PCP to ZK‑PCP transformation

Identify whether there exists a black‑box transformation that, given any (non‑zero‑knowledge) PCP construction, produces a zero‑knowledge PCP while preserving the original PCP’s parameters (e.g., query complexity and proof length).

Background

Prior approaches to zero‑knowledge PCPs often transform existing PCPs but introduce adaptivity or weaken zero‑knowledge guarantees, and none preserve O(1) query complexity. In contrast, black‑box transformations exist for related interactive proof models (e.g., MIP and MIP*), motivating the question of whether a similar generic transformation is possible for PCPs.

The authors’ construction leverages the structure of BFLS‑style PCPs and a ZK‑PCP for sumcheck, suggesting that genuinely black‑box methods would require new ideas.