Witness Authenticating NIZKs and Applications

We initiate the study of witness authenticating NIZK proof systems (waNIZKs), in which one can use a witness w of a statement x to identify whether a valid proof for x is indeed generated using w. Such a new identification functionality enables more diverse applications, and it also puts new requirements on soundness that: (1) no adversary can generate a valid proof that will not be identified by any witness; (2) or forge a proof using her valid witness to frame others. To work around the obvious obstacle towards conventional zero-knowledgeness, we define entropic zero-knowledgeness that requires the proof to leak no partial information, if the witness has sufficient computational entropy.