Subject: [Sip] IETF solution for pairing cellular hosts

From: "Pars Mutaf" <[email-masked]>
Date: Thu, 27 Sep 2007 15:49:13 +0200

[sorry for cross posting. this is an invitation]

Pairing Cellular Hosts

https://www1.ietf.org/mailman/listinfo/humanresolvers

Currently there are two approaches for obtaining contact information for a
target cell phone: (i) consulting a phonebook, (ii) manually exchanging
phone numbers upon face-to-face user contact. Both approaches have
their own limitations.

The following is a new abstract solution, a third alternative, a protocol
for "pairing" two cellular hosts:

Model of operation

1. The querier user types the target user's "human name" (as if he were
   consulting a phonebook), or a pseudoynm.
2. The pairing request is forwarded to the target phone.
3. The query, along with the querier user's name, are displayed on the
   target phone's screen.
4. The target user approves the request in real-time by pushing on the YES
   button of the phone.
5. The two phones exchange their Mobile IPv6 home addresses, SIP URIs, and
   establish an IPsec security association (using IKEv2).

The target user does not need to publish his/her private SIP URI and home
address (as recommended in [1] in SIP context). Cell phone users do not
publish their phone numbers today.

The users do not need to manually exchange their SIP URIs and home
addresses which are too long (an IPv6 address is 16 bytes long and random
looking, a SIP URI can be very long e.g. up to 30 characters and even more
with a random part for privacy).

The protocol also works in the absence of user contact, for example when
the target user's SIP URI is lost (loss of state, new phone), or this is
the user's first phone, and hence his/her contact list is initially empty.
Thousands of cell phones are sold everyday..

[1] Peterson, J., "A Privacy Mechanism for the Session Initiation Protocol",

    RFC3323, November 2002.

=======================

Interested folks could you please subscribe to the mailing list created
for this discussion:

https://www1.ietf.org/mailman/listinfo/humanresolvers

We already had some discussions on the IETF list recently.
You may want to take a look at the archives for an introduction:

http://www1.ietf.org/mail-archive/web/ietf/current/msg48129.html

There is also a side discussion on CAPTCHAs:

http://www1.ietf.org/mail-archive/web/ietf/current/msg48172.html

Regards,
pars mutaf
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From: Dean Willis <[email-masked]>
Date: Thu, 27 Sep 2007 13:01:02 -0500

> for "pairing" two cellular hosts:

This, I believe, is an obvious combination of directory lookup and  
the SIP CONSENT framework.

Doesn't mean it isn't useful.

--
Dean

---

From: [email-masked]
Date: Thu, 27 Sep 2007 17:38:11 -0400

From: "Pars Mutaf" <[email-masked]>

   Model of operation

How do you make this work?  Step 2 seems to require that you have
already located the target phone, whereas the protocol's *purpose* is
to locate the target phone.

Dale

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From: Dean Willis <[email-masked]>
Date: Thu, 27 Sep 2007 19:23:16 -0500

> to locate the target phone.

One possibility is that the directory service is operating on behalf  
of the target, not the searcher. As such, the directory service is  
trusted to know the display name to userID binding. When it receives  
a query, the directory service uses the target's SIP contact  
registration to send a consent request to the target user. If the  
target user response positively, then the directory service returns  
the directory's query result to the searcher.

Basically, another layer of indirection (directory) in front of a  
watcher pattern.

There are probably other embodiments, but that's the obvious one.

--
Dean

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From: "Pars Mutaf" <[email-masked]>
Date: Fri, 28 Sep 2007 13:17:56 +0200

Hello,

Thanx for the message, I hope you and (other SIP experts)
subscribe to the ML:

Personally, I'm not sure if we need a store/forward
solution. We probably don't want to store a pairing
request message while the user is off-line. Because
the request message itself can be used for SPAM.

Maybe a real-time solution is preferable. I.e., if
the target user is off-line we don't care. The querier
needs to try later to get the user's consent.

Personally, I'm also against a SIP-based solution.
This is my personal opinion and of course open to
discussion.

I really hope we can talk about these issues.

Thanks,
pars