Subject: RE: [Sipping] Authentication issues with emergency and other serv ices

From: "Rosen, Brian" <[email-masked]>
Date: Fri, 20 Dec 2002 11:58:21 -0500

Well, the basic problem is that you need a global PKI to
have the signature of the signer verified.  That is
a hard problem no one has solved.  You might be able to
provide some traceability using the P-asserted-identity
header, or the subsequent work Jon Peterson has proposed.
That would imply that there is a trusted service provider,
and it wouldn't give you any information about the network
beyond the "demarc".

We have talked about the other side of that problem = 
authenticating that the caller is talking to a bona fide
PSAP.  Even that is seen as an impossibly hard problem =
getting all PSAPs to get a cert signed by a global PSAP
CA.

Brian

> -----Original Message-----
> From: James Hamlin [mailto:[email-masked]]
> Sent: Friday, December 20, 2002 11:31 AM
> To: [email-masked]
> Subject: [Sipping] Authentication issues with emergency and other
> services
> 
> 
> Hi
> 
> The sos draft says: "It appears unlikely that classical
> authentication mechanisms can be required by emergency call centers,
> but SIP proxy servers may be able to add identifying information."
> This is very much in line with existing emergency services. However
> access to the existing services is generally over networks that have
> good means of tracing the geographic location of a caller. The
> Internet does not really have this. I'm concerned that without any way
> for verification of the user's location, an emergency service on the
> Internet would be open to attack from people who reside outside the
> area of jurisdiction in which the emergency service operates.  To
> avoid this it would be better if emergency services gave priority to
> callers who's location was verifiable. Prioritising would still ensure
> that all calls were accepted but that calls from authenticated users
> could not be "swamped" by malicious calls from outside the geographic
> area of the service.
> 
> This leads to the question of what type of authentication to
> use. Digest authentication would not be adequate as one couldn't
> expect every user or proxy to have its own user-name and password for
> the emergency service. A user or a proxy needs to sign the permanent
> parts of the message header, including a certificate that proves their
> geographic location.
> 
> Can SIP fully support this? From what I've read so far, the inclusion
> of an SMIME encoded copy of the header could be added by a proxy or a
> user agent or both so as to verify the identity of the user as well as
> geographic location.
> 
> Can anyone comment on the practicalities of this? In particular are
> there any difficulties with both the user agent and a proxy putting in
> separate authentication with separate certificates?
> 
> Another reason for being interested in this type of authentication is
> that for the purposes of billing for trans-coding, PSTN breakout and
> other services, a user must authenticate themselves. Again users (or
> rather user agents) should not be required to hold separate user-names
> and passwords for each service, they need one standard way to
> authenticate themselves to anyone they call so that each service can
> charge their account seamlessly.
> 
> James Hamlin
> RNID
> [email-masked]
> 
> 
> 
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