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

"Salz, Rich" <rsalz@akamai.com> Wed, 27 May 2020 13:33 UTC

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From: "Salz, Rich" <rsalz@akamai.com>
To: Kurt Roeckx <kurt@roeckx.be>, Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de>
CC: "mlichvar@redhat.com" <mlichvar@redhat.com>, Hal Murray <hmurray@megapathdsl.net>, "ntp@ietf.org" <ntp@ietf.org>
Thread-Topic: [Ntp] Antw: [EXT] Re: Post NTS, Is shared key authentication interesting?
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Date: Wed, 27 May 2020 13:33:00 +0000
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Subject: Re: [Ntp] Antw: [EXT] Re: Post NTS, Is shared key authentication interesting?
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>    sending an error message that something with the crypto was bad
    it a bad idea. You should pretend that everything was ok. An
    attacker should not be able to see the difference between an ok
    and a not ok message. Look for instance at the TLS RFCs what they
    write about a Bleichenbacher attack.

Yes!

This is known as an oracle, and from this kind of thing, it is possible to do pretty fine-grain timings and figure out keys.  This is often surprising to folks, but look up "Lucky Thirteen" as an example.