Re: 64bit or 1024bit - will it make a difference? (fwd)

Jeff Simmons (
Mon, 12 May 1997 10:58:16 -0700 (PDT)

> Remember also, that when we talk about 1024-bit RSA keys, we are trying
> to find the two prime factors of a very large number. To brute force an
> RSA key, you actually only have to examine the PRIMES between 0 and the
> key length. It's been estimated (see Schneier) that a 2304-bit RSA key has
> roughly the resistance to a brute force attack that a 128-bit symetric
> key has.
> It's still computationally infeasable. In "Applied Cryptography",
> Schneier estimates that for $10,000,000,000,000, you could build a
> special purpose key cracker that could brute force a 128 bit key in
> only 100,000,000,000 years. Note that the same machine could crack
> a 56 bit DES key in approximately 1 millisecond.
> >
> > I'm curious about something - and I will grant that I am not technically
> > knoweldgable about the subject as I should be. If it takes us using spare
> > cycles a few months to crack a 64 (56 really) bit by brute force, why in 10
> > years couldn't the same exact thing be done to a 1024 bit key? We've all
> > seen the amazing leaps and bounds by which processors (not to mention RAM,
> > etc) have come in the last 5 or 6 years. Somehow I think there must be a
> > better way than just making the key longer. Because as the keys get
> > longer, the computers will get better. And even now, its possible to crack
> > a 1024 bit code. Yeah, it'd take a heck of lot longer - but for
> > $120,000,000 worth of equipment - it could probably be done in a decent
> > amount of time.

Jeff Simmons

Hey, man, got any spare CPU cycles? Help crack DES.