From: MIGUELDIAZ@megaweb.com ()
Date: Mon, 2 Oct 95 18:49:44 PDT
To: cypherpunks@toad.com
Subject: Re: One-Time-Pad generation from audio device
Message-ID: <199510030146.VAA09247@mail-e1a.megaweb.com>
MIME-Version: 1.0
Content-Type: text/plain



>Date:	Mon, 2 Oct 1995 16:42:04 +0100 (BST)
>From:	"Rev. Mark Grant" <mark@unicorn.com>
>Sender:	owner-cypherpunks@toad.com
>To:	cypherpunks@toad.com
>Subject:	One-Time-Pad generation from audio device
>
>
>Over the weekend I hacked up a one-time-pad generator from
> the random 
>number code I've been writing for Privtool, which uses noise
> from the 
>audio device to generate random numbers.
>
>The code basically reads in a 512-byte block from
> /dev/audio, then takes
>the MD5 of that block to generate 16 bytes of the OTP. The
> raw audio data
>I'm getting is not particularly random and will compress by
> 3:1 using gzip
>or compress, so I'm assuming that using a 32:1 ratio here
> via MD5 will
>give a truly random output (it's certainly uncompressible).
>
>Before I release the source code to the Net, can anyone give
> me any good
>reasons to believe that this won't produce physically random
> output, or
>make suggestions on how to test, or improve, the generated
> output ? There's
>a #define which can be used to easily increase the amount of
> data fed into
>the MD5, but at the moment it will only generate about 1 MB
> per hour on a
>Sparcstation (limited by the audio input rate), so I don't
> want to
>increase that if I don't have to. 
>
>	Mark

There are many ways to test for randomness. you might want to 
start by accumulating instance of "1" and "0" and over a long 
time you should have roughly an equal number of both.  If you 
have access to a spectrum analyzer with an auto-correlation 
function (or cross-correlation will do) feed in similar 
lengths of output at different time intervals and check to 
ensure a low (close to zero) correlation exists.  Also while 
you are at it you might want to checks the ouput's frequency 
spectrum, it should be fairly uniform accross the generating 
range.  Noise (or randomness) which is not normally 
distributed can lead to nasty hacks.

Be Well!!
>