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Random numbers from CPU execution time jitter

Random numbers from CPU execution time jitter

Posted Apr 30, 2015 9:17 UTC (Thu) by intgr (subscriber, #39733)
In reply to: Random numbers from CPU execution time jitter by alonz
Parent article: Random numbers from CPU execution time jitter

> on a well-designed system, we usually saw a variance of less than 1% in boot process timing (measured at the clock-cycle level).

In terms of percentages, sure, that seems like a small number. But in absolute terms, if you're executing billions of instructions per second, the number of non-deterministic clock cycles in that "less than 1%" is still enormous. In a large sample like yours, such random events will tend to even out, so on a per-instruction basis the non-determinism may be even greater.

To sufficiently seed a random number generator, all you need is 128 random bits -- 128 unpredictable clock cycles.


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Random numbers from CPU execution time jitter

Posted Apr 30, 2015 14:22 UTC (Thu) by dgm (subscriber, #49227) [Link]

At 1% it means waiting for 12,800 cycles, which is not much.


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