Wirt,

But what are the chances that it would be possible to receive the EMI
from an HP3000 and reassemble that mess into something intelligible? I
would agree that intercepting a really noisy CRT would be easy.

John Zoltak
North American Mfg Co

> -----Original Message-----
> From: [log in to unmask] [SMTP:[log in to unmask]]
> Sent: Thursday, August 27, 1998 11:28 AM
> To:   [log in to unmask]; [log in to unmask]
> Subject:      Re: NO data recovery - TEMPEST
>
> John Zoltak writes:
>
> > Personally, I don't believe that someone could do this. It would
> require
> >  so much storage space and processing power that doesn't exist yet.
> If we
> >  had that much processing power, DES would be useless.
>
> Actually, it was fairly easy to demonstrate that it could be done,
> that you
> could read what someone was typing on a CRT's screen, at least over
> short
> distances.
>
> During the time that Tempest'ing things was the rage, we built
> standalone word
> processors/terminals out of HP2645s. These terminals were extremely
> radiative
> devices, as were almost all devices prior to the initiation of the
> FCC's rules
> on EMI/RFI suppression.
>
> We tried several times to sell the word processors to the military and
> the
> CIA. Most agencies couldn't buy them because of the Tempest rules --
> and it
> simply wasn't worth our effort to modify and Tempest-qualify the
> terminals.
> However, some agencies did buy them and were restricted to using the
> machines
> only in ray-proof rooms (which are more common than you think).
>
> What actually makes it so easy to accomplish what you might otherwise
> think
> would be difficult was the fact that the CRT drivers and wiring were
> among the
> primary sources of the emitted radiation. In fact, it was easy enough
> (and
> still is if you have a working 2645) that you could demonstrate it to
> yourself. The trick was to take a TV set (actually its antenna) and
> aim it at
> the 2645. If you then also put a weak signal on Channel 4, 5, 6, or 7
> so as to
> create a stable reference pattern and observe whichever channel you
> selected,
> you could actually watch the 2645's various screen patterns change the
> nature
> of the digital interference patterns on the TV. It didn't take much
> imagination to believe that you could build a device to properly
> resync the
> CRT's scan information into a perfectly readable replica of the 2645
> you were
> monitoring.
>
> Wirt Atmar