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Re: [TLS] The TLS_FALLBACK_SCSV time bomb (was: Re: Working Group Last Call for draft-ietf-tls-downgrade-scsv-00)

Andrei Popov <Andrei.Popov@microsoft.com> Mon, 20 October 2014 22:28 UTC

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From: Andrei Popov <Andrei.Popov@microsoft.com>
To: "Salz, Rich" <rsalz@akamai.com>, Hubert Kario <hkario@redhat.com>
Thread-Topic: [TLS] The TLS_FALLBACK_SCSV time bomb (was: Re: Working Group Last Call for draft-ietf-tls-downgrade-scsv-00)
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Date: Mon, 20 Oct 2014 22:27:45 +0000
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Subject: Re: [TLS] The TLS_FALLBACK_SCSV time bomb (was: Re: Working Group Last Call for draft-ietf-tls-downgrade-scsv-00)
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Having both SCSV and extension would indeed be worse than just having the SCSV. I'm advocating extension as a less hacky, more forward-looking mechanism that also potentially allows more flexibility in the fallback sequence.

Cheers,

Andrei

-----Original Message-----
From: Salz, Rich [mailto:rsalz@akamai.com] 
Sent: Monday, October 20, 2014 2:02 PM
To: Andrei Popov; Hubert Kario
Cc: tls@ietf.org
Subject: RE: [TLS] The TLS_FALLBACK_SCSV time bomb (was: Re: Working Group Last Call for draft-ietf-tls-downgrade-scsv-00)

> >1.3 to 1.2. Over 10% of Internet web servers are intolerant to 1.3 
> >ClientHello

Shrug, since it's not defined I don't think it matters that much.

> 1.3 to 1.2 could be protected by an extension; I think SCSV is only 
> needed to protect the downgrade from TLS1.0 to SSL3.

I would rather not have two mechanisms that do the exact same thing.

--
Principal Security Engineer, Akamai Technologies
IM: rsalz@jabber.me Twitter: RichSalz

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