RC5-72 is gonna take forever, though.
You bet it is, even with the Pentium4s and AMD Athlons everyone and their granny seems to have nowadays.
If I worked this out correctly (2^72), then this many keys will have to be tested:
4,722,366,482,869,645,213,696
I don't even know how to say that number!
Compared to RC5-64, which had:
18,446,744,073,709,551,616.
That's 256 times as much. Since RC5-64 began 5 years ago and took 330,000 computers to crack it, at the present rate of CPU speed advancement...well, i guess that CPUs aren't 256 times faster than they were in 1997 - maybe 10 times faster.
So RC-72 would take maybe 25 years, if CPUs stayed the same. But they won't, they'll again increase tenfold, so 25 becomes a multiplier of 2.5 against 5 years...
So it'll take 12.5 years to complete, I think, if the user numbers stay the same. :-)
I could be totally wrong, maths was never my strong suit.
