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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 4035

DNS Extensions                                                 R. Arends
Internet-Draft                                      Telematica Instituut
Expires: March 30, 2004                                        M. Larson
                                                                VeriSign
                                                              R. Austein
                                                                     ISC
                                                               D. Massey
                                                                 USC/ISI
                                                                 S. Rose
                                                                    NIST
                                                      September 30, 2003


         Protocol Modifications for the DNS Security Extensions
                  draft-ietf-dnsext-dnssec-protocol-02

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on March 30, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   This document is part of a family of documents which describes the
   DNS Security Extensions (DNSSEC).  The DNS Security Extensions are a
   collection of new resource records and protocol modifications which
   add data origin authentication and data integrity to the DNS.  This
   document describes the DNSSEC protocol modifications.  This document



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   defines the concept of a signed zone, along with the requirements for
   serving and resolving using DNSSEC.  These techniques allow a
   security-aware resolver to authenticate both DNS resource records and
   authoritative DNS error indications.

   This document obsoletes RFC 2535 and incorporates changes from all
   updates to RFC 2535.

Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  4
   1.1   Background and Related Documents . . . . . . . . . . . . . .  4
   1.2   Reserved Words . . . . . . . . . . . . . . . . . . . . . . .  4
   1.3   Editors' Notes . . . . . . . . . . . . . . . . . . . . . . .  4
   1.3.1 Open Technical Issues  . . . . . . . . . . . . . . . . . . .  4
   1.3.2 Technical Changes or Corrections . . . . . . . . . . . . . .  4
   1.3.3 Typos and Minor Corrections  . . . . . . . . . . . . . . . .  5
   2.    Zone Signing . . . . . . . . . . . . . . . . . . . . . . . .  6
   2.1   Including DNSKEY RRs in a Zone . . . . . . . . . . . . . . .  6
   2.2   Including RRSIG RRs in a Zone  . . . . . . . . . . . . . . .  6
   2.3   Including NSEC RRs in a Zone . . . . . . . . . . . . . . . .  7
   2.4   Including DS RRs in a Zone . . . . . . . . . . . . . . . . .  8
   2.5   Changes to the CNAME Resource Record.  . . . . . . . . . . .  8
   2.6   Example of a Secure Zone . . . . . . . . . . . . . . . . . .  8
   3.    Serving  . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   3.1   Including RRSIG RRs in a Response  . . . . . . . . . . . . .  9
   3.2   Including DNSKEY RRs In a Response . . . . . . . . . . . . . 10
   3.3   Including NSEC RRs In a Response . . . . . . . . . . . . . . 10
   3.3.1 Case 1: QNAME is Associated with RRsets, but RR Type Not
         Present  . . . . . . . . . . . . . . . . . . . . . . . . . . 11
   3.3.2 Case 2: QNAME Does Not Exist, and No Wildcard Matches  . . . 11
   3.3.3 Case 3: QNAME Does Not Exist, but Wildcard Matches . . . . . 11
   3.4   Including DS RRs In a Response . . . . . . . . . . . . . . . 12
   3.5   Responding to Queries for DS RRs . . . . . . . . . . . . . . 12
   3.6   Responding to Queries for Type AXFR or IXFR  . . . . . . . . 13
   3.7   Setting the AD and CD Bits in a Response . . . . . . . . . . 14
   3.8   Example DNSSEC Responses . . . . . . . . . . . . . . . . . . 15
   4.    Resolving  . . . . . . . . . . . . . . . . . . . . . . . . . 19
   4.1   Recursive Name Servers . . . . . . . . . . . . . . . . . . . 21
   4.2   Stub resolvers . . . . . . . . . . . . . . . . . . . . . . . 22
   5.    Authenticating DNS Responses . . . . . . . . . . . . . . . . 24
   5.1   Special Considerations for Islands of Security . . . . . . . 25
   5.2   Authenticating Referrals . . . . . . . . . . . . . . . . . . 25
   5.3   Authenticating an RRset Using an RRSIG RR  . . . . . . . . . 26
   5.3.1 Checking the RRSIG RR Validity . . . . . . . . . . . . . . . 27
   5.3.2 Reconstructing the Signed Data . . . . . . . . . . . . . . . 28
   5.3.3 Checking the Signature . . . . . . . . . . . . . . . . . . . 29
   5.3.4 Authenticating A Wildcard Expanded RRset Positive



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         Response . . . . . . . . . . . . . . . . . . . . . . . . . . 30
   5.4   Authenticated Denial of Existence  . . . . . . . . . . . . . 30
   5.5   Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 31
   5.5.1 Example of Re-Constructing the Original Owner Name . . . . . 31
   5.5.2 Examples of Authenticating a Response  . . . . . . . . . . . 32
   6.    IANA Considerations  . . . . . . . . . . . . . . . . . . . . 33
   7.    Security Considerations  . . . . . . . . . . . . . . . . . . 34
   8.    Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 35
         Normative References . . . . . . . . . . . . . . . . . . . . 36
         Informative References . . . . . . . . . . . . . . . . . . . 37
         Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 37
   A.    Algorithm For Handling Wildcard Expansion  . . . . . . . . . 39
   B.    Signed Zone Example  . . . . . . . . . . . . . . . . . . . . 40
         Intellectual Property and Copyright Statements . . . . . . . 46





































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1. Introduction

   The DNS Security Extensions (DNSSEC) are a collection of new resource
   records and protocol modifications which add data origin
   authentication and data integrity to the DNS. This document defines
   the DNSSEC protocol modifications. Section 2 of this document defines
   the concept of a signed zone and lists the requirements for zone
   signing. Section 3 describes the modifications to authoritative name
   server behavior necessary to handle signed zones. Section 4 describes
   the behavior of entities which include security-aware resolver
   functions. Finally, Section 5 defines how to use DNSSEC RRs to
   authenticate a response.

1.1 Background and Related Documents

   The reader is assumed to be familiar with the basic DNS concepts
   described in RFC1034 [RFC1034] and RFC1035 [RFC1035].

   This document is part of a family of documents which define DNSSEC.
   An introduction to DNSSEC and definition of common terms can be found
   in [I-D.ietf-dnsext-dnssec-intro].  A definition of the DNSSEC
   resource records can be found in [I-D.ietf-dnsext-dnssec-records].

1.2 Reserved Words

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119. [RFC2119].

1.3 Editors' Notes

1.3.1 Open Technical Issues

1.3.2 Technical Changes or Corrections

   Please report technical corrections to dnssec-editors@east.isi.edu.
   To assist the editors, please indicate the text in error and point
   out the RFC that defines the correct behavior.  For a technical
   change where no RFC that defines the correct behavior, or if there's
   more than one applicable RFC and the definitions conflict, please
   post the issue to namedroppers.

   An example correction to dnssec-editors might be: Page X says
   "DNSSEC RRs SHOULD be automatically returned in responses."  This was
   true in RFC 2535, but RFC 3225 (Section 3, 3rd paragraph) says the
   DNSSEC RR types MUST NOT be included in responses unless the resolver
   indicated support for DNSSEC.




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1.3.3 Typos and Minor Corrections

   Please report any typos corrections to dnssec-editors@east.isi.edu.
   To assist the editors, please provide enough context for us to find
   the incorrect text quickly.

   An example message to dnssec-editors might be: page X says "the
   DNSSEC standard has been in development for over 1 years".   It
   should read "over 10 years".










































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2. Zone Signing

   DNSSEC is built around the concept of signed zones.  A signed zone
   includes DNSKEY, RRSIG, NSEC and (optionally) DS records according to
   the rules specified in Section 2.1, Section 2.2, Section 2.3 and
   Section 2.4, respectively.  Any zone which does not include these
   records according to the rules in this section MUST be considered
   unsigned for the purposes of the DNS security extensions.

   DNSSEC requires a change to the definition of the CNAME resource
   record.  Section 2.5 changes the CNAME RR to allow RRSIG and NSEC RRs
   to appear at the same owner name as a CNAME RR.

   Section 2.6 shows a sample signed zone.

2.1 Including DNSKEY RRs in a Zone

   To sign a zone, the zone's administrator generates one or more
   public/private key pairs and uses the private key(s) to sign
   authoritative RRsets in the zone.  For each private key used to
   create RRSIG RRs, there SHOULD be a corresponding zone DNSKEY RR
   stored in the zone.  A zone key DNSKEY RR has the Zone Key bit of the
   flags RDATA field set to one -- see Section 2.1.1 of
   [I-D.ietf-dnsext-dnssec-records].  Public keys associated with other
   DNS operations MAY be stored in DNSKEY RRs that are not marked as
   zone keys.

   If the zone is delegated and does not wish to act as an island of
   security, the zone MUST have at least one DNSKEY RR at the apex to
   act as a secure entry point into the zone.  This DNSKEY would then be
   used to generate a DS RR at the delegating parent (see
   [I-D.ietf-dnsext-dnssec-records]).  This DNSKEY RR SHOULD be either a
   zone key or a DNSKEY signing key (see [I-D.ietf-dnsext-dnssec-intro]
   for definition).  The DNSKEY RRset at the zone apex MUST be signed by
   at least one zone signing or DNSKEY signing private key.

   DNSKEY RRs MUST NOT appear at delegation points.

2.2 Including RRSIG RRs in a Zone

   For each authoritative RRset in a signed zone (which excludes both NS
   RRsets at delegation points and glue RRsets), there MUST be at least
   one RRSIG record that meets all of the following requirements:

   o  The RRSIG owner name is equal to the RRset owner name;

   o  The RRSIG class is equal to the RRset class;




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   o  The RRSIG Type Covered field is equal to the RRset type;

   o  The RRSIG Original TTL field is equal to the TTL of the RRset;

   o  The RRSIG RR's TTL is equal to the TTL of the RRset;

   o  The RRSIG Labels field is equal to the number of labels in the
      RRset owner name, not counting the null root label and not
      counting the wildcard label if the owner name is a wildcard;

   o  The RRSIG Signer's Name field is equal to the name of the zone
      containing the RRset; and

   o  The RRSIG Algorithm, Signer's Name, and Key Tag fields identify a
      zone key DNSKEY record at the zone apex.

   The process for constructing the RRSIG RR for a given RRset is
   described in [I-D.ietf-dnsext-dnssec-records]. An RRset MAY have
   multiple RRSIG RRs associated with it.

   An RRSIG RR itself MUST NOT be signed, since signing an RRSIG RR
   would add no value and would create an infinite loop in the signing
   process.

   The NS RRset which appears at the zone apex name MUST be signed, but
   the NS RRsets which appear at delegation points (that is, the NS
   RRsets in the parent zone which delegate the name to the child zone's
   name servers) MUST NOT be signed. Glue address RRsets associated with
   delegations MUST NOT be signed.

   The difference between the set of owner names which require RRSIG
   records and the set of owner names which require NSEC records is
   subtle and worth highlighting.  RRSIG records are present at the
   owner names of all authoritative RRsets.  NSEC records are present at
   the owner names of all names for which the signed zone is
   authoritative and also at the owner names of delegations from the
   signed zone to its children.  Neither NSEC nor RRSIG records are
   present (in the parent zone) at the owner names of glue address
   RRsets.  Note, however, that this distinction is for the most part
   only visible during the zone signing process, because NSEC RRsets are
   authoritative data, and are therefore signed, thus any owner name
   which has an NSEC RRset will have RRSIG RRs as well in the signed
   zone.

2.3 Including NSEC RRs in a Zone

   Each owner name in the zone MUST have an NSEC resource record, except
   for the owner names of any glue address RRsets.  The process for



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   constructing the NSEC RR for a given name is described in
   [I-D.ietf-dnsext-dnssec-records].

   The type bitmap of every NSEC resource record in a signed zone MUST
   indicate the presence of both the NSEC record itself and its
   corresponding RRSIG record.

2.4 Including DS RRs in a Zone

   The DS resource record establishes authentication chains between DNS
   zones.  A DS RRset SHOULD be present at a delegation point when the
   child zone is signed.  The DS RRset MAY contain multiple records,
   each referencing a key used by the child zone to sign its apex DNSKEY
   RRset.  All DS RRsets in a zone MUST be signed and DS RRsets MUST NOT
   appear at non-delegation points nor at a zone's apex.

   A DS RR SHOULD point to a DNSKEY RR which is present in the child's
   apex DNSKEY RRset, and the child's apex DNSKEY RRset SHOULD be signed
   by the corresponding private key.

   Construction of a DS RR requires knowledge of the corresponding
   DNSKEY RR in the child zone, which implies communication between the
   child and parent zones.  This communication is an operational matter
   not covered by this document.

2.5 Changes to the CNAME Resource Record.

   If a CNAME RRset is present at a name in a signed zone, appropriate
   RRSIG and NSEC RRsets are REQUIRED at that name. Other types MUST NOT
   be present at that name.

   This is a modification to the original CNAME definition given in
   [RFC1034].  The original definition of the CNAME RR did not allow any
   other types to co-exist with a CNAME record, but a signed zone
   requires NSEC and RRSIG RRs for every authoritative name.  To resolve
   this conflict, this specification modifies the definition of the
   CNAME resource record to allow it to co-exist with NSEC and RRSIG
   RRs.

2.6 Example of a Secure Zone

   Appendix B shows a complete example of a small signed zone.









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3. Serving

   This section describes the behavior of a security-aware authoritative
   name server.  A security-aware authoritative name server MUST support
   the EDNS0 [RFC2671] message size extension, MUST support a message
   size of at least 1220 octets, and SHOULD support a message size of
   4000 octets [RFC3226].  Since functions specific to security-aware
   recursive name servers included components of both resolving and
   serving, issues specific to security-aware recursive name servers are
   described in Section 4.

   Upon receiving a relevant query which has the EDNS [RFC2671] OPT
   pseudo-RR DO bit [RFC3225] set to one, a security-aware authoritative
   name server for a signed zone MUST include additional RRSIG, NSEC,
   and DS RRs according to the following rules:

   o  RRSIG RRs which can be used to authenticate a response MUST be
      included in the response according to the rules in Section 3.1;

   o  NSEC RRs which can be used to provide authenticated denial of
      existence MUST be included in the response automatically according
      to the rules in Section 3.3;

   o  Either DS RRs or an NSEC RR proving that no DS RRs exist MUST be
      included in referrals automatically according to the rules in
      Section 3.4.

   DNSSEC does not change the DNS zone transfer protocol.  Zone transfer
   requirements are reviewed in Section 3.6.

   A security-aware name server which receives a DNS query which does
   not include the EDNS OPT pseudo-RR or which has the DO bit set to
   zero MUST treat the RRSIG, DNSKEY, and NSEC RRs as it would any other
   RRset, and MUST NOT perform any of the additional processing
   described above.  Since the DS RR type has the peculiar property of
   only existing in the parent zone at delegation points, DS RRs always
   require some special processing, as described in Section 3.5.

3.1 Including RRSIG RRs in a Response

   When a query has the DO bit set to one, the authoritative name server
   SHOULD attempt to send RRSIG RRs which can be used to authenticate
   the RRsets in the response.  Inclusion of RRSIG RRs in a response is
   subject to the following rules:

   o  When placing a signed RRset in the Answer section, the name server
      MUST also place its RRSIG RRs in the Answer section.  The RRSIG
      RRs have a higher priority for inclusion than any other RRsets



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      which may need to be included.  If space does not permit inclusion
      of these RRSIG RRs, the name server MUST set the TC bit.

   o  When placing a signed RRset in the Authority section, the name
      server MUST also place its RRSIG RRs in the Authority section.
      The RRSIG RRs have a higher priority for inclusion than any other
      RRsets that may need to be included.  If space does not permit
      inclusion of these RRSIG RRs, the name server MUST set the TC bit.

   o  When placing a signed RRset in the Additional section, the name
      server MUST also place its RRSIG RRs in the Additional section.
      If space does not permit inclusion of these RRSIG RRs, the name
      server MUST NOT set the TC bit solely because these RRSIG RRs
      didn't fit.


3.2 Including DNSKEY RRs In a Response

   When a query has the DO bit set to one and requests the SOA or NS RRs
   at the apex of a signed zone, a security-aware authoritative name
   server for that zone MAY return the DNSKEY RRset with the same name
   in the Additional section.  In this situation, the DNSKEY RR set and
   associated RRSIG RRs have lower priority than any other information
   that would be placed in the additional section.  The name server
   should include the DNSKEY RRset if and only if there is enough space
   in the response for both the DNSKEY RRset and associated RRSIG RR(s).
   If there is not enough space to include these DNSKEY and RRSIG RRs,
   the name server MUST omit them and MUST NOT set the TC bit solely
   because these RRs didn't fit.

3.3 Including NSEC RRs In a Response

   When a query has the DO bit set to one, security-aware authoritative
   name servers for a signed zone MUST include NSEC RRs in each of the
   following cases:

   Case 1: The QNAME has RRsets associated with it in the zone, but the
      requested RR type does not exist.

   Case 2: The QNAME, QTYPE, QCLASS tuple does not exist, and no
      wildcard can be expanded to answer the query.

   Case 3: The QNAME (or search name) does not exist, but a wildcard can
      be expanded to positively answer the query.

   Note that, in each case, a set of NSEC RRs is included to provide
   authenticated denial of existence.




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3.3.1 Case 1: QNAME is Associated with RRsets, but RR Type Not Present

   If there are RR types associated with a given QNAME, but the
   requested RR type is not present at the name, then the name server
   MUST include the NSEC RR associated with the query name and any RRSIG
   RRs associated with the NSEC RR in the Authority section (see Section
   3.1).  If space does not permit inclusion of the NSEC RR or its
   associated RRSIG RRs, the name server MUST set the TC bit.

   Note that, since the query name exists, no wildcard expansion applies
   to this query, and a single NSEC RR suffices to prove the requested
   RR type does not exist.

3.3.2 Case 2: QNAME Does Not Exist, and No Wildcard Matches

   If the query name does not exist in the zone, and no wildcard
   expansion matches both the query name and the query type, the name
   server MUST include the following NSEC RRs in the Authority section,
   along with their associated RRSIG RRs:

   o  An NSEC RR proving that there was no exact match for the name; and

   o  An NSEC RR combination proving that there was no wildcard which
      would have matched the query.  See [I-D.ietf-dnsext-wcard-clarify]
      for further information on NSEC coverage.

   If space does not permit inclusion of these NSEC and RRSIG RRs, the
   name server MUST set the TC bit (see Section 3.1).

   Appendix A provides an algorithm which computes the appropriate NSEC
   RRs to prove that no wildcard matches a given query name.

3.3.3 Case 3: QNAME Does Not Exist, but Wildcard Matches

   If the query name does not exist, but a wildcard expansion can be
   used to return a positive match to the query, the name server MUST
   include the wildcard-expanded answer and the corresponding
   wildcard-expanded RRSIG RRs in the Answer section.  The Authority
   section of the response MUST include the following NSEC RRs along
   with their corresponding RRSIG RRs:

   o  An NSEC RR which proves that there were no exact matches for the
      QNAME and QTYPE; and

   o  An NSEC RR combination which proves that there are no closer
      wildcard entries which could have been expanded to match the
      query.  See [I-D.ietf-dnsext-wcard-clarify] for further
      information on NSEC coverage.



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   If space does not permit inclusion of these NSEC and RRSIG RRs, the
   name server MUST set the TC bit (see Section 3.1).

   Appendix A provides an algorithm which computes the appropriate NSEC
   RRs to prove that no closer wildcard matches the query name.

3.4 Including DS RRs In a Response

   When a query has the DO bit set to one, and a DS RR exists at the
   query name, an authoritative security-aware name server returning a
   referral for the delegation MUST include both the NS RRset and also
   the DS RRset and its associated RRSIG RR(s).  The name server MUST
   place the NS RRset before the DS RRset and its associated RRSIG RRs.

   When a query has the DO bit set to one, and no DS RR exists at the
   query name, an authoritative security-aware name server returning a
   referral for the delegation MUST include both the NS RRset and also
   the NSEC RR and associated RRSIG RR(s) which proves that the DS RRset
   does not exist.  The name server MUST place the NS RRset before the
   NSEC RRset and its associated RRSIG RR(s).

   Including these DS and RRSIG RRs increases the size of referral
   messages, and may cause some or all glue RRs to be omitted.  If space
   does not permit inclusion of the DS or NSEC RRset and associated
   RRSIG RRs, the name server MUST set the TC bit.

   Security-aware name servers also include NSEC RRs in a referral
   response when no DS RR is present; in this case, the NSEC RR proves
   that no DS RR exists for the delegation. Section 3.4 discusses
   referrals in more detail.

3.5 Responding to Queries for DS RRs

   The DS resource record type is unusual in that it appears only on the
   parent zone's side of a zone cut.  In other words, the DS record for
   the delegation of "example.com" is only stored in the "com" zone.
   This introduces novel name server behavior, since the name server for
   the child zone is authoritative for the name by the normal DNS rules
   but the child zone does not contain the DS RR.  An authoritative name
   server's response to a DS query depends on whether the name server is
   authoritative for the parent zone, the child zone, or both, as
   described below.

   If a name server is authoritative for the parent zone, and receives a
   query for the DS record at the delegated name, then the name server
   MUST return the DS RRset from the parent zone.  This rule applies
   regardless of whether or not the name server is also authoritative
   for the child zone.



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   If the name server is authoritative for the child zone, is not
   authoritative for the parent zone, and receives a query for the DS
   record at the delegated name, there is no obvious response, because
   the child zone is not authoritative for the DS record at the child
   zone's apex, and the authoritative DS RR is only stored at the
   parent.

   If the name server allows recursion, and the RD bit is set in the
   query, the name server MAY perform recursion to find the DS record
   for the delegated name from the parent zone, and MAY return the DS
   record from its cache.  In this case, the AA bit MUST NOT be set in
   the response.

   If the name server does not perform recursion to find the DS RR,  the
   name server MUST reply with:

         RCODE:             NOERROR
         AA bit:            set
         Answer Section:    Empty
         Authority Section: SOA [+ RRSIG(SOA) + NSEC + RRSIG(NSEC)]

   In other words, a name server which is authoritative for the child
   zone but not for the parent zone answers as if the DS record does not
   exist.  Note that security-aware resolvers will query the parent zone
   at delegation points, and thus will not be affected by this behavior.

   For example, suppose that "example.com" is a delegation point, and a
   name server receives a query for the "example.com" DS RRset.

   o  If the name server is authoritative for "com", the name server
      MUST reply with the "example.com" DS RRset from the "com" zone.

   o  If the name server is authoritative for "example.com", is not
      authoritative for "com", and the RD bit is set to one in the
      query, the name server MAY perform recursion to find the
      "example.com" DS record.  If the name server does not use
      recursion to obtain the DS RR, the name server MUST reply as
      though the DS RR did not exist:

            RCODE:             NOERROR
            AA bit:            set
            Answer Section:    Empty
            Authority Section: SOA [+ RRSIG(SOA) + NSEC + RRSIG(NSEC)]


3.6 Responding to Queries for Type AXFR or IXFR

   DNSSEC does not change the DNS zone transfer process.  A signed zone



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   will contain RRSIG, DNSKEY, NSEC, and DS resource records, but these
   records have no special meaning with respect to a zone transfer
   operation, and these RRs are treated as any other resource record
   type.

   An authoritative name server is not required to verify that a zone is
   properly signed before sending or accepting a zone transfer.
   However, an authoritative name server MAY choose to reject the entire
   zone transfer if the zone fails meets any of the signing requirements
   described in Section 2.  The primary objective of a zone transfer is
   to ensure that all authoritative name servers have identical copies
   of the zone.  An authoritative name server which chooses to perform
   its own zone validation MUST NOT selectively reject some RRs and
   accept others.

   Note that the DS RR appears only in the parental side of a delegation
   and is authoritative data in the parent zone. For example, the DS RR
   for "example.com" is stored in the "com" zone (the parent zone)
   rather than in the "example.com" zone (the child zone).  As with any
   other authoritative RRset, the "example.com" DS RR MUST be included
   the "com" zone transfer.

   Note that authoritative NSEC RRs appear in both the parent and child
   zones at a delegated name, and that the NSEC RRs for the delegated
   name in the parent and child zones are never identical to each other.
   As with any other authoritative RRset, the parental NSEC RR at a
   delegated name MUST be included zone transfers of the parent zone,
   while the NSEC at the zone apex of the child zone MUST be included in
   zone transfers of the child zone.

3.7 Setting the AD and CD Bits in a Response

      Editors' note: This section seems a little lost here. Perhaps we
      should rearrange the section ordering slightly, or provide a
      pointer to this subsection at the beginning of Section 3.

   DNSSEC allocates two new bits in the DNS message header: The CD
   (Checking Disabled) bit and the AD (Authentic Data) bit.

   The CD bit is set in query messages by the resolver, and MUST be
   copied into the response by the name server.  If the CD bit is set to
   one, it indicates that the resolver is willing to perform whatever
   authentication its local policy requires, and thus that the name
   server need not perform authentication on the RRsets in the response.

   Regardless of the setting of the CD bit, the name server MAY choose
   whether or not to perform authentication according to its own local
   name server policy, and the name server MAY use the CD bit as input



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   to its own local policy.  However, if the resolver has set the CD
   bit, a name server SHOULD, if possible, return the requested data to
   the resolver even if the name server's local authentication policy
   would reject the records in question.  That is, by setting the CD
   bit, the resolver has taken responsibility for performing its own
   authentication, and the name server should not interfere in this
   case.

   The AD bit is set by name servers, and indicates the data in the
   response has been authenticated by the name server, according to the
   local name server policy.  The AD bit MUST NOT be set on a response
   unless all of the RRsets in the Answer and Authority sections have
   met the name server's local authentication policy.  A resolver MUST
   NOT trust the AD bit unless it communicates with the name server over
   a secure transport mechanism and is explicitly configured to trust
   the name server's policy.

3.8 Example DNSSEC Responses

      Editors' note: these examples probably ought to move to an
      appendix and probably ought to use the "real" signed example zone
      that's already in an appendix.

   The examples in this section use the following example zone to
   demonstrate the formation of replies by an authoritative name server.
   The zone has two name servers, a single child, and a wildcard MX RR.
   The zone is completely signed and has a full NSEC chain.

      example.com.    SOA     (...)
                      RRSIG     SOA ...
                      NS      a.example.com.
                      NS      b.example.com.
                      RRSIG     NS ...
                      MX      10 a.example.com
                      RRSIG     MX ...
                      DNSKEY     ...
                      RRSIG     DNSKEY ...
                      NSEC     *.example.com.
      *               MX      10 a.example.com.
                      RRSIG     MX ...
                      NSEC     a.example.com.
      a               A       10.10.10.1
                      RRSIG     A ...
                      NSEC     b.example.com.
      b               A       10.10.10.2
                      RRSIG     A ...
                      NSEC     c.example.com.
      c               CNAME   a.example.com.



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                      RRSIG     CNAME
                      NSEC     sub.example.com.
      sub             NS      ns.sub.example.com.
                      RRSIG     NS
                      DS      ...
                      RRSIG     DS
                      NSEC     *.example.com.
      ns.sub          A       10.10.10.3
      sub-nosig       NS      ns.sub-nosig.example.com.
                      NSEC     example.com.
      ns.sub-nosig    A       10.10.10.4

   A query to the authoritative name server for this zone for
   QNAME="c.example.com", QCLASS=IN, QTYPE=A would produce:

      Flags:  QR=1, AA=1, RCODE=0 (NOERROR)
      EDNS:   DO=1, size=4000
      QUERY:
         c.example.com.         IN A
      ANSWER:
         c.example.com.         IN A   a.example.com
                                IN RRSIG CNAME
         a.example.com.         IN A   10.10.10.1
                                IN RRSIG A
      AUTHORITY:
         example.com.           IN NS  a.example.com.
                                IN NS  b.example.com.
                                IN RRSIG NS ...
      ADDITIONAL:
         a.example.com.         IN A   10.10.10.1
                                IN RRSIG A ...
         b.example.com.         IN A   10.10.10.2
                                IN RRSIG A ...

   A query for QNAME="www.sub.example.com", QCLASS=IN, QTYPE=A would
   results in a referral to a signed zone.  The resolver can determine
   that "sub.example.com" is signed because of the presence of the DS RR
   with the hash of the "sub.example.com" zone key.

      Flags:  QR=1, AA=1, RCODE=0 (NOERROR)
      EDNS:   DO=1, size=4000
      QUERY:
         www.sub.example.com.  IN   A
      ANSWER:
         ;; empty
      AUTHORITY:
         sub.example.com.      IN  NS  ns.sub.example.com.
                               IN  DS  ...



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                               IN  RRSIG DS ...
      ADDITIONAL:
         ns.sub.example.com.   IN  A   10.10.10.3

   A query for QNAME="www.sub-nosig.example.com", QCLASS=IN, QTYPE=A
   would result in a referral to an unsigned zone. The resolver knows
   not to expect DNSSEC RRs from "sub-nosig.example.com", because the DS
   bit in the NSEC RR bitmap in the referral is not set.  Even if DNSSEC
   RRs are present in responses from "sub-nosig.example.com" name
   servers, the resolver will not be able to construct a authentication
   chain, since there is a break between "sub-nosig.example.com" and its
   delegating parent zone.

      Flags:  QR=1, AA=1, RCODE=0 (NOERROR)
      EDNS:   DO=1, size=4000
      QUERY:
         www.sub-nosig.example.com.  IN  A
      ANSWER:
         ;; empty
      AUTHORITY:
         sub-nosig.example.com.      IN  NS  ns.sub-nosig.example.com.
                                     IN  NSEC ;; (DS bit not set)
                                     IN  RRSIG NSEC ...
      ADDITIONAL:
         ns.sub-nosig.example.com.   IN  A   10.10.10.4

   A query for QNAME="f.example.com", QCLASS=IN, QTYPE=A returns a name
   error, because the name does not exist and is not covered by wildcard
   expansion.  Therefore, the name server must present proof that the
   name does not exist, and that no wildcard expansion is present which
   could have been used to answer the query.

      Flags:  QR=1, AA=1, RCODE=3 (NXDOMAIN)
      EDNS:   DO=1, size=4000
      QUERY:
         f.example.com.        IN  A
      ANSWER:
         ;; empty
      AUTHORITY:
         example.com.          IN  SOA ...
                               IN  RRSIG SOA ...
         c.example.com.        IN  NSEC sub.example.com. ...
                               IN  RRSIG NSEC ...
         *.example.com.        IN  NSEC a.example.com. ...
                               IN  RRSIG NSEC ...
      ADDITIONAL:
         example.com.          IN  DNSKEY ...
                               IN  RRSIG DNSKEY ...



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   A query for QNAME="f.example.com" QCLASS=IN, QTYPE=MX returns an MX
   RR synthesized via wildcard expansion.  The name server must prove
   that no exact match exists.

      Flags:  QR=1, AA=1, RCODE=0 (NOERROR)
      EDNS:   DO=1, size=4000
      QUERY:
         f.example.com.        IN  MX
      ANSWER:
         f.example.com.        IN  MX  10 a.example.com.
                               IN  RRSIG MX ...
      AUTHORITY:
         example.com.          IN  NS  a.example.com.
                               IN  NS  b.example.com.
                               IN  RRSIG NS ...
         c.example.com.        IN  NSEC sub.example.com.
                               IN  RRSIG NSEC ...
      ADDITIONAL:
         a.example.com.        IN  A   10.10.10.1
                               IN  RRSIG A ...
         b.example.com.        IN  A   10.10.10.2
                               IN  RRSIG A ...

   If these responses came from a recursive name server which had all of
   the necessary RRsets in its cache instead of from an authoritative
   server, the only differences would be the TTLs and the header flags.
   The AA bit would not be set, and the AD bit would be set if (and only
   if) all the RRsets in a response passed the security policy checks of
   the recursive name server.






















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4. Resolving

   This section describes the behavior of entities which include
   security-aware resolver functions.  In many cases such functions will
   be part of a security-aware recursive name server, but a stand-alone
   security-aware resolver has many of the same requirements.  Functions
   specific to security-aware recursive name servers are described in a
   separate subsection.

   A security-aware resolver MUST include an EDNS [RFC2671] OPT
   pseudo-RR with the DO [RFC3225] bit set to one when sending queries.

   A security-aware resolver MUST support a message size of at least
   1220 octets, SHOULD support a message size of 4000 octets, and MUST
   advertise the supported message size using the "sender's UDP payload
   size" field in the EDNS OPT pseudo-RR. A security-aware resolver MUST
   handle fragmented UDP packets correctly regardless of whether any
   such fragmented packets were received via IPv4 or IPv6.  Please see
   [RFC3226] for discussion of these requirements.

   A security-aware resolver MUST support the signature verification
   mechanisms described in Section 5, and MUST apply them to every
   received response except when:

   o  The security-aware resolver is part of a security-aware recursive
      name server, and the response is the result of recursion on behalf
      of a query received with the CD bit set;

   o  The response is the result of a query generated directly via some
      form of application interface which instructed the security-aware
      resolver not to perform validation for this query; or

   o  Validation for this query has been disabled by local policy.

   A security-aware resolver's support for signature verification MUST
   include support for verification of wildcard owner names.

   A security-aware resolver MUST attempt to retrieve missing DS,
   DNSKEY, or RRSIG RRs via explicit queries if the resolver needs these
   RRs in order to perform signature verification.

   A security-aware resolver MUST attempt to retrieve missing a NSEC RR
   which the resolver needs to authenticate a NODATA response.  In
   general it is not possible for a resolver to retrieve missing NSEC
   RRs, since the resolver will have no way of knowing the owner name of
   the missing NSEC RR, but in the specific case of a NODATA response,
   the resolver does know the name of the missing NSEC RR, and must
   therefore attempt to retrieve it.



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   A security-aware resolver MUST be able to determine whether or not it
   should expect a particular RRset to be signed.  More precisely, a
   security-aware resolver must be able to distinguish between three
   cases:

   1.  An RRset for which the resolver is able to build a chain of
       signed DNSKEY and DS RRs from a trusted starting point to the
       RRset.  In this case, the RRset should be signed, and is subject
       to signature validation as described above.

   2.  An RRset for which the resolver knows that it has no chain of
       signed DNSKEY and DS RRs from any trusted starting point to the
       RRset.  This can occur when the target RRset lies in an unsigned
       zone or in a descendent of an unsigned zone.  In this case, the
       RRset may or may not be signed, but the resolver will not be able
       to verify the signature.

   3.  An RRset for which the resolver is not able to determine whether
       or not the RRset should be signed, because the resolver is not
       able to obtain the necessary DNSSEC RRs. This can occur when the
       security-aware resolver is not able to contact security-aware
       name servers for the relevant zones.

   A security-aware resolver MUST be capable of being preconfigured with
   at least one trusted public key, and MUST be capable of being
   preconfigured with multiple trusted public keys or DS RRs. Since a
   security-aware resolver will not be able to validate signatures
   without such a preconfigured trusted key, the resolver SHOULD have
   some reasonably robust mechanism for obtaining such keys when it
   boots.

   A security-aware resolver SHOULD cache each response as a single
   atomic entry, indexed by the triple <QNAME, QTYPE, QCLASS>, with the
   single atomic entry containing the entire answer, including the named
   RRset and any associated DNSSEC RRs. The resolver SHOULD discard the
   entire atomic entry when any of the RRs contained in it expire.

   A security-aware resolver SHOULD NOT cache data with invalid
   signatures under normal circumstances.  However, a security-aware
   resolver SHOULD take steps to rate limit the number of identical
   queries it generates, which may require the resolver to retain some
   data about recently generated queries. Conceptually, this is similar
   to negative caching [RFC2308], but since the resolver has no way of
   obtaining the appropriate caching TTL from received data in this
   case, the TTL will have to be set by the implementation.  This
   document refers data retained as part of such a rate limiting
   mechanism as the "BAD cache".




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4.1 Recursive Name Servers

   As explained in [I-D.ietf-dnsext-dnssec-intro], a security-aware
   recursive name server is an entity which acts in both the
   security-aware name server and security-aware resolver roles. This
   section uses the terms "name server side" and "resolver side" to
   refer to the code within a security-aware recursive name server which
   implements the security-aware name server role and the code which
   implements the security-aware resolver role, respectively.

   A security-aware recursive name server MUST NOT attempt to answer a
   query by piecing together cached data it received in response to
   previous queries that requested different QNAMEs, QTYPEs, or
   QCLASSes.  A security-aware recursive name server MUST NOT use NSEC
   RRs from one negative response to synthesize a response for a
   different query.  A security-aware recursive name server MUST NOT use
   a previous wildcard expansion to generate a response to a different
   query.

   The name server side of a security-aware recursive name server MUST
   pass the sense of the CD bit to the resolver side along with the rest
   of an initiating query, so that the resolver side will know whether
   whether or not it is required to verify the response data it returns
   to the name server side.

   The resolver side of a security-aware recursive name server MUST set
   the DO bit when sending requests, regardless of the state of the DO
   bit in the initiating request received by the name server side.  If
   the DO bit in an initiating query is not set, the name server side
   MUST strip any authenticating DNSSEC RRs from the response, but but
   MUST NOT strip any DNSSEC RRs that the initiating query explicitly
   requested.

   The resolver side MUST follow the usual rules for caching and
   negative caching which would apply to any security-aware resolver.

   If the name server side receives a query which matches an entry in
   the resolver side's BAD cache, the name server side's response
   depends on the setting of the CD bit in the original query.  If the
   CD bit is set, the name server side SHOULD return the data from the
   BAD cache; if the CD bit is not set, the name server side SHOULD
   return RCODE 2 (server failure).

   The name server side of a security-aware recursive name server MUST
   NOT set the AD bit in a response unless the name server considers all
   RRsets in the Answer or Authority sections of the response to be
   authentic, and SHOULD set the AD bit if and only if the name server
   considers all RRsets in the Answer section and any relevant negative



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   response RRs in the Authority section to be authentic.  How the name
   server side of a security-aware recursive name server determines
   whether an RRset is authentic depends on the origin of the RRset.  If
   the RRset came from the resolver side of the recursive name server
   (the normal case), recursive name server MUST follow the procedure
   described in Section 5.  If the RRset came from a zone for which the
   name server side of the recursive name server is authoritative, local
   policy MAY consider the RRset to be authentic without further
   verification simply because the RRset came from an authoritative
   zone, but the name server SHOULD NOT do so unless the it obtained the
   authoritative zone via secure means (such as a secure zone transfer
   mechanism), and MUST NOT do so unless this behavior has been
   configured explicitly.

4.2 Stub resolvers

   A security-aware stub resolver MUST include an EDNS [RFC2671] OPT
   pseudo-RR with the DO [RFC3225] bit set to one when sending queries.

   A security-aware stub resolver MUST support a message size of at
   least 1220 octets, SHOULD support a message size of 4000 octets, and
   MUST advertise the supported message size using the "sender's UDP
   payload size" field in the EDNS OPT pseudo-RR. A security-aware stub
   resolver MUST handle fragmented UDP packets correctly regardless of
   whether any such fragmented packets were received via IPv4 or IPv6.
   Please see [RFC3226] for discussion of these requirements.

   A security-aware stub resolver MUST support the DNSSEC RR types, at
   least to the extent of not mishandling responses just because they
   contain DNSSEC RRs.   A security-aware stub resolver MAY include the
   DNSSEC RRs returned by a security-aware recursive name server as part
   of the data that it the stub resolver hands back to the application
   which invoked it but is not required to do so.

   A security-aware stub resolver SHOULD NOT set the CD bit when sending
   queries, since, by definition, a security-aware stub resolver does
   not validate signatures and thus depends on the security-aware
   recursive name server to perform validation on its behalf.

   A security-aware stub resolver MAY chose to examine the setting of
   the AD bit in response messages that it receives in order to
   determine whether the security-aware recursive name server which sent
   the response claims to have cryptographically verified the data in
   the Answer and Authority sections of the response message.  Note,
   however, that the responses received by a security-aware stub
   resolver are heavily dependent on the local policy of the
   security-aware recursive name server, so as a practical matter there
   may be little practical value to checking the status of the AD bit



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   except perhaps as a debugging aid.  In any case, a security-aware
   stub resolver MUST NOT place any reliance on signature validation
   allegedly performed on its behalf except when the security-aware stub
   resolver obtained the data in question from a trusted security-aware
   recursive name server via a secure channel.














































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5. Authenticating DNS Responses

   In order to use DNSSEC RRs for authentication, a security-aware
   resolver requires preconfigured knowledge of at least one
   authenticated DNSKEY or DS RR.  The process for obtaining and
   authenticating this initial DNSKEY or DS RR is achieved via some
   external mechanism.  For example, a resolver could use some off-line
   authenticated exchange to obtain a zone's DNSKEY RR or obtain a DS RR
   that identifies and authenticates a zone's DNSKEY RR.  The remainder
   of this section assumes that the resolver has somehow obtained an
   initial set of authenticated DNSKEY RRs.

   An initial DNSKEY RR can be used to authenticate a zone's apex DNSKEY
   RRset.  To authenticate an apex DNSKEY RRset using an initial key,
   the resolver MUST:

   1.  Verify that the initial DNSKEY RR appears in the apex DNSKEY
       RRset, and verify that the DNSKEY RR has the Zone Key Flag
       (DNSKEY RDATA bit 7) set to one.

   2.  Verify that there is some RRSIG RR which covers the apex DNSKEY
       RRset, and that the combination of the RRSIG RR and the initial
       DNSKEY RR authenticates the DNSKEY RRset.  The process for using
       an RRSIG RR to authenticate an RRset is described in Section 5.3.

   Once the resolver has authenticated the apex DNSKEY RRset using an
   initial DNSKEY RR, delegations from that zone can be authenticated
   using DS RRs.  This allows a resolver to start from an initial key,
   and use DS RRsets to proceed recursively down the DNS tree obtaining
   other apex DNSKEY RRsets.  If the resolver were preconfigured with a
   root DNSKEY RR, and if every delegation had a DS RR associated with
   it, then the resolver could obtain and validate any apex DNSKEY
   RRset.  The process of using DS RRs to authenticate referrals is
   described in Section 5.2.

   Once the resolver has authenticated a zone's apex DNSKEY RRset,
   Section 5.3 shows how the resolver can use DNSKEY RRs in the apex
   DNSKEY RRset and RRSIG RRs from the zone to authenticate any other
   RRsets in the zone.  Section 5.4 shows how the resolver can use
   authenticated NSEC RRsets from the zone to prove that an RRset is not
   present in the zone.

   When a resolver indicates support for DNSSEC, a security-aware name
   server should attempt to provide the necessary DNSKEY, RRSIG, NSEC,
   and DS RRsets in a response (see Section 3).  However, a
   security-aware resolver may still receive a response which that lacks
   the appropriate DNSSEC RRs, whether due to configuration issues such
   as a security-oblivious recursive name server which accidentally



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   interfere with DNSSEC RRs or due to a deliberate attack in which an
   adversary forges a response, strips DNSSEC RRs from a response, or
   modifies a query so that DNSSEC RRs appear not to be requested.  The
   absence of DNSSEC data in a response MUST NOT by itself be taken as
   an indication that no authentication information exists.

   A resolver SHOULD expect authentication information from signed
   zones. A resolver SHOULD believe that a zone is signed if the
   resolver has been configured with public key information for the
   zone, or if the zone's parent is signed and the delegation from the
   parent contains a DS RRset.

5.1 Special Considerations for Islands of Security

   Islands of security (see [I-D.ietf-dnsext-dnssec-intro]) are signed
   zones for which it is not possible to construct an authentication
   chain to the zone from its parent.  Validating signatures within an
   island of security requires the validator to have some other means of
   obtaining a trusted zone key.  If a validator cannot obtain such a
   key, it will have to choose whether to accept the unvalidated
   responses or not based on local policy.

   All the normal processes for validating responses apply to islands of
   security.  The only difference between normal validation and
   validation within an island of security is in how the validator
   obtains a trusted starting point for the authentication chain.

5.2 Authenticating Referrals

   Once the apex DNSKEY RRset for a signed parent zone has been
   authenticated, DS RRsets can be used to authenticate the delegation
   to a signed child zone.  A DS RR identifies a DNSKEY RR in the child
   zone's apex DNSKEY RRset, and contains a cryptographic digest of the
   child zone's DNSKEY RR.  A strong cryptographic digest algorithm
   ensures that an adversary can not easily generate a DNSKEY RR that
   matches the digest.  Thus, authenticating the digest allows a
   resolver to authenticate the matching DNSKEY RR.  The resolver can
   then use this child DNSKEY RR to authenticate the entire child apex
   DNSKEY RRset.

   Given a DS RR for a delegation, the child zone's apex DNSKEY RRset
   can be authenticated if all of the following hold:

   o  The DS RR has been authenticated using some DNSKEY RR in the
      parent's apex DNSKEY RRset (see Section 5.3);

   o  The Algorithm and Key Tag in the DS RR match the Algorithm field
      and the key tag of a DNSKEY RR in the child zone's apex DNSKEY



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      RRset which, when hashed using the digest algorithm specified in
      the DS RR's Digest Type field, results in a digest value which
      matches the Digest field of the DS RR; and

   o  The matching DNSKEY RR in the child zone has the Zone Flag bit set
      to one, the corresponding private key has signed the child zone's
      apex DNSKEY RRset, and the resulting RRSIG RR authenticates the
      child zone's apex DNSKEY RRset.

   If the referral from the parent zone did not contain a DS RRset, the
   response should have included a signed NSEC RRset proving that no DS
   RRset exists for the delegated name (see Section 3.4).  A
   security-aware resolver MUST query the name servers for the parent
   zone for the DS RRset if the referral includes neither a DS RRset nor
   a NSEC RRset proving that the DS RRset does not exist (see Section
   4).

   If the resolver authenticates an NSEC RRset which proves that no DS
   RRset is present for this zone, then there is no authentication path
   leading from the parent to the child.  If the resolver has an initial
   DNSKEY or DS RR which belongs to the child zone or to any delegation
   below the child zone, this initial DNSKEY or DS RR MAY be used to
   re-establish an authentication path.  If no such initial DNSKEY or DS
   RR exists, the resolver can not authenticate RRsets in or below the
   child zone.

   Note that, for a signed delegation, there are two NSEC RRs associated
   with the delegated name.  One NSEC RR resides in the parent zone, and
   can be used to prove whether a DS RRset exists for the delegated
   name.  The second NSEC RR resides in the child zone, and identifies
   which RRsets are present at the apex of the child zone.  The parent
   NSEC RR and child NSEC RR can always be distinguished, since the SOA
   bit will be set in the child NSEC RR and clear in the parent NSEC RR.
   A security-aware resolver MUST use the parent NSEC RR when attempting
   to prove that a DS RRset does not exist.

5.3 Authenticating an RRset Using an RRSIG RR

   A resolver can use an RRSIG RR and its corresponding DNSKEY RR to
   attempt to authenticate RRsets.  The resolver first checks the RRSIG
   RR to verify that it covers the RRset, has a valid time interval, and
   identifies a valid DNSKEY RR.  The resolver then constructs the
   canonical form of the signed data by appending the RRSIG RDATA
   (excluding the Signature Field) with the canonical form of the
   covered RRset.  Finally, resolver uses the public key and signature
   to authenticate the signed data.  Section 5.3.1, Section 5.3.2, and
   Section 5.3.3 describe each step in detail.




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5.3.1 Checking the RRSIG RR Validity

   A security-aware resolver can use an RRSIG RR to authenticate an
   RRset if all of the following conditions hold:

   o  The RRSIG RR and the RRset MUST have the same owner name and the
      same class;

   o  The RRSIG RR's Signer's Name field MUST be the name of the zone
      that contains the RRset;

   o  The RRSIG RR's Type Covered field MUST equal the RRset's type;

   o  The number of labels in the RRset owner name MUST be greater than
      or equal to the value in the RRSIG RR's Labels field;

   o  The resolver's notion of the current time MUST be less than or
      equal to the time listed in the RRSIG RR's Expiration field;

   o  The resolver's notion of the current time MUST be greater than or
      equal to the time listed in the RRSIG RR's Inception field;

   o  The RRSIG RR's Signer's Name, Algorithm, and Key Tag fields MUST
      match the owner name, algorithm, and key tag for some DNSKEY RR in
      the zone's apex DNSKEY RRset;

   o  The matching DNSKEY RR MUST be present in the zone's apex DNSKEY
      RRset, and MUST have the Zone Flag bit (DNSKEY RDATA Flag bit 7)
      set to one.

   It is possible for more than one DNSKEY RR to match the conditions
   above.  In this case, the resolver can not predetermine which DNSKEY
   RR to use to authenticate the signature, MUST try each matching
   DNSKEY RR until the resolver has either validated the signature or
   has run out of matching keys to try.

   Note that this authentication process is only meaningful if the
   resolver authenticates the DNSKEY RR before using it to validate
   signatures.  The matching DNSKEY RR is considered to be authentic if:

   o  The apex DNSKEY RRset containing the DNSKEY RR is considered
      authentic; or

   o  The RRset covered by the RRSIG RR is the apex DNSKEY RRset itself,
      and the DNSKEY RR either matches an authenticated DS RR from the
      parent zone or matches a DS RR or DNSKEY RR which the resolver has
      been preconfigured to believe to be authentic.




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5.3.2 Reconstructing the Signed Data

   Once the RRSIG RR has met the validity requirements described in
   Section 5.3.1, the resolver needs to reconstruct the original signed
   data.  The original signed data includes RRSIG RDATA (excluding the
   Signature field) and the canonical form of the RRset.  Aside from
   being ordered, the canonical form of the RRset might also differ from
   the received RRset due to DNS name compression, decremented TTLs, or
   wildcard expansion.  The resolver should use the following to
   reconstruct the original signed data:

         signed_data = RRSIG_RDATA | RR(1) | RR(2)...  where

            "|" denotes concatenation

            RRSIG_RDATA is the wire format of the RRSIG RDATA fields
               with the Signature field excluded and the Signer's Name
               in canonical form.

            RR(i) = name | class | type | OrigTTL | RDATA length | RDATA

               name is calculated according to the function below

               class is the RRset's class

               type is the RRset type and all RRs in the class

               OrigTTL is the value from the RRSIG Original TTL field

               All names in the RDATA field are in canonical form

               The set of all RR(i) is sorted into canonical order.

            To calculate the name:
               let rrsig_labels = the value of the RRSIG Labels field

               let fqdn = RRset's fully qualified domain name in
                               canonical form

               let fqdn_labels = RRset's fully qualified domain name in
                               canonical form

               if rrsig_labels = fqdn_labels,
                   name = fqdn

               if rrsig_labels < fqdn_labels,
                  name = "*." | the leftmost rrsig_label labels of the
                                fqdn



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               if rrsig_labels > fqdn
                  the RRSIG RR did not pass the necessary validation
                  checks and MUST NOT be used to authenticate this
                  RRset.

   Section 5.5.1 gives an example of original name calculation.  The
   canonical forms for names and RRsets are defined in
   [I-D.ietf-dnsext-dnssec-records].

   NSEC RRsets at a delegation boundary require special processing.
   There are two distinct NSEC RRsets associated with a signed delegated
   name.  One NSEC RRset resides in the parent zone, and specifies which
   RRset are present at the parent zone.  The second NSEC RRset resides
   at the child zone, and identifies which RRsets are present at the
   apex in the child zone.  The parent NSEC RRset and child NSEC RRset
   can always be distinguished since only the child NSEC RRs will
   specify an SOA RRset exists at the name. When reconstructing the
   original NSEC RRset for the delegation from the parent zone, the NSEC
   RRs MUST NOT be combined with NSEC RRs from the child zone, and when
   reconstructing the original NSEC RRset for the apex of the child
   zone, the NSEC RRs MUST NOT be combined with NSEC RRs from the parent
   zone.

   Note also that each of the two NSEC RRsets at a delegation point has
   a corresponding RRSIG RR with an owner name matching the delegated
   name, and each of these RRSIG RRs is authoritative data associated
   with the same zone which contains the corresponding NSEC RRset.  If
   necessary, a resolver can tell these RRSIG RRs apart by checking the
   Signer's Name field.

5.3.3 Checking the Signature

   Once the resolver has validated the RRSIG RR as described in Section
   5.3.1 and reconstructed the original signed data as described in
   Section 5.3.2, the resolver can attempt to use the cryptographic
   signature to authenticate the signed data, and thus (finally!)
   authenticate the RRset.

   The Algorithm field in the RRSIG RR identifies the cryptographic
   algorithm to generate the signature.  The signature itself is
   contained in the Signature field of the RRSIG RDATA, and the public
   key to used generate the signature is contained in the Public Key
   field of the matching DNSKEY RR(s) (found in Section 5.3.1).
   [I-D.ietf-dnsext-dnssec-records] provides a list of algorithm types,
   and provides pointers to the documents that define each algorithm's
   use.

   Note that it is possible for more than one DNSKEY RR to match the



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   conditions in Section 5.3.1.  In this case, the resolver can only
   determine which DNSKEY RR by trying each matching key until the
   resolver either succeeds in validating the signature or runs out of
   keys to try.

   If the Labels field of the RRSIG RR is not equal to the number of
   labels in the RRset's fully qualified owner name, then the RRset is
   either invalid or the result of wildcard expansion.  The resolver
   MUST verify that wildcard expansion was applied properly before
   considering the RRset to be authentic.  Section 5.3.4 describes how
   to determine whether a wildcard was applied properly.

   If other RRSIG RRs also cover this RRSIG RR, the local resolver
   security policy determines whether the resolver also needs to test
   these RRSIG RRs, and determines how to resolve conflicts if these
   RRSIG RRs lead to differing results.

   If the resolver accepts the RRset as authentic, the resolver MUST set
   the TTL of the RRSIG RR and each RR in the authenticated RRset to a
   value no greater than the minimum of:

   o  The RRset's TTL as received in the response;

   o  The RRSIG RR's TTL as received in the response; and

   o  The value in the RRSIG RR's Original TTL field.


5.3.4 Authenticating A Wildcard Expanded RRset Positive Response

   If the number of labels in an RRset's fully qualified domain name is
   greater than the Labels field in the covering RRSIG RDATA, then the
   RRset and its covering RRSIG RR were created as a result of wildcard
   expansion.  Once the resolver has verified the signature as described
   in Section 5.3, the resolver must take additional steps to verify the
   non-existence of an exact match or closer wildcard match for the
   query.   Section 5.4 discusses these steps.

   Note that the response received by the resolver should include all
   NSEC RRs needed to authenticate the response (see Section 3.3).

5.4 Authenticated Denial of Existence

   A resolver can use authenticated NSEC RRs to prove that an RRset is
   not present in a signed zone.  Security-aware name servers should
   automatically include any necessary NSEC RRs for signed zones in
   their responses to security-aware resolvers.




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   Security-aware resolvers MUST first authenticate NSEC RRsets
   according to the standard RRset authentication rules described in
   Section 5.3, then apply the NSEC RRsets as follows:

   o  If the requested RR name matches the owner name of an
      authenticated NSEC RR, then the NSEC RR's type bit map field lists
      all RR types present at that owner name, and a resolver can prove
      that the requested RR type does not exist by checking for the RR
      type in the bit map.  Since the existence of the authenticated
      NSEC RR proves that the owner name exists in the zone, wildcard
      expansion could not have been used to match the requested RR owner
      name and type.

   o  If the requested RR name would appear after an authenticated NSEC
      RR owner name and before the name listed in that NSEC RR's Next
      Domain Name field according to the canonical DNS name order
      defined in [I-D.ietf-dnsext-dnssec-records], then no exact match
      for the requested RR name exists in the zone. However, it is
      possible that a wildcard could be used to match the requested RR
      owner name and type, so proving that the requested RRset does not
      exist also requires proving that no possible wildcard exists which
      could have been used to generate a positive response.

   To prove non-existence of an RRset, the resolver must be able to
   verify both that the queried RRset does not exist and that no
   relevant wildcard RRset exists.  Proving this may require more than
   one NSEC RRset from the zone.  If the complete set of necessary NSEC
   RRsets is not present in a response (perhaps due to truncation), then
   a security-aware resolver MUST resend the query in order to attempt
   to obtain the full collection of NSEC RRs necessary to verify
   non-existence of the requested RRset.   As with all DNS operations,
   however, the resolver MUST bound the work it puts into answering any
   particular query.

   Since a verified NSEC RR proves the existance of both itself and its
   corresponding RRSIG RR, a verifier MUST ignore the settings of the
   NSEC and RRSIG bits in an NSEC RR.

5.5 Examples

      Editors' note: perhaps  all of this should move to an appendix?


5.5.1 Example of Re-Constructing the Original Owner Name

   Suppose that a security-aware resolver receives a response containing
   an answer RRset with an owner name of is "www.a.b.c.example.com".
   This fully qualified domain name has 6 labels: "www", "a", "b", "c",



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   "example", and "com". What name the resolver should use when
   reconstructing the original signed data depends on the value of the
   RRSIG RR's Labels field.

   If the value of the RRSIG RR's Labels field is 6, then the RRSIG RR's
   Labels field matches the number of labels in the owner name, and the
   resolver should assume that this RRset is not the result of wildcard
   expansion.  The resolver should therefore use "www.a.b.c.example.com"
   as the owner name when reconstructing the original signed data for
   the signature check.

   If the value of the RRSIG RR's Labels field is less than 6, then the
   RRSIG RR's Labels count is less than the number of labels in the
   RRset's owner name, and the resolver should assume that this RRset is
   the result of wildcard expansion.  The resolver should therefore
   reconstruct the original owner name by replacing the labels which
   appear to be the result of wildcard expansion with a single "*."
   label.  For example, if the RRSIG RR's Labels field is 3, the
   resolver should reconstruct the original owner name by prepending
   "*." to the last 3 labels of the owner name of the answer RRset.
   Thus, the resolver should use "*.c.example.com" as the owner name
   when reconstructing the original signed data.

   If the value of the RRSIG RR's Labels field is greater than 6, then
   this RRSIG RR cannot possibly be valid for the answer RRset, and
   there is no point in attempting to validate the signature.

5.5.2 Examples of Authenticating a Response

      Editors' note: Eventually this will be an example of the
      authentication process for "www.example.com", starting from an
      initial root key.

      Editors' note: Eventually this will be an example of the
      authentication process for non-existent "www.a.b.c.example.com",
      starting from an initial root key.















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6. IANA Considerations

   [I-D.ietf-dnsext-dnssec-records] contains a review of the IANA
   considerations introduced by DNSSEC.  The additional IANA
   considerations discussed in this document:

   [RFC2535] reserved the CD and AD bits in the message header.  The
   meaning of the AD bit was redefined in [I-D.ietf-dnsext-ad-is-secure]
   and the meaning of both the CD and AD bit are restated in this
   document.  No new bits in the DNS message header are defined in this
   document.

   [RFC2671] introduced EDNS and [RFC3225] reserved the DNSSEC OK bit
   and defined its use.  The use is restated but not altered in this
   document.




































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7. Security Considerations

   This document describes how the DNS security extensions use public
   key cryptography to sign and authenticate DNS resource record sets.

   DNSSEC introduces a number of denial of service issues.  These issues
   will also be addressed in a future version of these security
   considerations.

   Please see [I-D.ietf-dnsext-dnssec-intro] for general security
   considerations related to DNSSEC.








































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8. Acknowledgements

   This document was created from the input and ideas of several members
   of the DNS Extensions Working Group and working group mailing list.
   The co-authors of this draft would like to express their thanks for
   the comments and suggestions received during the revision of these
   security extension specifications.












































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Normative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, November 1987.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC1982]  Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
              August 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2181]  Elz, R. and R. Bush, "Clarifications to the DNS
              Specification", RFC 2181, July 1997.

   [RFC2671]  Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC
              2671, August 1999.

   [RFC3225]  Conrad, D., "Indicating Resolver Support of DNSSEC", RFC
              3225, December 2001.

   [RFC3226]  Gudmundsson, O., "DNSSEC and IPv6 A6 aware server/resolver
              message size requirements", RFC 3226, December 2001.

   [I-D.ietf-dnsext-dnssec-intro]
              Arends, R., Austein, R., Larson, M., Massey, D. and S.
              Rose, "DNS Security Introduction and Requirements",
              draft-ietf-dnsext-dnssec-intro-06 (work in progress),
              September 2003.

   [I-D.ietf-dnsext-dnssec-records]
              Arends, R., Austein, R., Larson, M., Massey, D. and S.
              Rose, "Resource Records for DNS Security Extensions",
              draft-ietf-dnsext-dnssec-records-04 (work in progress),
              September 2003.














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Informative References

   [RFC2308]  Andrews, M., "Negative Caching of DNS Queries (DNS
              NCACHE)", RFC 2308, March 1998.

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

   [RFC2930]  Eastlake, D., "Secret Key Establishment for DNS (TKEY
              RR)", RFC 2930, September 2000.

   [RFC2931]  Eastlake, D., "DNS Request and Transaction Signatures (
              SIG(0)s)", RFC 2931, September 2000.

   [I-D.ietf-dnsext-delegation-signer]
              Gudmundsson, O., "Delegation Signer Resource Record",
              draft-ietf-dnsext-delegation-signer-15 (work in progress),
              June 2003.

   [I-D.ietf-dnsext-wcard-clarify]
              Halley, B. and E. Lewis, "Clarifying the Role of Wild Card
              Domains in the Domain Name System",
              draft-ietf-dnsext-wcard-clarify-01 (work in progress),
              August 2003.

   [I-D.ietf-dnsext-ad-is-secure]
              Gudmundsson, O. and B. Wellington, "Redefinition of DNS AD
              bit", draft-ietf-dnsext-ad-is-secure-06 (work in
              progress), June 2002.


Authors' Addresses

   Roy Arends
   Telematica Instituut
   Drienerlolaan 5
   7522 NB  Enschede
   NL

   EMail: roy.arends@telin.nl











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   Matt Larson
   VeriSign, Inc.
   21345 Ridgetop Circle
   Dulles, VA  20166-6503
   USA

   EMail: mlarson@verisign.com


   Rob Austein
   Internet Software Consortium
   40 Gavin Circle
   Reading, MA  01867
   USA

   EMail: sra@isc.org


   Dan Massey
   USC Information Sciences Institute
   3811 N. Fairfax Drive
   Arlington, VA  22203
   USA

   EMail: masseyd@isi.edu


   Scott Rose
   National Institute for Standards and Technology
   100 Bureau Drive
   Gaithersburg, MD  20899-8920
   USA

   EMail: scott.rose@nist.gov

















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Appendix A. Algorithm For Handling Wildcard Expansion

   For zone (Z) and a name (N) that may occur in Z, the following
   algorithm finds all wildcard RRsets that match N or returns an NSEC
   RRset that proves no wildcard expansion matches N. The algorithm was
   written for clarity, not efficiency:

         0. INPUT: a name (N) and a zone (Z).
            INIT: NSEC_SET = NULL

         1. Construct S = sequence of all names in Z, sorted
                          into canonical order.

         2. If N exists in S
               There is an exact match for N.
               Return all RRsets associated with N
            Else
               Add the name that would immediately
               precede N in S to NSEC_SET.
            EndIf

         3. Replace the leftmost label of N with *

         4. If N exists in S and answers the query
               There is a positive wildcard match for N.
               Return all RRsets associated with N
            Else
               Add the NSEC for name that would immediately
               precede N in S to NSEC_SET.
               Return the NSEC_SET.
            EndIf

         5. Remove the leading * from N.

         6. If N exists in S
               There is a name that terminates the wildcard search.
               Add the NSEC for N to NSEC_SET and return NSEC_SET.
            Else
               Add the NSEC for name that would immediately
               precede N in S to NSEC_SET.
               Return the NSEC_SET.
            EndIf









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Appendix B. Signed Zone Example

   The following example shows a (small) complete signed zone.

   example.       3600 IN SOA ns1.example. bugs.ns1.example. (
                              1064876255
                              3600
                              300
                              3600000
                              3600
                              )
                  3600 RRSIG  SOA 1 1 3600 20031029215736 (
                              20030929215736 4638 example.
                              Bo6PBV6UOrnCzptCZg0lTQQqsZ4qqIn16vbA
                              KQobYD2wNxs5hxNYlvNRlNPB0nfSD9o2daBE
                              v0Q/Q5mEanr2R28a62PHwkHNwHUx/spGWAGJ
                              h5u28d5wMNQQvMsFgB+kSSnNEcL1Z7uLjRal
                              ahgGvtiSMzzSS7n65xfxc1X78Nw= )
                  3600 NS     ns1.example.
                  3600 NS     ns2.example.
                  3600 RRSIG  NS 1 1 3600 20031029215736 (
                              20030929215736 4638 example.
                              WeJdApmzK+GIrOQKYmkABF5POWu5SDU6opwd
                              wOjWrVFGRNhFHe1Z/KZwT1Ii5YjH2X9dTRRh
                              YG3U/wcqvWLJ1882FoUZakwmtzGFotdONcs3
                              DzhFMxTawVlBb+MLsPj8J2GuZiR28eTyPB6i
                              TYq3Ed0R9VStJwtiKmoXqubFAr0= )
                  3600 MX     1 xx.example.
                  3600 RRSIG  MX 1 1 3600 20031029215736 (
                              20030929215736 4638 example.
                              eBXNS2Vi/MhqX76VCIlpbK4yq9UWzvYcSBV9
                              Cx0t6rl9CWOpdFVzV/lL0wyVYQjZXBlZ1gpo
                              djLXl0QTEE+9MrRO3c8j7NyVsOEJQdnWdEAW
                              BL8f+F3fwayjj5dIsq1NngF8neGXROao1bJM
                              5gmIc/F6gzUL3/KyJA8zPF2fUVA= )
                  3600 NSEC   a.example. NS SOA MX RRSIG NSEC
                  3600 RRSIG  NSEC 1 1 3600 20031029215736 (
                              20030929215736 4638 example.
                              t3VabTtmQ3uEgohzbuHKk2bFEDqYWa3hgTi2
                              D1Sv+eN+IkV1xExBvsvuE6Oovf+QlDqV7sU/
                              XP2kRzob5V9N40xQCZMBFx2GgAim8px788EX
                              ZuS7u0fKeHfaP/2sSTktGnpK77Mx4fM6RK8x
                              DBRONckIWXn2chGDeicQuEHjhfQ= )
                  3600 DNSKEY 256 3 1 (
                              AQPbGuRKgswzNd2Qb7ck1Tdai9FFbapP3mUO
                              G80mSowM5s9aMao+JOeFl/4f33cs2hWHznn3
                              LZ5EuIlA/lvvG+f5h46OvCR+CFXHmqEPyMmd
                              kiCdJmHcvRuMIzekHM2DSDcG7i1lZG/jXvaG



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                              mK5G3NeHjqssh1AujDaqHFf5IRIeQQ==
                              )
                  3600 DNSKEY 257 3 1 (
                              AQPGkQLwyHHfD8nkDxZSbErTBHLYdOKkVIoq
                              SJkBnpfABtFdiJBgZYcjCNExAFjlc/olW42g
                              TJYBRjs1INw3I08/h43L595Iq8fyhEyBoGOR
                              +6db+Q3oQ9G2EKpfMEPDLU6f7gYrHpzDHIjO
                              rsSftzmRYHou70oVQ7aBjd9ePPCOVw==
                              )
                  3600 RRSIG  DNSKEY 1 1 3600 20031029215736 (
                              20030929215736 4638 example.
                              GMZI2r4bwFYpKIs0Dv//4aWg5HhpzMBkm5Vk
                              4KFg4hEkOabYgWoBJdZdjRBTrjwkrtiPH9KF
                              kJKlzFfeeELbFEfhgZ3SujDqNQmGfoZ1i7a2
                              lH47jc1JOeos75e9QK8fUFjIxOF8fkZNO9Fx
                              lOyOxNDJPATE3Wm+AX0SmQSJ3XY= )
   a.example.     3600 IN NS  ns1.a.example.
                  3600 IN NS  ns2.a.example.
                  3600 DS     23677 1 1 (
                              F248F32298280A061736C93FB078A51C17CC
                              C291 )
                  3600 RRSIG  DS 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              k6fA3VfeR5UHu9L/+4y8HJrUubVHBdyFzMaa
                              8EpDYqw3vYEVsrL5YvXwoqrSZsSAxdIrUXoB
                              SzjbKFOq6HRxXjuLsJ2TLT90p6mg9ZHL57jH
                              FfmrNPuq58QwRWvwuOyaExJWEdxMIEIbvETz
                              YJs3G/9tNte9i25YtAuLHbD2UqY= )
                  3600 NSEC   ai.example. NS DS RRSIG NSEC
                  3600 RRSIG  NSEC 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              tQbGVL6yxb2vBQ5ItcQ1XQyxNxz3+zHTTkgs
                              T/WSk9YXr+swug7h+Wq20RPXfsEl7lVMi/By
                              d60s6Q7lEibGucIQCLLx0Xe68zQOmWx7fmU6
                              iSDTQgc7TOsG/blDba7MiRENTeI6iynyZHw9
                              gURpK8RlfEPb7O98rrYLWZbzg3o= )
   ns1.a.example. 3600 IN A   192.0.2.5
   ns2.a.example. 3600 IN A   192.0.2.6
   ai.example.    3600 IN A   192.0.2.9
                  3600 RRSIG  A 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              UCegsbGngHOwgyxevtBrCSsV6Jv6OxGWApvY
                              RsbwL2XZBFc4saU6Zujiz8i2urkVLSlFM2MM
                              OHuEMN5E+cjGDjqfaI8O5eILapsGRqHUPM9t
                              5wCOb9BqANn03UUFUhAnKBkv3fHFM5hg+IZQ
                              vVNUzslGEBlQ0SJZkWJcCtRDo5c= )
                  3600 HINFO  "KLH-10" "ITS"
                  3600 RRSIG  HINFO 1 2 3600 20031029215736 (



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                              20030929215736 4638 example.
                              CP6bRkIyQ3FnhsBWO63uQN1QtJse8mWNRTf2
                              jXqR33dekEfKNhlQtw0yzepa7lX75uyQTAlP
                              NBBK73Zlim5g1bw3ulLl0vXnTpQRSK80SJw9
                              uPPTYBDq68jMKn1a3RvGnR5MynQR33UY2vGT
                              6IAiGfqY/zYFXWSIsmJr0875PQ0= )
                  3600 AAAA   2001:db8::f00:baa9
                  3600 RRSIG  AAAA 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              VnpRe+HGt+mCalDopO4wtHtRvs9CKdjr3FoG
                              zv8BPFvC1FdDJAjxpAgJs6Ihx+174Hl+jlZU
                              Z3HOd0MBwch0XH1UDcU0/opQRquW+oYwV3E4
                              esgKhsy9EUj3NtoW/GQ/1dJEbuUZah4/IPGH
                              KI0DhRWJC/iKs6J963WLNdPnwKk= )
                  3600 NSEC   b.example. A HINFO AAAA RRSIG NSEC
                  3600 RRSIG  NSEC 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              A7MtS+oATUFf6t3nj/0GL7lBbt86ozzkbbJM
                              J3tLwFkGebf1XV+MnpPeSzeRXm4QeqohDvVZ
                              U5SluyOHT397x4WQPwHCRXojos1lQnWhPUji
                              qjKaXLVRHv4x2O2fzWu0OE65GJkL6zAnFqCL
                              SpV8hBOC+EAcLjnuAi5DJJlONmc= )
   b.example.     3600 IN NS  ns1.b.example.
                  3600 IN NS  ns2.b.example.
                  3600 NSEC   ns1.example. NS RRSIG NSEC
                  3600 RRSIG  NSEC 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              lGZ+rJ1vtIEtLjXKG4Iruipq6KoXrre89QHZ
                              dBgSPcomROrsSElhUBFLcl2+KMCnKCqtEJZ7
                              YPOTK07WCwFU6Rek+xD+OuuJrQRWTbiCmFMX
                              N9ZMk87lkIWHAXMk1YM3f1/FUytbb8RI8RfH
                              u2x/e3zoBQdHAId3LCOO9jYDzCc= )
   ns1.b.example. 3600 IN A   192.0.2.7
   ns2.b.example. 3600 IN A   192.0.2.8
   ns1.example.   3600 IN A   192.0.2.1
                  3600 RRSIG  A 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              u/uV4xcu7KSVV+3Vtg8O0qTGlGHeFKU1vBQJ
                              x1QKLtolw/ZstzqIuRBI5fuF4JYxSwMoaI7b
                              JBFyZ3KkCCK88r1VjZTkicNvFG7RO3G2faxb
                              MualMbGfhcexJzRcoZsIXSb3+qtbAr4aKF7c
                              fdZ587NLR1Ns2GraGTztUDMSK/A= )
                  3600 NSEC   ns2.example. A RRSIG NSEC
                  3600 RRSIG  NSEC 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              bsz0NVY6tQ0kmIpKOR3QHNEradwR39uNikey
                              jQIr7TMOvNVDX6tVBNoDuKxUy6zHR5CS6oBs
                              nN5OPPKEjTdOGWUfHavSZgZGT7b8xfL++Ahi



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                              Cgeg0ofB6Ext7KfeMkTrxP/8BsDMJm8R8Ome
                              I2mIq/WvuXTr2XKcJDbxYIdSyss= )
   ns2.example.   3600 IN A   192.0.2.2
                  3600 RRSIG  A 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              mCzjw1wydcnYx0d7kbPbJTXVw+FnksdLnTmq
                              DrIdy269MeGL4AGJSV8g8Gt0Zbq3hGo6+/Tz
                              S9VIp4QZtKgRZ1nlI0XQOlkASOLPjvo7hHRr
                              PPiFqGyznqy9+QHdIalqTO4BOrfS3f5bIgJW
                              IGUMRh8nFi+wnG09+OH46IlkB9s= )
                  3600 NSEC   *.w.example. A RRSIG NSEC
                  3600 RRSIG  NSEC 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              FS6W/8Na26DIs1DYB1Xhhxc1GyRlzj5XkG/3
                              pY6H6PQGc/nP6CVM1eHEkmvYAG8kWfk9ZdDZ
                              64cOb2tisSH1o7WMLg7hWUS5nnXyxyyj5/Gs
                              n3CpVCDptq9JnQe+jjH0empKdbTYoeVIX8h/
                              2aw1RkmYb4LbuhP0uwN/lZqQVik= )
   *.w.example.   3600 IN MX  1 ai.example.
                  3600 RRSIG  MX 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              MHxP6z3ozpA9AICDnEW0T06o2GlIOtj0+oGm
                              TC4nqveQj2QSKOEUNXgVaUkBTT9F/FIVy9q+
                              FAAe4SXnBcVpIvTVN2NhU4Jm9976hU8HTEfi
                              EMlnhmn4vJ1qZ+DI1WgWK+iKSU/N6ShdN/Fi
                              G7zd/X4PmuWIIYG+5IAzmtB2UJs= )
                  3600 NSEC   x.w.example. MX RRSIG NSEC
                  3600 RRSIG  NSEC 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              tXBqjlbdFl70S+dzovir86EQBHavroozeo4f
                              Spsc9BlorSdTTSwbf7lh+GRIS0hCtaJxMFog
                              0XhGhO6sn1Yai3s7NeV6viQpy8gPfJ0wfr9Y
                              H1nYv76o6oXX2KlGTJrd4J7f7Hxz2DsOWVoK
                              w1LXOATBvP/kCRgmq4KdFNwTiBc= )
   x.w.example.   3600 IN MX  1 xx.example.
                  3600 RRSIG  MX 1 3 3600 20031029215736 (
                              20030929215736 4638 example.
                              p/BQOuDk4Wg3pZreH6kmxws0A1hNYIkJTTlP
                              rHoI9T/HMfA50p/qnXQHxgYh1IDnsxjeswaE
                              LL7B/q0QxmaT1/0wNbZTn58/rqDSpV43Qxjl
                              QHK0fDgp6al4VNxvK+uIJIHO525jCH146BEC
                              +tqUhrmtTxtItfpV/8Q7i6+B2bY= )
                  3600 NSEC   x.y.w.example. MX RRSIG NSEC
                  3600 RRSIG  NSEC 1 3 3600 20031029215736 (
                              20030929215736 4638 example.
                              c2/unp4ewGHNJIOVKiw9O/aA+PfXJ5Thwjt4
                              EyleUaXFp01H5RkDVxMVicJEHcfslqfzF8XP
                              M9pPTwU7DPAFrxXo71pMez/EqA3pnhxnUcEi



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                              lVextpfIxIZam0Oj5Q+nCLJJs95Q3I8E5J29
                              IgHVoBYahu8hE0DycgzLredhC5A= )
   x.y.w.example. 3600 IN MX  1 xx.example.
                  3600 RRSIG  MX 1 4 3600 20031029215736 (
                              20030929215736 4638 example.
                              nwe5rxko6mbV2f0edTn0/H1CbDd8T4ZHg2Wg
                              Os3Lh5Rz092PVbAnbzCp4Y95MdPPwMUd3cKk
                              h7tvjBJgPPBhAWufdv2uVcq2lnINs1+LsJH7
                              CtJobsu9LxcORCkcYEKG1bc4fInPPnuUnlXD
                              JYEmK1UOpYTDRx+lKLRI5tLzKmc= )
                  3600 NSEC   xx.example. MX RRSIG NSEC
                  3600 RRSIG  NSEC 1 4 3600 20031029215736 (
                              20030929215736 4638 example.
                              UjlRFPbR2LzHtiP+CDGsJnaSo0iyooOkZ2By
                              vyqOGHg+0OudJ4/+VYC/8C0dJNRUzAAm17GG
                              ox272n3P0BHERCeegWAFCjYCARhZwkfpq8sQ
                              ynkJRjpFlkxgdSFiHDZOAQz/s0a9ZaFDKP27
                              rKbS4qvhL+dfOnPBPNI099W7EAw= )
   xx.example.    3600 IN A   192.0.2.10
                  3600 RRSIG  A 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              irvnPlRadiUTTM3feA/mNNKnxRIRY7vZ0r3d
                              foc+IgbvYJeHi8UYThPrinjF2SPcwQ29g+6h
                              aFA8ne9ZpRwL1lEQ6U3OTGLKd1OtGCTizEmN
                              fgmPU/wIUuNaR7AG4i6FekWhciHbrjfRF/NN
                              zJKlxAUeVRQ2ufYCoSY7wa6cIV4= )
                  3600 HINFO  "KLH-10" "TOPS-20"
                  3600 RRSIG  HINFO 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              NL6VSnSkuPX41EgJChuPiVF9JzIsJ/p7pQ61
                              DG8oWhtZjTP1uYWdwHPMM3EDxQykJBwJShE9
                              5Mg7myUpRFAuLHZJZ35227AZ6+eo0UoikJSA
                              opuXW50OLYARZTy4lRqSUU41B5Km1vvYaIoq
                              hjNlRggyhvEmSNw4kvl5w99jqKg= )
                  3600 AAAA   2001:db8::f00:baaa
                  3600 RRSIG  AAAA 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              wkkCfIYfNeQ2YK0fL/bceo9oONGfZNkp/MnQ
                              yllq11xEoelJbWjqlS7RbfUViOVbrxJbV+8j
                              AYnLEC3/YGdoDUeVBPk2hqfGB8vMZfsu/d1Y
                              bhcMej6fIoXj/q4HIXNSD9UcP0CNtLR6n7Bq
                              ndtF5V/pM6xI0tiE51KudVttsJI= )
                  3600 NSEC   example. A HINFO AAAA RRSIG NSEC
                  3600 RRSIG  NSEC 1 2 3600 20031029215736 (
                              20030929215736 4638 example.
                              fi2La99VLlZhIPUgGd/Fd6MH8wJZ6ziSPW34
                              k214lDIQQBlu0X4V0z4DcZ/PDBeqvKOORmEI
                              AhZLwELtWv5XSAmALYUr3Rrtp/H066R4EpAu



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                              YrS4pZ8/QFM+HnPUcofSK3IzLBucXsnDSYr0
                              fQ5nfoBQ++eHo+IEohbqrwnE60E= )

   The apex DNSKEY set includes two DNSKEY RRs, and the DNSKEY RDATA
   Flags indicate that each of these DNSKEY RRs is a zone key.  One of
   these DNSKEY RRs also has the SEP flag set and has been used to sign
   the apex DNSKEY RRset; this is the key which should be hashed to
   generate a DS record to be inserted into the parent zone.  The other
   DNSKEY is used to sign all the other RRsets in the zone.

   The zone includes a wildcard entry "*.w.example".  Note that the name
   "*.w.example" is used in constructing NSEC chains, and that the RRSIG
   covering the "*.w.example" MX RRset has a label count of 2.

   The zone also includes two delegations.  The delegation to
   "b.example" includes an NS RRset, glue address records, and an NSEC
   RR; note that only the NSEC RRset is signed.  The delegation to
   "a.example" provides a DS RR; note that only the NSEC and DS RRsets
   are signed.
































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   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION



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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.











































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