Re: Sources of randomness

I'm puzzled by the implication that thermal noise or avalanche or Zener
noise is somehow inferior to noise from radioactive sources.  It's not.

Take as an example Johnson noise, the voltage noise from a
resistance.  It's the result of the interaction of vast numbers
of electrons.  It is unpredictable in the same way that individual
radioactive decay events are unpredictable, and they are both
results of friendly quantum mechanics.

Small biases/interferences that come from nonideally sampling such
voltages do not matter, since the entropy is still 1-epsilon bits per
sample (more for nonbinary samples).  There is no "chink in the
armor" available for cryptanalysis---the user need only acquire
N*(1+epsilon) random bits rather than N bits.

The video-snow-noise described by Tim May is mostly Johnson noise
in the low-noise-amplifier electonics, not atmospheric or ionospheric
noise, at least above 50 MHz or so.

Cheers,
Peter Monta   pmonta@qualcomm.com
Qualcomm, Inc./Globalstar

Peter Monta writes:
> I'm puzzled by the implication that thermal noise or avalanche or Zener
> noise is somehow inferior to noise from radioactive sources.  It's not.

I didn't contend that its inferior. I contended that its difficult to
distinguish from sources of electronic interference and is easy to get
wrong.

> Take as an example Johnson noise, the voltage noise from a
> resistance.  It's the result of the interaction of vast numbers
> of electrons.  It is unpredictable in the same way that individual
> radioactive decay events are unpredictable, and they are both
> results of friendly quantum mechanics.

However, its very easy to be sure that the event in a radiation
detector was a radioactive decay event. It takes expertise to make
sure that the noise you hear off a noisy circuit isn't just
interference from other parts of the machine feeding back into the
circuit. The reason I like radioactive sources is that they are simple
and unambiguous in this way.

Someone can gimmick a zener diode or get it "wrong" a lot more easily
than they can get a radation event wrong.

Perry

On Fri, 3 Nov 1995, Peter Monta wrote:

> I'm puzzled by the implication that thermal noise or avalanche or Zener
> noise is somehow inferior to noise from radioactive sources.  It's not.

How much do the appropriate Zener diodes (it *is* diodes we're talking 
about, right?) cost? Are these things widely available? (sorry I really don't
remember my electronics lessons)

How would you get your first two sources? (the thermal and avalanche)