4 ms·
The frequency change is observable by the whole algorithm taking a different time to run - the algorithm is constant-time, but because the clock speed is changi
by kevingadd 4y ago
The frequency change is observable by the whole algorithm taking a different time to run - the algorithm is constant-time, but because the clock speed is changing based on the data, it's not constant-wall-clock-time and you can perform a timing attack.
- karussell 4y agoAnd also when I set the scaling governor to "performance" (under Linux)? Is the frequency in that case still adjusted based on the data or always "maximum"?
- adrian_b 4y agoWith the performance governor, the clock frequency is continuously adjusted between the "base frequency" and the "maximum turbo frequency", e.g. between 3.7 GHz and 4.8 GHz, for my computer. With the powersave governor, the clock frequency is continuously adjusted between a frequency much lower than the "base frequency", and also the "maximum turbo frequency", e.g. between 2.2 GHz and 4.8 GHz, for my computer.
- pyrolistical 4y agoHaha so constant time algorithm isn’t constant time
- jaza 4y agoTime itself isn't constant, so arguably a constant time algorithm is an oxymoron! But that's a whole 'nother topic.