... you might as well publish it on the internet. they're gonna tell at least one other person - their spouse, and since that person isn't necessarily your friend, they'll probably tell someone else, and so on, and so on, and so on.
after having this happen to me in a bad way, i ran a test case to check the theorem with a lie, and sure enough, the same disloyal shitbag leaked it along the same fucking grapevine, but this time i got to laugh when someone finally asked me if i really had leukemia.
ah, the ways of the world....