Re: [tlug] Your computer is speaking your private key out loud?!

["Nikolay Elenkov" <nick@example.com>]

Darren Cook writes:
>>> I fully understand how the sound of your CPU will change when under
>>> load. ...
>
>> CPU noises correspond to certain operations on the processor if you know
>> what code the processor is running you can match the noises back to the
>> code paths in the machine code for the program, ...
>
> When reading what you wrote, I realized I was wrong: I don't have a clue
> how my CPU makes sounds. (I was thinking of the CPU fan, and perhaps a
> small buzz from heat emission or from drawing power)
> I've just had a flashback about 30 years back to reading about p and n
> type silicon... and I still cannot find anything in my knowledge between
> then and now about how different CPU instructions could make different
> sounds!!
>

Read the actual paper for details, but sounds comes from voltage regulator
circuits, most probably capacitors. As the CPU power consumption changes
for different operations, so does the emitted frequency. By sending you a
lot of specially crafted emails (with a lot of zero bits) and correlating
observed frequencies while decrypting those they can recover the key piece
by piece.

http://www.tau.ac.il/~tromer/papers/acoustic-20131218.pdf

It doesn't have to be acoustic either, they can achieve the same effect by
hooking up to the computer case and monitoring potential changes.

And that is why you don't do crypto in software :)