I just used Kingo, one program to download, it probably downloads extra files automatically (it's multi device) and I have root, pretty much painless. I'm assuming Knox flag is not tripped, but I'm too lazy to look for info how to check, since it would be too late now to do anything anyhow. Surprisingly it did not work with my older back up phone GS3, updated to 4.3, Knox included. Kingo will also unroot your phone as well with one click. Can't help with Safestrap, as I just wanted to remove region lock and kill some bloatware.