Re: Quantum computing

Scott Hopwood (shopwood@nospam.staff.cs.su.oz.au)
Mon, 8 May 1995 09:15:10 +1000 (EST)

On Fri, 5 May 1995, Cameron Hutchison wrote:

> Once upon a time Ian Woolf said...
> >
> > The blackbox in the movie Sneakers is now a technical possibility, its
> > only a matter of time. factoring large numbers turns out to be the
> > easiest application to program on a Quantum logic based computer. You can
> > crack all public key large-prime-number based algorithms in seconds with
> > such a device when its finally built.
>
> I dont understand how this black box is possible. If we have a box with
> ten thousand times the computing power of the current biggest supercomputer,
> cant we just use that box to generate our keys (1,000,000 bit key lengths)?

I think you are assuming that with QC there is a linear relationship
between the time to break a 1000 bit key and a 1000000 bit key. This may
not be the case. Once you can make a QC to break the small key, it might
require no more time, just a larger QC, to break then 10^6 bit key. In
that case, the length of the key provides no (additional) security.

I should point out that I am only guessing (based on the way I *think* QC
works).

Scott Hopwood 'A monkey throws,
(02) 351-3788 A spinning bone,
shopwood@nospam.staff.cs.su.oz.au A silent spaceship'
shopwood@nospam.socs.uts.edu.au