[Cryptography] [RNG] /dev/random initialisation

Jerry Leichter leichter at lrw.com
Thu Oct 31 06:49:16 EDT 2013


On Oct 30, 2013, at 8:46 PM, Peter Todd wrote:
>> So:  For extra sources to always be harmless, it must be the case that the bits are unpredictable *even if no new entropy arrives*.  All that matters, in effect, is that the internal state be unknown and unpredictable *once*.  BBS has this property, as (on different assumptions) do crypto-based PRNG's like Yarrow.  But this has a performance cost, and I'm not sure that a Linux-style generator does.  If you have it ... why would you need to allow additional (allegedly random) sources?
> 
> This is why the Linux RNG allows anyone to add data to the pool as an
> unprivileged operation, but requires root to change the estimates of how
> much entropy is in the pool.
Ah, so like FIPS, Linux only accepts "real" entropy from "authenticated" sources.  :-)
                                                        -- Jerry



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