Probabilistically Checkable Proofs of Proximity with Zero-Knowledge.
Yuval Ishai, Mor Weiss · IACR Cryptology ePrint Archive · 2017
A probabilistically Checkable Proof (PCP) allows a randomized verifier, with oracle access to a purported proof, to probabilistically verify an input statement of the form “x ∈ L” by querying only few bits of the proof. A PCP of proximity (PCPP) has the additional feature of allowing the verifier to query only few bits of the input x, where if the input is accepted then the verifier is guaranteed that (with high probability) the input is close to some x′ ∈ L.