From: donb@netcom.com (Don Bellenger)
Date: Fri, 27 Nov 92 17:11:14 PST
To: cypherpunks@toad.com
Subject: Re: Random numbers
Message-ID: <9211280107.AA08614@netcom2.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain


> > 
> >     It has lately been discussed different ways to construct pure
> > random number generators by means of radiactive decay. I must admit
> > that this is a very good way to produce such numbers, but for a
> > number of reasons it is impractical to use such a device. (High
> > radiation levels are needed too produce a significant amount of data.)
> 
> 
> The way to make good random numbers is to take about 20 stages of flops
> and feedback 2 or three terms.  Clock the thing as fast as you can, Say
> 50 mhz, and asychronously to your main processor clock.  The shift register
> needs its own crystal.  The selection of feedback points is based on
> Linear Congruential Method of Pseudo random numbers generated by most
> machines.
> 
> The numbers generated are very, very uniform.
> 
> The way to test random number generators for randomness is to generate
> the numbers in pairs and plot them on a scatter plot.  This simple
> cross check will show up many poor generators.  Checking for uniform
> density in higher dimensions will uncover even more subtle variations
> from uniformity.  There is an enormous literature on this topic.  Obviously
> you can screw it up, but it isnt that hard to get right either.  There
> is an excellent book just out on simulations that covers  this.  If
> anyone wants the reference, I can dig it up.
> 
> Bottom line is that you don't need anything exotic.  But the 8 or simple 16
> bit methods on the small processors are no good.
> 
> Don Bellenger
> donb@netcom.com
> 
> 
> 
> > 
> 


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