Internet-Draft                                                        Pars Mutaf
Expires: July, 2007                     Institut National des Telecommunications
                                                                    Evry, France
                                                                   January, 2007



                           Private Information Queries

                               (Problem statement)


                         <draft-mutaf-piqproblem-00.txt>

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Abstract

   This document makes a problem statement for the "Private Information Queries"
   protocol.


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. Introduction

   By current practice, for privacy reasons, cellular phone numbers are not
   made publicly available nor predictable (this is also suggested in [SIPPRI]).
   Today, cellular users are obligated to manually share their phone numbers
   with their colleagues, friends, family members, etc., through face-to-face
   communication (i.e. oral communication). This is unfortunate. Some wireless
   technologies e.g. Bluetooth or IrDA can allow for sharing a phone number and
   other information in a more convenient way. Nevertheless, these technologies
   operate over very short distances, hence also require user contact. It is
   very desirable to have a protocol that allows for sharing phone numbers, or
   other private information over much longer distances.

   There is also anecdotal evidence that users often loose the list
   of their correspondents accidentally upon loss of state, or when their
   cellular device is lost/stolen/changed. Recovering the list of correspondents
   is very difficult for the same reasons described above.

. Private information queries

   Private information queries is an application-layer IP protocol. It can be
   used to request private information *directly* from the target user's
   device. It is an Internet protocol, consequently it is possible to request
   the phone number of a user, via a cellular network i.e. over a very large
   distance. Figure 1 illustrates the basic protocol operation:


                  Cellular host                   Cellular host
                 (John Hoffman)                  (Alice Collins)

             1.         ------ Request(phone number)------>

             2.                                      user approval

             3.         <----- Response(phone number)------

                        Figure 1. Private information
                                  request/response


   The request is sent directly to Alice Collins's host's IP address. Upon
   receipt of the private information request, the responder application
   displays a message:

                     John Hoffman requested your phone number.
                     Do you wish to return it? [YES/NO]

   If approved by the user, the responder application returns the requested
   information. The target user may know John Hoffman and may accept the
   request. Or, the target user may not know John Hoffman but may have an idea
   who he is and/or why he is trying to contact, and hence may accept the
   request (or not). The decision belongs to the target user. It is taken in
   real-time.

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. Example solution: multicast name resolution

   How one can get the IP address a phone, if that phone's SIP URI is unknown?

   A solution can be built on top of multicast name resolution [MNR] or an
   improved version of it. Although this protocol is currently limited to
   link-local scope, within a wireless access subnet that covers a large number
   of cells, one can reach a user over very large distances. This is already
   an important progress compared to using a short-range wireless technology
   e.g. Bluetooth (current practice).

   In this approach, the responder configures a name from the user's human name,
   for example "alicecollins". The requester user will enter the name Alice
   Collins, and the application will trigger a multicast name resolution request
   to the name "alicecollins". The request will be multicast over the subnet,
   and the target host will return an IP address.

   At this point, the requester application can send a private information
   query to the destination user's host. The target user's phone number can be
   obtained (if accepted by the target user). Next time, the target user can be
   contacted using his/her phone number i.e. regardless of location.


. Security considerations

   The requester's identity (found in the request message) must be
   authenticated. Public key cryptography and certificates may be used to
   address this problem.

   The responder's identity (found in the response message) must be also
   authenticated in order to avoid phone number spoofing.


. Conclusion, future work

   This document presented the need for requesting private information directly
   from another user's IP device. An initial solution based on multicast name
   resolution was discussed.

   Although this document was focused on phone numbers and SIP URIs, other
   private information e.g. e-mail address, DNS names, IP addresses may also
   be requested.













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Internet-Draft             PIQ problem statement                    January 2007

References

  [SIPPRI] J. Peterson, "A Privacy Mechanism for the Session Initiation
           Protocol (SIP)", RFC 3323, November 2002.
  [MNR] http://en.wikipedia.org/wiki/Zeroconf

Author's Address

   Pars Mutaf
   Institut National des Telecommunications
   Email: pars.mutaf@int-evry.fr

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