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Random numbers for embedded devicesRandom numbers for embedded devicesPosted Jul 19, 2012 15:19 UTC (Thu) by cpeterso (guest, #305)Parent article: Random numbers for embedded devices
Can the expensive mixing operations be moved to get_random_bytes(), so the mixing is only done when needed and the cost is paid by the caller, not interrupt handlers?
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Random numbers for embedded devices Posted Jul 20, 2012 0:53 UTC (Fri) by pr1268 (subscriber, #24648) [Link] That might make get_random_bytes() very expensive (relatively speaking). My suggestion is that the mixing operations happen only when the entropy pool gets below a low-water mark (but then again perhaps this might make the RNG a little more vulnerable; I'm not totally sure about this).
Random numbers for embedded devices Posted Jul 23, 2012 17:14 UTC (Mon) by tytso (subscriber, #9993) [Link]
The expensive (i.e., cryptographic) operations are already in get_random_bytes(). What we do amortized across multiple interrupts is a few xors, a rotate, and some memory accesses into a per-CPU memory pool. So the bulk of the cost is already paid by the processes that need random numbers.
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