Secure Telephone Identity Problem Statement and Requirements
RFC 7340

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Internet Engineering Task Force (IETF)                       J. Peterson
Request for Comments: 7340                                 NeuStar, Inc.
Category: Informational                                   H. Schulzrinne
ISSN: 2070-1721                                      Columbia University
                                                           H. Tschofenig
                                                          September 2014

      Secure Telephone Identity Problem Statement and Requirements

Abstract

   Over the past decade, Voice over IP (VoIP) systems based on SIP have
   replaced many traditional telephony deployments.  Interworking VoIP
   systems with the traditional telephone network has reduced the
   overall level of calling party number and Caller ID assurances by
   granting attackers new and inexpensive tools to impersonate or
   obscure calling party numbers when orchestrating bulk commercial
   calling schemes, hacking voicemail boxes, or even circumventing
   multi-factor authentication systems trusted by banks.  Despite
   previous attempts to provide a secure assurance of the origin of SIP
   communications, we still lack effective standards for identifying the
   calling party in a VoIP session.  This document examines the reasons
   why providing identity for telephone numbers on the Internet has
   proven so difficult and shows how changes in the last decade may
   provide us with new strategies for attaching a secure identity to SIP
   sessions.  It also gives high-level requirements for a solution in
   this space.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7340.

Peterson, et al.              Informational                     [Page 1]
RFC 7340                 STIR Problem Statement           September 2014

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Table of Contents

   1. Introduction ....................................................3
   2. Problem Statement ...............................................4
   3. Terminology .....................................................6
   4. Use Cases .......................................................6
      4.1. VoIP-to-VoIP Call ..........................................7
      4.2. VoIP-PSTN-VoIP Call ........................................7
      4.3. PSTN-to-VoIP Call ..........................................8
      4.4. VoIP-to-PSTN Call ..........................................9
      4.5. PSTN-VoIP-PSTN Call .......................................10
      4.6. PSTN-to-PSTN Call .........................................11
   5. Limitations of Current Solutions ...............................11
      5.1. P-Asserted-Identity .......................................12
      5.2. SIP Identity ..............................................14
      5.3. VIPR ......................................................17
   6. Environmental Changes ..........................................19
      6.1. Shift to Mobile Communication .............................19
      6.2. Failure of Public ENUM ....................................19
      6.3. Public Key Infrastructure Developments ....................20
      6.4. Prevalence of B2BUA Deployments ...........................20
      6.5. Stickiness of Deployed Infrastructure .....................20
      6.6. Concerns about Pervasive Monitoring .......................21
      6.7. Relationship with Number Assignment and Management ........21
   7. Basic Requirements .............................................22
   8. Acknowledgments ................................................23
   9. Security Considerations ........................................23
   10. Informative References ........................................23