Using DANE to Associate OpenPGP public keys with email addresses
draft-wouters-dane-openpgp-00

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Network Working Group                                         P. Wouters
Internet-Draft                                                   Red Hat
Intended status: Standards Track                           July 15, 2013
Expires: January 16, 2014

    Using DANE to Associate OpenPGP public keys with email addresses
                     draft-wouters-dane-openpgp-00

Abstract

   OpenPGP is a message format for email (and file) encryption, that
   lacks a standarized secure 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
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on January 16, 2014.

Copyright Notice

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

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  The OPENPGPKEY Resource Record . . . . . . . . . . . . . . . .  4
     2.1.  Location of the OpenPGPKEY record  . . . . . . . . . . . .  4
     2.2.  The OPENPGPKEY RDATA Format  . . . . . . . . . . . . . . .  5
   3.  OpenPGP public key considerations  . . . . . . . . . . . . . .  5
     3.1.  Public Key UIDs and email addresses  . . . . . . . . . . .  5
     3.2.  Public Key UIDs and IDNA . . . . . . . . . . . . . . . . .  5
     3.3.  Public Key UIDs and synthesized DNS records  . . . . . . .  5
     3.4.  Public Key size and DNS record size  . . . . . . . . . . .  6
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  6
     4.1.  Email address information leak . . . . . . . . . . . . . .  7
     4.2.  OpenPGP security and DNSSEC  . . . . . . . . . . . . . . .  7
     4.3.  MTA behaviour  . . . . . . . . . . . . . . . . . . . . . .  7
     4.4.  MUA behaviour  . . . . . . . . . . . . . . . . . . . . . .  8
     4.5.  Email client behaviour . . . . . . . . . . . . . . . . . .  8
     4.6.  Subject: line encryption . . . . . . . . . . . . . . . . .  9
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
     5.1.  OPENPGPKEY RRtype  . . . . . . . . . . . . . . . . . . . .  9
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     7.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10

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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 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 different front-end web pages.

   Currently deployed key servers have no method of validating any
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