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[TLS] Re: [EXTERNAL] Re: Disallowing reuse of ephemeral keys

Joseph Birr-Pixton <jpixton@gmail.com> Mon, 16 December 2024 14:41 UTC

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From: Joseph Birr-Pixton <jpixton@gmail.com>
Date: Mon, 16 Dec 2024 14:40:22 +0000
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To: Andrei Popov <Andrei.Popov=40microsoft.com@dmarc.ietf.org>
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Subject: [TLS] Re: [EXTERNAL] Re: Disallowing reuse of ephemeral keys
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On Fri, 13 Dec 2024 at 00:30, Andrei Popov <Andrei.Popov=
40microsoft.com@dmarc.ietf.org> wrote:

>
>    - If there are significant implementations which do reuse…
>
> By default, servers using Windows TLS stack reuse ECDHE keys for up to 30
> sec. Reuse time can be configured or altogether disabled by the system
> admin. Disabling comes at a significant performance cost (for a busy TLS
> server).
>

I'd be interested if you have published performance data for this? Right
now a typical laptop-grade CPU can do ~180,000 X25519 base multiplies per
second per core (P256 around 115,000, P384 around 25,000) -- ISTM this is
not a good complexity/performance tradeoff (maybe it was more beneficial in
the past?)

Thanks,
Joe

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