[Cryptography] Speculation re Intel HW cockup; reqs. OS rewrites & slow execution
Bill Frantz
frantz at pwpconsult.com
Fri Jan 5 17:47:41 EST 2018
On 1/4/18 at 8:38 PM, frantz at pwpconsult.com (Bill Frantz) wrote:
>On 1/4/18 at 5:06 PM, nico at cryptonector.com (Nico Williams) wrote:
>
>>Speculative execution is necessarily side-effect-having by its potential
>>cache thrashing impact and ability to be impacted by cache thrashing.
>>This necessarily creates side-channels. It seems unavoidable except by
>>having sandboxed caches, but that's probably not an option for many
>>reasons (including power consumption).
>
>I can imagine speculative execution which does not proceed if
>the needed data is not already in the cache. If the caching is
>working as advertised, this will have a small effect on overall
>performance. (MOst of the data needed is already in the cache.)
>It will defeat the attacks which use cache presence or absence
>as a signaling path.
I am informed by an expert in computer speculation that much of
the performance gain from speculation comes from pre-loading the
cache with data that will be needed soon, so this idea just
won't fly.
Cheers - Bill
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