Guidance for NSEC3 parameter settings
draft-hardaker-dnsop-nsec3-guidance-02

Document Type Active Internet-Draft (individual)
Authors Wes Hardaker  , Viktor Dukhovni 
Last updated 2021-02-19
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Network Working Group                                        W. Hardaker
Internet-Draft                                                   USC/ISI
Intended status: Best Current Practice                       V. Dukhovni
Expires: August 23, 2021                                 Bloomberg, L.P.
                                                       February 19, 2021

                 Guidance for NSEC3 parameter settings
                 draft-hardaker-dnsop-nsec3-guidance-02

Abstract

   NSEC3 is a DNSSEC mechanism providing proof of non-existence by
   promising there are no names that exist between two domainnames
   within a zone.  Unlike its counterpart NSEC, NSEC3 avoids directly
   disclosing the bounding domainname pairs.  This document provides
   guidance on setting NSEC3 parameters based on recent operational
   deployment experience.

Status of This Memo

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   This Internet-Draft will expire on August 23, 2021.

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   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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Hardaker & Dukhovni      Expires August 23, 2021                [Page 1]
Internet-Draft                    title                    February 2021

   the Trust Legal Provisions and are provided without warranty as
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . .   3
   2.  Recommendation for zone publishers  . . . . . . . . . . . . .   3
     2.1.  Algorithms  . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Flags . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.3.  Iterations  . . . . . . . . . . . . . . . . . . . . . . .   3
     2.4.  Salt  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Best-practice for zone publishers . . . . . . . . . . . . . .   5
   4.  Recommendation for validating resolvers . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  Operational Considerations  . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .   6
   Appendix B.  Github Version of this document  . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   As with NSEC [RFC4035], NSEC3 [RFC5155] provides proof of non-
   existence that consists of signed DNS records establishing the non-
   existence of a given name or associated Resource Record Type (RRTYPE)
   in a DNSSEC [RFC4035] signed zone.  In the case of NSEC3, however,
   the names of valid nodes in the zone are obfuscated through (possibly
   multiple iterations of) hashing via SHA-1. (currently only SHA-1 is
   in use within the Internet).

   NSEC3 also provides "opt-out support", allowing for blocks of
   unsigned delegations to be covered by a single NSEC3 record.  Opt-out
   blocks allow large registries to only sign as many NSEC3 records as
   there are signed DS or other RRsets in the zone - with opt-out,
   unsigned delegations don't require additional NSEC3 records.  This
   sacrifices the tamper-resistance proof of non-existence offered by
   NSEC3 in order to reduce memory and CPU overheads.

   NSEC3 records have a number of tunable parameters that are specified
   via an NSEC3PARAM record at the zone apex.  These parameters are the
   Hash Algorithm, processing Flags, the number of hash Iterations and
   the Salt.  Each of these has security and operational considerations
   that impact both zone owners and validating resolvers.  This document
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