I can't believe someone posted the answer that's pretty lame. John is a password cracker, its probably "the password cracker." John has optimized assembly instructions for many hashes for many cpus so its blazingly fast for a CPU attack. Reallocating GPUs from btc mining to this would have been a waste given that the answer was in /usr/share/dict
I'm not sure who or what john is :) I just thought it was a fun exercise, and since the solution was already posted, I figured it could be beneficial to post one way of doing it.