It might require that knowledge implicitly, in the tools and parts the evil idiot would use, but they presumably would procure these tools and parts, not invent or even manufacture them themselves.
Even that is insanely difficult. There's a great book by Michael Levi called On Nuclear Terrorism, which never got any PR because it is the anti-doomer book.
He methodically goes through all the problems that an ISIS or a Bin Laden would face getting their hands on a nuke or trying to manufacture one, and you can see why none of them have succeeded and why it isn't likely any of them would.
They are incredibly difficult to make, manufacture or use.
