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Versions: 00 01                                                         
Network Working Group                                           S. Brim
Internet Draft                                               M. Linsner
Intended status: Informational                            B. McLaughlin
Expires: September 15, 2011                                 K. Wierenga
                                                         March 14, 2011

                           Mobility and 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
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   This Internet-Draft will expire on September 15, 2011.

Copyright Notice

   Copyright (c) 2011 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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   Section 4.e of the Trust Legal Provisions and are provided without
   warranty as described in the Simplified BSD License.


   Choices in Internet mobility architectures may have profound effects
   on privacy.  This draft revisits this issue, stresses its increasing
   importance, and makes recommendations.

Table of Contents

   1. Introduction...................................................2
   2. The risks of Being Traceable...................................3
   3. Current Guidance on Privacy....................................4
   4. Basic Mobility Requirements....................................6
   5. Avoid Making a Mobile Node Traceable...........................7
   6. Recommendations................................................9
   7. Security Considerations.......................................10
   8. IANA Considerations...........................................10
   9. Acknowledgements..............................................10
   10. Normative References.........................................10

1. Introduction

   Significant steps are being taken right now to make the Internet's
   architecture more scalable and robust in routing, addressing,
   multihoming, mobility, including work on locator/identifier
   separation.  However, since the Internet infrastructure is rapidly
   becoming an essential part of daily life for people around the
   world, our architectural changes need to take fundamental social
   issues and rights into account as a primary consideration.  One of
   those is privacy, and in this case particularly privacy of end-user
   personal data.  If we do not, we run the risk of colliding with
   established IETF principles (see for example [RFC3693]) as well as
   legal policy in many countries around the world.

   When the Internet was designed, IP addresses were associated with
   timesharing machines and not with particular users.  In the 1980s it
   began to be likely that a device and thus an IP address would be
   associated with a single user.  Now a single IP address is very
   likely to be associated with a specific human being.  Meanwhile, at
   the top of the stack, there has been a convergence of life functions
   using single devices using specific addresses.  A person now uses
   his mor her personal device and associated IP address for any
   activities: work, shopping, talking, exchanging mail and files,
   reading, listening to music, etc.

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   It is this convergence at both the top and bottom of the stack - to
   a single person per device and to many applications on that device -
   - that makes the social issues more and more significant in IETF
   work. People use the Internet for many, more personal, activities
   than before.  The Internet needs to fulfill the obligations expected
   of a communications system essential to modern human society.  Our
   lower layer protocol designs have privacy implications beyond their
   intended scope.

2. The risks of Being Traceable

   Issues with revealing geographic location are well-established
   elsewhere.  For example the RAND review of the European Data
   Directive [RAND-EDPD] points out that "the interpretation of
   location data (e.g. which locations are visited, suggesting which
   shops are frequented, and which products and services are bought),
   may in the future permit the identification of the health, social,
   sexual or religious characteristics of the data subject" (section
   3.3.1).  The less well-known problem that this document focuses on
   is tracing the movement of mobile devices.  Because mobile devices
   are used for so many things, any possibility of tracing them has
   significant, probably unpredictable, social implications, perhaps
   more so than revealing a single location. If an association can be
   made between a mobile device and a person at any location, if that
   device can be traced to a different geographic location then the
   association with the person can be inferred, usually correctly, even
   if the person believes they are anonymous at the new location.
   Consider scenarios such as:

   - You are looking for a job, interviewing at other companies over
   your lunch hour, but you don't want your current management to know.

   - You are planning a surprise gift or party for your spouse and are
   visiting specialty stores.

   - You are a journalist gathering information on a corrupt politician
   from sources who wish to hide that they are dealing with you.

   - You are infiltrating an organized crime ring and don't want them
   to know when you sneak in the back door of police headquarters.

   - You are a very famous person trying to avoid paparazzi and
   assassins who are able to find you sporadically.

   Mobility mechanisms need to take this issue into account.  Obviously
   a mobile node must be reachable somehow, but a mobile node must be
   able to hide its actual movement from public view if it wishes.

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3. Current Guidance on Privacy

   In an attempt to define what privacy means to an end-user and the
   Internet, we have to start narrowing down the broad definition of
   "the state or condition of being free from being observed or
   disturbed by other people."

   In this section we will examine a sampling of policies in various
   geographies to gain a sense of regulatory guidance around privacy.
   The data extracted from these policies will offer guidance in
   evaluating solution architectures and what pieces of data might be
   deemed a privacy risk.

   The Internet exists within the remit of telecommunications
   legislation.  It beholds the Internet community to be aware of and
   be able to adapt to the requirements of the legislative ecosystem to
   which our protocols and Architectures are to be deployed.

   Here we will outline The European Union position as an example as it
   has existed for many years and has been well debated and understood
   globally.  To be clear this is not a endorsement of specific
   legislation but is used merely an example of the requirements our
   combined work will need operate within.

   In October 1995 the EU introduced Directive 95/46/EC for the
   protection of individuals with regard to the processing of personal
   data.  Included in Objective 1 of this directive is "fundamental
   rights and freedoms of natural persons, and in particular their
   right to privacy with respect to the processing of 'personal data'.

   Personal data was defined as: 'personal data' shall mean any
   information relating to an identified or identifiable natural person
   ('data subject'); an identifiable person is one who can be
   identified, directly or indirectly, in particular by reference to an
   identification number or to one or more factors specific to his
   physical, physiological, mental, economic, cultural or social

   Directive 2002/58/EC included the following explicit mention of the
   Internet: The Internet is overturning traditional market structures
   by providing a common, global infrastructure for the delivery of a
   wide range of electronic communications services. Publicly available
   electronic communications services over the Internet open new

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   possibilities for users but also new risks for their personal data
   and privacy.

   Also explicitly mentioned is requirement for consent for a valued
   added service beyond the contracted communications service.

   "(30) Systems for the provision of electronic communications
   networks and services should be designed to limit the amount of
   personal data necessary to a strict minimum. Any activities related
   to the provision of the electronic communications service that go
   beyond the transmission of a communication and the billing thereof
   should be based on aggregated, traffic data that cannot be related
   to subscribers or users. Where such activities cannot be based on
   aggregated data, they should be considered as value added services
   for which the consent of the subscriber is required."

   DIRECTIVE 2009/136/EC includes in section 56 explicit mention of

   "To achieve this aim, it is necessary to ensure that all fundamental
   rights of individuals, including the right to privacy and data
   protection, are safeguarded. When such devices are connected to
   publicly available electronic communications networks or make use of
   electronic communications services as a basic infrastructure, the
   relevant provisions of Directive 2002/58/EC (Directive on privacy
   and electronic communications), including those on security, traffic
   and location data and on confidentiality, should apply."

   It should be noted that the legislative framework is evolving just
   as society and technology is evolving. A new principle is now
   proposed that rather than retrofitting privacy systems should be
   designed with privacy in mind. In 2009 a consultative document for
   the EU was published which discussed the technological requirements
   for Privacy by Design

   "Technological standards should be developed and taken into
   consideration in the phase of system analysis by hardware and
   software engineers, so that difficulties in defining and specifying
   requirements deriving from the principle of 'privacy by design' are

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   minimized. Such standards may be general or specific with regard to
   various processing purposes and technologies.

4. Basic Mobility Requirements

   A mobile node may need to be reachable by others, or it may act
   purely as a client of Internet-based services.  Even if it is purely
   a client, it still needs at least two things:

   - An authentication and authorization identifier that it can use
   with each access network it connects to.  (Not required for open
   access networks.)

   - A Layer 3 way for its correspondents to get packets back to it.
   This may no longer be simple due to potential innovations in routing

   In addition, if the mobile node wants to be reachable as a peer or
   to offer services, it needs a few more things:

   - An identifier (or identifiers) by which the node may be found by
   others, and a mechanism by which this identifier can be mapped to IP
   addresses/locators.  Examples are domain names, SIP URIs, and the
   corresponding services.

   - An IP address/locator for initially contacting the mobile node.
   This does not have to be associated with the mobile node's actual
   topological location.  It can instead be associated with a
   rendezvous point or agent.

   - A mechanism for "route optimization", whereby such an agent can be
   eliminated from a data path between the mobile node and a

   - An identifier or identifiers by which the mobile node can
   authenticate itself to its correspondents during initial contact,
   route optimization, and/or change of topological location.  These
   identifiers can be at any layer, from 2 to 7.  They can be
   associated with the mobile device's whole IP stack, individual
   transport sessions, or individual application instances.

   - Identifiers by which the mobile node can be referred to by third

   If all mobile nodes are reduced to being clients only -- if they are

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   willing to register with servers in order to use the Internet and
   have others be able to reach them -- then there are fewer
   requirements.  However, over the evolution of the Internet we have
   seen several times that it is not good to give up the symmetry of
   Internet communication and "permission-free" networking, i.e. the
   ability for anyone anywhere to communicate as a peer with other
   nodes on the Internet.  For the rest of this document we assume that
   the IETF still wants to retain this model.

   Every identifier listed above has a scope in which it needs to be
   known, but it is only required to be known in that scope.  For
   example, an access authentication identifier only needs to be known
   to the mobile node, the access network, and a trusted third party (a
   mobile node's home network administration, or a bank, etc.).  A
   session identifier only needs to be known among the parties using
   it, but not by the access network.

5. Avoid Making a Mobile Node Traceable

   As a mobile node moves, if L3 or higher layer mobility mechanisms
   are used it will change its IP addresses/locators.  The Internet
   already has sophisticated publicly available services for
   determining where a node is based on IP address alone.  These
   mechanisms are not always precise or accurate, but they are in very
   many cases and even imprecise information is information.  Protocol
   designers must assume that whatever IP address or locator a node
   has, it is likely that there is a service to turn that into a
   geographic location.

   The tracing problem occurs when it is possible for a third party to
   correlate IP addresses/locators and something unique about the
   mobile node.  Data can be gathered either through monitoring traffic
   or by    accessing public information.  It does not have to be done
   continuously -- periodic snapshots can make the mobile node just as
   vulnerable.  Once the data is gathered, the third party can search
   for correlations.

   Using identifiers for multiple purposes makes leakage of tracing
   information more likely.  Different entities in different scopes may
   know different things about a mobile node or a person.  Using
   overlapping identifiers mixes scopes and may make new, perhaps
   unexpected, correlations easier.  For example if an access
   identifier such as a mobile phone's IMEI (hard-coded and not
   changeable, primarily used for access authentication) is also used
   for session continuity, or is registered in an Internet database
   service that is    publicly accessible, changes in that device's IP
   addresses (and thus geographic location) can be traced.

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   Long-lasting identifiers make correlation easier as a device moves.
   They should not be used in scopes where they are not necessary.

   The biggest concern is if information that makes a mobile node
   traceable is required to be publicly available in order for the
   Internet to function.  If it is, it can be accessed not only without
   the mobile node's consent but even without its knowledge, perhaps
   without any audit trail of who is accessing the information that
   could be looked at after the fact.  Some architecture for mobility
   and/or routing and addressing described in [I-D.irtf-rrg-
   recommendation] assume the use of DNS or other public mapping
   systems.  In these, the mobile node is required to publish a
   mapping between its identifier and its current IP addresses/locators
   in order to be reachable, even if a mobile node is acting purely as
   a client (because otherwise packets would not get back to it).  This
   architectural assumption removes all of the mobile node's freedom of
   choice about how much confidentiality to preserve -- either it
   exposes all of its movement to all of the world or it is simply not
   reachable.  Public information systems like DNS are not designed to
   support confidentiality.

   MIPv6's "home agent" [I-D.ietf-mext-rfc3775bis] is an example of how
   to avoid this problem: Contact with a mobile node is initially
   through a home agent, a rendezvous point for both data and control
   traffic.  The home agent acts on behalf of the mobile node and
   encapsulates traffic to it.  After an exchange of packets, the
   mobile node may decide, on its own, if it wants to reveal its
   topological location, and thus probably its geographic location, to
   the   correspondent node.  It controls its own location information.
   The decision to reveal it can be based on anything, including local

   The principle of hiding information that can expose geographic
   location in both data and control planes, and deferring revealing
   more until the mobile node or its agent decides what it wants to do,
   is essential.  This can be included in any mobility architecture
   that    is designed to allow it and does not insist on exposing
   location to a wide audience in order to gain efficiency.  The
   obvious way to do it is an indirection mechanism such as a home
   agent, but this is just one way to do it.  Any way will do.

   Monitoring is a more subtle issue than exposure in public services,
   but still real, even if the mobile node is client-only.  If packets
   contain an identifier that uniquely identifies the mobile node for
   some period of time, someone able to gather data on packet traffic
   can easily trace the mobile node's movements as the IP
   address/locator changes.  It is not necessary for the watcher to be

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   able to gather this information in real time if it can access logs
   gathered by others.  Here, approaches to the problem are more
   difficult to    define because there is a conflict between three
   goals: to avoid overhead, to preserve session continuity with low
   delay, and to keep control over location information.  Some designs
   such already try to find their balance.  All protocol work should
   consider the tradeoffs with privacy and explicitly find a balance

6. Recommendations

   Members of the Internet community who are creating or reviewing
   proposed architectural changes, particularly in mobility but also in
   other areas that impinge on mobility such as routing and addressing,
   should consider the following points:

   - Architectural changes MUST avoid requiring the exposer of a
   mapping between any of a node's identifiers and IP
   addresses/locators to unknown observers.  If they require exposure,
   they will experience a head-on collision with basic principles of
   the IETF and with       privacy policies around the world.  It will
   simply not be acceptable to require the loss of this much individual

   - An architectural proposal MAY make it possible to use public
   information systems to optimize traffic flow, but ideally it should
   do so without sacrificing privacy.  If it cannot do so without
   sacrificing privacy, the default case built into the
   architecture SHOULD be to preserve privacy instead of optimizing.
   The reason is that most users will not change defaults, and the
   default be one of privacy, only moving away from it by customer

   - If possible, information about who is gathering data about a user
   SHOULD be available to that user.  Everyone deserves to know who is
   watching them.

   - Proposals SHOULD address the issue of loss of geographic location
   privacy due to monitoring of packets crossing the Internet, and find
   an explicit balance between conflicting goals.

   - Protocols SHOULD avoid using identifiers for multiple purposes.
   Different identifier scopes do not need to overlap. Confidentiality
   boundaries can be established by clearly defining limited

   - Protocols SHOULD avoid using long-lasting identifiers in scopes

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   where they are not necessary.

   7. Security Considerations

   In a sense this entire document is about security.

   8. IANA Considerations

   This document makes no request of IANA

   Note to RFC Editor: this section may be removed on publication as an

   9. Acknowledgements

   Thanks to many with whom we have discussed this issue in recent

   This document was prepared using 2-Word-v2.0.template.dot.

   10. Normative References


   Perkins, C., Johnson, D., and J. Arkko, "Mobility  Support in IPv6",
   draft-ietf-mext-rfc3775bis-08 (work in progress), October 2010.


   Li, T., "Recommendation for a Routing Architecture", draft-irtf-rrg-
   recommendation-14 (work in progress), September 2010.


   Robinson, N., Graux, H., Botterman, M., and L. Valeri, "Review of
   the European Data Protection Directive", May 2009.


   Bradner, S., "Key words for use in RFCs to Indicate Requirement
   Levels", BCP 14, RFC 2119, March 1997.


   Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. Polk,

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   "Geopriv Requirements", RFC 3693, February 2004.

   Authors' Addresses

      Scott Brim

      Email: scott.brim@gmail.com

      Marc Linsner

      Email: mlinsner@cisco.com

      Bryan McLaughlin

      Email: brmclaug@cisco.com


     Email: kwiereng@cisco.com

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