Security, Zero Knowledge Proofs, Snark, Cryptography, Research.
with the public input x=gʷ (and the random coins r to parameterize its random tapes) and waits to receive the first prover message a=gʳ. Extractor E chooses a random bit e ∈ {0,..q-1}, sends e to the prover P and waits to receive the response z=r+ew. Now it rewinds the prover P to step 2.