Re: [Ntp] Post NTS, Is shared key authentication interesting?

Miroslav Lichvar <mlichvar@redhat.com> Tue, 26 May 2020 15:23 UTC

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Date: Tue, 26 May 2020 17:23:28 +0200
From: Miroslav Lichvar <mlichvar@redhat.com>
To: Watson Ladd <watsonbladd@gmail.com>
Cc: Daniel Franke <dfoxfranke@gmail.com>, NTP WG <ntp@ietf.org>
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Subject: Re: [Ntp] Post NTS, Is shared key authentication interesting?
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On Tue, May 26, 2020 at 10:55:41AM -0400, Watson Ladd wrote:
> On Mon, May 25, 2020 at 9:29 AM Daniel Franke <dfoxfranke@gmail.com> wrote:
> > I would like NTPv5's shared key authentication to be a little more closely integrated with NTS. Either accomplish it by doing a PSK TLS handshake for NTS-KE, or skip NTS-KE and have pre-shared S2C/C2S keys and a shorter cookie giving just a key ID.
> 
> I think PSK TLS is a better idea: all the complexity gets dumped on
> the TLS stack, while the NTP specific parts don't change.

A different point of view would be to avoid exposing the NTS+TLS stack
to attackers if not necessary. The complexity of the NTP MAC is
minimal when compared to that.

-- 
Miroslav Lichvar