Re: [TLS] What would make TLS cryptographically better for TLS 1.3

"Dan Harkins" <dharkins@lounge.org> Fri, 01 November 2013 22:38 UTC

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Date: Fri, 1 Nov 2013 15:38:06 -0700 (PDT)
From: "Dan Harkins" <dharkins@lounge.org>
To: "Robert Ransom" <rransom.8774@gmail.com>
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Subject: Re: [TLS] What would make TLS cryptographically better for TLS 1.3
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On Fri, November 1, 2013 2:34 pm, Robert Ransom wrote:
> On 10/31/13, Nico Williams <nico@cryptonector.com> wrote:
>
>>  - Many fewer nonce bytes and random IVs where possible.  Nonce payloads
>>    should be sent when needed, if needed.  For example, to derive a
>>    session key from an DHE shared secret one does not really need
>>    nonces.  This means that counter modes are better, for example, than
>>    CBC modes.
>
> If the server sends a nonce during a DHE/ECDHE key exchange, the
> server can safely reuse its DH keypair for multiple clients with no
> further design or implementation considerations.

  I don't believe that's true. If the server reuses its ephemeral D-H key
then caveat emptor applies-- it should validate the client's public key,
regardless of whether a nonce is sent or not.

  Dan.