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Re: [TLS] RI, TLS Extension tolerance and version tolerance in

David-Sarah Hopwood <david-sarah@jacaranda.org> Tue, 15 December 2009 03:51 UTC

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Date: Tue, 15 Dec 2009 03:51:36 +0000
From: David-Sarah Hopwood <david-sarah@jacaranda.org>
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Subject: Re: [TLS] RI, TLS Extension tolerance and version tolerance in
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Yngve Nysaeter Pettersen wrote:
> On Mon, 14 Dec 2009 20:11:48 +0100, Martin Rex <mrex@sap.com> wrote:
> 
>> What you could use is either the MS SGC logic (which internally
>> restarts the handshake mid-way), or successfully complete the
>> handshake and renegotiate immediately after with better features.
> 
> Not a good idea since it requires that the server knows about it. MS was
> in charge of both sides for SGC.

Indeed, when MS SGC was first implemented, it completely broke
interoperability:

<http://support.microsoft.com/kb/249863>

# Web clients may fail to connect to Web sites that use Server Gated
# Cryptography (SGC) for strong encryption when a secure connection is
# required. If either the Internet server or Web client is running Microsoft
# products, then the connection may fail. If the Internet server and Web
# client are both running Microsoft products, then no problem occurs.

I don't know how this was fixed, but it seems as though encouraging
the use of an MS SGC-style protocol in other implementations is just
asking for more interoperability problems.

-- 
David-Sarah Hopwood  ⚥  http://davidsarah.livejournal.com

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