From owner-freebsd-hackers  Tue Aug  1 13:16:17 2000
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From: John Cochran <jdc@fiawol.org>
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Subject: Re: How to make *real* random bits.
In-Reply-To: <5924.965073661@critter.freebsd.dk> "from Poul-Henning Kamp at Jul
 31, 2000 10:01:01 pm"
To: Poul-Henning Kamp <phk@FreeBSD.ORG>
Date: Tue, 1 Aug 2000 16:16:00 -0400 (EDT)
Cc: freebsd-hackers@FreeBSD.ORG
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 [snip...]
 
> If I generate true random bits it takes 3 timestamps to get one
> bit of randomness:
> 
> 	T1: Time of event 1
> 	T2: Time of event 2
> 	T3: Time of event 3
> 
> 	if (T2 - T1 > T3 - T2)
> 		return 0;
> 	else if (T2 - T1 < T3 - T2)
> 		return 1;
> 	else
> 		try again.
> 
> In my rather crude setup it produces about 5 bits per second [3].

It seems to me that if you get about 15 events per second, then you
should be able to produce about 7 to 8 random bits per second instead
of only 5. What you're looking for is the difference (greater or less)
between events. Because of this your T3 value can be considered the T1
value for the next random bit you generate. Also, someone else has
already done this to generate truly random bits. Take a look at:

     http://www.fourmilab.ch/hotbits/

 [snip]


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