ISO/IEC 13888-3:2020

INTERNATIONAL ISO/IEC
STANDARD 13888-3
Third edition
2020-09
Information security — Non-
repudiation —
Part 3:
Mechanisms using asymmetric
techniques
Sécurité de l'information — Non-répudiation —
Partie 3: Mécanismes utilisant des techniques asymétriques
Reference number
ISO/IEC 13888-3:2020(E)
©
ISO/IEC 2020

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ISO/IEC 13888-3:2020(E)

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© ISO/IEC 2020
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ISO/IEC 13888-3:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Requirements . 3
6 Trusted third party involvement . 3
7 Digital signatures . 4
8 Use of non-repudiation tokens with and without delivery authorities .4
9 Evidence produced by the end entities . 5
9.1 General . 5
9.2 Non-repudiation of origin . 5
9.2.1 Non-repudiation of origin token . 5
9.2.2 Mechanism for non-repudiation of origin . 6
9.3 Non-repudiation of delivery . 6
9.3.1 Non-repudiation of delivery token . 6
9.3.2 Mechanism for non-repudiation for delivery . 7
10 Evidence produced by a delivery authority . 8
10.1 General . 8
10.2 Non-repudiation of submission . 8
10.2.1 Non-repudiation of submission token . 8
10.2.2 Mechanism for non-repudiation of submission . 9
10.3 Non-repudiation of transport. 9
10.3.1 Non-repudiation of transport token . 9
10.3.2 Mechanism for non-repudiation of transport .10
11 Mechanisms to ensure that an NRT was signed before a time t .11
11.1 General .11
11.2 Mechanism using a time-stamping service .11
11.3 Mechanism using a time-marking service .11
Bibliography .13
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ISO/IEC 13888-3:2020(E)

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).
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) or the IEC
list of patent declarations received (see http:// patents .iec .ch).
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.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 27, Information security, cybersecurity and privacy protection.
This third edition cancels and replaces the second edition (ISO/IEC 13888-3:2009), which has been
technically revised.
The main changes compared to the previous edition are as follows:
— Clause 3 has been clarified;
— the terminology and notation issues have been fixed;
— a requirement has been changed into a recommendation in Clause 7; and
— a new requirement has been introduced in Clause 5.
A list of all parts in the ISO/IEC 13888 series can be found on the ISO website.
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.
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ISO/IEC 13888-3:2020(E)

Introduction
The goal of the non-repudiation service is to generate, collect, maintain, make available and validate
evidence concerning a claimed event or action in order to resolve disputes about the occurrence or non-
occurrence of the event or action.
Such evidence can be produced either directly by an end entity or by a trusted third party.
This document only addresses the following non-repudiation services:
— non-repudiation of origin;
— non-repudiation of delivery;
— non-repudiation of submission;
— non-repudiation of transport.
Non-repudiation mechanisms involve the exchange of non-repudiation tokens specific for each non-
repudiation service. The non-repudiation mechanisms defined in this document consist of digital
signatures and additional data. Non-repudiation tokens are stored as non-repudiation information and
are used subsequently in the event of disputes.
Additional information is required to complete the non-repudiation token. Depending on the non-
repudiation policy in effect for a specific application and the legal environment within which the
application operates, that additional information takes one of the following two forms:
— information provided by a time-stamping authority which provides assurance that the signature of
the non-repudiation token was created before a given time;
— information provided by a time-marking service which provides assurance that the signature of the
non-repudiation token was recorded before a given time.
Non-repudiation can only be provided within the context of a clearly defined security policy for
a particular application and its legal environment. Non-repudiation policies are described in
ISO/IEC 10181-4.
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INTERNATIONAL STANDARD ISO/IEC 13888-3:2020(E)
Information security — Non-repudiation —
Part 3:
Mechanisms using asymmetric techniques
1 Scope
This document specifies mechanisms for the provision of specific, communication-related,
non-repudiation services using asymmetric cryptographic techniques.
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 9796 (all parts), Information technology — Security techniques — Digital signature schemes
giving message recovery
ISO/IEC 13888-1, Information technology — Security techniques — Non-repudiation — Part 1: General
ISO/IEC 14888 (all parts), IT Security techniques — Digital signatures with appendix
ISO/IEC 18014-1, Information technology — Security techniques — Time-stamping services — Part 1:
Framework
ISO/IEC 29192-4, Information technology — Security techniques — Lightweight cryptography — Part 4:
Mechanisms using asymmetric techniques
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 13888-1 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
time-marking service
service providing evidence that a hash code together with an identifier of a hash-function have been
recorded before a certain point in time
3.2
time-stamping service
service providing evidence that a data item existed before a certain point in time
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ISO/IEC 13888-3:2020(E)

4 Symbols
A claimed message originator
B message recipient or the intended message recipient
C Trusted third party
D ith delivery authority, a trusted third party (1≤i≤n, where n is the number of
i
delivery authorities in the system)
f data term (flag) indicating the type of non-repudiation service in effect (i ∊{ori-
i
gin, delivery, submission, transport})
ID , ID , ID , ID distinguishing identifiers of the entities A, B, C and D
A B C D i
i
Imp(y) imprint of data y, consisting of either y or the hash-code of y together with an
identifier of the hash-function being used
m message which is sent from entity A to entity B in respect of which non-repudia-
tion services are provided
NRDT non-repudiation of delivery token
NROT non-repudiation of origin token
NRST non-repudiation of submission token
NRTT non-repudiation of transport token
Pol distinguishing identifier of the non-repudiation policy (or policies) which applies
(apply) to the evidence
Q optional data item that may contain additional information, e.g., the
distinguishing identifiers of the message m, signature mechanism, or
hash-function
SIG (m) signed message generated on data m by entity X using its private key
X
T date and time that the i th type of event or action took place (i is the index of
i
events or actions, i ∊{1, 2, 3, 4})
NOTE The date and time can be represented according to ISO 8601 (all parts). The
date and time can be obtained by using a time source, as specified in ISO 14641.
T date and time when the evidence was generated
g
text optional data item that may contain additional information, e.g., a key identifier
i
and/or the message identifier (i ∊{1, 2, 3, 4, 5, 6})
X, Y variables used to indicate entity names
(y, z) result of the concatenation of y and z in that order.
When concatenating data items, an appropriate encoding shall be used so that
the individual data items can be unambiguously recovered from the concatenat-
ed string
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ISO/IEC 13888-3:2020(E)

5 Requirements
Depending on the basic mechanism used for generating non-repudiation tokens, and independent of the
non-repudiation service supported by the non-repudiation mechanisms, the following requirements
hold for the entities involved in a non-repudiation exchange in this document.
— The entities of a non-repudiation exchange shall trust any TTP involved in the exchange.
— The signature key belonging to an entity shall be kept secret by that entity.
— An agreed way of obtaining an imprint of data shall be supported by all entities in the non-
repudiation service. The identity function or a collision-resistant hash-function as defined in
ISO/IEC 10118 (all parts) shall be used for this purpose.
— The digital signature mechanism used shall satisfy the security requirements specified by the non-
repudiation policy.
— Prior to the generation of evidence, the evidence generator shall know which non-repudiation policy
is acceptable to the verifier(s), the kind of evidence that is required and the set of mechanisms that
are acceptable to the verifier(s).
— Either the mechanisms for generating or verifying evidence shall be available to the entities of
the particular non-repudiation exchange, or a trusted authority shall be available to provide the
mechanisms and perform the necessary functions on behalf of the evidence requester.
— Either the evidence generator or the evidence verifier needs to use a time-stamping service or a
time-marking service.
— The mechanisms in this document require that the digital signatures are certificate-based digital
signatures. Identity-based digital signatures are not permitted.
6 Trusted third party involvement
Trusted third parties are involved in the provision of non-repudiation services, their precise role
depending on the mechanisms used and the non-repudiation policy in effect. A TTP may act in one or
more of the following roles.
— A delivery authority is trusted to deliver the message to the intended recipient and to provide the
non-repudiation of submission or non-repudiation of transport token.
— The use of asymmetric cryptographic techniques may require the involvement of a TTP to guarantee
the authenticity of the public verification keys, as described, for example, in ISO/IEC 9594-8.
— The non-repudiation policy in effect may require that the evidence is generated partly or totally
by a TTP.
— A time-stamping token issued by a time-stamping authority may also be used to ensure that a non-
repudiation token remains valid.
— A time-marking authority may be involved to provide assurance that the signature of a given non-
repudiation token was recorded before a given time.
— An evidence recording authority may be involved to record evidence that can later be retrieved if
there is a dispute.
Trusted third parties may be involved to differing degrees in the various phases of the provision of
a non-repudiation service. When exchanging evidence, the parties shall know, or agree, which non-
repudiation policy is to be applicable to the evidence.
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ISO/IEC 13888-3:2020(E)

7 Digital signatures
For the mechanisms specified in this document, non-repudiation tokens are created using SIGs. The
digital signature technique used to generate these SIGs shall conform to ISO/IEC 9796 (all parts),
ISO/IEC 14888 (all parts) or ISO/IEC 29192-4.
The public key to be used to verify a signature shall be included in a public key certificate. This
certificate shall include a time period indicating the period during which the CA handles the revocation
status of the certificate.
A signature from an NR token shall be verifiable at least during the validity period of the certificates
to be used to validate the public verification key used to verify the signature, and also once the validity
period of these certificates has expired. In order to achieve this goal, the use of either a time-stamping
service or a time-marking service is necessary (see Clause 11). The mechanisms described in Clause
11 should be used to guarantee that the non-repudiation token remains valid once the certificate to be
used to verify the signature of the NR token has expired, or if that certificate is revoked.
8 Use of non-repudiation tokens with and without delivery authorities
The use of non-repudiation tokens in the case where delivery authorities are not used is shown in
Figure 1. Mechanisms adhering to this model are spec
...