On Fri, 16 May 2008, Timothy Murphy wrote:
> Because we know far more about mathematical functions than we do
> about the physical processes you are talking about.
I can understand the behaviour of the mathematical function is easier
to examine and reason about, yes - it requires little in the way of
equipment (except perhaps a computer).
> Take the time distribution of emissions from radioactive material,
> which is often taken as a model of a random process.
If they're not random processes, then they are systems so complex as
to be far beyond our capacity to model them (for the foreseeable
future at least), is my understanding. I.e. they're still far better
PRNGs than our mathematical ones (at heart).
> There are any number of reasons why this might not in fact be
> random, eg the measuring apparatus might be defective, there may be
> cosmic ray emissions from a completely different source, the rate
> of emission may not be independent of the temperature, the
> direction of the magnetic field may affect the result, etc, etc.
These sound like factors that would affect the intensity and
direction of the radiation*. That's not where the entropy lies
though, so that's not what you'd try measure - the variation in the
measure of your radiation is what you want.
There are engineering challenges, sure. It just seems to me that
those are easier to address than coming up with a good function to
make a PRNG.
Anyway.. interesting ;)
* excluding the possibility of some nasty attacker shooting
sub-atomic particles at you with per-particle control - which I'm
not sure is feasible, but even if it is, it only affects the use of
the RNG for cryptographic purposes.
Paul Jakma paul at clubi.iepaul at jakma.org Key ID: 64A2FF6A
Those who cannot remember the past are condemned to repeat it.
-- George Santayana
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