pretty Easy privacy (pEp): Header Protection
draft-luck-lamps-pep-header-protection-01

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Last updated 2019-03-11
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Network Working Group                                            C. Luck
Internet-Draft                                            pEp Foundation
Intended status: Informational                              B. Hoeneisen
Expires: September 13, 2019                                      Ucom.ch
                                                          March 12, 2019

              pretty Easy privacy (pEp): Header Protection
               draft-luck-lamps-pep-header-protection-01

Abstract

   Issues with email header protection in S/MIME have been recently
   raised in the IETF LAMPS Working Group.  The need for amendments to
   the existing specification regarding header protection was expressed.

   The pretty Easy privacy (pEp) implementations currently use a
   mechanism quite similar to the currently standardized message
   wrapping for S/MIME.  The main difference is that pEp is using PGP/
   MIME instead, and adds space for carrying public keys next to the
   protected message.

   In LAMPS voices have also been expressed, that whatever mechanism
   will be chosen, it should not be limited to S/MIME, but also
   applicable to PGP/MIME.

   This document aims to contribute to this discussion and share pEp
   implementation experience with email header protection.

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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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 13, 2019.

Luck & Hoeneisen       Expires September 13, 2019               [Page 1]
Internet-Draft            pEp Header Protection               March 2019

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  The OpenPGP Radix-64  . . . . . . . . . . . . . . . . . .   4
       2.1.1.  Radix-64 in the Context of MIME Messages  . . . . . .   5
   3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Interactions  . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Protection Levels . . . . . . . . . . . . . . . . . . . .   6
   4.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  General Requirements  . . . . . . . . . . . . . . . . . .   7
       4.1.1.  Sending Side  . . . . . . . . . . . . . . . . . . . .   7
       4.1.2.  Receiving Side  . . . . . . . . . . . . . . . . . . .   8
     4.2.  Additional Requirements for Backward-Compatibility With
           Legacy Clients Unaware of Header Protection . . . . . . .   8
       4.2.1.  Sending side  . . . . . . . . . . . . . . . . . . . .   8
       4.2.2.  Receiving side  . . . . . . . . . . . . . . . . . . .   8
     4.3.  Additional Requirements for Backward-Compatibility with
           Legacy Header Protection Systems (if supported) . . . . .   8
       4.3.1.  Sending Side  . . . . . . . . . . . . . . . . . . . .   9
       4.3.2.  Receiving Side  . . . . . . . . . . . . . . . . . . .   9
   5.  Message Format for progressive header disclosure  . . . . . .   9
     5.1.  Design principles . . . . . . . . . . . . . . . . . . . .   9
     5.2.  Compatibility . . . . . . . . . . . . . . . . . . . . . .  10
     5.3.  Inner message . . . . . . . . . . . . . . . . . . . . . .  11
     5.4.  Content-Type property "forwarded" . . . . . . . . . . . .  11
     5.5.  Outer message . . . . . . . . . . . . . . . . . . . . . .  12
     5.6.  Transport message . . . . . . . . . . . . . . . . . . . .  14
     5.7.  S/MIME Compatibility  . . . . . . . . . . . . . . . . . .  15
   6.  Candidate Header Fields for Header Protection . . . . . . . .  15
   7.  Stub Outside Headers  . . . . . . . . . . . . . . . . . . . .  15
   8.  Processing Incoming Email under Progressive Header Disclosure  16
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