[Cryptography] 'The intelligence coup of the century'

[John Young]

At 12:15 PM 2/14/2020, you wrote:
> > >BTW, IBM mainframes had powerful radio side-channels: in the early
> > >1960's, one of the programmers that worked with me used to put an
> > >ordinary portable radio on top of the IBM CPU so that he could
> > >"listen" to his program go through its paces.  Any change in the
> > >audio would indicate a problem with the software.
>
> > >I would guess that this radio technique would have been sufficient
> > >to enable a person listening to pick out the individual bits in a
> > >modular exponentiation, as those computers weren't all that fast.
>
> > >We didn't have a name for it, but in retrospect we should have
> > >called it 'ADB' -- 'Audio Debugging Bridge'.
>
> > >I never tested the *range* of these radio signals, but I suspect
> > >that they could easily have been heard outside the building
> > >where the computer was located.
>
> > Is this a TEMPEST tool, perhaps long used, even now? Ross 
> Anderson aware of it?
>
>     Listening to CPUs with radios was common.  I haven't tried it in
>years but I recall being surprised that when I had a TEMPEST-shielded
>Sun workstation in the '90s, it could be heard on the radio.  I don't
>recall much about what is sounded like.  With the PDP-6, I recall that
>you could hear the different phases of a radix sort.
>
>                            Whit


Several others have noted audio signals from early computers. 
Wikipedia provides a report on "Acoustic cryptanalysis:"

https://en.wikipedia.org/wiki/Acoustic_cryptanalysis

Not specifically about radio, though.

NSA's partially declassified NACSEM-5112 addresses NONSTOP radio 
communication systems

https://cryptome.org/nacsem-5112.htm (from January 2000)

What's the current protection for compromising radio signals?