Yes, multiply and add, or any set of operations necessary to create an arbitrary Boolean function, which then would have encrypted input and output. From that

Yes, multiply and add, or any set of operations necessary to create an arbitrary Boolean function, which then would have encrypted input and output. From that you get "Turing completeness" because, for any computation you want to do, you can unwind it into a static Boolean circuit that computes (some appropriately sized version of) it. Note that this means you're limited to primitive recursive functions i.e. all loops must be compile-time bounded. The use case is stuff like, "add up my numbers without knowing what the numbers are or their sum is". I think there are also end-to-end auditable voting systems that preserve privacy.