TEMPEST protection (was Rolm Computers: 1602, 1602A, 1602B, 1666, MSExx)

[Brent Hilpert]

On 2016-May-05, at 6:17 AM, Noel Chiappa wrote:
>> From: Erik Baigar
> 
>> very interesting reading
> 
> If you want to see a great example of why it was important, check out the
> so-called 'Berlin Tunnel':
> 
>  https://en.wikipedia.org/wiki/Operation_Gold
>  http://www.fas.org/irp/cia/product/tunnel-200702.pdf
> 
> Some of the traffic that was intercepted was teletype traffic - which had
> been encrypted. However, the equipment that connected the gear to the line
> allowed a tiny electronic whisper of the original plain-text onto the line,
> along with the encrypted form, and it was possible to read the plaintext off
> the line with suitable gear.

A Model 28 teletype with DND (Ca. Department of National Defence) tags on it I was working on a couple years ago had been modified for what I can only presume to be TEMPEST qualification.
All the standard wiring and electrical stuff - not just the current loop signal wiring but even the basic AC line wiring for the motor and such, all the way out to the wall plug - had been removed and replaced with shielded cable and connectors. The normal keyboard contacts and print selection magnets were replaced with units enclosed in shielded housings. The power line had a large noise filter in it's own RF-shielded housing.