From: Carl Ellison <cme@TIS.COM>
Date: Fri, 17 Nov 1995 03:34:41 +0800
To: pmonta@qualcomm.com
Subject: Re: Hardware-random-bits interface
In-Reply-To: <199511152205.OAA27271@comsec.com>
Message-ID: <9511161835.AA00247@tis.com>
MIME-Version: 1.0
Content-Type: text/plain


>Date: Tue, 14 Nov 1995 14:31:46 -0800
>From: Peter Monta <pmonta@qualcomm.com>

>A rate of 300 kB/s will make a 600 MB one-time pad in an hour
>(assuming software is similarly fast).  I'm wondering if any
>of the mail systems have convenient hooks to use pads (though
>it would not be difficult to write up).
>
>Suggestions welcome.  I'll put the design on the Web
>once it's finished; replicating it should be pretty easy.
>People can also grab the device driver if they wish.

I'd be nervous about using a radio receiver which can be fed with a signal
by the adversary.  A noisy resistor or diode should be less subject to bias
by an active opponent.

Whatever you use for a source of bits, it should be carefully measured to
determine how much real entropy is in the source.  Don't assume all the
bits you get are independent, flat distribution bits.

You might need to hash bits down until you get independence.  You also
might want to provide some further ranno conditioning.

	cf. http://www.clark.net/pub/cme/P1363/ranno.html  (on ranno theory)
	and http://www.clark.net/pub/cme/html/ranno.html   (on conditioning)

 - Carl

+--------------------------------------------------------------------------+
|Carl M. Ellison      cme@tis.com    http://www.clark.net/pub/cme	   |
|Trusted Information Systems, Inc.   http://www.tis.com/                   |
|3060 Washington Road          PGP 2.6.2:  61E2DE7FCB9D7984E9C8048BA63221A2|
|Glenwood MD  21738         Tel:(301)854-6889      FAX:(301)854-5363       |
+--------------------------------------------------------------------------+