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

Daniel Franke <dfoxfranke@gmail.com> Mon, 25 May 2020 21:45 UTC

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From: Daniel Franke <dfoxfranke@gmail.com>
Date: Mon, 25 May 2020 17:45:01 -0400
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To: Harlan Stenn <stenn@nwtime.org>
Cc: NTP WG <ntp@ietf.org>
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Subject: Re: [Ntp] Post NTS, Is shared key authentication interesting?
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On Mon, May 25, 2020 at 5:22 PM Harlan Stenn <stenn@nwtime.org> wrote:

>
>
> On 5/25/2020 6:29 AM, Daniel Franke wrote:
> > Yes, shared-key authentication is still interesting.
> >
> > Putting the MAC in an extension field is clearly how NTPv4 should have
> > done things from the start,
>
> Wow.  Exactly how would that have worked?
>

 This is a bizarre question coming from a co-author of
draft-mayer-ntp-mac-extension-field. What do you think would have been
troublesome? If NTPv4 — the same version which introduced extension fields
— had specified that everything following the header is an extension field,
specified one such extension field containing a key-id and MAC, and
forbidden NTPv3-style legacy MACs from appearing in v4 packets, then
everything would be straightforward, there would be no syntactic ambiguity,
and RFC 7822 would not have been needed.