Re: [Sip] New I-D on RFC4474 and phone numbers

["Tschofenig, Hannes (NSN - FI/Espoo)" <[e-mail]>]

Hi Jonathan, 
Hi Paul,

thanks for raising the aspect of E.164 and ENUM usage. There was an offline discussion between Dan Wing, Klaus Darilion, Kai Fischer, David Schwartz, Hadriel Kaplan, John Elwell, and myself about E.164 and SIP Identity. As part of the discussion Klaus and I polished a former document of Alexander Mayrhofer on the usage of ENUM for E.164 numbers (see draft-mayrhofer-enum-domainkeys-00). As we moved along with the work we obviously came across a couple of problems (as one can easily imagine) and the document triggered a long discussion among us. Dispite a couple of challenges, we published the document today (see http://www.ietf.org/internet-drafts/draft-darilion-sip-e164-enum-00.txt). I learned a lot while working on that document. 

In addition to publishing the document a few of us have also worked on a document that captures some of our discussion on E.164 number ownership. I will publish it very soon -- just a bit more proof-reading. 

Ciao
Hannes 

> -----Ursprüngliche Nachricht-----
> Von: [e-mail] [mailto:[e-mail]] Im 
> Auftrag von ext Jonathan Rosenberg
> Gesendet: Montag, 18. Februar 2008 21:36
> An: Paul Kyzivat
> Cc: IETF SIP List
> Betreff: Re: [Sip] New I-D on RFC4474 and phone numbers
> 
> I agree that something along the lines of enum could solve 
> this problem, 
> and I believe there was a draft that proposed such a thing. This has 
> been discussed since the start of rfc4474.
> 
> However, I fear that saying, 'use enum' is kind of like saying, we'll 
> just use an All-Knowing Oracle, so lets figure out the interface 
> protocol to the Oracle. The easy part is the interface (the enum 
> mechanism). The actual hard problem is how to get those entries 
> populated. The deployment of public enum has been - shall we 
> say - less 
> than spectacular. I'd hate for that to be our only solution. Not that 
> its obvious what else to do; though I do suggest in my draft 
> how domain 
> based authentication, when combined with whitelists and 
> blacklists, can 
> help.
> 
> -Jonathan R.
> 
> Paul Kyzivat wrote:
> > Jonathan,
> > 
> > I guess the time has come for this discussion, since John 
> Ewell has also 
> > submitted a draft on this subject.
> > 
> > I thought the problem was already well known, but perhaps 
> not. IMO the 
> > main thing now is to figure out the *solution* to the problem!
> > IMO a solution is to use a 4474-style approach, but where the 
> > certificate is tied to just the phone number, not to some arbitrary 
> > domain name. That of course would depend on a model where 
> the "owner" of 
> > the phone number is the one who may obtain the certificate 
> for that number.
> > 
> > My thought is that we already have an algorithmic mapping 
> from an E.164 
> > phone number to a domain name, defined by enum. If the 
> sender puts an 
> > E.164 number in From, and can sign it with a cert for the 
> enum mapped 
> > domain name corresponding to that number, then that ought 
> to be valid 
> > proof of the validity of the sender.
> > 
> > In those places where public enum is in operation, I think there is 
> > already a legal mechanism in place to give the owner of record of a 
> > particular phone number control over the contents of the 
> corresponding 
> > DNS entry. That should also be sufficient to allow a certificate 
> > authority to assign a cert to that same owner.
> > 
> > Combine all that and you have a complete e2e identity model 
> for phone 
> > numbers, based on public enum. And that can be true even if 
> public enum 
> > isn't used to *route* the calls to that number. So it could 
> be used for 
> > "unlisted" numbers.
> > 
> > To use this approach the From header should contain either 
> a TEL URI, or 
> > a sip/sips URI containing the enum-mapped domain name 
> corresponding to 
> > the phone number. (I would rather see the TEL used for this 
> - it is more 
> > user friendly.)
> > 
> >     Thanks,
> >     Paul
> > 
> > Jonathan Rosenberg wrote:
> >> I just submitted:
> >> 
> http://www.ietf.org/internet-drafts/draft-rosenberg-sip-rfc447
> 4-concerns-00.txt 
> >>
> >>
> >> This is basically a discussion on the security properties 
> of rfc4474 
> >> with phone numbers, and a comparison to rfc3325 in this 
> case. Also a 
> >> discussion on what happens to dtls-srtp.
> >>
> >> Comments welcome.
> >>
> >> -Jonathan R.
> > 
> 
> -- 
> Jonathan D. Rosenberg, Ph.D.                   499 Thornall St.
> Cisco Fellow                                   Edison, NJ 08837
> Cisco, Voice Technology Group
> [e-mail]
> http://www.jdrosen.net                         PHONE: [phone]
> http://www.cisco.com
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