STIR Out of Band Architecture and Use Cases
draft-rescorla-stir-fallback-01

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Network Working Group                                        E. Rescorla
Internet-Draft                                                   Mozilla
Intended status: Standards Track                             J. Peterson
Expires: May 4, 2017                                             Neustar
                                                        October 31, 2016

              STIR Out of Band Architecture and Use Cases
                  draft-rescorla-stir-fallback-01.txt

Abstract

   Existing work has defined ways to secure the identity of SIP calls,
   but the in-band mechanisms defined in that work do not properly
   transit the PSTN.  This document defines out-of-band mechanisms which
   do not require modifying the messages that pass over the PSTN.

Status of This Memo

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   Copyright (c) 2016 IETF Trust and the persons identified as the
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Rescorla & Peterson        Expires May 4, 2017                  [Page 1]
Internet-Draft                STIR Fallback                 October 2016

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Operating Environments  . . . . . . . . . . . . . . . . . . .   4
   4.  Dataflows . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Case 1: VoIP to PSTN Call . . . . . . . . . . . . . . . .   6
     5.2.  Case 2: Two Smart PSTN endpoints  . . . . . . . . . . . .   6
     5.3.  Case 3: PSTN to VoIP Call . . . . . . . . . . . . . . . .   6
     5.4.  Case 4: Gateway Out-of-band . . . . . . . . . . . . . . .   7
   6.  Solution Architecture . . . . . . . . . . . . . . . . . . . .   7
     6.1.  Credentials and Phone Numbers . . . . . . . . . . . . . .   7
     6.2.  Solution Architecture . . . . . . . . . . . . . . . . . .   8
     6.3.  Security Analysis . . . . . . . . . . . . . . . . . . . .   9
     6.4.  Substitution Attacks  . . . . . . . . . . . . . . . . . .   9
   7.  Call Placement Service Discovery and Interface  . . . . . . .  10
   8.  Some Potential Enhancements . . . . . . . . . . . . . . . . .  11
     8.1.  Encrypted PASSporTs . . . . . . . . . . . . . . . . . . .  11
       8.1.1.  Credential Lookup . . . . . . . . . . . . . . . . . .  12
     8.2.  Federated Call Placement Services . . . . . . . . . . . .  12
     8.3.  Escalation to VoIP  . . . . . . . . . . . . . . . . . . .  13
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  13
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  13
   12. Informative References  . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   The STIR problem statement [RFC7340] describes widespread problems
   enabled by impersonation in the telephone network, including illegal
   robocalling, voicemail hacking, and swatting.  As telephone services
   are increasingly migrating onto the Internet, and using Voice over IP
   (VoIP) protocols such as SIP [RFC3261], it is necessary for these
   protocols to support stronger identity mechanisms to prevent
   impersonation.  For example, [I-D.ietf-stir-rfc4474bis] defines an
   Identity header of SIP requests capable of carrying a PASSporT
   [I-D.ietf-stir-passport] object in SIP as a means to
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