Date: Sun, 11 Apr 2004 09:38:27 +0100 From: Mark Murray <mark@grondar.org> To: Nate Lawson <nate@root.org> Cc: cvs-all@FreeBSD.ORG Subject: Re: cvs commit: src/sys/modules/random Makefile src/sys/dev/random harvest.c hash.c hash.h nehemiah.c nehemiah.h probe.c randomdev.c randomdev.h randomdev_soft.c randomdev_soft.h yar Message-ID: <200404110838.i3B8cRIn075336@grimreaper.grondar.org> In-Reply-To: Your message of "Sat, 10 Apr 2004 15:55:42 PDT." <20040410155306.W58852@root.org>
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Nate Lawson writes: > > Cryptographic strength is of lesser importance here, as the key > > input is Very Nicely Random(tm), however AES's speed and spectral > > qualities make it a good choice. It is important to remember that > > the hash is purely there to destroy any trends/tendencies that the > > hardware generator may have, and for that purpose an LFSR may work > > just fine. The hash is a "Whitener", and its requirements here are > > that its output spectrum is flat. > > An LFSR is not a cryptographic hash function. Do not use one to implement > a PRNG. The input is 99% random. It follows that if the hash/whitener is done properly the output should be 99% random. LFSR was an illustration; the intent is to use AES. M -- Mark Murray iumop ap!sdn w,I idlaH
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