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

Töma Gavrichenkov <ximaera@gmail.com> Sat, 08 December 2018 16:49 UTC

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From: =?UTF-8?Q?T=C3=B6ma_Gavrichenkov?= <ximaera@gmail.com>
Date: Sat, 8 Dec 2018 19:49:14 +0300
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Subject: Re: [TLS] draft-dkg-tls-reject-static-dh
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On Wed, Dec 5, 2018 at 10:47 PM R duToit <r@nerd.ninja> wrote:
> 2. The DoS (prevention) engineers should also weigh in on this.  Would servers not start reusing TLS 1.3 keyshare values when under DoS attack?

DDoS (mitigation) engineer here,

I'll reiterate the idea I've raised before in quic-wg. The operation
of a server (or a client, because a client could be attacked too)
under a DDoS attack should be as close to a normal way of operation as
possible. Every single case where it's different should be seen as
opening a motivation for an attacker to hunt exactly for that
difference. E.g. if you add RTTs under an attack, then an attacker can
play with jitter, or make your server appear slower for clients than
their server (assuming the attack is ordered by your market
competition).

(This is by the way the reason why fast open wasn't a nice idea from
the DDoS mitigation perspective)

So no. TLS keyshare reuse is visible from the attacker's point of
view, so must not be done under a DDoS attack.

| Töma Gavrichenkov
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