Using DANE to Associate OpenPGP public keys with email addresses
draft-wouters-dane-openpgp-01

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Network Working Group                                         P. Wouters
Internet-Draft                                                   Red Hat
Intended status: Standards Track                        October 21, 2013
Expires: April 24, 2014

    Using DANE to Associate OpenPGP public keys with email addresses
                     draft-wouters-dane-openpgp-01

Abstract

   OpenPGP is a message format for email (and file) encryption, that
   lacks a standarized lookup mechanism to obtain OpenPGP public keys.
   This document specifies a standarized method for securely publishing
   and locating OpenPGP public keys in DNS using a new OPENPGPKEY DNS
   Resource Record.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on April 24, 2014.

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   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Wouters                  Expires April 24, 2014                 [Page 1]
Internet-Draft        DANE for OpenPGP public keys          October 2013

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  The OPENPGPKEY record presence  . . . . . . . . . . . . . . .   3
   3.  The OPENPGPKEY Resource Record  . . . . . . . . . . . . . . .   4
     3.1.  Location of the OpenPGPKEY record . . . . . . . . . . . .   4
     3.2.  The OPENPGPKEY RDATA Format . . . . . . . . . . . . . . .   5
   4.  OpenPGP public key considerations . . . . . . . . . . . . . .   5
     4.1.  Public Key UIDs and email addresses . . . . . . . . . . .   5
     4.2.  Public Key UIDs and IDNA  . . . . . . . . . . . . . . . .   5
     4.3.  Public Key UIDs and synthesized DNS records . . . . . . .   5
     4.4.  Public Key size and DNS record size . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
     5.1.  Email address information leak  . . . . . . . . . . . . .   7
     5.2.  OpenPGP security and DNSSEC . . . . . . . . . . . . . . .   7
     5.3.  MTA behaviour . . . . . . . . . . . . . . . . . . . . . .   7
     5.4.  MUA behaviour . . . . . . . . . . . . . . . . . . . . . .   8
     5.5.  Email client behaviour  . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     6.1.  OPENPGPKEY RRtype . . . . . . . . . . . . . . . . . . . .   9
   7.  Generating OPENPGPKEY RRdata  . . . . . . . . . . . . . . . .   9
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   To encrypt a message to a target recipient using OpenPGP [RFC4880],
   possession of the recipient's OpenPGP public key is required.  To
   obtain that public key, two problems need to be solved by the
   sender's email client, MUA or MTA.  Where does one find the
   recipient's public key and how does one trust that the found key
   actually belongs to the intended recipient.

   Obtaining a public key is not a straightforward process as there are
   no trusted standarized locations for publishing OpenPGP public keys
   indexed by email address.  Instead, OpenPGP clients rely on "well-
   known key servers" that are accessed using the web based HKP protocol
   or manually by users using a variety of differently formatted front-
   end web pages.

   Currently deployed key servers have no method of validating any
   uploaded OpenPGP public key.  The key servers simply store and
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