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Re: [TLS] Downgrade SCSV info

Martin Thomson <martin.thomson@gmail.com> Tue, 11 November 2014 23:28 UTC

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Date: Tue, 11 Nov 2014 15:28:27 -0800
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From: Martin Thomson <martin.thomson@gmail.com>
To: Bodo Moeller <bmoeller@acm.org>
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Subject: Re: [TLS] Downgrade SCSV info
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On 11 November 2014 14:10, Bodo Moeller <bmoeller@acm.org> wrote:
> TLS 1.0 with TLS_FALLBACK_SCSV?

I don't believe so.

>> It is my opinion that this is not that large a risk.  We are highly
>> likely - in my opinion, and based on the numbers we have - to have few
>> TLS 1.1 servers that are both intolerant to the TLS 1.2 handshake AND
>> implement the downgrade SCSV.
>
> Right, although it couldn't hurt for the client to try TLS 1.1 next in case
> it sees an inappropriate_fallback alert. (Then in the end you have
> essentially the same outcome as if trying the protocols in decreasing order,
> in the presence of an active attacker forcing you to downgrade.)

The 1.1 handshake would need the SCSV.

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