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RFC 6014 - Cryptographic Algorithm Identifier Allocation for DNS

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Internet Engineering Task Force (IETF)                        P. Hoffman
Request for Comments: 6014                                VPN Consortium
Updates: 4033, 4034, 4035                                  November 2010
Category: Standards Track
ISSN: 2070-1721

        Cryptographic Algorithm Identifier Allocation for DNSSEC


   This document specifies how DNSSEC cryptographic algorithm
   identifiers in the IANA registries are allocated.  It changes the
   requirement from "standard required" to "RFC Required".  It does not
   change the list of algorithms that are recommended or required for
   DNSSEC implementations.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

1.  Introduction

   [RFC2535] specifies that the IANA registry for DNS Security Algorithm
   Numbers be updated by IETF Standards Action only, with the exception
   of two values -- 253 and 254.  In essence, this means that for an
   algorithm to get its own entry in the registry, the algorithm must be
   defined in an RFC on the Standards Track as defined in [RFC2026].
   The requirement from RFC 2535 is repeated in [RFC3755] and the
   combination of [RFC4033], [RFC4034], and [RFC4035].

   RFC 2535 allows algorithms that are not on the Standards Track to use
   private values 253 and 254 in signatures.  In each case, an
   unregistered private name must be included with each use of the
   algorithm in order to differentiate different algorithms that use the

2.  Requirements for Assignments in the DNS Security Algorithm Numbers

   This document changes the requirement for registration from requiring
   a Standards Track RFC to requiring a published RFC of any type.
   There are two reasons for relaxing the requirement:

   o  There are some algorithms that are useful that may not be able to
      be in a Standards Track RFC.  For any number of reasons, an
      algorithm might not have been evaluated thoroughly enough to be
      able to be put on the Standards Track.  Another example is that
      the algorithm might have unclear intellectual property rights that
      prevents the algorithm from being put on the Standards Track.

   o  Although the size of the registry is restricted (about 250
      entries), new algorithms are proposed infrequently.  It could
      easily be many decades before there is any reason to consider
      restricting the registry again.

   Some developers will care about the standards level of the RFCs that
   are in the registry.  The registry has been updated to reflect the
   current standards level of each algorithm listed.

   To address concerns about the registry eventually filling up, the
   IETF should re-evaluate the requirements for entry into this registry
   when approximately 120 of the registry entries have been assigned.
   That evaluation may lead to tighter restrictions or a new mechanism
   for extending the size of the registry.  In order to make this
   evaluation more likely, IANA has marked about half of the currently
   available entries as "Reserved" in order to make the timing for that
   re-evaluation more apparent.

   The private-use values, 253 and 254, are still useful for developers
   who want to test, in private, algorithms for which there is no RFC.
   This document does not change the semantics of those two values.

3.  Expectations for Implementations

   It is important to note that, according to RFC 4034, DNSSEC
   implementations are not expected to include all of the algorithms
   listed in the IANA registry; in fact, RFC 4034 and the IANA registry
   list an algorithm that implementations should not include.  This
   document does nothing to change the expectation that there will be
   items listed in the IANA registry that need not be (and in some
   cases, should not be) included in all implementations.

   There are many reasons why a DNSSEC implementation might not include
   one or more of the algorithms listed, even those on the Standards
   Track.  In order to be compliant with RFC 4034, an implementation
   only needs to implement the algorithms listed as mandatory to
   implement in that standard, or updates to that standard.  This
   document does nothing to change the list of mandatory-to-implement
   algorithms in RFC 4034.  This document does not change the
   requirements for when an algorithm becomes mandatory to implement.
   Such requirements should come in a separate, focused document.

   It should be noted that the order of algorithms in the IANA registry
   does not signify or imply cryptographic strength or preference.

4.  IANA Considerations

   This document updates allocation requirements for unassigned values
   in the "Domain Name System Security (DNSSEC) Algorithm Numbers"
   registry located at http://www.iana.org/assignments/
   dns-sec-alg-numbers, in the sub-registry titled "DNS Security
   Algorithm Numbers".  The registration procedure for values that are
   assigned after this document is published is "RFC Required".

   IANA has marked values 123 through 251 as "Reserved".  The registry
   notes that this reservation is made in RFC 6014 (this RFC) so that
   when most of the unreserved values are taken, future users and IANA
   will have a pointer to where the reservation originated and its

   IANA has added a textual notation to the "References" column in the
   registry that gives the current standards status for each RFC that is
   listed in the registry.

5.  Security Considerations

   An algorithm described in an RFC that is not on the Standards Track
   may have weaker security than one that is on the Standards Track; in
   fact, that may be the reason that the algorithm was not allowed on
   Standards Track.  Note, however, that not being on the Standards
   Track does not necessarily mean that an algorithm is weaker.
   Conversely, algorithms that are on the Standards Track should not
   necessarily be considered better than algorithms that are not on the
   Standards Track.  There are other reasons (such as intellectual
   property concerns) that can keep algorithms that are widely
   considered to be strong off the Standards Track.

6.  References

6.1.  Normative References

   [RFC2535]  Eastlake, D., "Domain Name System Security Extensions",
              RFC 2535, March 1999.

   [RFC3755]  Weiler, S., "Legacy Resolver Compatibility for Delegation
              Signer (DS)", RFC 3755, May 2004.

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "DNS Security Introduction and Requirements",
              RFC 4033, March 2005.

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, March 2005.

   [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Protocol Modifications for the DNS Security
              Extensions", RFC 4035, March 2005.

6.2.  Informative References

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, October 1996.

Appendix A.  Experimental and Documentation Values

   During the early discussion of this document, it was proposed that
   maybe there should be a small number of values reserved for
   "experimental" purposes.  This proposal was not included in this
   document because of the long history in the IETF of experimental
   values that became permanent.  That is, a developer would release
   (maybe "experimentally") a version of software that had the
   experimental value associated with a particular extension,
   competitors would code their systems to test interoperability, and
   then no one wanted to change the values in their software to the
   "real" value that was later assigned.

   There was also a proposal that IANA should reserve two values to be
   used in documentation only, similar to the way that "example.com" has
   been reserved as a domain name.  That proposal was also not included
   in this document because all values need to be associated with some
   algorithm, and there is no problem with having examples that point to
   commonly deployed algorithms.

Author's Address

   Paul Hoffman
   VPN Consortium

   EMail: paul.hoffman@vpnc.org


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