Subject: [humanresolv] Trying to open discussion

From: "Pars Mutaf" <[email-masked]>
Date: Thu, 20 Mar 2008 19:49:27 +0200

Hello humanresolvers,

Hoping that this ML is not my personal IETF blog ;-)
I would like to ask your opinion on the following idea.

Pairing protocol (basic)
========================

What it does?

1. Mutual authentication using [SAS].
2. Sign each other's certificate.
3. Exchange SIP URIs.
4. Exchange Mobile IPv6 home addresses and other information.

What is the outcome?

1. IPsec or TSL can be used.
2. No need to use SIP triangle nor trapezoid.
	->More reliable
        ->Faster connection establishment.

[SAS] Vaudenay, S., "Secure Communications over Insecure
      Channels Based on Short Authenticated Strings", Advances
      in Cryptology, CRYPTO 2005.

Review of [SAS]:
One user tells (i.e. orally) to the other a short auth
string and their phone get mutually authenticated. The
contribution of [SAS] is that it shortens and simplifies very
much the authentication string. 15-20 bits are enough. The
general belief is that the pairing problem was solved
by this paper.
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From: "Pars Mutaf" <[email-masked]>
Date: Fri, 21 Mar 2008 10:44:47 +0200

More detailed:

IP Pairing protocol

1. Face-to-face

Alice and Bob have face-to-face contact.
Bob tells his pseudo to Alice.
Alice enterw the pseudo.
They perform mutual authentication using a short authentication
string [SAS].
Alice and Bob sign each other's certificate, exchange SIP URIs and
mobile IPv6 home addresses. Note that Alice and Bob can communicate
without using SIP infrastructure since they know each other's home
address.

2. Remote

2.1 Web of trust

Bob finds Carol's home address or DNS name on the web. Bob makes a
query to Carol by clicking on the home address, and shows his
certificate signed by Alice. Carol knows Alice, hence she accepts
to return a SIP URI and possibly another home address to Bob.

2.2 Certification authority (CA)

Bob and Carol may also have cerfiticates signed by the same SA.
In this case, Carol can accept Bob's query.

3. Pairing update

The pairing protocol should take care of pairing state
changes e.g. SIP URIs, home addresses, requesting additional
information HTTP access to the target phone etc.