Network Working Group                                         P. Hoffman
Internet-Draft                                            VPN Consortium
Updates: 2535, 3755, 4034                               January 20, 25, 2010
(if approved)
Intended status: Standards Track
Expires: July 24, 29, 2010

        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.

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1.  Introduction

   [RFC2535] specifies that that 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 [RFC4034].

   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 example, any number of reasons, an
      algorithm might be
      sponsored by a government and use cryptography that has 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 should be 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 is requested to mark 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 the 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 because 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
   dns-sec-alg-numbers/dns-sec-alg-numbers.xhtml, in the sub-registry
   titled "DNS Security Algorithm Numbers".  The registration procedure
   for values that are assigned after this document is published is "RFC

   IANA is requested to mark values 123 through 250 as "Reserved".

   IANA is requested to add 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 of 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.

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

Appendix B.  Change History

   This section is to be removed before publication as an RFC.

B.1.  Differences between draft-hoffman-dnssec-alg-allocation-00 and -01

   A few editorial nits that really should have been caught in the -00.

   Added the section on "Expectations For Implementations" to clarify
   that this document is not changing any such expectations or updating
   that part of RFC 4034.

B.2.  Differences between draft-hoffman-dnssec-alg-allocation-01 and

   First WG draft.

   Clarified the intent of the document in the Abstract by adding "It
   does not change the list of algorithms that are recommended or
   required for DNSSEC implementations".

   Added to Section 3: "It should be noted that the order of algorithms
   in the IANA registry does not signify or imply cryptographic strength
   or preference."

B.3.  Differences between draft-ietf-dnsext-dnssec-alg-allocation-00 and

   Various editorial changes and clarifications that came during WG LC.

   Asked IANA to mark values 123 through 250 as "Reserved".

   In the expectations for implementers, added "This document does not
   change the requirements for when an algorithm because mandatory to
   implement.  Such requirements should come in a separate, focused

B.4.  Differences between draft-ietf-dnsext-dnssec-alg-allocation-01 and

   Reworded the first bullet in Section 2 to remove "government".

Author's Address

   Paul Hoffman
   VPN Consortium