Re: [TLS] draft-dkg-tls-reject-static-dh

Tony Arcieri <bascule@gmail.com> Sat, 08 December 2018 16:06 UTC

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From: Tony Arcieri <bascule@gmail.com>
Date: Sat, 8 Dec 2018 08:05:57 -0800
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To: Peter Gutmann <pgut001@cs.auckland.ac.nz>
Cc: Nico Williams <nico@cryptonector.com>, "<tls@ietf.org>" <tls@ietf.org>
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Subject: Re: [TLS] draft-dkg-tls-reject-static-dh
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On Thu, Dec 6, 2018 at 11:14 PM Peter Gutmann <pgut001@cs.auckland.ac.nz>
wrote:

> [0] "In principal" because there's a fair bit of SCADA gear that does this
>     because it doesn't have the CPU power to generate new DHE values, as I
>     found out when I turned on non-DHE checking some years ago.
>

I think these concerns can largely be addressed by ECDHE with e.g. X25519:

https://eprint.iacr.org/2015/343.pdf

This implementation does variable-base X25519 scalar multiplication in
13,900,397 cycles, or ~0.869s on a 16MHz AVR CPU commonly found on
Arduinos. I imagine fixed-base scalar multiplication can be further
optimized.

-- 
Tony Arcieri