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Re: key material
From: "Greg Kilford" <greg_kilford () hotmail com>
Date: Fri, 23 Apr 2004 08:14:09 -0600

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


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.

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


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