Re: [Ntp] The NTP WG has placed draft-schiff-ntp-chronos in state "Call For Adoption By WG Issued"

Neta R S <> Tue, 10 September 2019 10:33 UTC

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From: Neta R S <>
Date: Tue, 10 Sep 2019 13:33:22 +0300
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To: Hal Murray <>
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Subject: Re: [Ntp] The NTP WG has placed draft-schiff-ntp-chronos in state "Call For Adoption By WG Issued"
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Please see my responses inline.

On Tue, Sep 10, 2019 at 1:10 PM Hal Murray <> wrote:

> said:
> > *Threat model: *Chronos considers a powerful form of man-in-the-middle
> (MitM)
> > Byzantine attacker, capable of determining precisely the values of the
> time
> > samples gathered by the Chronos client from a subset of the NTP servers
> in
> > its server pool (up to one-third of the pool).
> I consider that "up to one-third" to be a serious problem.  It doesn't
> cover
> the case where the bad guy has taken over your ISP (or is your ISP) and
> thus
> controls all the traffic to the servers you try to use.  I think that's
> going
> to be a common case.

In this scenario the attacker can drop all the packets from the servers.
I am not sure there is a good solution for this case.
However, we are currently working on extending the threat model.


[Disclaimer: I work on NTS so I'm probably biased.]
> Why should we work on this rather than getting NTS deployed?
I think NTS is important extension for NTP.
We suggest Chronos as a watchdog (for example for cases where the MitM
drops packets).

> There is an additional complication.  You are inventing a new method of
> processing the data from packets that get past your filters.
We suggest to run Chronos side by side with NTP (as a watchdog).

> --
> These are my opinions.  I hate spam.
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