1. Emergency call assurance

2. Highest-level goals Protect PSAP resources
network resources
call takers
Protect first-responder resources
unnecessary dispatch
No worse than today
local attack vs. non-local
discourage abuse

3. Threats (D) DDOS (bots) (C) Hoax/crank calls (humans)
(L) from within local service area
(R) outside local area
(C) Hoax/crank calls (humans)
(L) at correct location
(R) at another (fake) location

4. Discouragement Distinguish bots from humans
including silent calls
Catch likely remote (bogus) calls
Catch perpetrators after the call
discourages crank calls

5. can be signature or transitive trust (reference)
Tools and impact
can be signature or transitive trust (reference)
Coarse-grained location assertion
e.g., IP address, provider POP, DSLAM, ...
addresses D/R
Fine-grained location
e.g., geo, street address
can be by value (“signing”) or reference
address C/L
Coarse-grained identity
provider (VSP)
addresses C/R?
Fine-grained identity
responsible party (caller) name & address
may not be useful if outside jurisdiction
addresses D/L, C/L, C/R (some)

6. Nothing is perfect
Unlikely that every legitimate call will have the “good” bits set (signed, recognizable signer, trusted reference, ...)
Realistic goal is that “almost all” good calls are verifiable
rest is treated as suspicious when call taker resources are available
similar to payphone calls today
and will be lower priority during overload (“ranking”)
Thus, don’t need perfection in any single technique
combination of techniques likely works better
choose easiest-to-deploy
every call should have one at least one “is good” indicator

7. Deployment scenarios, from easy to hard
ISP = VSP
includes large enterprise
well-known (to PSAP) VSP, well-known ISP
well-known VSP with strong customer authentication
e.g., credit card address (“can sue”)
could be emergency-only VSP
well-known ISP with authentication
well-known ISP without authentication
“unauthenticated network access”
e.g., guest on corporate or home hot spot or public WiFi
unknown ISP/VSP
e.g., out of area (“Sierra Leonian VSP”)

8. Concerns: Delegation
identity assurance: subscriber identity within service provider
SIP identity, PAI
location signing: within enterprise (room/building level)
ISP customers gets signed LO
includes in calls
or private key to sign own LOs?
enterprise as trusted CA?

9. Questions: Value or Reference?
sign LO
fine-grained
or get LO from trusted/verifiable source via TLS?
e.g., corporate LIS