From: "Mark W. Eichin" <eichin@cygnus.com>
Date: Tue, 15 Dec 92 23:46:40 PST
To: tytso@ATHENA.MIT.EDU
Subject: re: ps -laxww for randmoness?
In-Reply-To: <9212160715.AA09133@tsx-11.MIT.EDU>
Message-ID: <9212160740.AA04597@tweedledumber.cygnus.com>
MIME-Version: 1.0
Content-Type: text/plain


Don Davis, of MIT Project Athena, did some research a number of years
back on getting good (physical) randomness out of a unix workstation.
If I recall correctly, the general idea was to look for trends and
biases, find explanations for them, and then filter them out or
normalize against them. Sources of "real" nondeterminism came from
things like variations in hard drive behavior (such as actual seek
time, which shows up indirectly in the paging system because it does
or does not cause time delays due to missed sectors...) I don't have a
reference handy, but if noone comes up with one I'll send him email
and see if he has it online.
	In other words, 'ps -laxww' itself is relatively useless --
but the underlying data does actually have randomness; you may have to
dig pretty hard for it, though.
							_Mark_

   SUB: Re: ps -laxww for randmoness?
   SUM: <tytso>, tytso (Theodore Ts'o)->avalon@coombs.anu.edu.au, cypherpunks@toad.com

      From: avalon@coombs.anu.edu.au (Darren Reed)
      Date: Wed, 16 Dec 92 2:30:49 EST

      Has anyone tried using the microsecond counter from unix as a random
      source ?  Its obviously *not* going to be good if you want a continuous
      stream of random numbers, but if you need them just 'every now and then',
      what about it ?

   This should be in an FAQ:  Unixes have different levels of granularity
   in the microsecond counter; some systems may only have a 10 ms (that's
   10000 microsecond) resolution to their clock.  So you can't necessarily
   depend on a getting lot of bits of randomness from this method.

						   - Ted