Apr 6, 2018

to prove something is either 2 or 0, you need ring signatures because they have the property that you know the signature came from a set of keys, but you don't know which key, so a signature is provided proving that the value is either 0 (using public key derived from first equation) or 2 (using public key derived from second equation) but you don't know which key specifically, just that it's either of them.