From: Peter Monta <pmonta@qualcomm.com>
Date: Thu, 16 Nov 1995 04:16:53 +0800
To: cypherpunks@toad.com
Subject: Re: Hardware-random-bits interface
In-Reply-To: <199511151905.OAA08439@jekyll.piermont.com>
Message-ID: <199511152003.MAA03762@mage.qualcomm.com>
MIME-Version: 1.0
Content-Type: text/plain


> > And if one is left with only internal noise, why not simply use a nice
> > clean source like a Zener diode?
> 
> Quite solidly agreed. Internal noise beats external noise, and there
> is no point in using a radio receiver when what you want is internal
> noise.

It may have been misleading to refer to a radio receiver chip:  the
noise generated by the chip will be entirely internal.  It doesn't
depend on any external signal "sneaking in"; the noise comes from
the effective resistance of the first amplifier stage.  Nothing
is being "received", in some sense; it's just a big hunk 'o gain.

A Zener diode would be fine, but the design is a bit more complex,
especially for wide bandwidths---you need to mess with biasing
voltages, speedy op-amps, interface to CMOS, and all that jazz.
You'd need external power (or a DC-DC converter).  I wanted a
super-simple design that people could just plonk down on a PC
board.  Two chips and some bypass capacitors.

Peter