From Polynomial IOP and Commitments to Non-malleable zkSNARKs

We study sufficient conditions for compiling simulation-extractable zkSNARKs from information-theoretic interactive oracle proofs (IOP) using a simulation-extractable commit-and-prove system for its oracles. Specifically, we define simulation extractability for opening and evaluation proofs of polynomial commitment schemes, which we then employ to prove the security of zkSNARKS obtained from polynomial IOP prove systems, such as Plonk and Marlin. To instantiate our methodology we additionally prove that KZG commitments satisfy our simulation extractability requirement, despite being naturally malleable. To this end, we design a relaxed notion of simulation extractability that matches how KZG commitments are used and optimized in real-world prove systems. Only the proof that KZG satisfies this relaxed simulation extractability property relies on the algebraic group model (AGM) and random oracle (RO). We thus isolate the use of (and thus the reliance on) these strong heuristics.