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One way to detect if your processor is bugged would be to run benchmarks. If the microcode is different, e.g. making backdoor operations between register acces
by diydsp 13y ago
One way to detect if your processor is bugged would be to run benchmarks. If the microcode is different, e.g. making backdoor operations between register accesses, your benchmark results will be different.
A battery of tedious, slightly-differing benchmarks would be necessary to probe individual instruction, but I don't think it would be possible to evade this detection technique. It's simply too hard to make a backdoor operations on top of regular operations without padding the original instruction execution.
- Tuna-Fish 13y agoAFAIK, intel microcode patching mechanism works in parallel with normal instruction execution. That is, the instructions are decoded and executed normally, and in parallel different circuitry looks for known fault cases, and traps if necessary. So long as you won't find the special case, the execution takes exactly as long. And there is not enough time in the universe to iterate through a 128-bit number, so you won't find the special case.
- ds9 13y agoThis technique would be assuming that it's a full-time backdoor. Some of the speculation has been that there are routines that are triggered only in certain special conditions. I don't actually subscribe to the "conspiracy theories" for the most part, including this one - really just making an academic point here. The whole backdoor theory, IMHO would have to rely on something in software to leverage the supposed backdoor. However, the "sabotaged RNG" idea noted below is more plausible. (Edit: Tuna beat me to the comment, I had not refreshed the page)