RE: crypto delay (Notes from Non-meeting)

> > Can you cite any evidence that authentication of the
> emergency center by
> > the end device is a requirement?
>
> No. Maybe I misunderstood your original comment about what
> might generate
> the delay.
>
>
> Acatually, I'm not sure whey we spend so much time discussing the
> E911 scenarios, though I'm clearly guilty of doing so myself.
> The reaction
> time thing just caught my eye.
>
One of the "users", probably the first user, of the geopriv object
is emergency calls in SIP. The requirements for emergency calls at the
top level are pretty straightforward, but are clearly subject to
interpretation as you dig down.

Emergency callers have some expectation of privacy. That expectation
is presently pretty limited. There is no harm in providing a higher
level of privacy, provided that you don't screw something up. Response
time is one of those things that can be screwed up. Phones, in general,
have fairly puny processors. SIP phones have beefier processors than
first gen cell phones, and 3G cell phones have processors capable of
non-trivial crypto, but I think we have to keep "fraction of a second
on embedded cpu" goals when we make crypto choices. If we are forced
to choose between increased security and increased response time on
emergency calls, it makes sense to me to choose increased security up
to the point where on a typical SIP phone or 3G handset, you either
overflow limited memory, or more likely limited MIPS. The latter is the
"fraction of a second" kind of thing. I'm presently worried about it,
but there are others who think there are solutions that achieve
strong assurances within the kinds of time/MIPS/Memory constraints
we deal with. I'm certainly not oppossed to trying.

I'll conceed the point that it's possible to have the location information
come later than the call completion. That is undesirable (because
it is actually very interesting to route the call in the emergency center
based on location, something not possible now), but it's concievable.
It's also not a great way to deal with in in SIP - rather than simply
shoving the location in the INVITE, we have to create a mid call dialog.
That is also possible, if undesirable.

Brian
Received on Wed Apr 3 08:29:23 2002