Re: DTLS-SRTP harming GETS [was RE: Additional use cases? (Re: Plan for moving forward)]

[Eric Rescorla <ekr@xxxxxxxxxxxxxxxxxxxx>]

At Tue, 12 Jun 2007 21:20:55 -0700,
Lakshminath Dondeti wrote:
> 
> Someone at the IETF recently said that I don't try enough :) , so I 
> guess I will continue on since you don't understand what I am trying to say.

Much appreciated.


> On 6/12/2007 8:38 PM, Eric Rescorla wrote:
> > At Tue, 12 Jun 2007 20:24:55 -0700,
> > Lakshminath Dondeti wrote:
> >> On 6/12/2007 7:55 PM, Dan Wing wrote:
> >>> That's reasonable.  But it is an optimization that saves ~600 bytes 
> >> Ah, the luxury!  This reminds me of the time when a few of us were given 
> >> a budget of 40 octets after some serious kicking and screaming :). 
> >> Different context for sure.
> 
> It looks like the 40 octet number was confusing, but I was just giving a 
> real example of a budget I got for each message of a security protocol 
> (unrelated to SRTP or SIP) in a wireless system.

And I was just pointing out that the analogy was likely to be inappropriate.

 
> > Well, I don't, at least if the implication is that you don't need to
> > authenticate both sides. On the contrary, as I've observed several
> > times, even where the callee has some in-band authentication
> > mechanism, it's desirable to cryptographically bind the media to the
> > signalling.
> 
> Where do these requirements that are universally applicable to all 
> scenarios come from? What if the callee (calling card gateway) does not 
> care which phone the calling card user may be using?  That is a real 
> scenario!

Yes, I've already addressed the reasons why it's still desirable to
tie the signalling to the media in this case several times.

-Ekr