SIST EN 319 421 V1.2.1:2023

EUROPEAN STANDARD
Electronic Signatures and Infrastructures (ESI);
Policy and Security Requirements for
Trust Service Providers issuing Time-Stamps

2 ETSI EN 319 421 V1.2.1 (2023-05)

Reference
REN/ESI-0019421v1.2.1
Keywords
e-commerce, electronic signature, security,
time-stamping, trust services
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ETSI
3 ETSI EN 319 421 V1.2.1 (2023-05)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definitions of terms, symbols, abbreviations and notation . 9
3.1 Terms . 9
3.2 Symbols . 9
3.3 Abbreviations . 10
3.4 Notation . 10
4 General concepts . 11
4.1 General policy requirements concepts . 11
4.2 Time-stamping services . 11
4.3 Time-Stamping Authority (TSA) . 11
4.4 Subscriber . 11
4.5 Time-stamp policy and TSA practice statement . 12
5 Introduction to time-stamp policies and general requirements . 12
5.1 General requirements . 12
5.2 Policy name and identification . 12
5.3 User community and applicability . 13
5.3.1 Best practices time-stamp policy . 13
6 Policies and practices . 13
6.1 Risk assessment . 13
6.2 Trust Service Practice Statement . 13
6.3 Terms and conditions . 13
6.4 Information security policy . 13
6.5 TSA obligations . 14
6.5.1 General . 14
6.5.2 TSA obligations towards subscribers . 14
6.6 Information for relying parties . 14
7 TSA management and operation . 14
7.1 Introduction . 14
7.2 Internal organization. 14
7.3 Personnel security. 15
7.4 Asset management . 15
7.5 Access control . 15
7.6 Cryptographic controls . 15
7.6.1 General . 15
7.6.2 TSU key generation . 15
7.6.3 TSU private key protection . 16
7.6.4 TSU public key certificate . 16
7.6.5 Rekeying TSU's key . 17
7.6.6 Life cycle management of signing cryptographic hardware . 17
7.6.7 End of TSU key life cycle . 17
7.7 Time-stamping . 18
7.7.1 Time-stamp issuance. 18
7.7.2 Clock synchronization with UTC . 18
7.8 Physical and environmental security . 19
7.9 Operation security . 19
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4 ETSI EN 319 421 V1.2.1 (2023-05)
7.10 Network security . 20
7.11 Incident management . 20
7.12 Collection of evidence . 20
7.13 Business continuity management . 20
7.14 TSA termination and termination plans . 21
7.15 Compliance. 21
8 Additional requirements for qualified electronic time-stamps as per Regulation (EU) No 910/2014 . 21
8.1 TSU public key certificate . 21
8.2 TSA issuing non-qualified and qualified electronic time-stamps as per Regulation (EU) No 910/2014 . 21
Annex A (informative): Potential liability in the provision of time-stamping services . 22
Annex B (informative): Model TSA disclosure statement . 23
B.1 Introduction . 23
B.2 TSA disclosure statement structure . 23
Annex C (informative): Coordinated Universal Time (UTC). 25
Annex D (informative): Long term verification of time-stamps . 26
Annex E (informative): Regulation (EU) No 910/2014 and qualified electronic time-stamp
policy cross-reference . 27
Annex F (informative): Possible implementation architectures - time-stamping service . 28
F.1 Managed time-stamping service . 28
F.2 Selective alternative quality . 28
Annex G (informative): Major changes from ETSI TS 102 023 . 30
Annex H (informative): Conformity Assessment Check list . 31
Annex I (informative): Change History . 32
History . 33

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5 ETSI EN 319 421 V1.2.1 (2023-05)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The declarations
pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (https://ipr.etsi.org/).
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its

Members. 3GPP™ and LTE™ are trademarks of ETSI registered for the benefit of its Members and of the 3GPP
Organizational Partners. oneM2M™ logo is a trademark of ETSI registered for the benefit of its Members and of the ®
oneM2M Partners. GSM and the GSM logo are trademarks registered and owned by the GSM Association.
Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Electronic Signatures and
Infrastructures (ESI).
The present document is derived from the requirements specified in ETSI TS 102 023 [i.8].

National transposition dates
Date of adoption of this EN: 1 May 2023
Date of latest announcement of this EN (doa): 31 August 2023
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 29 February 2024
Date of withdrawal of any conflicting National Standard (dow): 29 February 2024

Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
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6 ETSI EN 319 421 V1.2.1 (2023-05)
Introduction
The present document is aiming to meet the general requirements of the international community to provide trust and
confidence in electronic transactions including, amongst others, applicable requirements from Regulation (EU)
No 910/2014 [i.4].
The Regulation includes requirements for Trust Service Providers (TSP) providing services to the public, including
TSPs issuing time-stamps. Additionally, more specific requirements are identified in the Regulation for a specific class
of TSP called a Qualified TSP, with further specific requirements for those Qualified TSPs which issue qualified
time-stamps. The present document is aimed to meet the requirements of the Regulation for both Qualified and
non-Qualified TSPs issuing Qualified and non-Qualified electronic time-stamps respectively.
In order to verify an electronic signature, it can be necessary to prove that the signature from the signer was applied
when the signer's certificate was valid. This is necessary in two circumstances:
1) during the validity period of the signer's certificate, should the signer's certificate be revoked before the end of
its validity, e.g. because the signer's private key has been compromised;
2) after the end of the validity period of the signer's certificate, since CAs are not mandated to process revocation
status information beyond the end of the validity period of the certificates they have issued.
One method consists to use a time-stamp which allows proving that a datum existed before a particular time. This
technique allows proving that the signature was generated before the date contained in the time-stamp. Policy
requirements to cover that case are the primary aim of the present document.
However, these policy requirements allow addressing other needs.
Time-stamping is gaining an increasing interest by the business sector and is becoming an important component of
digital signatures, this is commonly based upon the Time-Stamp protocol from the IETF RFC 3161 [i.2] which is
profiled in ETSI EN 319 422 [5]. Agreed minimum security and quality requirements are necessary in order to ensure
trustworthy validation of long-term digital signatures.
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7 ETSI EN 319 421 V1.2.1 (2023-05)
1 Scope
The present document specifies policy and security requirements relating to the operation and management practices of
TSPs issuing time-stamps.
These policy requirements are applicable to TSPs issuing time-stamps. Such time-stamps can be used in support of
digital signatures or for any application requiring to prove that a datum existed before a particular time.
The present document can be used by independent bodies as the basis for confirming that a TSP can be trusted for
issuing time-stamps.
The present document does not specify protocols used to access the TSUs.
NOTE 1: A time-stamping protocol is defined in IETF RFC 3161 [i.2] including optional update in IETF
RFC 5816 [i.3] and profiled in ETSI EN 319 422 [5].
The present document does not specify how the requirements identified can be assessed by an independent party,
including requirements for information to be made available to such independent assessors, or requirements on such
assessors.
NOTE 2: See ETSI EN 319 403-1 [i.9] for guidance on assessment of TSP's processes and services.
NOTE 3: The present document references ETSI EN 319 401 [4] for general policy requirements common to all
classes of TSP's services.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] Recommendation ITU-R TF.460-6 (2002): "Standard-frequency and time-signal emissions".
[2] ISO/IEC 19790:2012: "Information technology -- Security techniques -- Security requirements for
cryptographic modules".
[3] ISO/IEC 15408 (parts 1 to 3): "Information security, cybersecurity and privacy protection --
Evaluation criteria for IT security ".
[4] ETSI EN 319 401: "Electronic Signatures and Infrastructures (ESI); General Policy Requirements
for Trust Service Providers".
[5] ETSI EN 319 422: "Electronic Signatures and Infrastructures (ESI); Time-stamping protocol and
time-stamp token profiles".
[6] FIPS PUB 140-2 (2002): "Security Requirements for Cryptographic Modules".
[7] FIPS PUB 140-3 (2019): "Security Requirements for Cryptographic Modules".
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8 ETSI EN 319 421 V1.2.1 (2023-05)
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI EN 319 122-1: "Electronic Signatures and Infrastructures (ESI); CAdES digital signatures;
Part 1: Building blocks and CAdES baseline signatures".
[i.2] IETF RFC 3161 (2001): "Internet X.509 Public Key Infrastructure: Time-Stamp Protocol (TSP)".
[i.3] IETF RFC 5816: "ESSCertIDV2 update to RFC 3161".
[i.4] Regulation (EU) No 910/2014 of the European Parliament and of the Council on electronic
identification and trust services for electronic transactions in the internal market and repealing
Directive 1999/93/EC.
[i.5] Council Directive 93/13/EEC of 5 April 1993 on unfair terms in consumer contracts.
[i.6] BIPM Circular T.
NOTE: Available from the BIPM website https://www.bipm.org/.
[i.7] ETSI TS 119 312: "Electronic Signatures and Infrastructures (ESI); Cryptographic Suites".
[i.8] ETSI TS 102 023: "Electronic Signatures and Infrastructures (ESI); Policy requirements for time-
stamping authorities".
[i.9] ETSI EN 319 403-1: "Electronic Signatures and Infrastructures (ESI); Trust Service Provider
Conformity Assessment; Part 1: Requirements for conformity assessment bodies assessing Trust
Service Providers".
[i.10] ETSI EN 319 411-1: "Electronic Signatures and Infrastructures (ESI); Policy and security
requirements for Trust Service Providers issuing certificates; Part 1: General requirements".
[i.11] ETSI EN 319 411-2: "Electronic Signatures and Infrastructures (ESI); Policy and security
requirements for Trust Service Providers issuing certificates; Part 2: Requirements for trust service
providers issuing EU qualified certificates".
[i.12] EN 419231: "Protection profile for trustworthy systems supporting time stamping", (produced by
CEN).
[i.13] TS 419221-2: "Protection profiles for TSP Cryptographic modules - Part 2: Cryptographic module
for CSP signing operations with backup", (produced by CEN).
[i.14] TS 419221-3: "Protection profiles for TSP Cryptographic modules - Part 3: Cryptographic module
for CSP key generation services", (produced by CEN).
[i.15] TS 419221-4: "Protection profiles for TSP Cryptographic modules - Part 4: Cryptographic module
for CSP signing operations without backup", (produced by CEN).
[i.16] EN 419221-5: "Protection profiles for TSP Cryptographic modules - Part 5: Cryptographic module
for trust services", (produced by CEN).
[i.17] ETSI TS 119 612: "Electronic Signatures and Infrastructures (ESI); Trusted Lists".
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9 ETSI EN 319 421 V1.2.1 (2023-05)
3 Definitions of terms, symbols, abbreviations and
notation
3.1 Terms
For the purposes of the present document, the terms given ETSI EN 319 401 [4] and the following apply:
NOTE: Where a definition is copied from a referenced document this is indicated by inclusion of the reference
identifier number at the end of the definition.
Coordinated Universal Time (UTC): time scale based on the second as defined in Recommendation ITU-R
TF.460-6 [1]
NOTE: For most practical purposes UTC is equivalent to mean solar time at the prime meridian (0°). More
specifically, UTC is a compromise between the highly stable atomic time (Temps Atomique International
- TAI) and solar time derived from the irregular Earth rotation (related to the Greenwich Mean Sidereal
Time (GMST) by a conventional relationship) (see annex C for more details).
relying party: recipient of a time-stamp who relies on that time-stamp
subscriber: legal or natural person to whom a time-stamp is issued and who is bound to any subscriber obligations
time-stamp: data in electronic form which binds other electronic data to a particular time establishing evidence that
these data existed at that time
time-stamp policy: named set of rules that indicates the applicability of a time-stamp to a particular community and/or
class of application with common security requirements
NOTE: This is a specific type of trust service policy as defined in ETSI EN 319 401 [4].
Time-Stamping Authority (TSA): TSP providing time-stamping services using one or more time-stamping units
time-stamping service: trust service for issuing time-stamps
Time-Stamping Unit (TSU): set of hardware and software which is managed as a unit and has a single time-stamp
signing key active at a time
trust service: electronic service that enhances trust and confidence in electronic transactions
Trust Service Provider (TSP): entity which provides one or more trust services
TSA Disclosure statement: set of statements about the policies and practices of a TSA that particularly require
emphasis or disclosure to subscribers and relying parties, for example to meet regulatory requirements
TSA practice statement: statement of the practices that a TSA employs in issuing time-stamp
NOTE: This is a specific type of trust service practice statement as defined in ETSI EN 319 401 [4].
TSA system: composition of IT products and components organized to support the provision of time-stamping services
UTC(k): time scale realized by the laboratory "k" and kept in close agreement with UTC, with the goal to reach
±100 ns
NOTE: A list of UTC(k) laboratories is given in clause 1 of Circular T [i.6] disseminated by BIPM and available
from the BIPM website (https://www.bipm.org/).
3.2 Symbols
Void.
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10 ETSI EN 319 421 V1.2.1 (2023-05)
3.3 Abbreviations
For the purposes of the present document, the abbreviations given in ETSI EN 319 401 [4] and the following apply:
BIPM Bureau International des Poids et Mesures
BTSP Best practices Time-Stamp Policy
CA Certification Authority
IERS International Earth Rotation and Reference System Service
IT Information Technology
OVR General requirement
TAI International Atomic Time
TIS Time-stamp Issuance Services
TSA Time-Stamping Authority
TSP Trust Service Provider
TSU Time-Stamping Unit
UTC Coordinated Universal Time
3.4 Notation
The requirements identified in the present document include:
a) Requirements applicable to any policy. Such requirements are indicated by clauses without any additional
marking.
b) Requirements applicable under certain conditions. Such requirements are indicated by clauses marked by
"[CONDITIONAL]".
c) Requirements that include several choices which ought to be selected according to the applicable situation.
Such requirements are indicated by clauses marked by "[CHOICE]".
Each requirement is identified as follows:
<3 letters service component> - < the clause number> - <2 digit number - incremental>.
The service components are:
• OVR: General requirement (requirement applicable to more than 1 component)
• TIS: Time-stamp Issuance Services
The management of the requirement identifiers for subsequent editions of the present document is as follows:
• When a requirement is inserted at the end of a clause, the 2 digit number above is incremented to the next
available digit.
• When a requirement is inserted between two existing requirements, capital letters appended to the previous
requirement identifier are used to distinguish new requirements.
• The requirement identifier for deleted requirements are left and completed with "Void".
• The requirement identifier for modified requirement are left void and the modified requirement is identified by
capital letter(s) appended to the initial requirement number.
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11 ETSI EN 319 421 V1.2.1 (2023-05)
4 General concepts
4.1 General policy requirements concepts
The present document references ETSI EN 319 401 [4] for generic policy requirements common to all classes of trust
service providers service.
These policy requirements are based upon the use of public key cryptography, public key certificates and reliable time
sources.
Subscriber and relying parties are expected to consult the TSA's practice statement to obtain further details of precisely
how this time-stamp policy is implemented by the particular TSA (e.g. protocols used in providing this service).
4.2 Time-stamping services
The provision of time-stamping services is broken down in the present document into the following component services
for the purposes of classifying requirements:
• Time-stamping provision: This service component generates time-stamps.
• Time-stamping management: This service component monitors and controls the operation of the
time-stamping services to ensure that the service provided is as specified by the TSA. This service component
has responsibility for the installation and de-installation of the time-stamping provision service.
EXAMPLE: Time-stamping management ensures that the clock used for time-stamping is correctly
synchronized with UTC.
This subdivision of services is only for the purposes of clarifying the requirements specified in the present document
and places no restrictions on any subdivision of an implementation of time-stamping services.
4.3 Time-Stamping Authority (TSA)
A Trust Service Provider (TSP) providing time-stamping services to the public, is called the Time-Stamping Authority
(TSA). The TSA has overall responsibility for the provision of the time-stamping services identified in clause 4.2. The
TSA has responsibility for the operation of one or more TSUs which creates and signs on behalf of the TSA. The TSA
responsible for issuing a time-stamp is identifiable (see TIS-7.7.1-08).
The TSA may make use of other parties to provide parts of the time-stamping services. However, the TSA always
maintains overall responsibility (as per clause 6.5) and ensures that the policy requirements identified in the present
document are met.
EXAMPLE: A TSA sub-contracts all the component services, including the services which generate
time-stamps using the TSU's keys. However, the private key or keys used to generate the time-
stamps are identified as belonging to the TSA which maintains overall responsibility for meeting
the requirements defined in the present document.
A TSA may operate several identifiable time-stamping units.
A TSA is a trust service provider as described in ETSI EN 319 401 [4] which issues time-stamps.
4.4 Subscriber
When the subscriber is an organization, it comprises several end-users or an individual end-user and some of the
obligations that apply to that organization will have to apply as well to the end-users. In any case the organization will
be held responsible if the obligations from the end-users are not correctly fulfilled and therefore such an organization is
expected to suitably inform its end users.
When the subscriber is an end-user, the end-user will be held directly responsible if its obligations are not correctly
fulfilled.
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12 ETSI EN 319 421 V1.2.1 (2023-05)
4.5 Time-stamp policy and TSA practice statement
This clause explains the relative roles of time-stamp policy and TSA practice statement. It places no restriction on the
form of a time-stamp policy or practice statement specification.
A time-stamp policy is a form of Trust Service Policy as specified in ETSI EN 319 401 [4] applicable to trust service
providers issuing time-stamps.
TSA Practice Statement is a form of Trust Service Practice Statement as specified in ETSI EN 319 401 [4] applicable to
trust service providers issuing time-stamps.
The present document specifies a time-stamp policy to meet general requirements for trusted time-stamping services.
TSAs specify in TSA practice statements how these requirements are met.
5 Introduction to time-stamp policies and general
requirements
5.1 General requirements
The policy requirements are defined in the present document in terms of a time-stamp policy. The present document
specifies one time-stamp policy: a Best practices Time-Stamp Policy (BTSP) for TSAs issuing time-stamps, supported
by public key certificates, with an accuracy of 1 second or better.
OVR-5.1-01: A TSA may define its own policy which enhances a policy defined in the present document.
OVR-5.1-02 [CONDITIONAL]: If the TSA defines its own policy it shall incorporate or further constrain the
requirements identified in the present document.
OVR-5.1-03 [CONDITIONAL]: If an accuracy of better than 1 second is provided by the TSA then the accuracy shall
be indicated in the TSA's disclosure statement (see clause 6.3) and in each time-stamp issued to an accuracy of better
than 1 second.
5.2 Policy name and identification
The identifier of the time-stamp policy specified in the present document is:
a) BTSP : a best practices policy for time-stamp.
itu-t(0) identified-organization(4) etsi(0)
time-stamp-policy(2023)
policy-identifiers(1) best-practices-ts-policy (1)

By including this object identifier in a time-stamp, the TSA claims conformance to the identified time-stamp policy.
OVR-5.2-01: A TSA shall include the identifier for the time-stamp policy being supported in the TSA disclosure
statement made available to subscribers and relying parties to indicate its claim of conformance.
OVR-5.2-02 [CONDITIONAL]: If the TSA uses its own identifier for the time-stamp policy, the TSA shall indicate in
its policy document and in its TSA disclosure statement, the ETSI time-stamping identifier (i.e. BSTP) being supported.
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5.3 User community and applicability
5.3.1 Best practices time-stamp policy
This policy is aimed at meeting the requirements of time-stamp for long term validity (e.g. as defined in ETSI
EN 319 122-1 [i.1]) but is generally applicable to any use which has a requirement for equivalent quality.
OVR-5.3-01: This policy may be used for public time-stamping services or time-stamping services used within a closed
community.
6 Policies and practices
6.1 Risk assessment
OVR-6.1-01: The requirements identified in ETSI EN 319 401 [4], clause 5 shall apply.
6.2 Trust Service Practice Statement
OVR-6.2-01: The requirements specified in ETSI EN 319 401 [4], clause 6.1 shall apply.
OVR-6.2-02: The Trust Service Practice Statement shall at least specify the following for each time-stamp policy
supported by the TSA:
a) the hashing algorithm (or algorithms) used to represent the datum being time-stamped;
b) the accuracy of the time in the time-stamps with respect to UTC;
c) any limitations on the use of the time-stamping service;
d) the subscriber's obligations as defined in clause 6.5.2, if any;
e) the relying party's obligations as defined in clause 6.6;
f) information on how to verify the time-stamp such that the relying party is considered to "reasonably rely" on
the time-stamp (see clause 6.6) and any possible limitations on the validity period; and
g) any claim to meet the requirements on time-stamping services under national law.
OVR-6.2-03: The TSA should include in its time-stamping disclosure statement availability of its service.
EXAMPLE: Expected mean time between failure of the time-stamping service, expected mean time to recovery
following a failure and provisions made for disaster recovery including back-up services.
OVR-6.2-04: The time-stamping disclosure statement may be created according to the TSA disclosure statement
template given in annex B.
OVR-6.2-05: The TSA disclosure statement may be provided as part of a subscriber/relying party agreement.
OVR-6.2-06: The TSA disclosure statement may be included in a TSA practice statement provided that it is
conspicuous to the reader.
6.3 Terms and conditions
OVR-6.3-01: The requirements identified in ETSI EN 319 401 [4], clause 6.2 shall apply.
6.4 Information security policy
OVR-6.4-01: The requirements identified in ETSI EN 319 401 [4], clause 6.3 shall apply.
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14 ETSI EN 319 421 V1.2.1 (2023-05)
6.5 TSA obligations
6.5.1 General
OVR-6.5-01: The TSA shall adhere to any additional obligations indicated in the time-stamp either directly or
incorporated by reference.
6.5.2 TSA obligations towards subscribers
The present document places no specific obligations on the subscriber beyond any TSA specific requirements stated in
the TSA's terms and conditions.
6.6 Information for relying parties
OVR-6.6-01: The terms and conditions made available to relying parties (see clause 6.3) shall include an obligation on
the relying party, when relying on a time-stamp, to:
a) verify that the time-stamp has been correctly signed and that the private key used to sign the time-stamp has
not been compromised until the time of the verification;
NOTE: During the TSU's certificate validity period, the validity of the signing key can be checked using current
revocation status for the TSU's certificate. If the time of verification exceeds the end of the validity period
of the corresponding certificate, see annex D for guidance.
b) take into account any limitations on the usage of the time-stamp indicated by the time-stamp policy; and
c) take into account any other precautions prescribed in agreements or elsewhere.
7 TSA management and operation
7.1 Introduction
These policy requirements are not meant to imply any restrictions on charging for TSA services.
The requirements are indicated in terms of the security objectives followed by more specific requirements for controls
to meet those objectives where considered necessary to provide the necessary confidence that those objective will be
met.
NOTE: The details of controls required to meet an objective is a balance between achieving the necessary
confidence whilst minimizing the restrictions on the techniques that a TSA can employ in issuing
time-stamps. In ETSI EN 319 401 [4], reference is made to other more general standards which can be
used as a source of more detailed control requirements. Due to these factors the specificity of the
requirements given under a given topic can vary.
The provision of a time-stamp in response to a request is at the discretion of the TSA depending on any service level
agreements with the subscriber.
7.2 Internal organization
OVR-7.2-01: The requirements identified in ETSI EN 319 401 [4], clause 7.1 shall apply.
In addition, the following particular requirements apply:
OVR-7.2-02: The TSA shall be a legal entity according to national law.
OVR-7.2-03: The TSA shall have a system or systems for quality and information security management appropriate
for the time-stamping services it is providing.
ETSI
15 ETSI EN 319 421 V1.2.1 (2023-05)
OVR-7.2-04: It shall employ a sufficient number of personnel having the necessary education, training, technical
knowledge and experience relating to the type, range and volume of work necessary to provide time-stamping
services.
NOTE: Personnel employed by a TSA include individual personnel contractually engaged in performing
functions in support of the TSA's time-stamping services. Personnel who are involved only in monitoring
the TSA services need not be TSA personnel.
7.3 Personnel security
OVR-7.3-01: The requirements identified in ETSI EN 319 401 [4], clause 7.2 shall apply.
7.4 Asset management
OVR-7.4-01: The requirements identified in ETSI EN 319 401 [4], clause 7.3 shall apply.
7.5 Access control
OVR-7.5-01: The requirements identified in ETSI EN 319 401 [4], clause 7.4 shall apply.
7.6 Cryptographic controls
7.6.1 General
OVR-7.6-01: The requirements identified in ETSI EN 319 401 [4], clause 7.5 shall apply.
7.6.2 TSU key generation
The following particular requirements apply:
TIS-7.6.2-01: The generation of the TSU's signing key(s) shall be undertaken in a physically secured environment
(as per clause 7.8) by personnel in trusted roles (as per clause 7.3) under, at least, dual control.
TIS-7.6.2-02: The personnel authorized to carry out this function shall be limited to those required to do so under
the TSA's practices.
TIS-7.6.2-03: The generation of the TSU's signing key(s) shall be carried out within a secure cryptographic device
which:
a) is a trustworthy system which is assured to EAL 4 or higher in accordance with ISO/IEC 15408 [3], or
equivalent national or internationally recognized evaluation criteria for IT security. This shall be to a
security target or protection profile which meets the requirements of the present document, based on a
risk analysis and taking into account physical and other non-technical security measures; or
NOTE 1: Standards specifying common criteria protection profiles for TSP cryptographic modules, in accordance
with ISO/IEC 15408 [3], are available within CEN as TS 419221-2 [i.13], TS 419221-3 [i.14],
TS 419221-4 [i.15], or EN 419221-5 [i.16].
b) meets the requirements identified in ISO/IEC 19790 [2], FIPS PUB 140-2 [6] level 3 or FIPS
PUB 140-3 [7] level 3.
TIS-7.6.2-04: The above secure cryptographic device should be assured as
...

SLOVENSKI STANDARD
01-junij-2023
Elektronski podpisi in infrastruktura (ESI) - Zahteve politike in varnosti za
ponudnike storitev zaupanja, ki izdajajo časovne žige
Electronic Signatures and Infrastructures (ESI) - Policy and Security Requirements for
Trust Service Providers issuing Time-Stamps
Ta slovenski standard je istoveten z: ETSI EN 319 421 V1.2.1 (2023-05)
ICS:
35.030 Informacijska varnost IT Security
35.040.01 Kodiranje informacij na Information coding in general
splošno
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
Electronic Signatures and Infrastructures (ESI);
Policy and Security Requirements for
Trust Service Providers issuing Time-Stamps

2 ETSI EN 319 421 V1.2.1 (2023-05)

Reference
REN/ESI-0019421v1.2.1
Keywords
e-commerce, electronic signature, security,
time-stamping, trust services
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All rights reserved.
ETSI
3 ETSI EN 319 421 V1.2.1 (2023-05)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definitions of terms, symbols, abbreviations and notation . 9
3.1 Terms . 9
3.2 Symbols . 9
3.3 Abbreviations . 10
3.4 Notation . 10
4 General concepts . 11
4.1 General policy requirements concepts . 11
4.2 Time-stamping services . 11
4.3 Time-Stamping Authority (TSA) . 11
4.4 Subscriber . 11
4.5 Time-stamp policy and TSA practice statement . 12
5 Introduction to time-stamp policies and general requirements . 12
5.1 General requirements . 12
5.2 Policy name and identification . 12
5.3 User community and applicability . 13
5.3.1 Best practices time-stamp policy . 13
6 Policies and practices . 13
6.1 Risk assessment . 13
6.2 Trust Service Practice Statement . 13
6.3 Terms and conditions . 13
6.4 Information security policy . 13
6.5 TSA obligations . 14
6.5.1 General . 14
6.5.2 TSA obligations towards subscribers . 14
6.6 Information for relying parties . 14
7 TSA management and operation . 14
7.1 Introduction . 14
7.2 Internal organization. 14
7.3 Personnel security. 15
7.4 Asset management . 15
7.5 Access control . 15
7.6 Cryptographic controls . 15
7.6.1 General . 15
7.6.2 TSU key generation . 15
7.6.3 TSU private key protection . 16
7.6.4 TSU public key certificate . 16
7.6.5 Rekeying TSU's key . 17
7.6.6 Life cycle management of signing cryptographic hardware . 17
7.6.7 End of TSU key life cycle . 17
7.7 Time-stamping . 18
7.7.1 Time-stamp issuance. 18
7.7.2 Clock synchronization with UTC . 18
7.8 Physical and environmental security . 19
7.9 Operation security . 19
ETSI
4 ETSI EN 319 421 V1.2.1 (2023-05)
7.10 Network security . 20
7.11 Incident management . 20
7.12 Collection of evidence . 20
7.13 Business continuity management . 20
7.14 TSA termination and termination plans . 21
7.15 Compliance. 21
8 Additional requirements for qualified electronic time-stamps as per Regulation (EU) No 910/2014 . 21
8.1 TSU public key certificate . 21
8.2 TSA issuing non-qualified and qualified electronic time-stamps as per Regulation (EU) No 910/2014 . 21
Annex A (informative): Potential liability in the provision of time-stamping services . 22
Annex B (informative): Model TSA disclosure statement . 23
B.1 Introduction . 23
B.2 TSA disclosure statement structure . 23
Annex C (informative): Coordinated Universal Time (UTC). 25
Annex D (informative): Long term verification of time-stamps . 26
Annex E (informative): Regulation (EU) No 910/2014 and qualified electronic time-stamp
policy cross-reference . 27
Annex F (informative): Possible implementation architectures - time-stamping service . 28
F.1 Managed time-stamping service . 28
F.2 Selective alternative quality . 28
Annex G (informative): Major changes from ETSI TS 102 023 . 30
Annex H (informative): Conformity Assessment Check list . 31
Annex I (informative): Change History . 32
History . 33

ETSI
5 ETSI EN 319 421 V1.2.1 (2023-05)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The declarations
pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (https://ipr.etsi.org/).
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its

Members. 3GPP™ and LTE™ are trademarks of ETSI registered for the benefit of its Members and of the 3GPP
Organizational Partners. oneM2M™ logo is a trademark of ETSI registered for the benefit of its Members and of the ®
oneM2M Partners. GSM and the GSM logo are trademarks registered and owned by the GSM Association.
Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Electronic Signatures and
Infrastructures (ESI).
The present document is derived from the requirements specified in ETSI TS 102 023 [i.8].

National transposition dates
Date of adoption of this EN: 1 May 2023
Date of latest announcement of this EN (doa): 31 August 2023
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 29 February 2024
Date of withdrawal of any conflicting National Standard (dow): 29 February 2024

Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
6 ETSI EN 319 421 V1.2.1 (2023-05)
Introduction
The present document is aiming to meet the general requirements of the international community to provide trust and
confidence in electronic transactions including, amongst others, applicable requirements from Regulation (EU)
No 910/2014 [i.4].
The Regulation includes requirements for Trust Service Providers (TSP) providing services to the public, including
TSPs issuing time-stamps. Additionally, more specific requirements are identified in the Regulation for a specific class
of TSP called a Qualified TSP, with further specific requirements for those Qualified TSPs which issue qualified
time-stamps. The present document is aimed to meet the requirements of the Regulation for both Qualified and
non-Qualified TSPs issuing Qualified and non-Qualified electronic time-stamps respectively.
In order to verify an electronic signature, it can be necessary to prove that the signature from the signer was applied
when the signer's certificate was valid. This is necessary in two circumstances:
1) during the validity period of the signer's certificate, should the signer's certificate be revoked before the end of
its validity, e.g. because the signer's private key has been compromised;
2) after the end of the validity period of the signer's certificate, since CAs are not mandated to process revocation
status information beyond the end of the validity period of the certificates they have issued.
One method consists to use a time-stamp which allows proving that a datum existed before a particular time. This
technique allows proving that the signature was generated before the date contained in the time-stamp. Policy
requirements to cover that case are the primary aim of the present document.
However, these policy requirements allow addressing other needs.
Time-stamping is gaining an increasing interest by the business sector and is becoming an important component of
digital signatures, this is commonly based upon the Time-Stamp protocol from the IETF RFC 3161 [i.2] which is
profiled in ETSI EN 319 422 [5]. Agreed minimum security and quality requirements are necessary in order to ensure
trustworthy validation of long-term digital signatures.
ETSI
7 ETSI EN 319 421 V1.2.1 (2023-05)
1 Scope
The present document specifies policy and security requirements relating to the operation and management practices of
TSPs issuing time-stamps.
These policy requirements are applicable to TSPs issuing time-stamps. Such time-stamps can be used in support of
digital signatures or for any application requiring to prove that a datum existed before a particular time.
The present document can be used by independent bodies as the basis for confirming that a TSP can be trusted for
issuing time-stamps.
The present document does not specify protocols used to access the TSUs.
NOTE 1: A time-stamping protocol is defined in IETF RFC 3161 [i.2] including optional update in IETF
RFC 5816 [i.3] and profiled in ETSI EN 319 422 [5].
The present document does not specify how the requirements identified can be assessed by an independent party,
including requirements for information to be made available to such independent assessors, or requirements on such
assessors.
NOTE 2: See ETSI EN 319 403-1 [i.9] for guidance on assessment of TSP's processes and services.
NOTE 3: The present document references ETSI EN 319 401 [4] for general policy requirements common to all
classes of TSP's services.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] Recommendation ITU-R TF.460-6 (2002): "Standard-frequency and time-signal emissions".
[2] ISO/IEC 19790:2012: "Information technology -- Security techniques -- Security requirements for
cryptographic modules".
[3] ISO/IEC 15408 (parts 1 to 3): "Information security, cybersecurity and privacy protection --
Evaluation criteria for IT security ".
[4] ETSI EN 319 401: "Electronic Signatures and Infrastructures (ESI); General Policy Requirements
for Trust Service Providers".
[5] ETSI EN 319 422: "Electronic Signatures and Infrastructures (ESI); Time-stamping protocol and
time-stamp token profiles".
[6] FIPS PUB 140-2 (2002): "Security Requirements for Cryptographic Modules".
[7] FIPS PUB 140-3 (2019): "Security Requirements for Cryptographic Modules".
ETSI
8 ETSI EN 319 421 V1.2.1 (2023-05)
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI EN 319 122-1: "Electronic Signatures and Infrastructures (ESI); CAdES digital signatures;
Part 1: Building blocks and CAdES baseline signatures".
[i.2] IETF RFC 3161 (2001): "Internet X.509 Public Key Infrastructure: Time-Stamp Protocol (TSP)".
[i.3] IETF RFC 5816: "ESSCertIDV2 update to RFC 3161".
[i.4] Regulation (EU) No 910/2014 of the European Parliament and of the Council on electronic
identification and trust services for electronic transactions in the internal market and repealing
Directive 1999/93/EC.
[i.5] Council Directive 93/13/EEC of 5 April 1993 on unfair terms in consumer contracts.
[i.6] BIPM Circular T.
NOTE: Available from the BIPM website https://www.bipm.org/.
[i.7] ETSI TS 119 312: "Electronic Signatures and Infrastructures (ESI); Cryptographic Suites".
[i.8] ETSI TS 102 023: "Electronic Signatures and Infrastructures (ESI); Policy requirements for time-
stamping authorities".
[i.9] ETSI EN 319 403-1: "Electronic Signatures and Infrastructures (ESI); Trust Service Provider
Conformity Assessment; Part 1: Requirements for conformity assessment bodies assessing Trust
Service Providers".
[i.10] ETSI EN 319 411-1: "Electronic Signatures and Infrastructures (ESI); Policy and security
requirements for Trust Service Providers issuing certificates; Part 1: General requirements".
[i.11] ETSI EN 319 411-2: "Electronic Signatures and Infrastructures (ESI); Policy and security
requirements for Trust Service Providers issuing certificates; Part 2: Requirements for trust service
providers issuing EU qualified certificates".
[i.12] EN 419231: "Protection profile for trustworthy systems supporting time stamping", (produced by
CEN).
[i.13] TS 419221-2: "Protection profiles for TSP Cryptographic modules - Part 2: Cryptographic module
for CSP signing operations with backup", (produced by CEN).
[i.14] TS 419221-3: "Protection profiles for TSP Cryptographic modules - Part 3: Cryptographic module
for CSP key generation services", (produced by CEN).
[i.15] TS 419221-4: "Protection profiles for TSP Cryptographic modules - Part 4: Cryptographic module
for CSP signing operations without backup", (produced by CEN).
[i.16] EN 419221-5: "Protection profiles for TSP Cryptographic modules - Part 5: Cryptographic module
for trust services", (produced by CEN).
[i.17] ETSI TS 119 612: "Electronic Signatures and Infrastructures (ESI); Trusted Lists".
ETSI
9 ETSI EN 319 421 V1.2.1 (2023-05)
3 Definitions of terms, symbols, abbreviations and
notation
3.1 Terms
For the purposes of the present document, the terms given ETSI EN 319 401 [4] and the following apply:
NOTE: Where a definition is copied from a referenced document this is indicated by inclusion of the reference
identifier number at the end of the definition.
Coordinated Universal Time (UTC): time scale based on the second as defined in Recommendation ITU-R
TF.460-6 [1]
NOTE: For most practical purposes UTC is equivalent to mean solar time at the prime meridian (0°). More
specifically, UTC is a compromise between the highly stable atomic time (Temps Atomique International
- TAI) and solar time derived from the irregular Earth rotation (related to the Greenwich Mean Sidereal
Time (GMST) by a conventional relationship) (see annex C for more details).
relying party: recipient of a time-stamp who relies on that time-stamp
subscriber: legal or natural person to whom a time-stamp is issued and who is bound to any subscriber obligations
time-stamp: data in electronic form which binds other electronic data to a particular time establishing evidence that
these data existed at that time
time-stamp policy: named set of rules that indicates the applicability of a time-stamp to a particular community and/or
class of application with common security requirements
NOTE: This is a specific type of trust service policy as defined in ETSI EN 319 401 [4].
Time-Stamping Authority (TSA): TSP providing time-stamping services using one or more time-stamping units
time-stamping service: trust service for issuing time-stamps
Time-Stamping Unit (TSU): set of hardware and software which is managed as a unit and has a single time-stamp
signing key active at a time
trust service: electronic service that enhances trust and confidence in electronic transactions
Trust Service Provider (TSP): entity which provides one or more trust services
TSA Disclosure statement: set of statements about the policies and practices of a TSA that particularly require
emphasis or disclosure to subscribers and relying parties, for example to meet regulatory requirements
TSA practice statement: statement of the practices that a TSA employs in issuing time-stamp
NOTE: This is a specific type of trust service practice statement as defined in ETSI EN 319 401 [4].
TSA system: composition of IT products and components organized to support the provision of time-stamping services
UTC(k): time scale realized by the laboratory "k" and kept in close agreement with UTC, with the goal to reach
±100 ns
NOTE: A list of UTC(k) laboratories is given in clause 1 of Circular T [i.6] disseminated by BIPM and available
from the BIPM website (https://www.bipm.org/).
3.2 Symbols
Void.
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10 ETSI EN 319 421 V1.2.1 (2023-05)
3.3 Abbreviations
For the purposes of the present document, the abbreviations given in ETSI EN 319 401 [4] and the following apply:
BIPM Bureau International des Poids et Mesures
BTSP Best practices Time-Stamp Policy
CA Certification Authority
IERS International Earth Rotation and Reference System Service
IT Information Technology
OVR General requirement
TAI International Atomic Time
TIS Time-stamp Issuance Services
TSA Time-Stamping Authority
TSP Trust Service Provider
TSU Time-Stamping Unit
UTC Coordinated Universal Time
3.4 Notation
The requirements identified in the present document include:
a) Requirements applicable to any policy. Such requirements are indicated by clauses without any additional
marking.
b) Requirements applicable under certain conditions. Such requirements are indicated by clauses marked by
"[CONDITIONAL]".
c) Requirements that include several choices which ought to be selected according to the applicable situation.
Such requirements are indicated by clauses marked by "[CHOICE]".
Each requirement is identified as follows:
<3 letters service component> - < the clause number> - <2 digit number - incremental>.
The service components are:
• OVR: General requirement (requirement applicable to more than 1 component)
• TIS: Time-stamp Issuance Services
The management of the requirement identifiers for subsequent editions of the present document is as follows:
• When a requirement is inserted at the end of a clause, the 2 digit number above is incremented to the next
available digit.
• When a requirement is inserted between two existing requirements, capital letters appended to the previous
requirement identifier are used to distinguish new requirements.
• The requirement identifier for deleted requirements are left and completed with "Void".
• The requirement identifier for modified requirement are left void and the modified requirement is identified by
capital letter(s) appended to the initial requirement number.
ETSI
11 ETSI EN 319 421 V1.2.1 (2023-05)
4 General concepts
4.1 General policy requirements concepts
The present document references ETSI EN 319 401 [4] for generic policy requirements common to all classes of trust
service providers service.
These policy requirements are based upon the use of public key cryptography, public key certificates and reliable time
sources.
Subscriber and relying parties are expected to consult the TSA's practice statement to obtain further details of precisely
how this time-stamp policy is implemented by the particular TSA (e.g. protocols used in providing this service).
4.2 Time-stamping services
The provision of time-stamping services is broken down in the present document into the following component services
for the purposes of classifying requirements:
• Time-stamping provision: This service component generates time-stamps.
• Time-stamping management: This service component monitors and controls the operation of the
time-stamping services to ensure that the service provided is as specified by the TSA. This service component
has responsibility for the installation and de-installation of the time-stamping provision service.
EXAMPLE: Time-stamping management ensures that the clock used for time-stamping is correctly
synchronized with UTC.
This subdivision of services is only for the purposes of clarifying the requirements specified in the present document
and places no restrictions on any subdivision of an implementation of time-stamping services.
4.3 Time-Stamping Authority (TSA)
A Trust Service Provider (TSP) providing time-stamping services to the public, is called the Time-Stamping Authority
(TSA). The TSA has overall responsibility for the provision of the time-stamping services identified in clause 4.2. The
TSA has responsibility for the operation of one or more TSUs which creates and signs on behalf of the TSA. The TSA
responsible for issuing a time-stamp is identifiable (see TIS-7.7.1-08).
The TSA may make use of other parties to provide parts of the time-stamping services. However, the TSA always
maintains overall responsibility (as per clause 6.5) and ensures that the policy requirements identified in the present
document are met.
EXAMPLE: A TSA sub-contracts all the component services, including the services which generate
time-stamps using the TSU's keys. However, the private key or keys used to generate the time-
stamps are identified as belonging to the TSA which maintains overall responsibility for meeting
the requirements defined in the present document.
A TSA may operate several identifiable time-stamping units.
A TSA is a trust service provider as described in ETSI EN 319 401 [4] which issues time-stamps.
4.4 Subscriber
When the subscriber is an organization, it comprises several end-users or an individual end-user and some of the
obligations that apply to that organization will have to apply as well to the end-users. In any case the organization will
be held responsible if the obligations from the end-users are not correctly fulfilled and therefore such an organization is
expected to suitably inform its end users.
When the subscriber is an end-user, the end-user will be held directly responsible if its obligations are not correctly
fulfilled.
ETSI
12 ETSI EN 319 421 V1.2.1 (2023-05)
4.5 Time-stamp policy and TSA practice statement
This clause explains the relative roles of time-stamp policy and TSA practice statement. It places no restriction on the
form of a time-stamp policy or practice statement specification.
A time-stamp policy is a form of Trust Service Policy as specified in ETSI EN 319 401 [4] applicable to trust service
providers issuing time-stamps.
TSA Practice Statement is a form of Trust Service Practice Statement as specified in ETSI EN 319 401 [4] applicable to
trust service providers issuing time-stamps.
The present document specifies a time-stamp policy to meet general requirements for trusted time-stamping services.
TSAs specify in TSA practice statements how these requirements are met.
5 Introduction to time-stamp policies and general
requirements
5.1 General requirements
The policy requirements are defined in the present document in terms of a time-stamp policy. The present document
specifies one time-stamp policy: a Best practices Time-Stamp Policy (BTSP) for TSAs issuing time-stamps, supported
by public key certificates, with an accuracy of 1 second or better.
OVR-5.1-01: A TSA may define its own policy which enhances a policy defined in the present document.
OVR-5.1-02 [CONDITIONAL]: If the TSA defines its own policy it shall incorporate or further constrain the
requirements identified in the present document.
OVR-5.1-03 [CONDITIONAL]: If an accuracy of better than 1 second is provided by the TSA then the accuracy shall
be indicated in the TSA's disclosure statement (see clause 6.3) and in each time-stamp issued to an accuracy of better
than 1 second.
5.2 Policy name and identification
The identifier of the time-stamp policy specified in the present document is:
a) BTSP : a best practices policy for time-stamp.
itu-t(0) identified-organization(4) etsi(0)
time-stamp-policy(2023)
policy-identifiers(1) best-practices-ts-policy (1)

By including this object identifier in a time-stamp, the TSA claims conformance to the identified time-stamp policy.
OVR-5.2-01: A TSA shall include the identifier for the time-stamp policy being supported in the TSA disclosure
statement made available to subscribers and relying parties to indicate its claim of conformance.
OVR-5.2-02 [CONDITIONAL]: If the TSA uses its own identifier for the time-stamp policy, the TSA shall indicate in
its policy document and in its TSA disclosure statement, the ETSI time-stamping identifier (i.e. BSTP) being supported.
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13 ETSI EN 319 421 V1.2.1 (2023-05)
5.3 User community and applicability
5.3.1 Best practices time-stamp policy
This policy is aimed at meeting the requirements of time-stamp for long term validity (e.g. as defined in ETSI
EN 319 122-1 [i.1]) but is generally applicable to any use which has a requirement for equivalent quality.
OVR-5.3-01: This policy may be used for public time-stamping services or time-stamping services used within a closed
community.
6 Policies and practices
6.1 Risk assessment
OVR-6.1-01: The requirements identified in ETSI EN 319 401 [4], clause 5 shall apply.
6.2 Trust Service Practice Statement
OVR-6.2-01: The requirements specified in ETSI EN 319 401 [4], clause 6.1 shall apply.
OVR-6.2-02: The Trust Service Practice Statement shall at least specify the following for each time-stamp policy
supported by the TSA:
a) the hashing algorithm (or algorithms) used to represent the datum being time-stamped;
b) the accuracy of the time in the time-stamps with respect to UTC;
c) any limitations on the use of the time-stamping service;
d) the subscriber's obligations as defined in clause 6.5.2, if any;
e) the relying party's obligations as defined in clause 6.6;
f) information on how to verify the time-stamp such that the relying party is considered to "reasonably rely" on
the time-stamp (see clause 6.6) and any possible limitations on the validity period; and
g) any claim to meet the requirements on time-stamping services under national law.
OVR-6.2-03: The TSA should include in its time-stamping disclosure statement availability of its service.
EXAMPLE: Expected mean time between failure of the time-stamping service, expected mean time to recovery
following a failure and provisions made for disaster recovery including back-up services.
OVR-6.2-04: The time-stamping disclosure statement may be created according to the TSA disclosure statement
template given in annex B.
OVR-6.2-05: The TSA disclosure statement may be provided as part of a subscriber/relying party agreement.
OVR-6.2-06: The TSA disclosure statement may be included in a TSA practice statement provided that it is
conspicuous to the reader.
6.3 Terms and conditions
OVR-6.3-01: The requirements identified in ETSI EN 319 401 [4], clause 6.2 shall apply.
6.4 Information security policy
OVR-6.4-01: The requirements identified in ETSI EN 319 401 [4], clause 6.3 shall apply.
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14 ETSI EN 319 421 V1.2.1 (2023-05)
6.5 TSA obligations
6.5.1 General
OVR-6.5-01: The TSA shall adhere to any additional obligations indicated in the time-stamp either directly or
incorporated by reference.
6.5.2 TSA obligations towards subscribers
The present document places no specific obligations on the subscriber beyond any TSA specific requirements stated in
the TSA's terms and conditions.
6.6 Information for relying parties
OVR-6.6-01: The terms and conditions made available to relying parties (see clause 6.3) shall include an obligation on
the relying party, when relying on a time-stamp, to:
a) verify that the time-stamp has been correctly signed and that the private key used to sign the time-stamp has
not been compromised until the time of the verification;
NOTE: During the TSU's certificate validity period, the validity of the signing key can be checked using current
revocation status for the TSU's certificate. If the time of verification exceeds the end of the validity period
of the corresponding certificate, see annex D for guidance.
b) take into account any limitations on the usage of the time-stamp indicated by the time-stamp policy; and
c) take into account any other precautions prescribed in agreements or elsewhere.
7 TSA management and operation
7.1 Introduction
These policy requirements are not meant to imply any restrictions on charging for TSA services.
The requirements are indicated in terms of the security objectives followed by more specific requirements for controls
to meet those objectives where considered necessary to provide the necessary confidence that those objective will be
met.
NOTE: The details of controls required to meet an objective is a balance between achieving the necessary
confidence whilst minimizing the restrictions on the techniques that a TSA can employ in issuing
time-stamps. In ETSI EN 319 401 [4], reference is made to other more general standards which can be
used as a source of more detailed control requirements. Due to these factors the specificity of the
requirements given under a given topic can vary.
The provision of a time-stamp in response to a request is at the discretion of the TSA depending on any service level
agreements with the subscriber.
7.2 Internal organization
OVR-7.2-01: The requirements identified in ETSI EN 319 401 [4], clause 7.1 shall apply.
In addition, the following particular requirements apply:
OVR-7.2-02: The TSA shall be a legal entity according to national law.
OVR-7.2-03: The TSA shall have a system or systems for quality and information security management appropriate
for the time-stamping services it is providing.
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15 ETSI EN 319 421 V1.2.1 (2023-05)
OVR-7.2-04: It shall employ a sufficient number of personnel having the necessary education, training, technical
knowledge and experience relating to the type, range and volume of work necessary to provide time-stamping
services.
NOTE: Personnel employed by a TSA include individual personnel contractually engaged in performing
functions in support of the TSA's time-stamping services. Personnel who are involved only in monitoring
the TSA services need not be TSA personnel.
7.3 Personnel security
OVR-7.3-01: The requirements identified in ETSI EN 319 401 [4], clause 7.2 shall apply.
7.4 Asset management
OVR-7.4-01: The requirements identified in ETSI EN 319 401 [4], clause 7.3 shall apply.
7.5 Access control
OVR-7.5-01: The requirements identified in ETSI EN 319 401 [4], clause 7.4 shall apply.
7.6 Cryptographic controls
7.6.1 General
OVR-7.6-01: The requirements identified in ETSI EN 319 401 [4], clause 7.5 shall apply.
7.6.2 TSU key generation
The following particular requirements apply:
TIS-7.6.2-01: The generation of the TSU's signing key(s) shall be u
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