RE: [Sipping-emergency] Comment about Charter [no privacy?]

["McCalmont, Patti" <[e-mail]>]

 A couple of comments, in line.

Patti McCalmont

-----Original Message-----
From: [e-mail]
[mailto:[e-mail]] On Behalf Of Henning
Schulzrinne
Sent: Friday, October 29, 2004 8:23 AM
To: Brian Rosen
Cc: 'James M. Polk'; [e-mail]; 'Tschofenig Hannes'
Subject: Re: [Sipping-emergency] Comment about Charter [no privacy?]

Brian Rosen wrote:

> I would think that given the history in geopriv over this issue, that 
> we aren't going to get IETF to publish an RFC where not reporting 
> location is incompliant with a spec; we have a sufficient number of 
> people who feel passionately that an individual cannot be COMPELLED to

> report location.  This is quite easily dealt with by using SHOULD
language.
> The emergency call system can choose to accept such calls or not, as 
> local regulations dictate.

It's a bit more complicated than that, as there are at least three
reasons not to provide location:

(1) The calling end system (and elements along the call path) may not
know the location; this is obviously going to be quite common,
particularly in the early days. Having the PSAP refuse all such calls
seems unwise.

<PLM> There needs to be location provided by some source to enable a
PSAP to assist with the emergency request. Developing systems without
the ability to provide location for an emergency call is unwise.

(2) The caller may refuse to give his location for good or bad reasons.

<PLM> In North America, this is not allowed. An area that supports E911
has all their callers in the ALI database (yes, there can be errors but
there is a process to correct these). No one can opt out. A solution
that compromises the current North American level of service would not
be acceptable.

(3) The caller may not be at the scene of the emergency or may report a
non-emergency-related issue and have a legitimate interest not to report
his location or identity. (I suspect quite a few crime tips are phoned
into 911, even though they might not be emergencies as such.)

<PLM> dialing 9-1-1 provides location so a user doesn't get a choice.

I don't think we need to deal with (3). A PSAP could simply tell the
caller that the call location is recorded and provide an anonymous tip
line number.

I don't think including "sorry, I wish I could provide my location, but
I can't" is particularly useful since bad guys will have little
compunction about fibbing.

<PLM> Agreed. That's why location must be validated and delivered to the
PSAP in conjunction with the call.

In addition, "providing location" is not binary. I might decide or be
able to provide location sufficient to route the call (e.g., town
level), but not to dispatch a fire engine (house level).

I'm not sure what to do about this. In classical 911, this is easy since
the system can compel you to provide location.

In practice, I don't think this is as big a problem. People routinely
call 911 from payphones or non-phase-II cell phones today, where even
knowing the location doesn't exactly help you to find malicious callers.

<PLM> But it can help, especially if there is an officer near the
location when the PSAP receives the prank call.

The best we can probably do is to provide degrees of assurance so that
the responder can better tell if he should be suspicious of the call and
maybe question the caller a bit more. ("What's the name of the cross
street? How come it's dead quiet in the background when you're on
Broadway and 42nd street?")

<PLM> Better to provide information within the record delivered to the
PSAP on the "assurance" of the caller's location rather than needing to
train all PSAPs to be more suspicious because the signaling interface
has changed.

Patti

> 
>  
> 
> The most straightforward method of providing authentication would be 
> to have the location object signed by a trusted entity.  I've had a 
> running dialog with James Winterbottom and his co-authors on this 
> subject; I maintain it is not practical to always have a trusted 
> entity, but let's say, for this discussion, that there is.  If only 
> the location object itself is signed, and no other identifying piece 
> of information that attaches an identity to the location, then you can

> assure that the location report itself has not been modified, but you 
> don't know that the object represents the location of the entity
presenting it (you are
> subject to a replay attack).   The only way to be assured that the 
> location object represents the entity presenting it would be to have a

> credential or other identifier in the signed object that was 
> verifiable by the entity receiving the call as belonging to the entity

> placing the call.  I have no idea what such a credential/identifier 
> could be because, as I will show, the entity that could reasonably 
> sign the LO doesn't have any identity for the entity placing the call 
> when it has to sign the object; they are entirely disconnected from 
> one another.  This thread is about how to make sure that whatever 
> identifier is used, it can't be used to specifically identify a 
> person.  That still doesn't solve the problems of what entities could 
> reasonably assert location validation, and how any form of anonymous, 
> but authenticated, location could be provided.  I have no suggestions.
> 
>  
> 
> Brian

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