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List:       webappsec
Subject:    Re: key material
From:       "Greg Kilford" <greg_kilford () hotmail ! com>
Date:       2004-04-23 14:14:09
Message-ID: BAY12-F39A6eqv6fi4D0000a15f () hotmail ! com
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Our discussion of A is as a generic bit stream of assumingly random nature 
from an arbitrary source, eg. mouse movements, etc.  But seriously speaking, 
it could be anything.  More importantly, what size of A would suffice in 
seeding the PRNG sufficiently for the output stream O after the seeding 
would be of sufficient entropy for RSA 1024/2048 modulo key materials.  Some 
of us are inclined to believe A should be of size/length 1024/2048 bits 
before the PRNG is seeded sufficiently while a few
of my pals are suggesting 64/128 or even 192 bits would suffice.  Very 
disparate gut feelings...


>From: Peter Conrad <conrad@tivano.de>
>To: webappsec@securityfocus.com
>Subject: Re: key material
>Date: Fri, 23 Apr 2004 10:05:23 +0200
>
>Hi,
>
>On Thu, Apr 22, 2004 at 11:29:36AM -0600, Greg Kilford wrote:
> >
> > I was juz discussing with my pals the other day on the appropriate 
>initial
> > input bit size to seed a PRNG of the structure below for it to be used 
>to
> > generate the random bits for RSA key material of modulus 1024 bits or 
>2048
> > bits.  Anyone know what would be the ideal length/size of A so that 
>there
> > is sufficient entropy to generate the key material for RSA 1024/2048 
>bits
> > keys?
>
>that'll depend on how you use the output of the PRNG to generate an RSA 
>key.
>As a general rule I'd say A should have one bit of entropy for every bit
>of O that you use. You didn't tell us anything about how A is constructed,
>so we can't say how long it should be.
>
>Bye,
>	Peter
>--
>Peter Conrad                        Tel: +49 6102 / 80 99 072
>[ t]ivano Software GmbH             Fax: +49 6102 / 80 99 071
>Bahnhofstr. 18                      http://www.tivano.de/
>63263 Neu-Isenburg
>
>Germany

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