This would be pretty easy to test. Just get a bunch of friends to start exchanging encrypted messages about bombing an embassy or govt office. If these douche-bags can break it, they'd be on you like white on rice.
can anyone think of a lower risk way to test...?
You all sign a notarized piece of paper that these conversations are to exercise artistic speech to create a book and that there is no intent to carry out the discussion that will take place beyond creating a work of fiction?