Subj : Re: Timing side channels To : comp.programming.threads From : David Hopwood Date : Wed Sep 21 2005 02:22 pm David Schwartz wrote: > "David Hopwood" wrote: > >>It's misleading to call timing side channels just a performance effect. >>I think most PGP users or SSL server operators would raise an eyebrow if >>you told them that compromise of their private key was just a performance >>effect, for instance. > > If they rely upon isolation that's not guaranteed, they get what they > deserve. Not really: - at the time the software was written, no implementation of x86 (or other platforms) used caches shared between processes executing in parallel. So it is just as reasonable to attribute the cause of the problem to {HT with shared caches} breaking an implicit security requirement, as to the software relying on isolation that was not guaranteed. - the software in question cannot do anything about caches being shared between mutually untrusting processes. Only the operating system can fix that. The software can try, to some extent, to reduce the amount of information leaked via the cache, but it is impossible to eliminate this leakage entirely. -- David Hopwood .