This tool is not open source, even if it was you couldn't modify exe file, first you need to modify the source code and recompile it to make a new exe. This dev is no longer among us unfortunately, he left these woods a couple of month ago.

At first I was just like you, I thought I could hit a key by "chance" until I got to know about public keys, if you are interested in hunting for puzzles, join us in a futile search for them.😂

Ps, I hope you are not going to post the same thing in every brute force related topic.😉  welcome and happy hunting.

Pss, check my python museum on this same board, I have the ultimate cracking scripts.🙃