Re: [Sip] A proposal for breaking the DTLS-SRTP vs RFC4474 gatewaydeadlock

["Fischer, Kai" <kai.fischer at siemens.com>]

If it is the goal to proceed with the DTLS-SRTP framework timely and to
reach the milestone, that's the only reasonable approach. However, I
hope there will be support to fix RFC 4474 and we can address the
backwards compatibility issues.

Kai


> -----Original Message-----
> From: sip-bounces at ietf.org [mailto:sip-bounces at ietf.org] On 
> Behalf Of Dean Willis
> Sent: Dienstag, 24. Juni 2008 19:22
> To: sip at ietf.org; Eric Rescorla; Jason Fischl
> Cc: Cullen Jennings; Keith Drage
> Subject: [Sip] A proposal for breaking the DTLS-SRTP vs 
> RFC4474 gatewaydeadlock
> 
> 
> We've gotten stuck on a fine point in DTLS-SRTP.
> 
> The current draft-ietf-sip-dtls-srtp-framework-01 uses an RFC 4474  
> Identity header to preserve the integrity of the media key's  
> fingerprint, thereby detecting a certain class of MITM attack.
> 
> However, RFC 4474 Identity headers are of questionable validity when  
> used with protocol gateways or B2BUAs.  More or less, they're 
> capable  
> of asserting the identity of the gateway, not the identity of the  
> calling party. But the recipient has no real way to figure out which  
> is which.
> 
> We've debated at some length, and with no good result, about whether  
> we should try and fix RFC 4474. We've had some suggestions that may  
> work for B2BUAs, and some other suggestions that may work for  
> gateways, but we certainly don't have a consensus.
> 
> That leaves our chartered deliverable of DTLS-SRTP hanging, and the  
> milestone has gone past months ago.
> 
> Here's a proposal:
> 
> We add a caveat about the limitation of RFC 4474 to draft-ietf-sip- 
> dtls-srtp-framework and go ahead and advance that specification. If  
> somebody later decides to fix RFC 4474, they can do so, and if  
> necessary update DTLS-SRTP if needed.
> 
> 
> Does that work for everybody?
> 
> If we agree to it, I suggest that we move the date for WGLC of draft- 
> ietf-sip-dtls-srtp-framework to July 2008, and move the 
> milestone for  
> delivery of that doc to the IESG into September.
> 
> --
> Dean
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