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Date:      Thu, 05 Aug 2004 08:33:44 +0100
From:      Mark Murray <mark@grondar.org>
To:        Sam Leffler <sam@errno.com>
Cc:        Robert Watson <rwatson@FreeBSD.ORG>
Subject:   Re: So much entropy it's coming out of our ears? 
Message-ID:  <200408050733.i757XiGC053052@grimreaper.grondar.org>
In-Reply-To: Your message of "Wed, 04 Aug 2004 21:39:52 PDT." <200408042139.52577.sam@errno.com> 

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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.

*nod*

M
--
Mark Murray
iumop ap!sdn w,I idlaH



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