Well, when RC5-64 started, the then current processor speeds put the 100% mark at (I believe) around 10-15 years. As processors got faster and faster, that improved to the 4 years it actually took us.
And who knows, maybe RC5-72 will be solved in the first 15% instead of the last 15%, so it could be over in a few months!
Note: Since each number passed 64 doubles the amount of keys, it isn't just 8 times harder... It is 2^8 times harder, or 256 times harder. That means using the same processing power we used for RC5-64 with no upgrades or new users... It would take us 1024 years to finish 100% of the keyspace (give or take a decade!)
Now, how's THAT for daunting!
JHutch
