diff --git a/src/fri/proof.rs b/src/fri/proof.rs index 793d0798..f6875fcc 100644 --- a/src/fri/proof.rs +++ b/src/fri/proof.rs @@ -14,6 +14,7 @@ use crate::hash::path_compression::{compress_merkle_proofs, decompress_merkle_pr use crate::iop::target::Target; use crate::plonk::circuit_data::CommonCircuitData; use crate::plonk::plonk_common::PolynomialsIndexBlinding; +use crate::plonk::proof::{FriInferredElements, ProofChallenges}; use crate::polynomial::polynomial::PolynomialCoeffs; /// Evaluations and Merkle proof produced by the prover in a FRI query step. @@ -164,9 +165,13 @@ impl, const D: usize> FriProof { initial_trees_proofs[i].push(proof); } for (i, query_step) in steps.into_iter().enumerate() { + let index_within_coset = index & ((1 << reduction_arity_bits[i]) - 1); index >>= reduction_arity_bits[i]; steps_indices[i].push(index); - steps_evals[i].push(query_step.evals); + let mut evals = query_step.evals; + // Remove the element that can be inferred. + evals.remove(index_within_coset); + steps_evals[i].push(evals); steps_proofs[i].push(query_step.merkle_proof); } } @@ -228,9 +233,10 @@ impl, const D: usize> FriProof { impl, const D: usize> CompressedFriProof { /// Decompress all the Merkle paths in the FRI proof and reinsert duplicate indices. - pub fn decompress( + pub(crate) fn decompress( self, - indices: &[usize], + challenges: &ProofChallenges, + fri_inferred_elements: FriInferredElements, common_data: &CommonCircuitData, ) -> FriProof { let CompressedFriProof { @@ -240,6 +246,11 @@ impl, const D: usize> CompressedFriProof { pow_witness, .. } = self; + let ProofChallenges { + fri_query_indices: indices, + .. + } = challenges; + let mut fri_inferred_elements = fri_inferred_elements.0.into_iter(); let cap_height = common_data.config.cap_height; let reduction_arity_bits = &common_data.fri_params.reduction_arity_bits; let num_reductions = reduction_arity_bits.len(); @@ -267,7 +278,12 @@ impl, const D: usize> CompressedFriProof { }) .collect::>(); - for mut index in indices.iter().copied() { + // Holds the `evals` vectors that have already been reconstructed at each reduction depth. + let mut evals_by_depth = vec![ + HashMap::>::new(); + common_data.fri_params.reduction_arity_bits.len() + ]; + for &(mut index) in indices { let initial_trees_proof = query_round_proofs.initial_trees_proofs[&index].clone(); for (i, (leaves_data, proof)) in initial_trees_proof.evals_proofs.into_iter().enumerate() @@ -277,11 +293,23 @@ impl, const D: usize> CompressedFriProof { initial_trees_proofs[i].push(proof); } for i in 0..num_reductions { + let index_within_coset = index & ((1 << reduction_arity_bits[i]) - 1); index >>= reduction_arity_bits[i]; - let query_step = query_round_proofs.steps[i][&index].clone(); + let FriQueryStep { + mut evals, + merkle_proof, + } = query_round_proofs.steps[i][&index].clone(); steps_indices[i].push(index); - steps_evals[i].push(flatten(&query_step.evals)); - steps_proofs[i].push(query_step.merkle_proof); + if let Some(v) = evals_by_depth[i].get(&index) { + // If this index has already been seen, get `evals` from the `HashMap`. + evals = v.to_vec(); + } else { + // Otherwise insert the next inferred element. + evals.insert(index_within_coset, fri_inferred_elements.next().unwrap()); + evals_by_depth[i].insert(index, evals.clone()); + } + steps_evals[i].push(flatten(&evals)); + steps_proofs[i].push(merkle_proof); } } diff --git a/src/fri/verifier.rs b/src/fri/verifier.rs index 0aae124d..add03a9d 100644 --- a/src/fri/verifier.rs +++ b/src/fri/verifier.rs @@ -15,7 +15,7 @@ use crate::util::{log2_strict, reverse_bits, reverse_index_bits_in_place}; /// Computes P'(x^arity) from {P(x*g^i)}_(i=0..arity), where g is a `arity`-th root of unity /// and P' is the FRI reduced polynomial. -fn compute_evaluation, const D: usize>( +pub(crate) fn compute_evaluation, const D: usize>( x: F, x_index_within_coset: usize, arity_bits: usize, @@ -92,7 +92,7 @@ pub(crate) fn verify_fri_proof, const D: usize>( challenges, precomputed_reduced_evals, initial_merkle_caps, - &proof, + proof, x_index, n, round_proof, @@ -118,14 +118,14 @@ fn fri_verify_initial_proof( /// Holds the reduced (by `alpha`) evaluations at `zeta` for the polynomial opened just at /// zeta, for `Z` at zeta and for `Z` at `g*zeta`. #[derive(Copy, Clone, Debug)] -struct PrecomputedReducedEvals, const D: usize> { +pub(crate) struct PrecomputedReducedEvals, const D: usize> { pub single: F::Extension, pub zs: F::Extension, pub zs_right: F::Extension, } impl, const D: usize> PrecomputedReducedEvals { - fn from_os_and_alpha(os: &OpeningSet, alpha: F::Extension) -> Self { + pub(crate) fn from_os_and_alpha(os: &OpeningSet, alpha: F::Extension) -> Self { let mut alpha = ReducingFactor::new(alpha); let single = alpha.reduce( os.constants @@ -146,7 +146,7 @@ impl, const D: usize> PrecomputedReducedEvals { } } -fn fri_combine_initial, const D: usize>( +pub(crate) fn fri_combine_initial, const D: usize>( proof: &FriInitialTreeProof, alpha: F::Extension, zeta: F::Extension, @@ -157,10 +157,6 @@ fn fri_combine_initial, const D: usize>( let config = &common_data.config; assert!(D > 1, "Not implemented for D=1."); let degree_log = common_data.degree_bits; - debug_assert_eq!( - degree_log, - common_data.config.cap_height + proof.evals_proofs[0].1.siblings.len() - config.rate_bits - ); let subgroup_x = F::Extension::from_basefield(subgroup_x); let mut alpha = ReducingFactor::new(alpha); let mut sum = F::Extension::ZERO; diff --git a/src/plonk/get_challenges.rs b/src/plonk/get_challenges.rs index 34034260..44249f7b 100644 --- a/src/plonk/get_challenges.rs +++ b/src/plonk/get_challenges.rs @@ -1,11 +1,15 @@ +use std::collections::HashSet; + use crate::field::extension_field::Extendable; use crate::field::field_types::RichField; +use crate::fri::verifier::{compute_evaluation, fri_combine_initial, PrecomputedReducedEvals}; use crate::hash::hashing::hash_n_to_1; use crate::iop::challenger::Challenger; use crate::plonk::circuit_data::CommonCircuitData; use crate::plonk::proof::{ - CompressedProofWithPublicInputs, ProofChallenges, ProofWithPublicInputs, + CompressedProofWithPublicInputs, FriInferredElements, ProofChallenges, ProofWithPublicInputs, }; +use crate::util::reverse_bits; impl, const D: usize> ProofWithPublicInputs { pub(crate) fn fri_query_indices( @@ -88,13 +92,6 @@ impl, const D: usize> ProofWithPublicInputs { } impl, const D: usize> CompressedProofWithPublicInputs { - pub(crate) fn fri_query_indices( - &self, - common_data: &CommonCircuitData, - ) -> anyhow::Result> { - Ok(self.get_challenges(common_data)?.fri_query_indices) - } - pub(crate) fn get_challenges( &self, common_data: &CommonCircuitData, @@ -135,7 +132,7 @@ impl, const D: usize> CompressedProofWithPublicInpu challenger.observe_cap(cap); challenger.get_extension_challenge() }) - .collect(); + .collect::>(); challenger.observe_extension_elements(&self.proof.opening_proof.final_poly.coeffs); @@ -152,7 +149,7 @@ impl, const D: usize> CompressedProofWithPublicInpu let fri_query_indices = (0..num_fri_queries) .map(|_| challenger.get_challenge().to_canonical_u64() as usize % lde_size) - .collect(); + .collect::>(); Ok(ProofChallenges { plonk_betas, @@ -165,4 +162,71 @@ impl, const D: usize> CompressedProofWithPublicInpu fri_query_indices, }) } + pub(crate) fn get_inferred_elements( + &self, + challenges: &ProofChallenges, + common_data: &CommonCircuitData, + ) -> FriInferredElements { + let ProofChallenges { + plonk_zeta, + fri_alpha, + fri_betas, + fri_query_indices, + .. + } = challenges; + let mut fri_inferred_elements = Vec::new(); + // Holds the indices that have already been seen at each reduction depth. + let mut seen_indices_by_depth = + vec![HashSet::new(); common_data.fri_params.reduction_arity_bits.len()]; + let precomputed_reduced_evals = + PrecomputedReducedEvals::from_os_and_alpha(&self.proof.openings, *fri_alpha); + let log_n = common_data.degree_bits + common_data.config.rate_bits; + // Simulate the proof verification and collect the inferred elements. + // The content of the loop is basically the same as the `fri_verifier_query_round` function. + for &(mut x_index) in fri_query_indices { + let mut subgroup_x = F::MULTIPLICATIVE_GROUP_GENERATOR + * F::primitive_root_of_unity(log_n).exp_u64(reverse_bits(x_index, log_n) as u64); + let mut old_eval = fri_combine_initial( + &self + .proof + .opening_proof + .query_round_proofs + .initial_trees_proofs[&x_index], + *fri_alpha, + *plonk_zeta, + subgroup_x, + precomputed_reduced_evals, + common_data, + ); + for (i, &arity_bits) in common_data + .fri_params + .reduction_arity_bits + .iter() + .enumerate() + { + let coset_index = x_index >> arity_bits; + if !seen_indices_by_depth[i].insert(coset_index) { + // If this index has already been seen, we can skip the rest of the reductions. + break; + } + fri_inferred_elements.push(old_eval); + let arity = 1 << arity_bits; + let mut evals = self.proof.opening_proof.query_round_proofs.steps[i][&coset_index] + .evals + .clone(); + let x_index_within_coset = x_index & (arity - 1); + evals.insert(x_index_within_coset, old_eval); + old_eval = compute_evaluation( + subgroup_x, + x_index_within_coset, + arity_bits, + &evals, + fri_betas[i], + ); + subgroup_x = subgroup_x.exp_power_of_2(arity_bits); + x_index = coset_index; + } + } + FriInferredElements(fri_inferred_elements) + } } diff --git a/src/plonk/proof.rs b/src/plonk/proof.rs index 4021f3cb..4dfa26bd 100644 --- a/src/plonk/proof.rs +++ b/src/plonk/proof.rs @@ -10,7 +10,8 @@ use crate::hash::hash_types::{HashOut, MerkleCapTarget}; use crate::hash::hashing::hash_n_to_hash; use crate::hash::merkle_tree::MerkleCap; use crate::iop::target::Target; -use crate::plonk::circuit_data::CommonCircuitData; +use crate::plonk::circuit_data::{CommonCircuitData, VerifierOnlyCircuitData}; +use crate::plonk::verifier::verify_with_challenges; use crate::util::serialization::Buffer; #[derive(Serialize, Deserialize, Clone, Debug, Eq, PartialEq)] @@ -118,9 +119,10 @@ pub struct CompressedProof, const D: usize> { impl, const D: usize> CompressedProof { /// Decompress the proof. - pub fn decompress( + pub(crate) fn decompress( self, - indices: &[usize], + challenges: &ProofChallenges, + fri_inferred_elements: FriInferredElements, common_data: &CommonCircuitData, ) -> Proof { let CompressedProof { @@ -136,7 +138,11 @@ impl, const D: usize> CompressedProof { plonk_zs_partial_products_cap, quotient_polys_cap, openings, - opening_proof: opening_proof.decompress(indices, common_data), + opening_proof: opening_proof.decompress( + &challenges, + fri_inferred_elements, + common_data, + ), } } } @@ -153,14 +159,38 @@ impl, const D: usize> CompressedProofWithPublicInpu self, common_data: &CommonCircuitData, ) -> anyhow::Result> { - let indices = self.fri_query_indices(common_data)?; - let compressed_proof = self.proof.decompress(&indices, common_data); + let challenges = self.get_challenges(common_data)?; + let fri_inferred_elements = self.get_inferred_elements(&challenges, common_data); + let compressed_proof = + self.proof + .decompress(&challenges, fri_inferred_elements, common_data); Ok(ProofWithPublicInputs { public_inputs: self.public_inputs, proof: compressed_proof, }) } + pub(crate) fn verify( + self, + verifier_data: &VerifierOnlyCircuitData, + common_data: &CommonCircuitData, + ) -> anyhow::Result<()> { + let challenges = self.get_challenges(common_data)?; + let fri_inferred_elements = self.get_inferred_elements(&challenges, common_data); + let compressed_proof = + self.proof + .decompress(&challenges, fri_inferred_elements, common_data); + verify_with_challenges( + ProofWithPublicInputs { + public_inputs: self.public_inputs, + proof: compressed_proof, + }, + challenges, + verifier_data, + common_data, + ) + } + pub(crate) fn get_public_inputs_hash(&self) -> HashOut { hash_n_to_hash(self.public_inputs.clone(), true) } @@ -202,9 +232,15 @@ pub(crate) struct ProofChallenges, const D: usize> pub fri_pow_response: F, + // Indices at which the oracle is queried in FRI. pub fri_query_indices: Vec, } +/// Coset element that can be inferred in the FRI reduction step. +pub(crate) struct FriInferredElements, const D: usize>( + pub Vec, +); + pub struct ProofWithPublicInputsTarget { pub proof: ProofTarget, pub public_inputs: Vec, @@ -273,6 +309,7 @@ mod tests { use crate::field::crandall_field::CrandallField; use crate::field::field_types::Field; + use crate::fri::reduction_strategies::FriReductionStrategy; use crate::iop::witness::PartialWitness; use crate::plonk::circuit_builder::CircuitBuilder; use crate::plonk::circuit_data::CircuitConfig; @@ -284,6 +321,7 @@ mod tests { const D: usize = 4; let mut config = CircuitConfig::large_config(); + config.fri_config.reduction_strategy = FriReductionStrategy::Fixed(vec![2, 1]); config.fri_config.num_query_rounds = 50; let pw = PartialWitness::new(); @@ -300,12 +338,14 @@ mod tests { builder.connect(zt, comp_zt); let data = builder.build(); let proof = data.prove(pw)?; + verify(proof.clone(), &data.verifier_only, &data.common)?; // Verify that `decompress ∘ compress = identity`. let compressed_proof = proof.clone().compress(&data.common)?; - let decompressed_compressed_proof = compressed_proof.decompress(&data.common)?; + let decompressed_compressed_proof = compressed_proof.clone().decompress(&data.common)?; assert_eq!(proof, decompressed_compressed_proof); - verify(proof, &data.verifier_only, &data.common) + verify(proof, &data.verifier_only, &data.common)?; + compressed_proof.verify(&data.verifier_only, &data.common) } } diff --git a/src/plonk/verifier.rs b/src/plonk/verifier.rs index 0ce9e3d0..e21fe328 100644 --- a/src/plonk/verifier.rs +++ b/src/plonk/verifier.rs @@ -5,7 +5,7 @@ use crate::field::field_types::{Field, RichField}; use crate::fri::verifier::verify_fri_proof; use crate::plonk::circuit_data::{CommonCircuitData, VerifierOnlyCircuitData}; use crate::plonk::plonk_common::reduce_with_powers; -use crate::plonk::proof::ProofWithPublicInputs; +use crate::plonk::proof::{ProofChallenges, ProofWithPublicInputs}; use crate::plonk::vanishing_poly::eval_vanishing_poly; use crate::plonk::vars::EvaluationVars; @@ -14,9 +14,17 @@ pub(crate) fn verify, const D: usize>( verifier_data: &VerifierOnlyCircuitData, common_data: &CommonCircuitData, ) -> Result<()> { - let public_inputs_hash = &proof_with_pis.get_public_inputs_hash(); - let challenges = proof_with_pis.get_challenges(common_data)?; + verify_with_challenges(proof_with_pis, challenges, verifier_data, common_data) +} + +pub(crate) fn verify_with_challenges, const D: usize>( + proof_with_pis: ProofWithPublicInputs, + challenges: ProofChallenges, + verifier_data: &VerifierOnlyCircuitData, + common_data: &CommonCircuitData, +) -> Result<()> { + let public_inputs_hash = &proof_with_pis.get_public_inputs_hash(); let ProofWithPublicInputs { proof, .. } = proof_with_pis; diff --git a/src/util/serialization.rs b/src/util/serialization.rs index d4a4ea1e..172b4d67 100644 --- a/src/util/serialization.rs +++ b/src/util/serialization.rs @@ -248,8 +248,9 @@ impl Buffer { fn read_fri_query_step, const D: usize>( &mut self, arity: usize, + compressed: bool, ) -> Result> { - let evals = self.read_field_ext_vec::(arity)?; + let evals = self.read_field_ext_vec::(arity - if compressed { 1 } else { 0 })?; let merkle_proof = self.read_merkle_proof()?; Ok(FriQueryStep { evals, @@ -281,7 +282,7 @@ impl Buffer { .fri_params .reduction_arity_bits .iter() - .map(|&ar| self.read_fri_query_step(1 << ar)) + .map(|&ar| self.read_fri_query_step(1 << ar, false)) .collect::>()?; fqrs.push(FriQueryRound { initial_trees_proof, @@ -424,7 +425,7 @@ impl Buffer { }); indices.dedup(); let query_steps = (0..indices.len()) - .map(|_| self.read_fri_query_step(1 << a)) + .map(|_| self.read_fri_query_step(1 << a, true)) .collect::>>()?; steps.push( indices