[Cryptography] 'The intelligence coup of the century'

[Phillip Hallam-Baker]

On Fri, Feb 14, 2020 at 12:08 PM John Young <jya at pipeline.com> wrote:

> At 12:08 AM 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?
>

The side channels were so powerful on the Commodore PET that some games
came with an audio channel that you picked up on an AM radio.

Which was really odd given that the case was metal.
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