Internet Draft                                                J. Cuellar
Document: draft-ietf-geopriv-reqs-01.txt draft-ietf-geopriv-reqs-02.txt                      Siemens AG

                                                     John B. Morris, Jr.
                                     Center for Democracy and Technology

                                                             D. Mulligan
                     Samuelson Law, Technology, and Public Policy Clinic

Expires in six months                                      November 2002                                           Jan 2003

                          Geopriv requirements

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   Location-based services, navigation applications, emergency
   services, management of equipment in the field, and other location-
   dependent services need geographic location information about a
   Target (such as a user, resource or other entity).  There is a need
   to securely gather and transfer location information for location
   services, while at the same time protecting the privacy of the
   individuals involved.

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                         Geopriv Requirements                 Nov 2002                 Jan 2003

   This document focuses on the authorization, integrity and privacy
   requirements for such location-dependent services.  Specifically, it
   describes the requirements for the geopriv Location Object (used to
   securely transfer location data and other privacy-enabling
   information) and for the protocols that use this Location Object.

Table of Contents

   1. Overview........................................................3
   2. Conventions used in this document...............................4
   3. Terminology.....................................................4
      3.1. Foundational Definitions...................................4
         3.1.1. Location Information (LI) and Sighting................4
         3.1.2. The Location Object...................................6
         3.1.3. Location Object vs. Using Protocol....................6
         3.1.4. Trusted vs. Non-trusted Data Flows....................6
      3.2. Geopriv Entities and Functions.............................7
         3.2.1. Primary Geopriv Entities..............................7
         3.2.2. Secondary Geopriv Entities............................8
         3.2.3. Geopriv Data Storage Functions........................9
      3.3. Privacy Policies and Rules.................................9
      3.4. Identifiers, Authentication and Authorization.............10
   4. Scenarios and Explanatory Discussion...........................11
      4.1. Scenarios of Data Flow....................................11
   5. Requirements...................................................14
      5.1. Location Object...........................................15
      5.2. The Using Protocol........................................16
      5.3. Policy based Location Data transfer.......................17 Transfer.......................17
      5.4. Location Object Privacy and Security......................17 Security......................18
      5.5. Identity Protection.......................................18
      5.6. Authentication Requirements...............................18
      5.7. Actions to be secured.....................................18
      5.8. Non-Requirements..........................................19
   6. Security Considerations........................................19
      6.1. Traffic Analysis..........................................19
      6.2. Securing the Privacy Policies.............................19
      6.3. Emergency Case............................................20
      6.4. Identities and Anonymity..................................20
      6.5. Unintended Target.........................................21
   7. Acknowledgements...............................................21
   8. References.....................................................21
   9. Protocol and LO Issues for later Consideration.................22
      9.1. Single Message Transfer...................................22
      9.2. Multiple Locations in one LO..............................22
      9.3.
      9.2. Translation Fields........................................22
      9.4.
      9.3. Specifying Desired Accuracy in a Request..................22
      9.4. Truth Flag................................................22

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      9.5. Truth Flag................................................22
      9.6. Timing Information Format.................................22
      9.7.
      9.6. The Name Space of Identifiers.............................22
   10. Author's Addresses............................................23
   11. Full Copyright Statement......................................23

1. Overview

   Location-based services (applications that require geographic
   location information as input) are becoming increasingly common.
   The collection and transfer of location information about a
   particular Device and/or Target can have important privacy
   implications.  A key goal of the protocols described in this
   document is to facilitate the protection of privacy pursuant to
   privacy policies set by the "user" (or, more precisely in the
   terminology of this document defined in Section 3 below, the "Rule
   Maker").

   The ability to derive or compute a Device's location, and access to
   the derived or computed location, are key elements of the location-
   based services privacy equation.  Central to a Target's privacy are
   (a) the identity of entities that have access to raw location data,
   derive or compute location, and/or have access to derived or
   computed location information, and (b) whether those entities can be
   trusted to know and follow the privacy policy of the user.

   The main principles guiding the requirements described in this
   document are:

   1) Security of the transmission of Location Object is essential to
      guarantee the integrity and confidentiality of the location
      information.  This includes authenticating the sender and
      receiver of the Location Object, and securing the Location Object
      itself.

   2) A critical role is played by user-controlled policies, which
      describe the restrictions imposed or permissions given by the
      "user" (or, as defined below, the "Rule Maker").  The policies
      specify the necessary conditions that allow a Location Server to
      forward Location Information to a Location Recipient, and the
      conditions under which and purposes for which the Location
      Information can be used.

   3) The Location Object should be able to carry a limited but core
      set of privacy policies.  This core set is defined below and
      discussed more extensively in a separate document.  Beyond the
      core set of privacy policies, the user or Rule Maker should be
      able to define a more robust and complex set of policies. The exact form or expressiveness of
      policies beyond in the core set or in the full set is not further
      discussed in this paper.

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      separate document.

   4) Whenever appropriate, the location information should not be
      linked to the real identity of the user or a static identifier
      easily linked back to the real identity of the user (e.g., the
      phone number).  Rather, the user should be able to specify which

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      local identifier, unlinked pseudonym, or private identifier is to
      be bound to the location information.

   5) The user may want to hide the real identities of himself and his
      partners not only to eavesdroppers but also to other entities
      participating in the protocol.

   Although complete anonymity may not be appropriate for some
   applications because of legal constraints or because some location
   services may in fact need explicit identifications, in most cases
   the location services only need some type of authorization
   information and/or perhaps anonymous identifiers of the entities in
   question.

2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in
   this document are to be interpreted as described in [RFC2119].

   Note that the requirements discussed here are requirements on the
   generic Location Object and on the using protocols for location
   services.  Thus the requirements discussed in this document mostly
   refer to the capabilities that are mandatory-to-implement. For
   example, requiring that implementations support integrity is not the
   same thing as requiring that all protocol traffic be authenticated.
   In other cases, the requirement may be that the user always obtains
   a notice when his location data was not authenticated. This practice
   is mandatory-to-use, not just to implement.

3. Terminology

   The terminology and definitions detailed below include both (1)
   terms used in the requirements section of this document, and (2)
   terms that provide additional detail about the usage model
   envisioned for the geopriv Location Object.  These latter terms will
   be utilized in a separate scenarios document.

3.1. Foundational Definitions

3.1.1. Location Information (LI) and Sighting

   The focus of the geopriv working group is on information about a
   Target's location that is NOT based on generally or publicly
   available sources, but instead on private information provided or
   created by a Target, a Target's Device, or a Target's network or
   service provider:

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      Location Information (LI):
         A relatively specific way of describing where a Device is
         located and that is (a) derived or computed from information
         generally not available to the general public (such as

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         information mainly available to a network or service
         provider), (b) determined by a Device that may be not
         generally publicly addressable or accessible, or (c) input or
         otherwise provided by a Target.

   As examples, LI could include (a) information calculated by
   triangulating on a wireless signal with respect to cell phone
   towers, (b) longitude and latitude information determined by a
   Device with GPS (global positioning satellite) capabilities, or (c)
   information manually entered into a cell phone or laptop by a Target
   in response to a query.

   Excluded from this definition is the determination of location
   information wholly without the knowledge or consent of the Target
   (or the Target's network or access service provider), based on
   generally available information such as an IP or e-mail address.  In
   some cases information like IP address can enable someone to
   estimate (at least roughly) a location.  Commercial services exist
   that offer to provide rough location information based on IP
   address.  Currently, this type of location information is typically
   less accurate and has a coarser granularity than the type of
   location information addressed in this document.  Although this type
   of location computation still raises significant potential privacy
   and public policy concerns, such scenarios are generally outside the
   scope of this document.

   Within any given location-based transaction, the INITIAL
   determination of location (and thus the initial creation of Location
   Information) is termed a Sighting:

      Sighting:
         The initial determination of location based on non-public
         information (as discussed in the definition of Location
         Information), and the initial creation of Location
         Information.

   Some variant of the sighting information is included in the Location
   Object.  Abstractly, it consists of two separate data fields:

              (Identifier, Location)

   where Identifier is the identifier assigned to a Target being
   sighted, and Location is the current position of that Target being
   sighted.  Not all entities may have access to exactly the same piece
   of sighting information.  A sighting may be transformed to a new
   sighting pair:

              (Identifier-1, Location-1)

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   before it is provided by a Location Sighter or Location Server to
   another Location Recipient (for instance, another Location Server).

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   In this case, Identifier-1 may be Pseudonym, and Location-1 may have
   less accuracy or granularity than the original value.

3.1.2. The Location Object

   A main goal of the geopriv working group is to define a Location
   Object (LO), to be used to convey both Location Information and
   basic privacy-protecting instructions:

      Location Object (LO): This data contains the Location Information
         of the Target, and other fields including an identity or
         pseudonym of the Target, time information, core privacy
         policies, authenticators, etc.  Most of the fields are
         optional, including the Location Information itself.

   Nothing is said about the semantics of a missing field.  For
   instance, a partially filled object MAY be understood implicitly as
   the request to complete it.  Or, if no time information is included,
   this MAY implicitly mean "at the current time" or "at a very recent
   time", but it could be interpreted in a different way, depending on
   the context.

3.1.3. Location Object vs. Using Protocol

   The "using protocol" is the protocol that uses (creates, reads or
   modifies) the Location Object.  A protocol that just transports the
   LO as a string of bits, without looking at them (like an IP storage
   protocol could do), is not a using protocol, but only a transport
   protocol.  Nevertheless, the entity or protocol that caused the
   transport protocol to move the LO is responsible of the correct
   distribution, protection, usage, retention, and storage of the LO.

   The security and privacy enhancing mechanisms used to protect the LO
   are of two types:  First, the Location Object definition MUST
   include (optional) fields or mechanisms used to secure the LO as
   such.  The LO MAY be secured, for example, using cryptographic
   checksums or encryption as part of the LO itself.  Second, the using
   protocol may also provide security mechanisms to securely transport
   the Location Object.

   The security mechanisms of the Location Object itself are to be
   preferred.

3.1.4. Trusted vs. Non-trusted Data Flows

   Location information can be used in very different environments.  In
   some cases the participants will have longstanding relationships,
   while in others participants may have discrete interactions with no
   prior contractual or other contact.

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   The different relationships raise different concerns for the
   implementation of privacy rules, including the need to communicate

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   privacy policies.  A public Rule Repository, for example, may be
   unnecessary in a trusted environment where more efficient methods of
   addressing privacy issues exist.  The following terms distinguish
   between the two basic types of data flows:

      Trusted Data Flow:
         A data flow that is governed by a pre-existing contractual
         relationship that addresses location privacy.

      Non-trusted Data Flow:
         The data flow is not governed by a pre-existing contractual
         relationship that addresses location privacy.

3.2. Geopriv Entities and Functions

   The entities of a geopriv application or transaction may be given
   explicit roles:

3.2.1. Primary Geopriv Entities

   Certain entities and roles are involved in most (and in some cases
   all) geopriv transactions:

      Target:
         The entity whose location is desired by the Location Seeker.
         In many cases the Target will be the human "user" of a Device
         or an object such as a vehicle or shipping container to which
         the Device is attached.  In some instances the Target will be
         the Device itself.

      Device:
         The technical device the location of which is tracked as a
         proxy for the location of a Target.  A Device might, for
         example, be a cell phone, a Global Positioning Satellite (GPS)
         receiver, a laptop equipped with a wireless access Device, or
         a transmitter that emits a signal that can be tracked or
         located.  In some situations, such as when a Target manually
         inputs location information (perhaps with a web browser), the
         Target is effectively performing the function of a Device.

      Rule Maker:
         The individual or entity that has the authorization to set the
         applicable privacy policies and rules.  In many cases this
         will be the owner of the Device, and in other cases this may
         be the user who is in possession of the Device.  For example,
         parents may control what happens to the location information
         derived from a child's cell phone. A company, in contrast, may
         own and provide a cell phone to an employee but permit the
         employee to set the privacy rules.

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      Location Seeker (LSeek):
         An individual or entity who seeks to receive location data
         about a Target.

   A Location Seeker may act in one or more of the following more
   specialized roles: as the Location Sighter, a Location Server, or as
   an Ultimate Location Recipient:

      Location Sighter (LoSi), or Location Data-Source
         The original source of the sighting of a Target in a given
         transaction.

      Location Server (LServ), or Intermediate Location Recipient:
         A Device or entity that provides access to Location
         Information (possibly after processing or altering it) in
         accordance with the privacy policies of the Rule Maker.  Some
         location tracking scenarios may involve a Target, Device, or
         Device user performing the function of a Location Server.

      Ultimate Location Recipient (ULR):
         An individual or entity who receives location data about a
         Target and does not transmit the location information or
         information based on the Target's location (such as driving
         directions to or from the Target) to any party OTHER than the
         Target or the Rule Maker.

3.2.2. Secondary Geopriv Entities

      Certain entities and functions are present or involved in only a
         subset of geopriv transactions:

      Data Transporter:
         An entity or network that receives and forwards data without
         processing or altering it.  A Data Transporter could
         theoretically be involved in almost any transmission between a
         Device and a Location Server, a Location Server and a second
         Location Server, or a Location Server and an Ultimate Location
         Recipient.  Some location tracking scenarios may not involve a
         Data Transporter.

      Initial Access Provider (IAP):
         The entity that provides the initial network access or other
         data communications services essential for the operation of
         communications functions of the Device or computer equipment
         in which the Device operates.  Often, the IAP -- which will be
         a wireless carrier, an Internet Service Provider, or an
         internal corporate network -- will be identical to the LoSi.
         In other cases the IAP has a "dumb" LoSi, one that transmits
         geopriv data but does not implement or use any part of the
         geopriv Location Object.  Other cases may involve no IAP at
         all or the IAP is only a Data Transporter.

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3.2.3. Geopriv Data Storage Functions

   Within the geopriv framework, certain data may be stored in various
   functional entities:

      Rule (or Policy) Storage
         A storage used to store privacy-protecting policies, and
         perhaps identifiers, credentials or keys.  A Private Rule
         Storage could be operated by a Device, a Location Server, or a
         third party service provider.

   How policies are authenticated and otherwise protected is outside of
   the scope of this document, but see the remarks in Section 6
   (Privacy Considerations).

      Location Storage:
         A Device or entity that stores raw or processed Location
         Information for any period of time longer than the duration
         necessary to complete an immediate transaction regarding the
         LI.

   The existence and data storage practices of Location Storage is
   crucial to privacy considerations, because this may influence what
   Location Information could eventually be revealed (through later
   distribution, technical breach, or legal processes).

3.3. Privacy Policies and Rules

   Privacy Policies are rules that regulate an entity's activities with
   respect to location and other information, including, but not
   limited to, the collection, use, disclosure, and retention of
   location information.  Such rules are generally based on fair
   information practices, as detailed in (for example) the OECD
   Guidelines on the Protection of Privacy and Transporter Flows of
   Personal Data [OECD].

      Privacy Policy or Privacy Rule:
         A rule or set of rules that regulate an entity's activities
         with respect to location information, including the
         collection, use, disclosure, and retention of location
         information.  In particular, the policy describes how location
         information may be used by an entity and which transformed
         location information may be released to which entities under
         which conditions.  Policies must be obeyed; they are not
         advisory.

   A full set of Privacy Rules will likely include both rules that have
   only one possible technical meaning, and rules that will be affected
   by a locality's prevailing laws and customs.  For example, a
   distribution rule of the form "my location can only be disclosed to
   the owner of such credentials and in such accuracy" has clear-cut

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   implications for the protocol that uses the LO. But other rules,

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   like retention or usage policies, may have unclear technical
   consequences for the protocol or for the involved entities.  For
   example, the precise scope of a retention rule stating "you may not
   store my location for more than 2 days" may in part turn on local
   laws or customs.

3.4. Identifiers, Authentication and Authorization

   Anonymity is the property of being not identifiable (within a set of
   subjects).  Anonymity serves as the base case for privacy: without
   the ability to remain anonymous, individuals cannot control their
   own privacy.  Unlinkability ensures that a user may make multiple
   uses of resources or services without others being able to link
   these uses together.  Unlinkability requires that entities are
   unable to determine whether the same user caused certain specific
   operations in the system. [ISO99]  A pseudonym is simply a bit
   string which is unique as ID and is suitable to be used for end-
   point authentication.

      Unlinked Pseudonym:
         A pseudonym where the linking between the pseudonym and its
         holder is, at least initially, not known to anybody with the
         possible exception of the holder himself or a trusted server
         of the user.  See [Pfi01] (there the term is called Initially
         Unlinked Pseudonym)

   The word authentication is used in different meanings.  Some require
   that authentication associates an entity with a more or less well-
   known identity.  This basically means that if A authenticates
   another entity B as being "id-B", then the label "id-B" is a well-
   known, or at least a linkable identity of the entity.  In this case,
   the label "id-B" is called a publicly known identifier, and the
   authentication is "explicit":

      Explicit Authentication:
         The act of verifying a claimed identity as the sole originator
         of a message (message authentication) or as the end-point of a
         channel (entity authentication). Moreover, this identity is
         easily linked back to the real identity of the entity in
         question, for instance being a pre-existing static label from
         a predefined name space (telephone number, name, etc.).

      Authorization
         The act of determining if a particular right, such as access
         to some resource, can be granted to the presenter of a
         particular credential.

   Depending on the type of credential, authorization may imply
   Explicit Authentication or not.

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4. Scenarios and Explanatory Discussion

4.1. Scenarios of Data Flow

   In this subsection we introduce short scenarios to illustrate how
   these terms and attributes describe location information
   transactions.

   SCENARIO 1: GPS Device with Internal Computing Power: Closed System

   In this example, the Target wishes to know his/her location using
   Global Positioning System (GPS) and the Device is capable of
   independently processing the raw data to determine its location.
   The location is derived as follows: the Device receives
   transmissions from the GPS satellites, internally computes and
   displays location. This is a closed system.  For the purpose of this
   and subsequent examples, it is assumed that the GPS satellite
   broadcasts some signal, and has no information about the identity or
   whereabouts of Devices using the signal.

        GPS Satellite
                |
                |
                |
                |
                V             GPS Device
         --------------------------------------------------
        /                                                  \
        |  Data         -----  Location  -----  Location   |
        |  Transporter          Server            Storage  |
        \                                           |      /
         -------------------------------------------|------
                                                    |
                                        ------------|------
                                       /            V      \
                                      / Target    Location  \
                                      |           Seeker     |
                                      |                      |
                                      \    Rule Maker       /
                                       \                   /
                                        -------------------

   In this scenario the GPS Device is both the IAP and the LoSi. The
   interaction occurs in a Trusted environment because it occurs in the
   Rule MakerĘs Device.

   SCENARIO 2:  Cell Phone Roaming

   In this example, a cell phone is used outside its home service area
   (roaming). Also, the cell phone service provider (cell phone Corp 2)

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   outsourced the accounting of cell phone usage. The cell phone is not
   GPS-enabled.  Location is derived by the cell phone network in which
   the Target and Device are roaming.  When the Target wishes to use
   the cell phone, cell phone Corp 1 (IAP) provides the roaming service
   for the Target, which sends the raw data about usage (e.g., duration
   of call, location ” roaming network, etc.) to cell phone Corp 2, the
   home service provider.  Cell phone Corp 2 submits the raw data to
   the accounting company, which processes the raw data for the
   accounting statements.  Finally, the raw data is sent to a data
   warehouse where the raw data is stored in a Location Server (e.g.,
   computer server).

                   Cell Phone Corp 1                Cell Phone Corp 2
                   -----------------               -----------------
         Sighting /                 \  Sighting   /                 \
    Device ----- | Data Transporter | ---------  | Data Transporter |
    Target        \                 /             \                 /
                   -----------------              / -----------------
                                                 /         |
                                                /  sighting|
                                               /           |
                                    -----------            |
                                   /                       V
                 ------------     /                  ----------
                /            \   /                  /          \
               /   Location   \ /                  |  Location  |
               |   Storage     |   Location Info   |  Storage   |
               |               |<----------------- |            |
               |   Location    |                   |  Location  |
               |   Seeker      |                   |  Seeker    |
                \             /                     \          /
                 -------------                       ----------

   Here cell phone corp 1 is the IAP and the LoSi. Cell phone corp 1
   could be Non-trusted (the Rule Maker does not have a contract
   protecting location information with corp 1 and there is no
   contractual relationship with privacy provisions between corp 1 and
   corp 2) or Trusted (contract with privacy protections between cell
   phone corp 2 and corp 1).  Cell phone corp 2 is Trusted.

   SCENARIO 3:  Mobile Communities and Location-Based Services

   The figure below shows a common scenario, where a user wants to find
   his friends or colleagues or wants to share his position with them
   or with a Location-Based Service Provider.  Some of the messages use
   a Location Object to carry for instance: identities or pseudonyms,
   credentials and proof-of-possession of them, Policies and Location
   Data Information, including Data Types and Accuracy.  They are shown
   in the figure by normal arrows ("--->"). Other messages do not use

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   the Location Object and are outside of the scope of the geopriv WG,
   but should be mentioned for understandability.  They are shown in
   the figure as starred arrows ("***>").

        +---------+                      +------------+
        | Location|                      | Public     |
        |  Data   |<**                   | Policy     |
        | Source  |    *                 | Repository |
        |  + IAP  |      *               +------------+
        +---------+\       *            *       *
            ^        \       *5     3a*         *
            *          \       *    *           *
            *            \       **             *
            *              \    *  *            *3a
         5a *                \*      *          *
            *               *  \       *        *
            *             *      \       *      *
            *           *          \6      *    *
      +----------+    *              \       *  V
      | Target   |  *                  \->+-----------+
      | +----------+           3          | Location  |
      +-|   Rule   |--------------------->| Server +  |
        |   Maker  |                      | Private   |
        +----------+<********************>| Repository|
             ^                  1         +-----------+
             |                                 ^  |
             |                                4|  |7
             |                                 |  V
             |                             +----------+
             |                             | Ultimate |
             +---------------------------->| Location |
                               2           | Recipient|
                                           +----------+

                   Figure 1: The Entities and Data Flows

      1: Registration:
         The Rule Maker registers himself and the Target with the
         Location Server. This registration process is outside of the
         scope of our discussion, but probably the Rule Maker has to
         prove that he indeed is the owner of the privacy rights of the
         Target (the Target is usually a Device owned by the Rule
         Maker).  The Rule Maker and the Location Server agree, as part
         of the Registration Process, which keys or credentials and
         proof-of-possession of the corresponding secrets they will use
         to authenticate each other, and in particular, to authenticate
         or sign the policies, or how they will agree on them or renew
         those keys or credentials.

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      2: End-to-End Negotiation:
         The Rule Maker and the Location Seeker exchange information
         about the service (if any) and negotiate it.  They also
         negotiate the pseudonyms that they will use later on and the
         credentials or keys that the Ultimate Location Recipient will
         use to prove his authorization to the Location Server.  This
         End-to-End Negotiation may contain several messages and may
         use or not the Location Object.

      3: Policy Transfer:
         The Rule Maker sends a Policy to the Location Server.  This
         Policy may be a field in a Location Object or not.

      3a:Signed Policy:
         As an alternative to the Policy Transfer, the Rule Maker may
         write a policy and place it in the Open Repository.  The
         entities access the repository to read the signed policies.

      4: Location Information Request:
         The Location Seeker requests location information for a
         Target.  In this request, the Location Seeker may select which
         location information data type it prefers.  One way of
         requesting Location Information MAY be sending a partially
         filled Location Object, including only the identities of the
         Target and Location Recipient and the desired Data Type and
         accuracy, and providing proof of possession of the required
         credentials.  But whether the using protocol understands this
         partially filled object as a request, this MAY depend on the
         using protocol or on the context.  The Location Seeker could
         also specify the need for periodic location information
         updates, but this is probably out of the scope of geopriv.

      5: Locate:
         When a Location Server receives an Location Information
         Request for a Target for which has no current location
         information, the server may send ask the Location Sighter to
         locate the Target.

      6: Location Information:
         The Location Sighter sends the "full" location information to
         the Location Server.  This Location Information may be
         embedded in a Location Object or not.

      7: Filtered Location Information:
         Then the Location Server sends the location information to the
         Location Recipient.  The information may be filtered in the
         sense that in general a less precise or a computed version of
         the information is being delivered.

5. Requirements

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                         Geopriv Requirements                 Nov 2002                 Jan 2003

5.1. Location Object

   Req. 1.  (Location Object generalities)

      1.1) Geopriv MUST define one Location Object (LO) -- both in
      syntax and semantics -- that must be supported by all geopriv
      entities.

      1.2) Some fields of the Location Object MAY be optional.  This
      means that an instance of a Location Object MAY contain the
      fields or not.

      1.3) Some fields of the Location Object MAY be defined as
      "extensions".  This means that the syntax or semantics of these
      fields is not fully defined in the basic Location Object
      definition, but their use may be private to one or more using
      protocols.

      1.4) The Location Object MUST be extensible, allowing the
      definition of new attributes or fields.

      1.5) The object MUST be suitable for requesting and receiving a
      location.

      1.6) The object MUST permit (but not require) the policy to be
      enforced by a third party.

      1.7) The object MUST be usable in a variety of protocols, such as
      HTTP and SIP, as well as local APIs.

      1.8) The object MUST be usable in a secure manner even by
      applications on constrained devices.

   Req. 2.  (Location Object fields) The Location Object definition
      MUST support the following (eventually optional) Fields (but not all LOs must use all
      fields)

      2.1) Target Identifier. Identifier

      2.2) Location Recipient Identity

      This identity may be a multicast or group identity, used to
      include the Location Object in multicast-based using protocols.

      2.3) Location Recipient Credential

      2.4) Location Recipient Proof-of-Possession of the Credential

      2.5) Location Field.

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                         Geopriv Requirements                 Jan 2003

      Each Location Field may contain one or more Location
      Representations, which can be also in different formats.

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                         Geopriv Requirements                 Nov 2002

      2.6) Location Data Type

      When transmitting the Location Object, the sender and the
      receiver must agree on the data type of the location information.
      The using protocol may specify that the data type information is
      part of the Location Object or that sender and receiver have
      agreed on it before the actual data transfer.

      2.7) Motion and direction vectors

      2.8) Timing information:
      (a) When was the LI accurate? (sighting time)
      (b) Until when considered current? TTL (Time-to-live) (This is
      different than a privacy rule setting a limit on data retention)

      2.9) Policy Field: this field MAY be a referral to an applicable
      policy (for instance, an URI to a full policy) policy), or it MAY contain
      a Limited Policy (see Req. 9). 9), or both.

      2.10) Security-headers and -trailers (for instance encryption
      information, hashes, or signatures) (see Req. 13).

      2.11) Version number

   Req. 3.  (Location Data Types)

      3.1) The Location Object MUST define at least one Location Data
      Type to be supported by all geopriv receivers (entities that
      receive LOs).

      3.2) The Location Object SHOULD define two Location Data Types:
      one for latitude / longitude / altitude coordinates and one for
      civil locations (City, Street, Number) supported by all geopriv
      receivers (entities that receive LOs).

      3.3) The latitude / longitude / altitude Data Type SHOULD also
      support a delta format in addition to an absolute one, used for
      the purpose of reducing the size of the packages or the security
      and confidentiality needs.

      3.4) The Location Object definition SHOULD agree on further
      Location Data Types supported by some geopriv entities and
      defined by other organizations.

5.2. The Using Protocol

   Req. 4.  The using protocol has to obey the privacy and security
      instructions coded in the Location Object and in the

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                         Geopriv Requirements                 Jan 2003

      corresponding Policy Rules regarding the transmission and storage
      of the LO.

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                         Geopriv Requirements                 Nov 2002

   Req. 5.  The using protocol will typically facilitate that the keys
      associated with the credentials are transported to the respective
      parties, that is, key agreement is responsibility of the using
      protocol.

   Req. 6.  (Single Message Transfer)  In particular for tracking of
      small target devices, the design should allow a single
      message/packet transmission of location as a complete
      transaction.

   Other requirements on the using protocol are out of the scope of
   this document.  See also Section 9 (Protocol and LO Issues for later
   Consideration)

5.3. Policy based Location Data Transfer

   Req. 6. 7.  (LServ Policies) The decision of a Location Server to
      provide a Location Seeker access to Location Information MUST be
      based on Rule Maker-defined Privacy Policies.

   It is outside of our scope how Privacy Policies are managed, how a
   Location Server has access to the Privacy Policies, and if he is or
   not aware of the full set of rules desired by the Rule-Maker.  Note
   that it might be that some rules contain private information not
   intended for untrusted parties.

   Req. 7. 8.  (LoSi Policies) Even if a Location Sighter is unaware of
      and lacks access to the full Privacy Policies defined by the Rule
      Maker, the Location Sighter MUST transmit Location Information in
      compliance with instructions set by the Rule Maker.  Such
      compliance MAY be accomplished by the Location Sighter
      transmitting LI only to a URI designated by the Rule Maker.

   Req. 8. 9.  (ULR Policies) An Ultimate Location Recipient does not need
      to be aware of the full policies defined by the Rule Maker
      (because an ULR SHOULD NOT retransmit Location Information), and
      thus an ULR SHOULD receive only the subset of Privacy Policies
      necessary for the ULR to handle the LI in compliance with the
      full Privacy Policies (such as, for example, an instruction on
      the time period for which then LI can be retained).

   Req. 9. 10.  (Full Policy language) Geopriv MAY specify a policy
      language capable of expressing a wide range of privacy rules
      concerning location information.  This policy language MAY be an
      existing one, an adaptation of an existing one or a new policy
      language, and it SHOULD be as simple as possible.

   Req. 10. 11.  (Limited Policy language) Geopriv MUST specify a limited
      policy language capable of expressing a limited set of privacy

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                         Geopriv Requirements                 Jan 2003

      rules concerning location information.  This policy language MAY
      be an existing one, an adaptation of an existing one or a new
      policy language.  The Location Object MUST include sufficient
      fields and data to express the limited set of privacy rules.

5.4. Location Object Privacy and Security

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                         Geopriv Requirements                 Nov 2002

5.5. Identity Protection

   Req. 11. 12.  (Identity Protection) The Location Object MUST support use
      of Unlinked Pseudonyms in the corresponding identification fields
      of Rule Maker, Target, Device, and Location Recipient.  Since
      Unlinked Pseudonyms are simply bit strings that are not linked
      initially to a well-known identity, this requirement boils down
      to saying that the name space for Identifiers used in the LO has
      to be large enough to contain many unused strings.

5.6. Authentication Requirements

   Req. 12. 13.  (Credential Requirements) The using protocol and the
      Location Object SHOULD allow the use of different credentials
      types, including privacy-enhancing credentials (like for instance
      the ones described in [Bra00] or [Cha85]).

5.7. Actions to be secured

   Req. 13. 14.  (Security Features) The Location Object MUST support
      fields suitable for protecting the Object to provide the
      following security features:

      13.1)

      14.1)     Mutual end-point authentication: the using protocol is
      able to authenticate both parties in a Location Object
      transmission,

      13.2)

      14.2)     Data object integrity: the LO is secured from
      modification by unauthorized entities during transmission and
      during storage,

      13.3)

      14.3)     Data object confidentiality: the LO is secured from
      eavesdropping (unauthorized reading) during transmission and
      during storage, and

      13.4)

      14.4)     Replay protection: an old LO may not be replayed by an
      adversary or by the same entity that used the LO itself (except
      perhaps during a small window of time that is configurable or
      accepted by the Rule Maker).

   Req. 14. 15.  (Minimal Crypto)

      14.1)

      15.1)     Geopriv MUST specify a minimum mandatory to implement
      Location Object security including mandatory to implement crypto

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                         Geopriv Requirements                 Jan 2003

      algorithms, for digital signature algorithms and encryption
      algorithms.

      14.2)

      15.2)     It MAY also define further mandatory to implement
      Location Object security mechanisms for message authentication
      codes (MACs) or other purposes.

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                         Geopriv Requirements                 Nov 2002

      14.3)

      15.3)     The protocol SHOULD allow a bypass if authentication
      fails in an emergency call.

   The issue addressed in the last point is that an emergency call in
   some very unfavorable situations my not be completed if the minimal
   authentication fails.  This is probably not what the user would like
   to see.  The user may prefer an unauthenticated call to an
   unauthenticated emergency server than no call completion at all,
   even at the risk that he is talking to an attacker or that his
   information is not secured.

5.8. Non-Requirements

   Non-Req. 1. (Bridging to non-IP networks) The geopriv specification
      SHOULD NOT specify the bridging to non-IP networks (PSTN, etc).

6. Security Considerations

   The purpose of the geopriv Location Object and the requirements on
   the using protocol are to allow a policy-controlled disclosure of
   location information for location services.

6.1. Traffic Analysis

   The information carried within the Location Object is secured in a
   way compliant with the privacy and security policies of the Rule
   Maker, but other information, carried in other objects or headers
   are in general not secured in the same way.  This means that geopriv
   does not as a general matter secure the Target against general
   traffic analysis attacks or other forms of privacy violations.

6.2. Securing the Privacy Policies

   The Privacy Policies of the Rule Maker regarding the location of the
   Target may be accessible to a Location Server in a Private Storage
   or in a Public Repository, or they may be carried by the Location
   Object, or they may be presented by the Location Seeker as
   capabilities or tokens.  Each of this types of policy has to be
   secured itĘs own particular way.

   The rules in a Private Storage are typically authenticated using a
   MAC (Message Authentication Code) or a signature, depending on the
   type of keys used.  The rules in a Public Repository (one that in

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                         Geopriv Requirements                 Jan 2003

   principle may be accessed directly by several entities, for instance
   several Location Servers) are typically digitally signed.  A Policy
   Field in a LO is secured as part of the LO itself.  A Geopriv Token
   (a token or ticket issued by the Rule Maker to a Location Seeker,
   expressing the explicit consent of the Rule Maker to access his
   location information) is authenticated or signed.

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                         Geopriv Requirements                 Nov 2002

6.3. Emergency Case

   One way of implementing the authentication bypass for emergency
   calls, mentioned in Req 14.3) is to let the user have the choice of
   writing a policy that says:
   -  "If the emergency server does not authenticate itself,
      nevertheless send the location", or
   -  "If the emergency server does not authenticate itself, let the
   call fail".

   In the case where the authentication of the emergency call fails
   because the user may not authenticate itself, the question arises:
   whose policy to use? It is reasonable to use a default one: this
   location information can only be sent to an emergency center.

   Another situation, which should be studied in more detail is: what
   to do if not only the user fails to authenticate itself, but also
   the emergency center is not authenticable? It is reasonable to send
   the Location Information anyway, but are there in this case any
   security threats that must be considered?

6.4. Identities and Anonymity

   The use of Unlinked Pseudonyms is necessary to obtain anonymity.

   The purpose of the use of Unlinked Pseudonyms is the following: the
   using protocol should be able to hide the real identity of the Rule
   Maker, the Target, and the Device, the and to Location Servers or
   Location Recipients.  Also, the using protocol SHOULD be able to
   hide the real identity of the Location Recipient to the Location
   Server.

   In this last case, the Target is not concerned about the Server
   identifying him and knowing his location, but identifying his
   business partners, and therefore his habits, etc.  Reasons for
   hiding the real identities of the Location Recipients include (a)
   that this knowledge may be used to infer the identity of the Target,
   (b) that knowledge of the identity of the Location Recipient may
   embarrass the Target or breach confidential information, and  (c)
   that the dossier telling who has obtained a Target's location
   information over a long period of time can give information on
   habits, movements, etc.  Even if the location service providers
   agree to respect the privacy of the user, are compelled by laws or
   regulations to protect the privacy of the user, and misbehavior or

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                         Geopriv Requirements                 Jan 2003

   negligence of the Location Server can be ruled out, there is still
   risk that personal data may become available to unauthorized persons
   through attacks from outsiders, unauthorized access from insiders,
   technical or human errors, or legal processes.

   In some occasions a Location Server has to know who is supplying
   policies for a particular Target, but in other situations it could

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                         Geopriv Requirements                 Nov 2002
   be enough to know that the supplier of the policies is authorized to
   do so.  Those considerations are outside of our scope.

6.5. Unintended Target

   An Unintended Target is a person or object tracked by proximity to
   the Target. This special case most frequently occurs if the Target
   is not a person.  For example, the Target may be a rental car
   equipped with a GPS Device, used to track car inventory.  The rental
   company may not care about the driver's location, but the driver's
   privacy is implicitly affected.

   Geopriv may or may not protect or affect the privacy of Unintended
   Targets, but the impact on Unintended Targets should be
   acknowledged.

7. Acknowledgements

   We wish to thank the members of the IETF geopriv WG for their
   comments and suggestions. Aaron Burstein, Mehmet Ersue, Allison
   Mankin, Randall Gellens, Jon Peterson, and the participants of the
   geopriv meetings in San Diego and Yokohama provided detailed
   comments or text.

8. References

   [Bra00] Stefan A.: Rethinking Public Key Infrastructures and Digital
           Certificates : Building in Privacy, MIT Press; ISBN:
           0262024918; 1st edition, August, 2000

   [Cha85] Chaum, David: Security without Identification, Card
           Computers to make Big Brother Obsolete. Original Verion
           appeared in: Communications of the ACM, vol. 28 no. 10,
           October 1985 pp. 1030-1044. Revised version available at
           http://www.chaum.com/articles/

   [ISO99] ISO99: ISO IS 15408, 1999, http://www.commoncriteria.org/.

   [OECD] OECD Guidelines on the Protection of Privacy and Transborder
           Flows of Personal Data, http://www.oecd.org.

   [Pfi01] Pfitzmann, Andreas; K÷hntopp, Marit: Anonymity,
           Unobservability, and Pseudonymity - A Proposal for
           Terminology; in: H Federrath (Ed.): Designing Privacy

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                         Geopriv Requirements                 Jan 2003

           Enhancing Technologies; Proc. Workshop on Design Issues in
           Anonymity and Unobservability; LNCS 2009; 2001; 1-9. Newer
           versions available at http://www.koehntopp.de/marit/pub/anon

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.

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                         Geopriv Requirements                 Nov 2002

9. Protocol and LO Issues for later Consideration

   It seems important to mention some issues on the Location Object or
   on the protocol, which have emerged during the discussion of earlier
   versions of this document.

9.1. Single Message Transfer

   For several purposes, and in particular for the tracking of small
   target devices, the design should not preclude a single
   message/packet transmission of location as a complete transaction.

9.2. Multiple Locations in one LO

   The possibility of inclusion of multiple locations is discussed in
   another draft, draft-morris-geopriv-location-object-issues-00.txt.

   An instance of a Location Object could contain zero, one, or several
   Location Fields, perhaps in different formats.  Several Location
   Fields would be used to report the same sighting in different
   formats, or multiple sightings at different times, or multiple
   sensor locations for the same device, or other purposes.

9.3.

9.2. Translation Fields

   It is possible to include fields to indicate that one of the
   locations is a translation of another.  If this is done, it is also
   possible to have a field to identify the translator, as identity and
   method.

9.4.

9.3. Specifying Desired Accuracy in a Request

   If the LO is used to request location information (leaving some
   fields empty), it is not clear how to specify the requested
   accuracy.  Are the data types "country/state/city" and
   "country/state" different data types or the same data type with
   different "accuracy" or "granularity"?

9.5.

9.4. Truth Flag

   Geopriv should not provide an attribute in object saying "I'm not
   telling you the whole truth."

9.6.

9.5. Timing Information Format

   The format of timing information is out of the scope of this
   document.

9.7.

9.6. The Name Space of Identifiers

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                         Geopriv Requirements                 Nov 2002                 Jan 2003

   Who defines the Identities: may the using protocol define the
   Identifiers or must the using protocol use and authenticate
   Pseudonyms proposed by the policies, chosen independently of the
   using protocol?  Of course, if the using protocol has an appropriate
   namespace, containing many unused names that may be used as
   pseudonyms and may be replaced by new ones regularly, then the
   Location Object may be able to use the name space. For this purpose,
   the user would probably have to write his policies using this name
   space.  Note that it is necessary to change the used pseudonyms
   regularly, because identifying the user behind an unlinked pseudonym
   can be very simple.

   There are several advantages of letting the using protocol to define
   the name space:
   o the embedded authentication would be easier, as the using protocol
     has often already the credentials for the authentication identity
     in place and the "embedded" authentication would be independent on
     the form of Identifiers,
   o the size of the names would be fixed.

   On the other hand, the benefits of the policy choosing the
   identifiers are:
   o the user has a control of his anonymity, and
   o the interworking of multiple systems with Location object across
     protocol boundaries is facilitated.

10. Author's Addresses

   Jorge R Cuellar
   Siemens AG
   Corporate Technology
   CT IC 3
   81730 Munich                   Email:  Jorge.Cuellar@mchp.siemens.de
   Germany

   John B. Morris, Jr.
   Director, Internet Standards, Technology & Policy Project
   Center for Democracy and Technology
   1634 I Street NW, Suite 1100
   Washington, DC 20006                         Email:  jmorris@cdt.org
   USA                                               http://www.cdt.org

   Deirdre K. Mulligan
   Samuelson Law, Technology and Public Policy Clinic
   Boalt Hall School of Law
   University of California
   Berkeley, CA 94720-7              Email:  dmulligan@law.berkeley.edu

11. Full Copyright Statement

   Copyright (C) The Internet Society (date).  All Rights Reserved.

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                         Geopriv Requirements                 Nov 2002                 Jan 2003

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph
   are included on all such copies and derivative works.  However, this
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   The limited permissions granted above are perpetual and will not be
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