Re: [humanresolv] Tentative problem statement

"Pars Mutaf" <pars.mutaf@gmail.com> Tue, 30 October 2007 18:10 UTC

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Date: Tue, 30 Oct 2007 19:09:31 +0100
From: "Pars Mutaf" <pars.mutaf@gmail.com>
To: "Alexandru Petrescu" <alexandru.petrescu@gmail.com>
Subject: Re: [humanresolv] Tentative problem statement
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A simplified alternate take based on Alex's comments.
Thanks,
pars

--------------

                  IP host pairing problem statement

In the current model of operation (phone number privacy obligates it),
cell phone users exchange their phone numbers upon user contact. This
model is likely to persist in IP telephony, yet under exploited and can be
extended using an IP protocol. Upon their meeting, an "IP host pairing"
protocol can allow two cell phone users to:

  1. Exchange their SIP URIs, mobile IPv6 home addresses, and possibly
     other information.
  2. Establish an IPsec security association using IKEv2.

under user control, i.e. _if accepted_ by the users. For example, one
user will initiate a pairing request, and the target user's phone display
the initiator user's human name and ask for approval.

Since there is user contact, IKEv2 authentication can be less challenging
than the general case. I.e., a global PKI hierarchy is probably not
needed. Solutions like password-based IKEv2 authentication can be applied.
Human name certificates can be applicable, certificate revocation may not
be needed, and human name collisions may not be harmful in this context.
Certificates may be signed by the cellular operators for example, or
PGP-like web of trust solutions may be applicable.

An IP-layer pairing solution can also allow for re-pairing or updating
the pairing state through the Internet. The users may change their
SIP URIs and/or Mobile IPv6 home addresses or other information. The users
will need to update these informations without waiting until their next
meeting. Or, they may need additional information which was not previously
exchanged when there was user contact.



On 10/29/07, Pars Mutaf <pars.mutaf@gmail.com>; wrote:
>
> Hi Alex,
>
> On 10/26/07, Alexandru Petrescu <alexandru.petrescu@gmail.com>; wrote:
> >
> > Pars Mutaf wrote:
> > > Hello, Please find below a tentative problem statement, comments are
> > > welcome. pars
> > >
> > >
> > > IP host pairing problem statement
> > >
> > > Today, cell phone numbers are not published in a phonebook for
> > > avoiding telemarketers, prank callers, Spam and SPIT (SPam over
> > > Internet Telephony). Users today exchange their phone numbers upon
> > > user contact, often through oral communication.
> > >
> > > In IP telephony, users will need a user friendly "pairing" protocol
> > > that identifies the two phones and let them exchange their SIP URIs
> > > and Mobile IPv6 home addresses, and possibly other information. The
> > > phones will establish an IPsec security association upon this first
> > > contact.
> >
> > IKE already does this (establish IPsec SA).
> >
> > > IPsec will be required not only for protecting their SIP URIs from
> > > eavesdroppers, but also for protecting data.
> >
> > IPsec already protects data.
>
>
> Our goal is to obtain a SIP URI and home address from the target device,
> and to establish an IPsec SA using IKE with the target device, **if
> accepted**
> by the target user.  For example, the target user will see a message on
> the
> screen "Pairing request from Michael Knight. Accept?" .  If accepted by
> the target user, the devices will exchange SIP URIs, home addresses, etc.,
> and create an IPsec SA using standard IKE(v2).
>
> IKE, for example, does not ask user authorization.
>
> We can also make IKE authentication easier.
> We can use human name certificates, or something like the PGP web of
> trust or self-signed certificates perhaps. Authentication is in general
> considered a difficult problem, and requires global PKI hierarchy. This
> is
> not true in our case. I hope we can talk about that. My guess is that
> we can use certificates.
>
>
> > "IP host pairing" is defined as a pairing protocol that can operate
> > > over IP;
> >
> > Is ND a host pairing protocol, if so can we say so.  Is Bluetooth a
> > pairing protocol, if so can we say so.
>
>
> ND is not a pairing protocol. Bluetooth has a pairing function.
>
> Pairing, in general, is about introducing two devices to each other
> (there is human intervention), creating a security association, and
> making sure that your device is paired with the intended device and
> not with an attacker's device.
>
> You may want to look at the following paper to have some ideas:
> sparrow.ece.cmu.edu/~adrian/projects/sib.pdf<http://sparrow.ece.cmu.edu/%7Eadrian/projects/sib.pdf>
>
>
> Is Bluetooth VCARD exchange a
> > means to achieve what IP host pairing tries to achieve.
>
>
>
> Please see above. I'm not sure Bluetooth pairing can be used for
> creating an IPsec SA. I also don't see why we would do this for
> Bluetooth. See also below, the problems (2) and (3) can not be addressed
> via Bluetooth.
>
>
> > upon user contact and also over the Internet i.e. long distances. It
> > > will address three problems of pairing:
> > >
> > > 1. Pairing when there is user contact: In this case, users can
> > > exchange their names or pseudonyms helping identify the hosts to each
> > >  other the first time they meet.
> >
> > Define better "user contact": visual contact?  Natural talk/hear
> > distance?  "Out-of-band" communication?  Letter-through-mail
> > communication?
>
>
> Good point.
>
> (When in a meeting and I want to talk to someone next to me, but talking
> > disturbs the meeting, and hushing is too incomprehensible - then I write
> > on paper and show the paper.)
> >
> > > 2. Re-pairing, or updating pairing state through the Internet: The
> > > users may change their SIP URIs and/or Mobile IPv6 home addresses or
> > > other information. The users will need to update these informations
> > > without waiting until their next meeting. Or, they may need
> > > additional information which was not previously exchanged when there
> > > was user contact.
> > >
> > > 3. Pairing without user contact (where possible): Users may know each
> > >  other but user contact may not be possible. Or, two previously
> > > paired hosts may lose pairing state. Users cannot probably wait until
> > >  their next meeting to recover from loss of state.
> > >
> > > Engineering problems:
> > >
> > > - Identifying the two hosts to each other in (1) and (3). -
> > > Preventing unauthorized and annoying pairing attempts from unknown
> > > users. - The design of the pairing protocol used to exchange and
> > > update the SIP URIs, home addresses and possibly other information.
> >
> > I think ND with link-local addresses, followed by an IKE exchange and
> > then by some extensions to "IPv6 Node Information Queries" rfc4620
> > (extensions to deliver the URI, or the phone number, instead of just the
> >
> > FQDN) - can do the trick.  Could this work?
>
>
> Please see above. We need more than that.
>
> Thanks,
> pars
>
>
> Alex
> >
> >
> > ______________________________________________________________________
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> >
>
>
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