Authenticated Received Chain (ARC) Protocol
draft-ietf-dmarc-arc-protocol-10

Document Type Active Internet-Draft (dmarc WG)
Last updated 2017-12-19
Replaces draft-andersen-arc
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DMARC Working Group                                          K. Andersen
Internet-Draft                                                  LinkedIn
Intended status: Standards Track                            B. Long, Ed.
Expires: June 22, 2018                                            Google
                                                           S. Jones, Ed.
                                                                     TDP
                                                           S. Blank, Ed.
                                                                ValiMail
                                                       December 19, 2017

              Authenticated Received Chain (ARC) Protocol
                    draft-ietf-dmarc-arc-protocol-10

Abstract

   The Authenticated Received Chain (ARC) protocol creates a mechanism
   whereby a series of handlers of an email message can conduct
   authentication of the email message as it passes among them on the
   way to its destination, and record the status of that authentication
   at each step along the handling path, for use by the final recipient
   in making choices about the disposition of the message.  Changes in
   the message that might break DKIM or DMARC can be identified through
   the ARC set of header fields.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on June 22, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Andersen, et al.          Expires June 22, 2018                 [Page 1]
Internet-Draft                ARC-Protocol                 December 2017

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Definitions and Terminology . . . . . . . . . . . . . . . . .   6
     3.1.  Referenced Definitions  . . . . . . . . . . . . . . . . .   6
   4.  Protocol Elements and Features  . . . . . . . . . . . . . . .   7
     4.1.  Features of the ARC Protocol  . . . . . . . . . . . . . .   7
       4.1.1.  Chain of Custody  . . . . . . . . . . . . . . . . . .   7
       4.1.2.  Optional Participation  . . . . . . . . . . . . . . .   8
       4.1.3.  Only one ARC Chain (One Chain to Rule Them All) . . .   8
       4.1.4.  All Failures are Permanent  . . . . . . . . . . . . .   8
       4.1.5.  Benign nature of an ARC Set . . . . . . . . . . . . .   9
       4.1.6.  Key Management  . . . . . . . . . . . . . . . . . . .   9
       4.1.7.  Trace Information . . . . . . . . . . . . . . . . . .   9
   5.  The ARC Header Fields . . . . . . . . . . . . . . . . . . . .   9
     5.1.  Instance ('i=') Tag . . . . . . . . . . . . . . . . . . .   9
       5.1.1.  Valid Range for Instance Tags . . . . . . . . . . . .  10
     5.2.  ARC-Authentication-Results (AAR)  . . . . . . . . . . . .  10
       5.2.1.  ptypes and properties for arc-info  . . . . . . . . .  11
     5.3.  ARC-Message-Signature (AMS) . . . . . . . . . . . . . . .  11
     5.4.  ARC-Seal (AS) . . . . . . . . . . . . . . . . . . . . . .  12
       5.4.1.  The 'cv' Tag  . . . . . . . . . . . . . . . . . . . .  12
       5.4.2.  Implicit Header Fields  . . . . . . . . . . . . . . .  13
   6.  Verifier Actions  . . . . . . . . . . . . . . . . . . . . . .  13
   7.  Signer Actions  . . . . . . . . . . . . . . . . . . . . . . .  15
   8.  Usage of ARC and Chain Validity . . . . . . . . . . . . . . .  16
     8.1.  Relationship between DKIM-Signature and AMS signing
           scopes  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     8.2.  Assessing Chain Validity Violations . . . . . . . . . . .  16
     8.3.  Marking and Sealing "cv=fail" (Invalid) Chains  . . . . .  16
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