Date: Sun, 24 Aug 2003 09:26:30 +0100 From: Mark Murray <mark@grondar.org> To: Mike Silbersack <silby@silby.com> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/libkern arc4random.c Message-ID: <200308240826.h7O8QUOI060733@grimreaper.grondar.org> In-Reply-To: Your message of "Sat, 23 Aug 2003 11:55:58 CDT." <20030823115345.N7877@odysseus.silby.com>
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Mike Silbersack writes: > > http://www.csua.berkeley.edu/~das/marsaglia/ . > > I can run it again if there's interest. > > Can you turn it into a port? :) That would be nifty :-) > > I'm not a cryptographer, but FWIW, I'm told that there are > > statistical tests that can differentiate an ARC4 sequence from a > > truly random sequence. However, it takes something like 2^31 bits > > of data to detect the statistical bias. > > According to the paper referenced in the comment, the pattern is > *especially* apparent in the first 256 words of output, which is why they > should be thrown out. (From my original reading of the paper, I was > unable to determine if by his terminology he meant the first 256 bytes, > words, dwords, quadwords, or what. So I throw away the first 256 dwords, > just to be safe.) It is the first 2048 _bits_. Throwing away more doesn't hurt. M -- Mark Murray iumop ap!sdn w,I idlaH
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