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Versions: 00 01 02 03 04 05 RFC 4509

Network Working Group                                        W. Hardaker
Internet-Draft                                                    Sparta
Expires: May 14, 2006                                  November 10, 2005


 Use of SHA-256 in DNSSEC Delegation Signer (DS) Resource Records (RRs)
                   draft-ietf-dnsext-ds-sha256-00.txt

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document defines the use of the SHA-256 digest type for creating
   digests of DNSKEY Resource Records (RRs).  These digests can then be
   published in Delegation Signer (DS) resource records (RRs) by a
   parent zone.








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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Implementing the SHA-256 algorithm for DS record support  . . . 3
     2.1.  DS record field values  . . . . . . . . . . . . . . . . . . 3
     2.2.  DS Record with SHA-256 Wire Format  . . . . . . . . . . . . 3
   3.  Implementation Requirements . . . . . . . . . . . . . . . . . . 4
   4.  Deployment Requirements . . . . . . . . . . . . . . . . . . . . 4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 5
   Appendix A.  Example  . . . . . . . . . . . . . . . . . . . . . . . 5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 6
   Intellectual Property and Copyright Statements  . . . . . . . . . . 7


































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1.  Introduction

   The DNSSEC [RFC4033] [RFC4034] [RFC4035] DS RR is published by parent
   zones to distribute a cryptographic digest of a child's Key Signing
   Key (KSK) DNSKEY RR.  This DS RR is signed using the parent zone's
   private half of it's DNSKEY and is published in a RRSIG record.


2.  Implementing the SHA-256 algorithm for DS record support

   This document specifies that the digest type code [XXX: To be
   assigned by IANA; likely 2] is to be assigned to SHA-256 [SHA256] for
   use within DS records.  The results of the digest algorithm MUST NOT
   be truncated and the entire 32 byte digest result is to be published
   in the DS record.

2.1.  DS record field values

   Using the SHA-256 digest algorithm within a DS record will make use
   of the following DS-record fields:

   Digest type: [XXX: To be assigned by IANA; likely 2]

   Digest: A SHA-256 bit digest value calculated by using the following
      formula ("|" denotes concatenation).  The resulting value is not
      truncated and the entire 32 byte result is to used in the
      resulting DS record and related calculations.

        digest = SHA_256(DNSKEY owner name | DNSKEY RDATA)

      where DNSKEY RDATA is defined by [RFC4034] as:

        DNSKEY RDATA = Flags | Protocol | Algorithm | Public Key

   The Key Tag field and Algorithm fields remain unchanged by this
   document and are specified in the [RFC4034] specification.

2.2.  DS Record with SHA-256 Wire Format

   The resulting packet format for the resulting DS record will be [XXX:
   IANA assignment should replace the 2 below]:










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                           1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Key Tag             |  Algorithm    | DigestType=2  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                                                               /
      /            Digest  (length for SHA-256 is 32 bytes)           /
      /                                                               /
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|


3.  Implementation Requirements

   Implementations MUST support the use of the SHA-256 algorithm in DS
   RRs.

   Implementations that support SHA-256 MUST prefer DS records with SHA-
   256 (digest type number [XXX: RFC to be assigned by IANA; likely 2])
   digests over DS records with SHA-1 (digest type number 1) digests.


4.  Deployment Requirements

   Deployments SHOULD publish both SHA-1 and SHA-256 based DS records
   for 2 years from the publication date of this RFC (XXX: RFC Editor:
   Please insert the calculated date here).


5.  IANA Considerations

   The Digest Type to be used for supporting SHA-256 within DS records
   needs to be assigned by IANA.  This document requests that the Digest
   Type value of 2 be assigned to the SHA-256 digest algorithm.


6.  Security Considerations

   Because of the weaknesses recently discovered within the SHA-1
   algorithm, users of DNSSEC are encouraged to deploy the use of SHA-
   256 as soon as software implementations in use allow for it.

   At the time of this publication, the SHA-256 algorithm is considered
   sufficiently strong for the immediate future.  It is considered also
   considered sufficient for use in DNSSEC DS RRs for the immediate
   future.  However, future published attacks may, of course, weaken the
   usability of this algorithm within the DS RRs.





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7.  Acknowledgments

   This document is a minor extension to the existing DNSSEC documents
   and those authors are gratefully appreciated for the hard work that
   went into the base documents.


8.  References

8.1.  Normative References

   [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.

   [SHA256]   National Institute of Standards and Technology, "Secure
              Hash Algorithm. NIST FIPS 180-2", August 2002.

8.2.  Informative References


Appendix A.  Example

   TBD



















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Author's Address

   Wes Hardaker
   Sparta
   P.O. Box 382
   Davis  95617
   US

   Email: hardaker@tislabs.com










































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   Internet Society.




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