DNSSEC Cryptographic Algorithms

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Table of Contents

1. Introduction

DNS Security Extensions (DNSSEC) [RFC4034] is used to provide authentication of DNS data. The DNSSEC signing algorithms are defined by various RFCs, including [RFC4034], [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, this document moves the canonical status of the algorithms from [RFC8624] to the IANA DNSSEC algorithm registries. [ 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. ]¶

This document simply moves the canonical list of algorithms from [RFC8624] to the IANA registry, and defines the registry policies for updating the registry. It does not change the status of any of the algorithms listed in [RFC8624]; this is left to future documents.¶

2. Adding "Recommended" Columns to existing IANA tables

Per this document, the following "Recommended" columns have been 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 both the "Recommended for DNSSSEC Signing" and "Recommended for DNSSSEC Validation" columns requires RFC publication. Adding a new entry to, or changing existing values in the "DNS System Algorithm Numbers" registry with a value in the "Recommended for DNSSSEC Signing" or "Recommended for DNSSSEC Validation" columns other than MAY requires a Standards Action.¶

Adding a new entry to the "Digest Algorithms" registry with a recommended value of MAY in the "Recommended" column requires RFC publication. Adding a new entry to the "Digest Algorithms" registry with a value in the "Recommended" column other 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 values transcribed from [RFC8624].¶

3. DNS System Algorithm Numbers Column Values

Initial recommendation columns of implementation recommendations for the "Domain Name System Security (DNSSEC) Algorithm Numbers" are show in Table 1.¶

                                Table 1

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

Initial recommendation columns of implementation recommendations for the "DNSSEC Delegation Signer (DS) Resource Record (RR) Type Digest Algorithms" registry are shown in Table 2.¶

                                Table 2

5. Security Considerations

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 new revisions of this document 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 as follows:¶

• Add "Recommended for DNSSSEC Signing" and "Recommended for DNSSSEC Validation" columns to the "DNS Security Algorithm Numbers" registry ([DNSKEY-IANA]) and populate these columens with the values from Table 1.¶

• Add a "Recommended" column to the "Digest Algorithms" registry ([DS-IANA]) and populate this column with the values from Table 2.¶

• Update the registration policy for the [DNSKEY-IANA] registry to match the text describing update requirements above.¶

  {Ed: We're not sure if this is the right policy, and this requires a good discussion with the WG. The purpose of much of this document is so that we can introduce TheNextBestAlgorithm by documenting TheNextBestAlgorithm in a new RFC and having it updating the IANA registry, instead of having to update RFC8624-bis-bis-bis-bis. We also, obviously, don't want someone to do something silly and mark an algorithm as "Recommended" without a good reason. This implies Standards Track. On the other hand we want to allow the ISE to add new algorithms (like the latest GOST algorithm), and, rightly or wrongly, the ISE doesn't publishes Std Track RFCs. Standards Action or IESG Approval seems like a reasonable compromise, but I'm not sure if it's the right one. We hope to present this to the WG at IEFT119 and get feedback.}¶

8. Acknowledgments

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

Appendix A. ChangeLog

Authors' Addresses