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Versions: 00                                                            
Distributed Mobility Management [dmm]                         C. Perkins
Internet-Draft                                                 Futurewei
Expires: April 29, 2015                                    S. Gundavelli
                                                          Cisco Networks
                                                        October 26, 2014


                     Privacy considerations for DMM
                    draft-perkins-dmm-privacy-00.txt

Abstract

   Recent events have emphasized the importance of privacy in protocol
   design.  This document describes ways in which DMM protocol designs
   and DMM networks can reduce certain threats to privacy.

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
   Task Force (IETF).  Note that other groups may also distribute
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   This Internet-Draft will expire on April 29, 2015.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Pseudo-home Address . . . . . . . . . . . . . . . . . . . . .   3
   3.  Source IPv6 Address Utilization . . . . . . . . . . . . . . .   3
   4.  MPTCP . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  MNID  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   6.  MAC Randomization . . . . . . . . . . . . . . . . . . . . . .   3
   7.  Non-issues  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   4
     10.2.  Informative References . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   There have been many recent disclosures about breaches of privacy,
   and the all-too-frequent news stories about identity theft, credit
   card services infiltrated, and other serious threats.  An extensive
   IAB discussion about the nature of such breaches is available
   [RFC6462].

   Within the IETF, there has been a greatly increased awareness of how
   to mitigate these threats by improved protocol design [RFC6973].  One
   major danger is the dissemination of long-lived identifiers as part
   of protocol transactions.  When a long-lived identifier can be
   observed in such transactions with disparate applications and
   servers, a history can be constructed about the person associated
   with that long-lived identier.  Remarkably accurate predications can
   then be made about the future behavior of that person -- a clear
   threat to privacy.  Notably, such predictions are not at all illegal,
   and yet most people would consider the ability to make such
   predictions as an unwanted outcome of using IETF protocols.
   Similarly, knowledge about the recent history of a person as inferred
   by tracking a long-lived identifier can provide strong hints about
   how to analyze the earlier actions (including personal interactions)
   of that person.

   This document details the mechanisms as currently understood within
   mobility management protocols in order to better avoid perpetuating
   potential threats to privacy within DMM.  As a general rule,
   trackable information in protocol messages should be avoided as much
   as possible [RFC4882].

   The following mechanisms are discussed.




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   o  Recommend implementation of pseudo-home address feature [RFC5726].
   o  Source IPv6 address for data packets could be used only for the
      lifetime of the application used for that address
   o  MPTCP may be useful for additional protection against traffic
      analysis
   o  MNID may contain confidential information.  Packets in which the
      MNID extension contains a confidential identifer should be
      encrypted.
   o  MAC randomization, recent Apple announcement

2.  Pseudo-home Address

   Recommend consideration of using the pseudo-home address feature from
   RFC 5726[RFC5726].  This has the effect of reducing or eliminating
   the ability to track the movement events related to a mobile node,
   which otherwise might be visible to snooping devices located anywhere
   between the mobile node and home agent.

3.  Source IPv6 Address Utilization

   Source IPv6 address for data packets could be used only for the
   lifetime of the application used for that address.  For this purpose,
   each new address can be generated as detailed in [RFC4941].

4.  MPTCP

   MPTCP [RFC6824] can be used for additional protection against traffic
   analysis.  This can be done by spreading traffic over several
   associated TCP endpoints, either randomly, or as chosen to emulate
   traffic patterns for unrelated applications.

5.  MNID

   MNID [RFC4283] may contain confidential information.  Control packets
   in which the MNID extension contains a confidential identifer should
   be encrypted.  Alternatively, the MN-ID could be generated based on
   CUI (Chargeable user identity), or some other temporary identifier.
   In that way, the access network would never have access to the real
   MN-ID.

6.  MAC Randomization

   While not under the jurisdiction of the IETF, MAC addresses are often
   included within IETF protocols.  For the purposes of better
   protecting privacy, there has been much recent discussion about
   randomization of MAC addresses.  As one example, see the recent
   announcement about Randomized Wi-Fi addresses by Apple Computers
   [apple-privacy].



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   Various protocols derived from Mobile IP are designed using certain
   assumptions related to the use of same MAC address.  For example, LMA
   looks up a MN session using the MN's MAC address.  This breaks when
   the MAC address changes.  It is recommended that mobility management
   protocols reduce or eliminate dependence on MAC addresses.  Some
   specific suggestions include the following:

   o  Require the MN to present a new MAC address in each access attach.
   o  Allow MN to present multiple MAC addresses during a single attach.
   o  Handover keys and other key material should be able to deal with
      MAC address changes.

7.  Non-issues

   There are many cases where nonces or cookies are used for temporary
   use during control signal sequences -- for instance nonces as used
   with Mobile IP route optimization [RFC6275].  Insofar as these fields
   are used only temporarily, they are not often useful for tracking
   user movements.  Even so, when the same value is used for a request
   and returned in a response, a small bit of information is leaked
   about the status of a protocol transaction.  This may not be
   important, but if so can be averted by encryption.

8.  Security Considerations

   This document is entirely concerned with raising important security
   considerations, but does not specify any new protocol that may affect
   existing security designs.

9.  IANA Considerations

   This document does not suggest any IANA actions.

10.  References

10.1.  Normative References

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC4283]  Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
              Chowdhury, "Mobile Node Identifier Option for Mobile IPv6
              (MIPv6)", RFC 4283, November 2005.

   [RFC4285]  Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
              Chowdhury, "Authentication Protocol for Mobile IPv6", RFC
              4285, January 2006.



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   [RFC4882]  Koodli, R., "IP Address Location Privacy and Mobile IPv6:
              Problem Statement", RFC 4882, May 2007.

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, September 2007.

   [RFC5726]  Qiu, Y., Zhao, F., and R. Koodli, "Mobile IPv6 Location
              Privacy Solutions", RFC 5726, February 2010.

   [RFC6275]  Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
              in IPv6", RFC 6275, July 2011.

   [RFC6462]  Cooper, A., "Report from the Internet Privacy Workshop",
              RFC 6462, January 2012.

   [RFC6824]  Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
              "TCP Extensions for Multipath Operation with Multiple
              Addresses", RFC 6824, January 2013.

   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973, July
              2013.

10.2.  Informative References

   [apple-privacy]
              Apple Computer, , "Randomized Wi-Fi Addresses", 2014,
              <https://www.apple.com/privacy/privacy-built-in/>.

Authors' Addresses

   Charles E. Perkins
   Futurewei Inc.
   2330 Central Expressway
   Santa Clara, CA  95050
   USA

   Phone: +1-408-330-4586
   Email: charliep@computer.org










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   Sri Gundavelli
   Cisco Networks
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: sgundave@cisco.com












































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