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Re: [TLS] Downgrade SCSV info

Rob Trace <Rob.Trace@microsoft.com> Thu, 13 November 2014 03:54 UTC

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From: Rob Trace <Rob.Trace@microsoft.com>
To: "tls@ietf.org" <tls@ietf.org>
Thread-Topic: Re: [TLS] Downgrade SCSV info
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Date: Thu, 13 Nov 2014 03:54:12 +0000
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Subject: Re: [TLS] Downgrade SCSV info
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> 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.)

When we looked at the fallback to HTTP 1.1, it was just as Martin stated and there were almost 0 times when the connection completed over TLS 1.1.  The 1.1 fallback was a lot of wasted roundtrips and did not provide any value.

I am not sure what a wasted fallback to HTTP 1.1 would provide with SCSV, in that the TLS 1.0 fallback would still result in the inappropriate_fallback before we send any data.

Thanks!!

-Rob

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