Andreas Bogk wrote:
> The usual setup for DPA involves a 10 Ohm resistor which sits in the
> power supply and measuring the voltage across that resistor. The
> countermeasure we're talking about is an on-chip capacitor that
> smoothes the power consumption, [...]
Has this been analyzed? It's got to take the high-freqency
information the attacker's looking for so far below the thermal noise
floor that it can't recovered by averaging multiple runs. I do DSP,
not EE, but I'd think this smoothing capacitor would effect a one-pole
lowpass filter.
If so, doubling the cap size halves the cutoff frequency (right?),
halving the leaked power. Integrating runs gives signal voltage
linear in n and noise voltage sqrt(n); voltage ratio is sqrt; power
ratio is linear. So leaked-signal power is
Theta( (attacker's number of runs) / (capacitor size) ).
No asymptotic edge either way; attacker wins against bounded cap size.
</handwave>
--
Eli Brandt | [EMAIL PROTECTED] | http://www.cs.cmu.edu/~eli/
