ISO/IEC TR 29149:2012

Information technology — Security techniques — Best practices for the provision and use of time-stamping services

ISO/IEC TR 29149:2012 explains how to provide and use time-stamping services so that time-stamp tokens are effective when used to provide timeliness, data integrity, and non-repudiation services in conjunction with other mechanisms. It defines: how time-stamp requesters should use time-stamp token generation services; how TSAs (time-stamping authorities) should provide a service of guaranteed quality; how TSAs should deserve trust based on good practices; which algorithms and parameters should be used in TST (time-stamp token) generation and TST renewal, so that TSTs resist during the time period during which the TSTs can be verified as being valid; how time-stamp verifiers should use the time-stamp token verification services, both when validating individual TSTs, and when validating sequences of renewal TSTs.

Technologies de l'information — Techniques de sécurité — Meilleures pratiques pour la fourniture et l'utilisation de services d'horodotage

General Information

• Status: Published
• Publication Date: 04-Mar-2012
• ICS: 35.030 - IT Security
• ICS: 35.040 - Information coding
• Technical Committee: ISO/IEC JTC 1/SC 27 - Information security, cybersecurity and privacy protection
• Drafting Committee: ISO/IEC JTC 1/SC 27/WG 3 - Security evaluation, testing and specification
• Current Stage: 9093 - International Standard confirmed
• Start Date: 29-Oct-2018
• Completion Date: 19-Apr-2025

Standards Content (Sample)

TECHNICAL ISO/IEC
REPORT TR
First edition
2012-03-15
Information technology — Security
techniques — Best practices for the
provision and use of time-stamping
services
Technologies de l'information — Techniques de sécurité — Meilleures
pratiques pour la fourniture et l'utilisation de services d'horodotage

Reference number
©
ISO/IEC 2012
©  ISO/IEC 2012
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 ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii © ISO/IEC 2012 – All rights reserved

Contents Page
Foreword . iv
Introduction . v
1  Scope . 1
2  Terms and definitions . 1
3  Symbols and abbreviated terms . 4
4  Time-stamping services. 5
5  Use cases for non-repudiation . 5
5.1  Introduction . 5
5.2  Use case #1 . 6
5.3  Use case #2 . 6
5.4  Use case #3 . 6
6  Potential issues . 7
6.1  Security requirements for custody of evidences . 7
6.2  Weak cryptography: hash-functions . 8
6.3  Weak cryptography: digital signatures . 10
6.4  Weak cryptography: message authentication codes . 10
6.5  Signature verification . 10
6.6  Time-stamp token renewal . 11
6.7  Time-stamping service availability . 12
6.8  Time-stamping service continuity . 12
7  Recommendations . 12
7.1  Recommendations for requesters of time-stamp tokens . 12
7.2  Recommendations for verifiers of time-stamp tokens . 13
7.3  Recommendations for time-stamp service providers . 13
7.4  Recommendations for signature verification . 16
7.5  Non-repudiation policy . 17
8  Algorithms . 17
8.1  Overview . 17
8.2  Hash functions . 17
8.3  Keyed message authentication algorithms . 18
8.4  Signature algorithms . 18
Bibliography . 19

© ISO/IEC 2012 – 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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
In exceptional circumstances, when the joint technical committee has collected data of a different kind from
that which is normally published as an International Standard (“state of the art”, for example), it may decide to
publish a Technical Report. A Technical Report is entirely informative in nature and shall be subject to review
every five years in the same manner as an International Standard.
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.
ISO/IEC TR 29149 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 27, IT Security techniques.

iv © ISO/IEC 2012 – All rights reserved

Introduction
This Technical Report explains how to provide and use time-stamping services so that time-stamp tokens are
effective when used to provide
 timeliness and data integrity services, or
 non-repudiation services (in conjunction with other mechanisms).
ISO/IEC 18014 specifies time-stamping services, explaining how to generate, renew, and verify time-stamp
tokens. The goal of a non-repudiation service is to treat evidence concerning a claimed event or action in
order to resolve disputes about the occurrence or non-occurrence of the event or action. Depending on the
non-repudiation service which is required, the non-repudiation policy in effect for a specific application, and
the legal environment within which the application operates, time-stamp tokens from time-stamping
authorities may be required as components of non-repudiation information.

© ISO/IEC 2012 – All rights reserved v

TECHNICAL REPORT ISO/IEC TR 29149:2012(E)

Information technology — Security techniques — Best
practices for the provision and use of time-stamping services
1 Scope
This Technical Report explains how to provide and use time-stamping services so that time-stamp tokens are
effective when used to provide timeliness, data integrity, and non-repudiation services in conjunction with
other mechanisms. It defines:
 how time-stamp requesters should use time-stamp token generation services;
 how TSAs (time-stamping authorities) should provide a service of guaranteed quality;
 how TSAs should deserve trust based on good practices;
 which algorithms and parameters should be used in TST (time-stamp token) generation and TST renewal,
so that TSTs resist during the time period during which the TSTs can be verified as being valid;
 how time-stamp verifiers should use the time-stamp token verification services, both when validating
individual TSTs, and when validating sequences of renewal TSTs.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
certification authority
CA
authority trusted by one or more users to create and assign public-key certificates
NOTE Optionally, the certification authority may create the users' keys.
[ISO/IEC 9594-8:2005]
2.2
digital signature
data appended to, or a cryptographic transformation of, a data unit that allows a recipient of the data unit to
prove the source and integrity of the data unit and protect against forgery, e.g. by the recipient
[ISO 7498-2:1989]
2.3
evidence
information which is used, either by itself or in conjunction with other information, to establish proof about an
event or action
NOTE Evidence does not necessarily prove the truth or existence of something, but can contribute to the
establishment of such a proof.
[ISO/IEC 13888-1:2009]
© ISO/IEC 2012 – All rights reserved 1

2.4
evidence user
entity that uses non-repudiation evidence
[ISO/IEC 13888-1:2009]
2.5
hash-function
function which maps strings of bits to fixed-length strings of bits, satisfying the following two properties:
 It is computationally infeasible to find for a given output, an input which maps to this output.
 It is computationally infeasible to find for a given input, a second input which maps to the same output.
NOTE Computational feasibility depends on the specific security requirements and environment.
[ISO/IEC 10118-1:2000]
2.6
hash-value
string of bits which is the output of a hash-function
[ISO/IEC 10118-1:2000, modified — The term “hash-code” is used to represent this concept in
ISO/IEC 10118-1:2000.]
2.7
imprint
string of bits, either the hash-value of a data string or the data string itself
[ISO/IEC 13888-1:2009]
2.8
message authentication code
MAC
string of bits which is the output of a MAC algorithm
NOTE A MAC is sometimes called a cryptographic check value (see for example ISO 7498-2).
[ISO/IEC 9797-1:2011]
2.9
non-repudiation
ability to prove an action or event has taken place, so that this event or action cannot be repudiated later
[ISO 7498-2:1989]
2.10
non-repudiation token
special type of security token as defined in ISO/IEC 10181-1, consisting of evidence, and, optionally, of
additional data
[ISO/IEC 13888-1:2009]
2.11
object identifier
OID
globally unique value associated with an object to unambiguously identify it
[ISO/IEC 8824-1:2002│ITU X.680:2002]
2 © ISO/IEC 2012 – All rights reserved

2.12
private key
that key of an entity's asymmetric key pair which should only be used by that entity
[ISO/IEC 9798-1:1997]
2.13
public key
that key of an entity's asymmetric key pair which can be made public
NOTE In the case of an asymmetric signature scheme, the public key defines the verification transformation. In the
case of an asymmetric encipherment system, the public key defines the encipherment transformation. A key that is
'publicly known' is not necessarily globally available. The key may only be available to all members of a pre-specified
group.
[ISO/IEC 11770-3:2008]
2.14
public key certificate
public key information of an entity signed by the certification authority and thereby rendered unforgeable
[ISO/IEC 11770-3:2008]
2.15
signer
entity generating a digital signature
[ISO/IEC 13888-1:2009]
2.16
time stamp
data item which denotes a point in time with respect to a common time reference
[ISO/IEC 11770-1:2010]
2.17
time-stamp token renewal
process of issuing a new time stamp token to extend the validity period of an earlier time-stamp token
[ISO/IEC 18014-1:2008, adapted]
2.18
time-stamp requester
entity which possesses data it wants to be time-stamped
NOTE A requester can also be a trusted third party including a time-stamping authority.
[ISO/IEC 18014-1:2008]
2.19
time-stamp token
TST
data structure containing a verifiable binding between a data items’ representation and a time-value
NOTE A time-stamp token can also include additional data items in the binding.
[ISO/IEC 18014-1:2008]
© ISO/IEC 2012 – All rights reserved 3

2.20
time-stamp verifier
entity which possesses data and wants to verify that it has a valid time-stamp bound to it
NOTE The verification process may be performed by the verifier itself or by a trusted third party.
[ISO/IEC 18014-1:2008]
2.21
time-stamping authority
TSA
trusted third party trusted to provide a time-stamping service
[ISO/IEC 18014-1:2008]
2.22
time-stamping policy
named set of rules that indicates the applicability of a time-stamp token to a particular community or class of
application
...