I believe "zero knowledge" refers to the third party here. That is, you give it A => B, and it tells you if B => A was given previously, without it knowing the

I believe "zero knowledge" refers to the third party here. That is, you give it A => B, and it tells you if B => A was given previously, without it knowing the actual values of A or B. While you might be able to brute force the system by trying every name you know, the third party can't unless you give the third party a registry of names to try. Related is the humorous paper "Solving the Dating Problem with the SENPAI Protocol" [1], though the solution in that paper does not rely on a third party. [1]: http://sigtbd.csail.mit.edu/pubs/2016/paper10.pdf http://sigtbd.csail.mit.edu/pubs/2016/paper10.pdf