So much entropy it's coming out of our ears?

Mark Murray mark at
Thu Aug 5 00:36:02 PDT 2004

Sam Leffler writes:
> Virtually all performance-sensitive installations will disable entropy 
> gathering through fast paths.  I've suggested for a long time that this sort 
> of collection should be enabled only under dire circumstances and never by 
> default.  Regardless the last time I looked at the entropy harvesting it used
> a model where entropy was unilateraly sent for harvest and discarded when too
> plentiful.  I term this the "push model".  I've advocated a "pull model" 
> where the PRNG requests entropy when a low water mark is hit and/or a hybrid 
> scheme where producers have some sort of flow control or feedback mechanism. 

Yarrow is not conducive to "water-mark" type flow-control, but I'm looking
at replacing Yarrow with Fortuna (code at an advanced stage). This should
improve things all-round.

> Everything that goes on inside the PRNG is a separate issue.


Mark Murray
iumop ap!sdn w,I idlaH

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