DNS-Based Authentication of Named Entities (DANE) Bindings for OpenPGP
RFC 7929

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Internet Engineering Task Force (IETF)                        P. Wouters
Request for Comments: 7929                                       Red Hat
Category: Experimental                                       August 2016
ISSN: 2070-1721

 DNS-Based Authentication of Named Entities (DANE) Bindings for OpenPGP

Abstract

   OpenPGP is a message format for email (and file) encryption that
   lacks a standardized lookup mechanism to securely obtain OpenPGP
   public keys.  DNS-Based Authentication of Named Entities (DANE) is a
   method for publishing public keys in DNS.  This document specifies a
   DANE method for publishing and locating OpenPGP public keys in DNS
   for a specific email address using a new OPENPGPKEY DNS resource
   record.  Security is provided via Secure DNS, however the OPENPGPKEY
   record is not a replacement for verification of authenticity via the
   "web of trust" or manual verification.  The OPENPGPKEY record can be
   used to encrypt an email that would otherwise have to be sent
   unencrypted.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  This document is a product of the Internet Engineering
   Task Force (IETF).  It represents the consensus of the IETF
   community.  It has received public review and has been approved for
   publication by the Internet Engineering Steering Group (IESG).  Not
   all documents approved by the IESG are a candidate for any level of
   Internet Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7929.

Wouters                       Experimental                      [Page 1]
RFC 7929                  DANE for OpenPGP Keys              August 2016

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

Wouters                       Experimental                      [Page 2]
RFC 7929                  DANE for OpenPGP Keys              August 2016

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Experiment Goal . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  The OPENPGPKEY Resource Record  . . . . . . . . . . . . . . .   5
     2.1.  The OPENPGPKEY RDATA Component  . . . . . . . . . . . . .   6
       2.1.1.  The OPENPGPKEY RDATA Content  . . . . . . . . . . . .   6
       2.1.2.  Reducing the Transferable Public Key Size . . . . . .   7
     2.2.  The OPENPGPKEY RDATA Wire Format  . . . . . . . . . . . .   7
     2.3.  The OPENPGPKEY RDATA Presentation Format  . . . . . . . .   7
   3.  Location of the OPENPGPKEY Record . . . . . . . . . . . . . .   8
   4.  Email Address Variants and Internationalization
       Considerations  . . . . . . . . . . . . . . . . . . . . . . .   9
   5.  Application Use of OPENPGPKEY . . . . . . . . . . . . . . . .  10
     5.1.  Obtaining an OpenPGP Key for a Specific Email Address . .  10
     5.2.  Confirming that an OpenPGP Key is Current . . . . . . . .  10
     5.3.  Public Key UIDs and Query Names . . . . . . . . . . . . .  10
   6.  OpenPGP Key Size and DNS  . . . . . . . . . . . . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
     7.1.  MTA Behavior  . . . . . . . . . . . . . . . . . . . . . .  12
     7.2.  MUA Behavior  . . . . . . . . . . . . . . . . . . . . . .  13
     7.3.  Response Size . . . . . . . . . . . . . . . . . . . . . .  14
     7.4.  Email Address Information Leak  . . . . . . . . . . . . .  14
     7.5.  Storage of OPENPGPKEY Data  . . . . . . . . . . . . . . .  14
     7.6.  Security of OpenPGP versus DNSSEC . . . . . . . . . . . .  15
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
     8.1.  OPENPGPKEY RRtype . . . . . . . . . . . . . . . . . . . .  15
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  15
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  16