refactor: remove ark_halo2_interop module (#1010)

# Rationale for this change
A previous PR updated the HyperKZG commitment scheme to run without the
Blitzar feature flag. In order to do this, a new module
`ark_halo2_interop` was copied from the Blitzar-rs project. This was not
necessary since functions that did the same work already existed in the
HyperKZG proof primitive.

This PR removes the `ark_halo2_interop` module and replaces the
appropriate functions with functions from the `halo2_conversions`
module.

# What changes are included in this PR?
- The `ark_halo2_interop` module is removed
- Functions in `halo2_conversions` module are made public and replace
functions that use to be found in the `ark_halo2_interop` module

# Are these changes tested?
Yes

Author: jacobtrombetta

crates/proof-of-sql/src/proof_primitive/hyperkzg/arkworks_halo2_interop.rs

@@ -2,7 +2,7 @@ use super::{BNScalar, HyperKZGCommitment, HyperKZGEngine, HyperKZGPublicSetup};
 use crate::{
     base::{commitment::CommitmentEvaluationProof, slice_ops},
     proof_primitive::hyperkzg::{
-        convert_to_halo2_bn256_g1_affine, nova_commitment::NovaCommitment,
+        convert_g1_affine_from_ark_to_halo2, nova_commitment::NovaCommitment,
     },
 };
 use ark_bn254::{G1Affine, G1Projective};
@@ -81,7 +81,7 @@ impl CommitmentEvaluationProof for HyperKZGCommitmentEvaluationProof {
 
         let span = span!(Level::DEBUG, "initialize nova_ck").entered();
         let nova_ck: CommitmentKey<HyperKZGEngine> = CommitmentKey::new(
-            slice_ops::slice_cast_with(setup, convert_to_halo2_bn256_g1_affine),
+            slice_ops::slice_cast_with(setup, convert_g1_affine_from_ark_to_halo2),
             Affine::default(),   // I'm pretty sure this is unused in the proof
             G2Affine::default(), // I'm pretty sure this is unused in the proof
         );
@@ -127,7 +127,7 @@ impl CommitmentEvaluationProof for HyperKZGCommitmentEvaluationProof {
             .fold(G1Projective::default(), Add::add)
             .into();
         let nova_commit = nova_snark::provider::hyperkzg::Commitment::new(
-            convert_to_halo2_bn256_g1_affine(&commit).into(),
+            convert_g1_affine_from_ark_to_halo2(&commit).into(),
         );
         let nova_eval = evaluations
             .iter()

crates/proof-of-sql/src/proof_primitive/hyperkzg/commitment_evaluation_proof.rs

@@ -1,3 +1,5 @@
+use halo2curves::group::prime::PrimeCurveAffine;
+
 fn convert_limbs_to_halo2_fq(value: [u64; 4]) -> halo2curves::bn256::Fq {
     unsafe { core::mem::transmute(value) }
 }
@@ -24,18 +26,23 @@ fn convert_fr_from_halo2_to_ark(field: halo2curves::bn256::Fr) -> ark_bn254::Fr
     ark_ff::Fp::new_unchecked(ark_ff::BigInt(convert_halo2_fr_to_limbs(field)))
 }
 
-fn convert_g1_affine_from_halo2_to_ark(point: halo2curves::bn256::G1Affine) -> ark_bn254::G1Affine {
-    use halo2curves::group::prime::PrimeCurveAffine;
-    if point == halo2curves::bn256::G1Affine::identity() {
+/// Converts a Halo2 BN256 G1 Affine point to an Arkworks BN254 G1 Affine point.
+pub fn convert_g1_affine_from_halo2_to_ark(
+    point: &halo2curves::bn256::G1Affine,
+) -> ark_bn254::G1Affine {
+    if point.is_identity().into() {
         ark_bn254::G1Affine::identity()
     } else {
         let x = convert_fq_from_halo2_to_ark(point.x);
         let y = convert_fq_from_halo2_to_ark(point.y);
         ark_bn254::G1Affine::new_unchecked(x, y)
     }
 }
-fn convert_g1_affine_from_ark_to_halo2(point: ark_bn254::G1Affine) -> halo2curves::bn256::G1Affine {
-    use halo2curves::group::prime::PrimeCurveAffine;
+
+/// Converts an Arkworks BN254 G1 Affine point to a Halo2 BN256 G1 Affine point.
+pub fn convert_g1_affine_from_ark_to_halo2(
+    point: &ark_bn254::G1Affine,
+) -> halo2curves::bn256::G1Affine {
     if point.infinity {
         halo2curves::bn256::G1Affine::identity()
     } else {
@@ -48,13 +55,13 @@ fn convert_g1_affine_from_ark_to_halo2(point: ark_bn254::G1Affine) -> halo2curve
 impl From<&super::HyperKZGCommitment> for halo2curves::bn256::G1Affine {
     fn from(commitment: &super::HyperKZGCommitment) -> Self {
         use ark_ec::CurveGroup;
-        convert_g1_affine_from_ark_to_halo2(commitment.commitment.into_affine())
+        convert_g1_affine_from_ark_to_halo2(&commitment.commitment.into_affine())
     }
 }
 impl From<halo2curves::bn256::G1Affine> for super::HyperKZGCommitment {
     fn from(point: halo2curves::bn256::G1Affine) -> Self {
         use ark_ec::AffineRepr;
-        let commitment = convert_g1_affine_from_halo2_to_ark(point).into_group();
+        let commitment = convert_g1_affine_from_halo2_to_ark(&point).into_group();
         Self { commitment }
     }
 }

crates/proof-of-sql/src/proof_primitive/hyperkzg/halo2_conversions.rs

@@ -22,13 +22,6 @@ pub use public_setup::{
 mod commitment;
 pub use commitment::HyperKZGCommitment;
 
-#[cfg(feature = "hyperkzg_proof")]
-mod arkworks_halo2_interop;
-#[cfg(feature = "hyperkzg_proof")]
-pub(crate) use arkworks_halo2_interop::{
-    convert_to_ark_bn254_g1_affine, convert_to_halo2_bn256_g1_affine,
-};
-
 #[cfg(feature = "hyperkzg_proof")]
 mod nova_commitment;
 
@@ -44,6 +37,10 @@ pub use commitment_evaluation_proof::HyperKZGCommitmentEvaluationProof;
 
 #[cfg(feature = "hyperkzg_proof")]
 mod halo2_conversions;
+#[cfg(feature = "hyperkzg_proof")]
+pub(crate) use halo2_conversions::{
+    convert_g1_affine_from_ark_to_halo2, convert_g1_affine_from_halo2_to_ark,
+};
 
 #[cfg(all(test, feature = "hyperkzg_proof"))]
 mod evm_tests;

crates/proof-of-sql/src/proof_primitive/hyperkzg/mod.rs

@@ -14,7 +14,8 @@ mod tests {
             scalar::Scalar,
         },
         proof_primitive::hyperkzg::{
-            nova_commitment_key_to_hyperkzg_public_setup, BNScalar, HyperKZGCommitment,
+            convert_g1_affine_from_ark_to_halo2, nova_commitment_key_to_hyperkzg_public_setup,
+            BNScalar, HyperKZGCommitment,
         },
     };
     use ark_bn254::G1Affine;
@@ -30,10 +31,7 @@ mod tests {
 
     fn ark_to_nova_commitment(commitment: HyperKZGCommitment) -> NovaCommitment {
         NovaCommitment::new(
-            blitzar::compute::convert_to_halo2_bn256_g1_affine(&G1Affine::from(
-                commitment.commitment,
-            ))
-            .into(),
+            convert_g1_affine_from_ark_to_halo2(&G1Affine::from(commitment.commitment)).into(),
         )
     }
 

crates/proof-of-sql/src/proof_primitive/hyperkzg/nova_commitment.rs

@@ -4,7 +4,7 @@ use crate::{
         proof::{Keccak256Transcript, Transcript},
         slice_ops,
     },
-    proof_primitive::hyperkzg::convert_to_ark_bn254_g1_affine,
+    proof_primitive::hyperkzg::convert_g1_affine_from_halo2_to_ark,
 };
 use nova_snark::{
     errors::NovaError,
@@ -55,5 +55,5 @@ impl TranscriptEngineTrait<HyperKZGEngine> for Keccak256Transcript {
 pub fn nova_commitment_key_to_hyperkzg_public_setup(
     setup: &CommitmentKey<HyperKZGEngine>,
 ) -> HyperKZGPublicSetupOwned {
-    slice_ops::slice_cast_with(setup.ck(), convert_to_ark_bn254_g1_affine)
+    slice_ops::slice_cast_with(setup.ck(), convert_g1_affine_from_halo2_to_ark)
 }