[TLS] Chatter on consensus

"Kemp, David P." <DPKemp@missi.ncsc.mil> Wed, 27 January 2010 14:40 UTC

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Date: Wed, 27 Jan 2010 09:39:34 -0500
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From: "Kemp, David P." <DPKemp@missi.ncsc.mil>
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Subject: [TLS] Chatter on consensus
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-----Original Message-----
From: Yoav Nir [mailto:ynir@checkpoint.com] 

> I've stayed out of this discussion so far, because my opinion has
> been noted, but since you've changed the subject...

Actually Martin and I failed to change the subject while changing the
Sorry.  Fixed.  Ietf list dropped.

> "SCSV means the client supports RI". There. That was easy to
> An empty extension is less easy IMO.

"RI means the client supports RI" is less easy?  That doesn't pass the
sniff test.

> And this would be very important, if the world was holding its breath
> waiting for RI. I think it will take several years before RI is really
> deployed in a useful way, so I don't agree that spending a few more
> weeks getting it right is wrong because we have to publish this thing

Agreed.  As noted earlier, I think -03 has already gotten it right in
terms of normative requirements -- MUST NOTs.  I have no position
on whether informative text should continue to be refined.

> To me RI looks like a hack just as much as SCSV. Hopefully in the
> the way to indicate support for secure renegotiation would be in the
> client version of the ClientHello.

I don't understand.  The essence of negotiation is "client sends
it supports, server responds with the intersection of what it supports."

* Client sending an extension to say it supports that extension is
* Client sending an extension with no prior context to signal that there
was no prior handshake sounds logical to me.
* Client sending an extension with prior context to signal that there
a prior handshake sounds logical to me.

* Client sending a ciphersuite to say it supports an extension, and
responding with an extension that was not sent by the client is an
unprecedented exception to a general rule (i.e., a hack).
* Client sending a ciphersuite to say it supports an extension in the
message that contains that extension is redundant (i.e., a hack).