hypernova_verifier.cpp

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// === AUDIT STATUS ===
// internal:    { status: Complete, auditors: [Sergei], commit: }
// external_1:  { status: not started, auditors: [], commit: }
// external_2:  { status: not started, auditors: [], commit: }
// =====================
 
#include "barretenberg/hypernova/hypernova_verifier.hpp"
#include "barretenberg/honk/proof_length.hpp"
#include "barretenberg/hypernova/hypernova_batching_challenges.hpp"
 
namespace bb {
 
template <typename Flavor_>
template <size_t N>
HypernovaFoldingVerifier<Flavor_>::Commitment HypernovaFoldingVerifier<Flavor_>::batch_mul(
    const RefArray<Commitment, N>& _points, std::vector<FF>& scalars)
{
    std::vector<Commitment> points(N);
    for (size_t idx = 0; idx < N; ++idx) {
        points[idx] = _points[idx];
    }
    return Commitment::batch_mul(points, scalars);
}
 
template <typename Flavor>
HypernovaFoldingVerifier<Flavor>::Accumulator HypernovaFoldingVerifier<Flavor>::sumcheck_output_to_accumulator(
    HypernovaFoldingVerifier<Flavor>::MegaSumcheckOutput& sumcheck_output,
    const std::shared_ptr<HypernovaFoldingVerifier::VerifierInstance>& instance)
{
    BB_BENCH_NAME("HypernovaFoldingVerifier::sumcheck_output_to_accumulator");
 
    // Generate challenges to batch shifted and unshifted polynomials/commitments/evaluation
    auto [unshifted_challenges, shifted_challenges] =
        get_hypernova_batching_challenges<FF>(transcript, NUM_UNSHIFTED_ENTITIES, NUM_SHIFTED_ENTITIES);
 
    // Batch evaluations
    FF batched_unshifted_evaluation(0);
    FF batched_shifted_evaluation(0);
 
    for (auto [eval, challenge] : zip_view(sumcheck_output.claimed_evaluations.get_unshifted(), unshifted_challenges)) {
        batched_unshifted_evaluation += eval * challenge;
    }
    for (auto [eval, challenge] : zip_view(sumcheck_output.claimed_evaluations.get_shifted(), shifted_challenges)) {
        batched_shifted_evaluation += eval * challenge;
    }
 
    // Batch commitments
    VerifierCommitments verifier_commitments(instance->get_vk(), instance->witness_commitments);
 
    Commitment batched_unshifted_commitment = batch_mul(verifier_commitments.get_unshifted(), unshifted_challenges);
    Commitment batched_shifted_commitment = batch_mul(verifier_commitments.get_to_be_shifted(), shifted_challenges);
 
    return Accumulator{ .challenge = sumcheck_output.challenge,
                        .non_shifted_evaluation = batched_unshifted_evaluation,
                        .shifted_evaluation = batched_shifted_evaluation,
                        .non_shifted_commitment = batched_unshifted_commitment,
                        .shifted_commitment = batched_shifted_commitment };
};
 
template <typename Flavor>
SumcheckOutput<Flavor> HypernovaFoldingVerifier<Flavor>::sumcheck_on_incoming_instance(
    const std::shared_ptr<typename HypernovaFoldingVerifier::VerifierInstance>& instance,
    const Proof& proof,
    size_t num_public_inputs)
{
    BB_BENCH_NAME("HypernovaFoldingVerifier::sumcheck_on_incoming_instance");
 
    vinfo("HypernovaFoldingVerifier: verifying Oink proof...");
    // Complete the incoming verifier instance
    transcript->load_proof(proof);
 
    OinkVerifier verifier{ instance, transcript, num_public_inputs };
    verifier.verify();
 
    instance->gate_challenges = transcript->template get_dyadic_powers_of_challenge<FF>(
        "HypernovaFoldingProver:gate_challenge", Flavor::VIRTUAL_LOG_N);
 
    // Sumcheck verification
    vinfo("HypernovaFoldingVerifier: verifying Sumcheck to turn instance into an accumulator...");
 
    SumcheckVerifier sumcheck(transcript, instance->alpha, Flavor::VIRTUAL_LOG_N);
    SumcheckOutput<Flavor> sumcheck_output = sumcheck.verify(instance->relation_parameters, instance->gate_challenges);
 
    return sumcheck_output;
};
 
template <typename Flavor>
std::pair<bool, typename HypernovaFoldingVerifier<Flavor>::Accumulator> HypernovaFoldingVerifier<Flavor>::
    instance_to_accumulator(const std::shared_ptr<typename HypernovaFoldingVerifier::VerifierInstance>& instance,
                            const Proof& proof)
{
    BB_BENCH_NAME("HypernovaFoldingVerifier::instance_to_accumulator");
 
    // Derive num_public_inputs from proof size (instance-to-accum proof structure)
    const size_t num_public_inputs =
        ProofLength::HypernovaInstanceToAccum<Flavor>::derive_num_public_inputs(proof.size(), Flavor::VIRTUAL_LOG_N);
 
    auto sumcheck_output = sumcheck_on_incoming_instance(instance, proof, num_public_inputs);
 
    auto accumulator = sumcheck_output_to_accumulator(sumcheck_output, instance);
 
    if (sumcheck_output.verified) {
        vinfo("HypernovaFoldingVerifier: Successfully turned instance into accumulator.");
    } else {
        vinfo("HypernovaFoldingVerifier: Failed to recursively verify Sumcheck to turn instance into an accumulator. "
              "Ignore if generating the VKs");
    }
 
    return { sumcheck_output.verified, accumulator };
};
 
template <typename Flavor>
std::tuple<bool, bool, typename HypernovaFoldingVerifier<Flavor>::Accumulator> HypernovaFoldingVerifier<
    Flavor>::verify_folding_proof(const std::shared_ptr<typename HypernovaFoldingVerifier::VerifierInstance>& instance,
                                  const HypernovaFoldingVerifier::Proof& proof)
{
    BB_BENCH_NAME("HypernovaFoldingVerifier::verify_folding_proof");
 
    vinfo("HypernovaFoldingVerifier: verifying folding proof...");
 
    // Derive num_public_inputs from proof size (folding proof structure includes batching)
    const size_t num_public_inputs =
        ProofLength::HypernovaFolding<Flavor, MultilinearBatchingFlavor>::derive_num_public_inputs(
            proof.size(), Flavor::VIRTUAL_LOG_N);
 
    auto sumcheck_output = sumcheck_on_incoming_instance(instance, proof, num_public_inputs);
 
    // Generate challenges to batch shifted and unshifted polynomials/commitments/evaluation
    const auto [unshifted_challenges, shifted_challenges] =
        get_hypernova_batching_challenges<FF>(transcript, NUM_UNSHIFTED_ENTITIES, NUM_SHIFTED_ENTITIES);
 
    VerifierCommitments verifier_commitments(instance->get_vk(), instance->witness_commitments);
 
    MultilinearBatchingVerifier batching_verifier(transcript);
    auto [sumcheck_batching_result, new_accumulator] =
        batching_verifier.verify_proof(sumcheck_output, verifier_commitments, unshifted_challenges, shifted_challenges);
 
    if (sumcheck_output.verified && sumcheck_batching_result) {
        vinfo("HypernovaFoldingVerifier: successfully verified folding proof.");
    } else if (!sumcheck_output.verified) {
        vinfo("HypernovaFoldingVerifier: Failed to recursively verify Sumcheck to turn instance into an accumulator. "
              "Ignore if generating the VKs");
    } else {
        vinfo("HypernovaFoldingVerifier: Failed to recursively verify Sumcheck to batch two accumulators. Ignore if "
              "generating the VKs");
    }
 
    return { sumcheck_output.verified, sumcheck_batching_result, new_accumulator };
};
 
template class HypernovaFoldingVerifier<MegaRecursiveFlavor_<MegaCircuitBuilder>>;
template class HypernovaFoldingVerifier<MegaFlavor>;
} // namespace bb