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Re: [TLS] Call for acceptance of draft-moeller-tls-downgrade-scsv

Adam Langley <agl@google.com> Tue, 28 January 2014 01:52 UTC

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From: Adam Langley <agl@google.com>
Date: Mon, 27 Jan 2014 20:52:22 -0500
Message-ID: <CAL9PXLxDWUMUq5rJXCHYaFRqX6rYfczN8gJaBRJa=pbkH4YWSA@mail.gmail.com>
To: Andrei Popov <Andrei.Popov@microsoft.com>
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Subject: Re: [TLS] Call for acceptance of draft-moeller-tls-downgrade-scsv
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On Mon, Jan 27, 2014 at 8:04 PM, Andrei Popov
<Andrei.Popov@microsoft.com> wrote:
> For my understanding: why is this proposal vitally dependent on the server sending inappropriate_fallback alert? If the server receives the SCSV, has a higher protocol version enabled than that in the ClientHello, and quietly aborts the handshake, isn't the downgrade attack thwarted?

Yes, just closing the connection is good enough for security. The
advantage of returning the fatal alert is that a) it stops the
fallback process faster and b) the client can report the error that
caused the original connection to fail, rather than that the final
fallback hit connection closed.


Cheers

AGL

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