[gengkev]

Suppose it takes 2 seconds of 100% cpu usage to compute the password hash (you probably wouldn't want to wait much longer).

Then brute forcing a 4 digit PIN will take 20000 seconds ≈ 6 hours maximum. There's no way around that, no matter what hash function you use.

[benatkin]

In that case make it take a week to unlock your password store, then it will take 200 years to unlock it!