rfc9905.original   rfc9905.txt 
Network Working Group W. Hardaker Internet Engineering Task Force (IETF) W. Hardaker
Internet-Draft USC/ISI Request for Comments: 9905 USC/ISI
Updates: 4034, 5155 (if approved) W. Kumari Updates: 4034, 5155 W. Kumari
Intended status: Standards Track Google Category: Standards Track Google
Expires: 14 March 2026 10 September 2025 ISSN: 2070-1721 October 2025
Deprecating the use of SHA-1 in DNSSEC signature algorithms Deprecating the Use of SHA-1 in DNSSEC Signature Algorithms
draft-ietf-dnsop-must-not-sha1-10
Abstract Abstract
This document deprecates the use of the RSASHA1 and This document deprecates the use of the RSASHA1 and
RSASHA1-NSEC3-SHA1 algorithms for the creation of DNS Public Key RSASHA1-NSEC3-SHA1 algorithms for the creation of DNS Public Key
(DNSKEY) and Resource Record Signature (RRSIG) records. (DNSKEY) and Resource Record Signature (RRSIG) records.
It updates RFC4034 and RFC5155 as it deprecates the use of these It updates RFCs 4034 and 5155 as it deprecates the use of these
algorithms. algorithms.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on 14 March 2026. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9905.
Copyright Notice Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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in the Revised BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Notation
2. Deprecating SHA-1 from DNSSEC Signatures and Delegation 2. Deprecating SHA-1 from DNSSEC Signatures and Delegation RRs
RRs . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Security Considerations
3. Security Considerations . . . . . . . . . . . . . . . . . . . 3 4. Operational Considerations
4. Operational Considerations . . . . . . . . . . . . . . . . . 3 5. IANA Considerations
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. Normative References
6. Normative References . . . . . . . . . . . . . . . . . . . . 4 Acknowledgments
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 5 Authors' Addresses
Appendix B. Current algorithm usage levels . . . . . . . . . . . 5
Appendix C. Github Version of this document . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
The security of the protection provided by the SHA-1 algorithm The security of the protection provided by the SHA-1 algorithm
[RFC3174] has been slowly diminishing over time as various forms of [RFC3174] has been slowly diminishing over time as various forms of
attacks have weakened its cryptographic underpinning. DNSSEC attacks have weakened its cryptographic underpinning. DNSSEC
[RFC9364] originally [RFC3110] made extensive use of SHA-1, for [RFC9364] (originally defined in [RFC3110]) made extensive use of
example as a cryptographic hash algorithm in RRSIG and Delegation SHA-1, for example, as a cryptographic hash algorithm in Resource
Signer (DS) records. Since then, multiple other algorithms with Record Signature (RRSIG) and Delegation Signer (DS) records. Since
stronger cryptographic strength have become widely available for DS then, multiple other algorithms with stronger cryptographic strength
records and for Resource Record Signature (DNSKEY) and DNS Public Key have become widely available for DS records and for RRSIG and DNS
(RRSIG) records [RFC4034]. Operators are encouraged to consider Public Key (DNSKEY) records [RFC4034]. Operators are encouraged to
switching to one of the recommended algorithms listed in the consider switching to one of the recommended algorithms listed in the
[DNSKEY-IANA] and [DS-IANA] tables, respectively. Further, support [DNSKEY-IANA] and [DS-IANA] tables, respectively. Further, support
for validating SHA-1 based signatures has been removed from some for validating SHA-1-based signatures has been removed from some
systems. As a result, SHA-1 as part of a signature algorithm is no systems. As a result, SHA-1 as part of a signature algorithm is no
longer fully interoperable in the context of DNSSEC. As adequate longer fully interoperable in the context of DNSSEC. As adequate
alternatives exist, the use of SHA-1 is no longer advisable. alternatives exist, the use of SHA-1 is no longer advisable.
This document thus further deprecates the use of RSASHA1 and This document thus deprecates the use of RSASHA1 and
RSASHA1-NSEC3-SHA1 for DNS Security Algorithms. RSASHA1-NSEC3-SHA1 for DNS Security Algorithms.
1.1. Requirements notation 1.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Deprecating SHA-1 from DNSSEC Signatures and Delegation RRs 2. Deprecating SHA-1 from DNSSEC Signatures and Delegation RRs
The RSASHA1 [RFC4034] and RSASHA1-NSEC3-SHA1 [RFC5155] algorithms The RSASHA1 [RFC4034] and RSASHA1-NSEC3-SHA1 [RFC5155] algorithms
MUST NOT be used when creating DS records. Operators of validating MUST NOT be used when creating DS records. Operators of validating
resolvers MUST treat RSASHA1 and RSASHA1-NSEC3-SHA1 DS records as resolvers MUST treat RSASHA1 and RSASHA1-NSEC3-SHA1 DS records as
insecure. If no other DS records of accepted cryptographic insecure. If no other DS records of accepted cryptographic
algorithms are available, the DNS records below the delegation point algorithms are available, the DNS records below the delegation point
MUST be treated as insecure. MUST be treated as insecure.
The RSASHA1 [RFC4034] and RSASHA1-NSEC3-SHA1 [RFC5155] algorithms The RSASHA1 [RFC4034] and RSASHA1-NSEC3-SHA1 [RFC5155] algorithms
MUST NOT be used when creating DNSKEY and RRSIG records. Validating MUST NOT be used when creating DNSKEY and RRSIG records. Validating
resolver implementations ([RFC9499] section 10) MUST continue to resolver implementations ([RFC9499], Section 10) MUST continue to
support validation using these algorithms as they are diminishing in support validation using these algorithms as they are diminishing in
use but still actively in use for some domains as of this use but still actively in use for some domains as of this
publication. Operators of validating resolvers MUST treat DNSSEC publication. Operators of validating resolvers MUST treat DNSSEC
signing algorithms RSASHA1 and RSASHA1-NSEC3-SHA1 as unsupported, signing algorithms RSASHA1 and RSASHA1-NSEC3-SHA1 as unsupported,
rendering responses insecure if they cannot be validated by other rendering responses insecure if they cannot be validated by other
supported signing algorithms. supported signing algorithms.
3. Security Considerations 3. Security Considerations
This document deprecates the use of RSASHA1 and RSASHA1-NSEC3-SHA1 This document deprecates the use of RSASHA1 and RSASHA1-NSEC3-SHA1
for DNSSEC Delegation and DNSSEC signing since these algorithms are for DNSSEC Delegation and DNSSEC signing since these algorithms are
no longer considered to be secure. no longer considered to be secure.
4. Operational Considerations 4. Operational Considerations
Zone owners currently making use of SHA-1 based algorithms should Zone owners currently making use of SHA-1-based algorithms should
immediately roll to algorithms with stronger cryptographic immediately roll to algorithms with stronger cryptographic
algorithms, such as the recommended algorithms in the [DNSKEY-IANA] algorithms, such as the recommended algorithms in the [DNSKEY-IANA]
and [DS-IANA] tables. and [DS-IANA] tables.
Operators should take care when deploying software packages and Operators should take care when deploying software packages and
operating systems that may have already removed support for the SHA-1 operating systems that may have already removed support for the SHA-1
algorithm. In these situations software may need to be manually algorithm. In these situations, software may need to be manually
built and deployed by an operator to continue supporting the required built and deployed by an operator to continue supporting the required
levels indicated by the "Use for DNSSEC Validation" and "Implement levels indicated by the "Use for DNSSEC Validation" and "Implement
for DNSSEC Validation" columns, which this document is not changing. for DNSSEC Validation" columns, which this document is not changing.
5. IANA Considerations 5. IANA Considerations
[Note to IANA, to be removed by the RFC Editor: the registry fields IANA has set the "Use for DNSSEC Delegation" column of the "Digest
listed above will be created by draft-ietf-dnsop-rfc8624-bis.] Algorithms" registry [DS-IANA] [RFC9904] to MUST NOT for SHA-1 (1)
and has added this document as a reference for the entry.
IANA is requested to set the "Use for DNSSEC Delegation" field of the
"Digest Algorithms" registry [DS-IANA] [I-D.ietf-dnsop-rfc8624-bis]
for SHA-1 (1) to MUST NOT.
IANA is requested to set the "Use for DNSSEC Signing" column of the IANA has set the "Use for DNSSEC Signing" column of the "DNS Security
DNS Security Algorithm Numbers registry [DNSKEY-IANA] Algorithm Numbers" registry [DNSKEY-IANA] [RFC9904] to MUST NOT for
[I-D.ietf-dnsop-rfc8624-bis] to MUST NOT for the RSASHA1 (5) and the RSASHA1 (5) and RSASHA1-NSEC3-SHA1 (7) algorithms and has added
RSASHA1-NSEC3-SHA1 (7) algorithms. this document as a reference for these entries.
All other columns should remain as currently specified. All other columns should remain as currently specified.
6. Normative References 6. Normative References
[DNSKEY-IANA] [DNSKEY-IANA]
IANA, "Domain Name System Security (DNSSEC) Algorithm IANA, "Domain Name System Security (DNSSEC) Algorithm
Numbers", n.d., <https://www.iana.org/assignments/dns-sec- Numbers",
alg-numbers/dns-sec-alg-numbers.xhtml>. <https://www.iana.org/assignments/dns-sec-alg-numbers>.
[DS-IANA] IANA, "Delegation Signer (DS) Resource Record (RR) Type [DS-IANA] IANA, "DNSSEC Delegation Signer (DS) Resource Record (RR)
Digest Algorithms", n.d., Type Digest Algorithms",
<http://www.iana.org/assignments/ds-rr-types>. <http://www.iana.org/assignments/ds-rr-types>.
[I-D.ietf-dnsop-rfc8624-bis]
Hardaker, W. and W. Kumari, "DNSSEC Cryptographic
Algorithm Recommendation Update Process", Work in
Progress, Internet-Draft, draft-ietf-dnsop-rfc8624-bis-13,
4 June 2025, <https://datatracker.ietf.org/doc/html/draft-
ietf-dnsop-rfc8624-bis-13>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3110] Eastlake 3rd, D., "RSA/SHA-1 SIGs and RSA KEYs in the [RFC3110] Eastlake 3rd, D., "RSA/SHA-1 SIGs and RSA KEYs in the
Domain Name System (DNS)", RFC 3110, DOI 10.17487/RFC3110, Domain Name System (DNS)", RFC 3110, DOI 10.17487/RFC3110,
May 2001, <https://www.rfc-editor.org/rfc/rfc3110>. May 2001, <https://www.rfc-editor.org/info/rfc3110>.
[RFC3174] Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1 [RFC3174] Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1
(SHA1)", RFC 3174, DOI 10.17487/RFC3174, September 2001, (SHA1)", RFC 3174, DOI 10.17487/RFC3174, September 2001,
<https://www.rfc-editor.org/rfc/rfc3174>. <https://www.rfc-editor.org/info/rfc3174>.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions", Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005, RFC 4034, DOI 10.17487/RFC4034, March 2005,
<https://www.rfc-editor.org/rfc/rfc4034>. <https://www.rfc-editor.org/info/rfc4034>.
[RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
Security (DNSSEC) Hashed Authenticated Denial of Security (DNSSEC) Hashed Authenticated Denial of
Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008, Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008,
<https://www.rfc-editor.org/rfc/rfc5155>. <https://www.rfc-editor.org/info/rfc5155>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC9364] Hoffman, P., "DNS Security Extensions (DNSSEC)", BCP 237, [RFC9364] Hoffman, P., "DNS Security Extensions (DNSSEC)", BCP 237,
RFC 9364, DOI 10.17487/RFC9364, February 2023, RFC 9364, DOI 10.17487/RFC9364, February 2023,
<https://www.rfc-editor.org/rfc/rfc9364>. <https://www.rfc-editor.org/info/rfc9364>.
[RFC9499] Hoffman, P. and K. Fujiwara, "DNS Terminology", BCP 219, [RFC9499] Hoffman, P. and K. Fujiwara, "DNS Terminology", BCP 219,
RFC 9499, DOI 10.17487/RFC9499, March 2024, RFC 9499, DOI 10.17487/RFC9499, March 2024,
<https://www.rfc-editor.org/rfc/rfc9499>. <https://www.rfc-editor.org/info/rfc9499>.
Appendix A. Acknowledgments [RFC9904] Hardaker, W. and W. Kumari, "DNSSEC Cryptographic
Algorithm Recommendation Update Process", RFC 9904,
DOI 10.17487/RFC9904, October 2025,
<https://www.rfc-editor.org/info/rfc9904>.
Acknowledgments
The authors appreciate the comments and suggestions from the The authors appreciate the comments and suggestions from the
following IETF participants in helping produce this document: Mark following IETF participants in helping produce this document: Mark
Andrews, Steve Crocker, Peter Dickson, Thomas Graf, Paul Hoffman, Andrews, Steve Crocker, Peter Dickson, Thomas Graf, Paul Hoffman,
Russ Housley, Shumon Huque, Barry Leiba, S Moonesamy, Yoav Nir, Russ Housley, Shumon Huque, Barry Leiba, S. Moonesamy, Yoav Nir,
Florian Obser, Peter Thomassen, Stefan Ubbink, Paul Wouters, Tim Florian Obser, Peter Thomassen, Stefan Ubbink, Paul Wouters, Tim
Wicinski, and the many members of the DNSOP working group that Wicinski, and the many members of the DNSOP Working Group that
discussed this draft. discussed this specification.
Appendix B. Current algorithm usage levels
The DNSSEC scanning project by Viktor Dukhovni and Wes Hardaker
highlights the current deployment of various algorithms on the
https://stats.dnssec-tools.org/ website.
<RFC Editor: please delete this section upon publication>
Appendix C. Github Version of this document
While this document is under development, it can be viewed, tracked,
fill here:
https://github.com/hardaker/draft-hardaker-dnsop-must-not-sha1
<RFC Editor: please delete this section upon publication>
Authors' Addresses Authors' Addresses
Wes Hardaker Wes Hardaker
USC/ISI USC/ISI
Email: ietf@hardakers.net Email: ietf@hardakers.net
Warren Kumari Warren Kumari
Google Google
Email: warren@kumari.net Email: warren@kumari.net
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