Thanks to those who responded. Looks like, at the moment, there
are both technical and economic reasons for using pseudo-random
numbers, even though the genuine article can be produced.
Hugo Mills <hugo@???> wrote:
> On Wed, May 14, 2008 at 11:37:33PM +0100, Chris Oattes wrote:
> > Nick Chalk said the following on 14/05/08 22:56:
> > >Peter Alefounder <p_alefounder@???> wrote:
> > >>Why are pseudo-random numbers used anyway? Is it
> > >>beyond the wit of man to devise a bit of
> > >>hardware that would produce genuine random
> > >>numbers?
> > >
> > >What is a "genuine" random number?
> > >
> >
> > As I understand it, a "genuine" random number is as follows:
> >
> > Assume you have a stream of numbers in base 10 (i.e. made up of a series
>
> > of digits from 0-9).
> >
> > This stream of numbers would be considered random if, given the first x
> > digits, it is impossible to determine the x+1 th digit with probability
> > > 1/10. That is to say, each digit is equally likely to be any one of
> > the possible values.
> >
> > I'm sure I will be corrected if I am wrong.
>
> Not wrong, possibly, but not helpful in practice. If I gave you a
> list of 100,000 numbers, could you use that definition to show that it
> was a stream of random numbers?
Even if you could not show that the numbers were random (whatever
that might mean to a mathematician), if it was impossible to
predict the sequence, wouldn't that be good enough for practical
cryptographic applications? Chris Oattes' definition seems to me
to be sufficient. Could a non-random but non-predictable (with
probability > 1/10 per decimal digit) sequence exist?
Peter Alefounder.
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