@joeyh Oh, nice approach.
The thing with exponentials is that the crack time starts getting really fast, really fast, a few generations out. The doubling rate matters far more than the cracking rate.
You might alternately set a budget for cracking and compute how long before the password will be hackable at, say, $1m, $1k, $100, and $1.
My intuition is that those will not be separated by much time.
OK, maybe _some_ time -- about 20 years. 3.3 years per OoM.
How much trouble are you worth?
@joeyh If I've got this figured right, the key is crackable for about $1 in 53 years, assuming Moore holds up.
Is your spot pricing following Amazon's pricing trends?