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Date: Mon, 10 Nov 2014 11:04:54 -0800
Message-ID: <CABkgnnVLOZSK_U2bDJKQ0fUyvkUyJ83W71Yym+GeZ2xnyLtxjg@mail.gmail.com>
From: Martin Thomson <martin.thomson@gmail.com>
To: Dan Brown <dbrown@certicom.com>
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Archived-At: http://mailarchive.ietf.org/arch/msg/tls/Z6jXze3arp7tDY8JZzDAlaWyhXA
Cc: "hoeteck@alum.mit.edu" <hoeteck@alum.mit.edu>,
 "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] rm Hello.random w/ (EC)DHE [was OPTLS: Signature-less TLS
 1.3]
Precedence: list

On 10 November 2014 09:58, Dan Brown <dbrown@certicom.com> wrote:
> When using (EC)DHE (inc. OPTLS below), the TLS random nonces
> (ClientHello.random and ServerHello.random) seem redundant (unless one
> re-uses ephemeral secret keys (but then maybe a counter or secure time wo=
uld
> be almost as good a nonce as a random in this case), or perhaps for some
> other reason I=E2=80=99m missing), and perhaps even a point of fragility =
(e.g. if a
> common generator for nonces and keys is weak, or corrupted). So, does it
> make sense to remove these Hello.randoms, when using (EC)DHE, or to repla=
ce
> them with something milder, like Hello.time, Hello.counter, or just
> Hello.nonce?

Aren't they still highly relevant in the resumption cases?  In which
case, a new source of entropy ensures that two sessions resumed from
the same base don't have synchronized keys.