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List:       nanog
Subject:    Re: NTP Sync Issue Across Tata (Europe)
From:       "Jay R. Ashworth" <jra () baylink ! com>
Date:       2023-08-14 0:34:56
Message-ID: 438745102.3142.1691973296658.JavaMail.zimbra () baylink ! com
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Gotcha.  The Bad Guys are smarter than me.  :-)

Cheers,
-- jra

----- Original Message -----
> From: "Forrest Christian (List Account)" <lists@packetflux.com>
> To: "jra" <jra@baylink.com>
> Cc: "nanog list" <nanog@nanog.org>
> Sent: Sunday, August 13, 2023 8:06:30 PM
> Subject: Re: NTP Sync Issue Across Tata (Europe)

> If I'm spoofing time, I'm going to produce an entire constellation of
> satellites.   That is, I'm going to provide a signal which looks like all
> of the satellites in view providing their timing signals on whatever time I
> want your GPS receiver to think it is.   All I have to do is ensure that
> your receiver receives my signal loud enough that it thinks the real
> satellites are noise, and my signal is the real one.
> 
> This isn't that hard to accomplish, especially since there are youtube
> videos showing you how.
> 
> On Sun, Aug 13, 2023 at 6:03 PM Jay R. Ashworth <jra@baylink.com> wrote:
> 
>> ----- Original Message -----
>> > From: "Forrest Christian (List Account)" <lists@packetflux.com>
>>
>> > Let me address your points:
>> [ ... ]
>> > Let's assume you have a typical GPS-derived NTP server using a typical
>> > commercially available timing GNSS module.  To convince that receiver
>> that
>> > it was a different time, I'd need to have an SDR that would operate in
>> the
>> > GPS band.  These are widely available for under $500.  You'd also need a
>> > laptop and a download of a GPS simulator from GitLab.   With a total
>> > investment of $500 (assuming I already have a laptop), I now have a
>> system
>> > that can generate a GPS signal to convince your GPS receiver that it's
>> any
>> > time at all.  If you're a tech neophyte, there are youtube videos on how
>> to
>> > do this.
>> >
>> > All I need to do now is add appropriate antennas and/or amplifiers to
>> > overcome the official GNSS signals.   As you pointed out, depending on
>> the
>> > location and directivity of your antenna, this is either trivial or
>> becomes
>> > slightly more difficult.   If I can see your antenna, it becomes a lot
>> > cheaper as I just need a relatively low-powered amplifier and a highly
>> > directional antenna.   If I can't see your antenna, I would opt for a
>> > higher-power amplifier and a less directional transmit antenna to
>> blanket a
>> > wide area with the spoofed signal.
>>
>> If I'm trying to get time out of a NAVSTAR (yes, I know, shut up) receiver,
>> it can see like 8-20 birds, right?  Is there not some voting and such
>> inside
>> such a receiver?  Just letting it see one 'bird' with spoofed time doesn't
>> seem like it ought to work, to me; what don't I know?
>>
>> Cheers,
>> -- jra
>> --
>> Jay R. Ashworth                  Baylink
>> jra@baylink.com
>> Designer                     The Things I Think                       RFC
>> 2100
>> Ashworth & Associates       http://www.bcp38.info          2000 Land
>> Rover DII
>> St Petersburg FL USA      BCP38: Ask For It By Name!           +1 727 647
>> 1274
>>
> 
> 
> --
> - Forrest

-- 
Jay R. Ashworth                  Baylink                       jra@baylink.com
Designer                     The Things I Think                       RFC 2100
Ashworth & Associates       http://www.bcp38.info          2000 Land Rover DII
St Petersburg FL USA      BCP38: Ask For It By Name!           +1 727 647 1274
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