DNSSEC Cryptographic Algorithm Recommendation Update Process

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Table of Contents

1. Introduction

DNS Security Extensions (DNSSEC) [RFC9364] is used to provide authentication of DNS data. The DNSSEC signing algorithms are defined by various RFCs, including [RFC4034], [RFC4509], [RFC5155], [RFC5702], [RFC5933], [RFC6605], [RFC8080].¶

To ensure interoperability, a set of "mandatory-to-implement" DNSKEY algorithms are defined in [RFC8624]. To make the current status of the algorithms more easily accessible and understandable, and to make future changes to these recommendations easier to publish, this document moves the canonical status of the algorithms from [RFC8624] to the IANA DNSSEC algorithm registries. Additionally, as advice to operators, it adds recommendations for deploying and the usage of these algorithms.¶

<Editor: This is similar to the process used for the [TLS-ciphersuites] registry, where the canonical list of ciphersuites is in the IANA registry, and the RFCs reference the IANA registry.>¶

2. Adding usage and implementation recommendations to the IANA DNSSEC tables

Per this document, the following columns are being added to the following DNSSEC algorithm tables registered with IANA:¶

Adding a new entry to the "DNS System Algorithm Numbers" registry with a recommended value of MAY in the "Use for DNSSSEC Signing", "Use for DNSSSEC Validation", "Implement for DNSSSEC Signing", or "Implement for DNSSSEC Validation" columns requires RFC publication. Adding a new entry to, or changing existing values in, the "DNS System Algorithm Numbers" registry for the "Use for DNSSSEC Signing", "Use for DNSSSEC Validation", "Implement for DNSSSEC Signing", or "Implement for DNSSSEC Validation" columns to any other value than MAY requires a Standards Action.¶

Adding a new entry to the "Digest Algorithms" registry with a recommended value of MAY in the "Use for DNSSSEC Delegation", "Use for DNSSSEC Validation", "Implement for DNSSSEC Delegation", or "Implement for DNSSSEC Validation" columns requires RFC publication. Adding a new entry to, or changing existing values in, the "DNS System Algorithm Numbers" registry for the "Use for DNSSSEC Delegation", "Use for DNSSSEC Validation", "Implement for DNSSSEC Delegation", or "Implement for DNSSSEC Validation" columns to any other value than MAY requires a Standards Action.¶

If an item is not marked as "RECOMMENDED", it does not necessarily mean that it is flawed; rather, it indicates that the item either has not been through the IETF consensus process, has limited applicability, or is intended only for specific use cases.¶

The following sections state the initial values to be populated into these rows, with Implementation values transcribed from [RFC8624]. Use for columns was also set to the same values from [RFC8624], as there is no existing documented values and general interpretation of the tables to date indicate they should be the same, although may differ in the future.¶

3. DNS System Algorithm Numbers Column Values

Initial recommendation columns of use and implementation recommendations for the "Domain Name System Security (DNSSEC) Algorithm Numbers" are shown in Table 2. When there are multiple RECOMMENDED algorithms in the "use" column, operators should choose the best algorithm according to local policy.¶

<Editor's note: A space was deliberately added to "RSASHA1-NSEC3- SHA1" to make the table fit within the standard internet draft text width. Additionally the algorithm number column was abbreviated to 'N'.>¶

4. DNSSEC Delegation Signer (DS) Resource Record (RR) Type Digest Algorithms Column Values

Initial recommendation columns of use and implementation recommendations for the "DNSSEC Delegation Signer (DS) Resource Record (RR) Type Digest Algorithms" registry are shown in Table 3. When there are multiple RECOMMENDED algorithms in the "use" column, operators should choose the best algorithm according to local policy.¶

5. Security Considerations

This document makes no modifications to the security of the existing protocol or recommendations described in [RFC8624]. Thus the security considerations remain the same, which we quote below.¶

The security of cryptographic systems depends on both the strength of the cryptographic algorithms chosen and the strength of the keys used with those algorithms. The security also depends on the engineering of the protocol used by the system to ensure that there are no non- cryptographic ways to bypass the security of the overall system.¶

This document concerns itself with the selection of cryptographic algorithms for the use of DNSSEC, specifically with the selection of "mandatory-to-implement" algorithms. The algorithms identified in this document as MUST or RECOMMENDED to implement are not known to be broken at the current time, and cryptographic research so far leads us to believe that they are likely to remain secure into the foreseeable future. However, this isn't necessarily forever, and it is expected that future documents will be issued from time to time to reflect the current best practices in this area.¶

Retiring an algorithm too soon would result in a zone signed with the retired algorithm being downgraded to the equivalent of an unsigned zone. Therefore, algorithm deprecation must be done very slowly and only after careful consideration and measurement of its use.¶

6. Operational Considerations

DNSKEY algorithm rollover in a live zone is a complex process. See [RFC6781] and [RFC7583] for guidelines on how to perform algorithm rollovers.¶

DS algorithm rollover in a live zone is also a complex process. Upgrading algorithm at the same time as rolling the new KSK key will lead to DNSSEC validation failures, and users MUST upgrade the DS algorithm first before rolling the Key Signing Key.¶

7. IANA Considerations

The IANA is requested to update the [DNSKEY-IANA] and [DS-IANA] registries according to the following sections.¶

8. Acknowledgments

This document is based on, and extends, RFC 8624, which was authored by Paul Wouters, and Ondrej Sury.¶

The contents of this document was heavily discussed by participants of the DNSOP working group. We appreciate the thoughtfulness of the many opinions expressed by working group participants that all helped shaped this document. We thank Paul Hoffman and Paul Wouters for their contributed text.¶

Appendix A. ChangeLog

Authors' Addresses