Internet-Draft MUST NOT DNSSEC with SHA-1 May 2024
Hardaker & Kumari Expires 15 November 2024 [Page]
Network Working Group
Intended Status:
Standards Track
W. Hardaker
W. Kumari

Remove SHA-1 from active use within DNSSEC


This document retires the use of SHA-1 within DNSSEC.

Status of This Memo

This Internet-Draft is submitted in full conformance with the 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

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This Internet-Draft will expire on 15 November 2024.

Table of Contents

1. Introduction

The security of the SHA-1 algorithm [RFC3174] has been slowly diminishing over time as various forms of attacks have weakened its cryptographic underpinning. DNSSEC [RFC4033] [RFC4034] [RFC4035] originally made extensive use of SHA-1 as a cryptographic verification algorithm in RRSIG and Delegation Signer (DS) records, for example. Since then, multiple other signing algorithms with stronger cryptographic strength are now widely available for DS records (such as SHA-256 [RFC4509], SHA-384 ([RFC6605])) and for DNSKEY and RRSIG records (such as RSASHA256 ([RFC5702]), RSASHA512 ([RFC5702]), ECDSAP256SHA256 [RFC6605], ECDSAP384SHA384 [RFC6605], ED25519 [RFC8080], and ED448 [RFC8080]). Further, support for validating SHA-1 based signatures has been removed from some systems. As a result, SHA-1 is no longer fully interoperable in the context of DNSSEC. As adequate alternatives exist, its use is no longer advisable.

This document thus deprecates the use of RSASHA1 and RSASHA1-NSEC3-SHA1 for DNS Security Algorithms.

1.1. Requirements notation

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

2. Deprecating SHA-1 algorithms in DNSSEC

The RSASHA1 [RFC4034], DSA-NSEC3-SHA1 [RFC5155], and RSASHA1-NSEC3-SHA1 [RFC5155] algorithms MUST NOT be used when creating DNSKEY and RRSIG records.

Validating resolvers SHOULD support validation using these algorithms but MAY treat RRSIG records created from DNSKEY records using these algorithms as an unsupported algorithm.

3. Security Considerations

This document reduces the risk that a zone cannot be validated due to lack of SHA-1 support in a validator, by guiding signers to choose a more interoperable signing algorithm.

4. Operational Considerations

Zone owners currently making use of SHA-1 based algorithms should immediately switch to algorithms with stronger cryptographic strengths, such as those listed in the introduction.

5. IANA Considerations

IANA is requested to set the "Status" field of the "Digest Algorithms" registry [DS-IANA] for SHA-1 (1) to OPTIONAL.

IANA is requested to set the "Recommended for DNSSEC Signing" column of the DNS Security Algorithm Numbers registry [DNSKEY-IANA] to MUST NOT:

IANA is requested to set the "Recommended for DNSSEC Validation" column of the DNS Security Algorithm Numbers registry [DNSKEY-IANA] to SHOULD:

6. References

6.1. Normative References

IANA, "Domain Name System Security (DNSSEC) Algorithm Numbers", n.d., <>.
IANA, "Delegation Signer (DS) Resource Record (RR) Type Digest Algorithms", n.d., <>.
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1 (SHA1)", RFC 3174, DOI 10.17487/RFC3174, , <>.
Daboo, C., "SIEVE Email Filtering: Spamtest and VirusTest Extensions", RFC 3685, DOI 10.17487/RFC3685, , <>.
Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS Security Introduction and Requirements", RFC 4033, DOI 10.17487/RFC4033, , <>.
Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "Resource Records for the DNS Security Extensions", RFC 4034, DOI 10.17487/RFC4034, , <>.
Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "Protocol Modifications for the DNS Security Extensions", RFC 4035, DOI 10.17487/RFC4035, , <>.
Hardaker, W., "Use of SHA-256 in DNSSEC Delegation Signer (DS) Resource Records (RRs)", RFC 4509, DOI 10.17487/RFC4509, , <>.
Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS Security (DNSSEC) Hashed Authenticated Denial of Existence", RFC 5155, DOI 10.17487/RFC5155, , <>.
Jansen, J., "Use of SHA-2 Algorithms with RSA in DNSKEY and RRSIG Resource Records for DNSSEC", RFC 5702, DOI 10.17487/RFC5702, , <>.
Hoffman, P. and W.C.A. Wijngaards, "Elliptic Curve Digital Signature Algorithm (DSA) for DNSSEC", RFC 6605, DOI 10.17487/RFC6605, , <>.
Sury, O. and R. Edmonds, "Edwards-Curve Digital Security Algorithm (EdDSA) for DNSSEC", RFC 8080, DOI 10.17487/RFC8080, , <>.

6.2. Informative References

Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.
Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS Terminology", RFC 8499, DOI 10.17487/RFC8499, , <>.

Appendix A. Acknowledgments


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 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:

Authors' Addresses

Wes Hardaker
Warren Kumari