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé Fax: [phone]
CH-1211 Geneva 20 [e-mail]
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
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The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
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and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

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IEC TR 62541-2 ®
Edition 2.0 2016-10
TECHNICAL
REPORT
colour
inside
OPC unified architecture –
Part 2: Security Model
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.040.40; 35.100.01 ISBN 978-2-8322-3641-3

– 2 – IEC TR 62541-2:2016 © IEC 2016
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references. 6
3 Terms, definitions and abbreviations . 8
3.1 Terms and definitions . 8
3.2 Abbreviations . 12
3.3 Conventions for security model figures . 12
4 OPC UA security architecture. 12
4.1 OPC UA security environment . 12
4.2 Security objectives . 13
4.2.1 Overview . 13
4.2.2 Authentication . 13
4.2.3 Authorization . 13
4.2.4 Confidentiality . 14
4.2.5 Integrity . 14
4.2.6 Auditability . 14
4.2.7 Availability . 14
4.3 Security threats to OPC UA systems . 14
4.3.1 Overview . 14
4.3.2 Message flooding . 14
4.3.3 Eavesdropping . 15
4.3.4 Message spoofing . 15
4.3.5 Message alteration . 15
4.3.6 Message replay . 15
4.3.7 Malformed Messages . 15
4.3.8 Server profiling . 16
4.3.9 Session hijacking . 16
4.3.10 Rogue Server . 16
4.3.11 Compromising user credentials . 16
4.4 OPC UA relationship to site security . 17
4.5 OPC UA security architecture . 17
4.6 SecurityPolicies . 19
4.7 Security Profiles . 20
4.8 User Authorization . 20
4.9 User Authentication . 20
4.10 Application Authentication . 20
4.11 OPC UA security related Services . 21
4.12 Auditing . 21
4.12.1 General . 21
4.12.2 Single Client and Server . 22
4.12.3 Aggregating Server . 23
4.12.4 Aggregation through a non-auditing Server . 23
4.12.5 Aggregating Server with service distribution . 24
5 Security reconciliation . 25
5.1 Reconciliation of threats with OPC UA security mechanisms . 25
5.1.1 Overview . 25

5.1.2 Message flooding . 25
5.1.3 Eavesdropping . 26
5.1.4 Message spoofing . 26
5.1.5 Message alteration . 26
5.1.6 Message replay . 26
5.1.7 Malformed Messages . 27
5.1.8 Server profiling . 27
5.1.9 Session hijacking . 27
5.1.10 Rogue Server . 27
5.1.11 Compromising user credentials . 27
5.2 Reconciliation of objectives with OPC UA security mechanisms . 27
5.2.1 Overview . 27
5.2.2 Application Authentication . 28
5.2.3 User Authentication . 28
5.2.4 Authorization . 28
5.2.5 Confidentiality . 28
5.2.6 Integrity . 28
5.2.7 Auditability . 28
5.2.8 Availability . 29
6 Implementation and deployment considerations . 29
6.1 Overview. 29
6.2 Appropriate timeouts . 29
6.3 Strict Message processing . 29
6.4 Random number generation . 29
6.5 Special and reserved packets . 30
6.6 Rate limiting and flow control . 30
6.7 Administrative access . 30
6.8 Alarm related guidance . 30
6.9 Program access . 30
6.10 Audit event management . 31
6.11 Certificate management . 31
Bibliography . 36

Figure 1 – OPC UA network model . 13
Figure 2 – OPC UA security architecture . 18
Figure 3 – Simple Servers . 22
Figure 4 – Aggregating Servers . 23
Figure 5 – Aggregation with a non-auditing Server . 24
Figure 6 – Aggregate Server with service distribution. 25
Figure 7 – Manual Certificate handling . 32
Figure 8 – CA Certificate handling . 33
Figure 9 – Certificate handling . 34

– 4 – IEC TR 62541-2:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPC UNIFIED ARCHITECTURE –
Part 2: Security Model
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory
...

IEC TR 62541-2 ®
Edition 2.0 2016-10
TECHNICAL
REPORT
colour
inside
OPC unified architecture –
Part 2: Security Model
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form

or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from

either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or

your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé Fax: [phone]

CH-1211 Geneva 20 [e-mail]
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 15 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: [e-mail].
IEC TR 62541-2 ®
Edition 2.0 2016-10
TECHNICAL
REPORT
colour
inside
OPC unified architecture –
Part 2: Security Model
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.040.40; 35.100.01 ISBN 978-2-8322-3641-3

– 2 – IEC TR 62541-2:2016 © IEC 2016

CONTENTS
FOREWORD . 4

1 Scope . 6

2 Normative references. 6

3 Terms, definitions and abbreviations . 8

3.1 Terms and definitions . 8

3.2 Abbreviations . 12

3.3 Conventions for security model figures . 12

4 OPC UA security architecture. 12
4.1 OPC UA security environment . 12
4.2 Security objectives . 13
4.2.1 Overview . 13
4.2.2 Authentication . 13
4.2.3 Authorization . 13
4.2.4 Confidentiality . 14
4.2.5 Integrity . 14
4.2.6 Auditability . 14
4.2.7 Availability . 14
4.3 Security threats to OPC UA systems . 14
4.3.1 Overview . 14
4.3.2 Message flooding . 14
4.3.3 Eavesdropping . 15
4.3.4 Message spoofing . 15
4.3.5 Message alteration . 15
4.3.6 Message replay . 15
4.3.7 Malformed Messages . 15
4.3.8 Server profiling . 16
4.3.9 Session hijacking . 16
4.3.10 Rogue Server . 16
4.3.11 Compromising user credentials . 16
4.4 OPC UA relationship to site security . 17
4.5 OPC UA security architecture . 17
4.6 SecurityPolicies . 19

4.7 Security Profiles . 20
4.8 User Authorization . 20
4.9 User Authentication . 20
4.10 Application Authentication . 20
4.11 OPC UA security related Services . 21
4.12 Auditing . 21
4.12.1 General . 21
4.12.2 Single Client and Server . 22
4.12.3 Aggregating Server . 23
4.12.4 Aggregation through a non-auditing Server . 23
4.12.5 Aggregating Server with service distribution . 24
5 Security reconciliation . 25
5.1 Reconciliation of threats with OPC UA security mechanisms . 25
5.1.1 Overview . 25

5.1.2 Message flooding . 25

5.1.3 Eavesdropping . 26

5.1.4 Message spoofing . 26

5.1.5 Message alteration . 26

5.1.6 Message replay . 26

5.1.7 Malformed Messages . 27

5.1.8 Server profiling . 27

5.1.9 Session hijacking . 27

5.1.10 Rogue Server . 27

5.1.11 Compromising user credentials . 27

5.2 Reconciliation of objectives with OPC UA security mechanisms . 27
5.2.1 Overview . 27
5.2.2 Application Authentication . 28
5.2.3 User Authentication . 28
5.2.4 Authorization . 28
5.2.5 Confidentiality . 28
5.2.6 Integrity . 28
5.2.7 Auditability . 28
5.2.8 Availability . 29
6 Implementation and deployment considerations . 29
6.1 Overview. 29
6.2 Appropriate timeouts . 29
6.3 Strict Message processing . 29
6.4 Random number generation . 29
6.5 Special and reserved packets . 30
6.6 Rate limiting and flow control . 30
6.7 Administrative access . 30
6.8 Alarm related guidance . 30
6.9 Program access . 30
6.10 Audit event management . 31
6.11 Certificate management . 31
Bibliography . 36

Figure 1 – OPC UA network model . 13
Figure 2 – OPC UA security architecture . 18
Figure 3 – Simple Servers . 22
Figure 4 – Aggregating Servers . 23
Figure 5 – Aggregation with a non-auditing Server . 24
Figure 6 – Aggregate Server with service distribution. 25
Figure 7 – Manual Certificate handling . 32
Figure 8 – CA Certificate handling . 33
Figure 9 – Certificate handling . 34

– 4 – IEC TR 62541-2:2016 © IEC 2016

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
OPC UNIFIED ARCHITECTURE –
Part 2: Security Model
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their
...