Following code generates random 64-char hex string and then starts bg processes and kills them after "$2" seconds.
I have to ask. Why? As has been stated earlier in this thread, and numerous times in other cracking threads, brute forcing the 2^160 space is pointless. If your random hex string happens to be 0000000000000000000000000000000000000000000000000000000000000000 then you'll find a bunch of toy keys -- with no funds of course -- but otherwise, the chances of finding any matches are essentially zero. You're more likely to die of old age than find a truly random key.