Not practically that I know of. The definition of "not bulletproof" is very vague; why can't the friends just agree not to "return true"? There are some theore

Not practically that I know of. The definition of "not bulletproof" is very vague; why can't the friends just agree not to "return true"? There are some theoretic foundations in this line of work: https://en.wikipedia.org/wiki/Verifiable_computing https://en.wikipedia.org/wiki/Verifiable_computing