Re: [stir] Permitted spoofing

[Hadriel Kaplan <[e-mail]>]

On Jun 7, 2013, at 10:23 PM, Henning Schulzrinne <[e-mail]> wrote:

> That's probably something we might want to flesh out a bit. My very rough vision in the central database case would be something like the following:
> 
> (1) Owner [doctors' office] says: "Please mint a cert that entitles Doctor Smith [public key attached] to use our number 555 1234." [signed by assignee]
> (2) Database returns cert, which is handed to doctor.
> (4) Doctor uses cert just like any other.

If we want such a thing to work in the near-term timeframe, I don't think it can work that way.  For one thing I don't expect phones to be able to do the signing themselves, nor their access service providers to believe/trust the phones.  As far as I know, today the Doctor phone's service provider has to be in on it, and the provider equipment is provisioned to know the Doctor's phone can claim another caller-id (e.g., P-Associated-URI).  I think it's a big jump to expect them to let any subscriber to claim to be any number just because the supposed holder of that number "authorized" them to.  Even ignoring the P/S-CSCF type equipment, there're a lot of other systems involved in this stuff, for billing, CALEA, troubleshooting, etc.

A more likely scenario is:
(1) Doctor's office submits a request form with its service provider to add Doctor's phone as authorized user for office number caller-id, or with Doctor phone's service provider as a pull request.

(2) The service providers fax each other authorization forms with legal signatures.

(2b) If there is some big central database model, then the Doctor phone's service provider gets added as second source for the Office number.

(3) The Doctor phone's service provider adds into its databases the Office caller-id as an authorized associated number for the phone to use for outbound calls, which triggers associated identity handling during next phone registration.

(4) The Doctor makes an outbound call using the Office number, which the service provider authorizes and signs using its own cert.

-hadriel