3 ms·
> Which is obviously not constant time, and will leak information through cache/timing sidechannels. This confuses me. Why is it in the kernel if it's not cons
by nshepperd 7y ago
> Which is obviously not constant time, and will leak information through cache/timing sidechannels.
This confuses me. Why is it in the kernel if it's not constant time? Isn't that a security risk? (Is there any context where it would be safe to invoke this?)
- cbsmith 7y agoSure. There's lots of cases where you are controlling for timing attacks elsewhere, or where a timing attack isn't a concern. This can particularly be true for a case where you are writing data to block storage with the idea that a potential attacker won't be accessing it until much later... at which point all timing information would be gone.
- nullc 7y agoUnfortunately cache sidechannels defeat a lot of measures that would otherwise destroy timing data. I agree that there can be some cases where it doesn't matter but it's extremely expensive to be sure that it doesn't matter-- making it usually cheaper, when you consider the total costs, to deploy code that doesn't have the sidechannels.
- cbsmith 7y agoIt's pretty cheap if the use case is, "the computer will be turned off before I worry about an attacker".