Re: Patch: new random pseudodevice

[Paul Koning <paulkoning%comcast.net@localhost>]

On Dec 11, 2011, at 5:18 PM, David Laight wrote:

> On Fri, Dec 09, 2011 at 02:41:25PM -0500, Paul Koning wrote:
>> ... That's essentially what old time Ethernet chips like Lance did
> 
> IIRC The lance's CSMACD backoff was deterministic, if you were
> really unlucky two systems could collide packets for ever!
> (On a network with only 2 hosts.)

You're thinking of the capture effect.  I think that had to do with deferral, 
not collision backoff.  The collision RNG in Lance is definitely NOT 
deterministic, that was an absolute requirement.  It used what was referred to 
as "flaky oscillators".
> 
> On a separate note, I've sometimes wondered how well RC4 would work as
> an entropy pool. Just cycle it in key-gen mode for any byte that might
> have any randomness in it.
> When you want data, cycle it a few times, take some bytes hash them
> (to remove any RC4-ness), and cycle it a few more times.
> Probably the same idea as Fortuna is using.
> Adding a small amount of randomness should impove things significantly
> - and you don't actual care if it is random.

That's a pretty good description of the basic idea of a cryptographic PRNG.

        paul