refactor: remove non_hiding_kzg module, split code where dependents n…

…eed it

- Moved `UniversalParams` and several dependent structures for the KZG10 scheme in the `kzg_commitment.rs` file.
- Deleted the `non_hiding_kzg.rs` file,
- Consolidated KZG related structs under the `kzg_commitment` module,
- Updated `mod.rs` to reflect the removal of the `non_hiding_kzg` module.

src/provider/hyperkzg.rs

@@ -9,8 +9,7 @@
 use crate::{
   errors::NovaError,
   provider::{
-    kzg_commitment::KZGCommitmentEngine,
-    non_hiding_kzg::{trim, KZGProverKey, KZGVerifierKey, UniversalKZGParam},
+    kzg_commitment::{KZGCommitmentEngine, KZGProverKey, KZGVerifierKey, UniversalKZGParam},
     pedersen::Commitment,
     traits::DlogGroup,
     util::iterators::DoubleEndedIteratorExt as _,
@@ -127,7 +126,7 @@ where
 
   fn setup(ck: Arc<UniversalKZGParam<E>>) -> (Self::ProverKey, Self::VerifierKey) {
     let len = ck.length() - 1;
-    trim(ck, len)
+    UniversalKZGParam::trim(ck, len)
   }
 
   fn prove(
@@ -437,36 +436,52 @@ mod tests {
     let ck: CommitmentKey<NE> =
       <KZGCommitmentEngine<E> as CommitmentEngineTrait<NE>>::setup(b"test", n);
     let ck = Arc::new(ck);
-    let (pk, _vk): (KZGProverKey<E>, KZGVerifierKey<E>) =
+    let (pk, vk): (KZGProverKey<E>, KZGVerifierKey<E>) =
       EvaluationEngine::<E, NE>::setup(ck.clone());
 
     // poly is in eval. representation; evaluated at [(0,0), (0,1), (1,0), (1,1)]
     let poly = vec![Fr::from(1), Fr::from(2), Fr::from(2), Fr::from(4)];
 
     let C = <KZGCommitmentEngine<E> as CommitmentEngineTrait<NE>>::commit(&ck, &poly);
-    let mut tr = Keccak256Transcript::<NE>::new(b"TestEval");
 
-    // Call the prover with a (point, eval) pair. The prover recomputes
-    // poly(point) = eval', and fails if eval' != eval
+    let test_inner = |point: Vec<Fr>, eval: Fr| -> Result<(), NovaError> {
+      let mut tr = Keccak256Transcript::<NE>::new(b"TestEval");
+      let proof =
+        EvaluationEngine::<E, NE>::prove(&ck, &pk, &mut tr, &C, &poly, &point, &eval).unwrap();
+      let mut tr = Keccak256Transcript::new(b"TestEval");
+      EvaluationEngine::<E, NE>::verify(&vk, &mut tr, &C, &point, &eval, &proof)
+    };
+
+    // Call the prover with a (point, eval) pair.
+    // The prover does not recompute so it may produce a proof, but it should not verify
     let point = vec![Fr::from(0), Fr::from(0)];
     let eval = Fr::ONE;
-    assert!(EvaluationEngine::<E, NE>::prove(&ck, &pk, &mut tr, &C, &poly, &point, &eval).is_ok());
+    assert!(test_inner(point, eval).is_ok());
 
     let point = vec![Fr::from(0), Fr::from(1)];
     let eval = Fr::from(2);
-    assert!(EvaluationEngine::<E, NE>::prove(&ck, &pk, &mut tr, &C, &poly, &point, &eval).is_ok());
+    assert!(test_inner(point, eval).is_ok());
 
     let point = vec![Fr::from(1), Fr::from(1)];
     let eval = Fr::from(4);
-    assert!(EvaluationEngine::<E, NE>::prove(&ck, &pk, &mut tr, &C, &poly, &point, &eval).is_ok());
+    assert!(test_inner(point, eval).is_ok());
 
     let point = vec![Fr::from(0), Fr::from(2)];
     let eval = Fr::from(3);
-    assert!(EvaluationEngine::<E, NE>::prove(&ck, &pk, &mut tr, &C, &poly, &point, &eval).is_ok());
+    assert!(test_inner(point, eval).is_ok());
 
     let point = vec![Fr::from(2), Fr::from(2)];
     let eval = Fr::from(9);
-    assert!(EvaluationEngine::<E, NE>::prove(&ck, &pk, &mut tr, &C, &poly, &point, &eval).is_ok());
+    assert!(test_inner(point, eval).is_ok());
+
+    // Try a couple incorrect evaluations and expect failure
+    let point = vec![Fr::from(2), Fr::from(2)];
+    let eval = Fr::from(50);
+    assert!(test_inner(point, eval).is_err());
+
+    let point = vec![Fr::from(0), Fr::from(2)];
+    let eval = Fr::from(4);
+    assert!(test_inner(point, eval).is_err());
   }
 
   #[test]

src/provider/kzg_commitment.rs

@@ -3,23 +3,219 @@
 
 use std::marker::PhantomData;
 
-use ff::PrimeFieldBits;
-use group::{prime::PrimeCurveAffine, Curve};
+use abomonation_derive::Abomonation;
+use ff::{Field, PrimeField, PrimeFieldBits};
+use group::{prime::PrimeCurveAffine, Curve, Group as _};
 use pairing::Engine;
 use rand::rngs::StdRng;
-use rand_core::SeedableRng;
+use rand_core::{CryptoRng, RngCore, SeedableRng};
 use serde::{Deserialize, Serialize};
+use std::sync::Arc;
 
-use crate::traits::{
+use crate::{traits::{
   commitment::{CommitmentEngineTrait, Len},
-  Engine as NovaEngine, Group,
-};
-
-use crate::provider::{
-  non_hiding_kzg::{UVKZGCommitment, UniversalKZGParam},
-  pedersen::Commitment,
-  traits::DlogGroup,
-};
+  Engine as NovaEngine, Group, TranscriptReprTrait,
+}, digest::SimpleDigestible};
+use crate::provider::traits::DlogGroup;
+use crate::provider::util::fb_msm;
+use crate::provider::pedersen::Commitment;
+
+/// `UniversalParams` are the universal parameters for the KZG10 scheme.
+#[derive(Debug, Clone, Eq, Serialize, Deserialize, Abomonation)]
+#[serde(bound(
+  serialize = "E::G1Affine: Serialize, E::G2Affine: Serialize",
+  deserialize = "E::G1Affine: Deserialize<'de>, E::G2Affine: Deserialize<'de>"
+))]
+#[abomonation_omit_bounds]
+pub struct UniversalKZGParam<E: Engine> {
+  /// Group elements of the form `{ β^i G }`, where `i` ranges from 0 to
+  /// `degree`.
+  // this is a hack; we just assume the size of the element.
+  // Look for the static assertions in provider macros for a justification
+  #[abomonate_with(Vec<[u64; 8]>)]
+  pub powers_of_g: Vec<E::G1Affine>,
+  /// Group elements of the form `{ β^i H }`, where `i` ranges from 0 to
+  /// `degree`.
+  // this is a hack; we just assume the size of the element.
+  // Look for the static assertions in provider macros for a justification
+  #[abomonate_with(Vec<[u64; 16]>)]
+  pub powers_of_h: Vec<E::G2Affine>,
+}
+
+impl<E: Engine> PartialEq for UniversalKZGParam<E> {
+  fn eq(&self, other: &Self) -> bool {
+    self.powers_of_g == other.powers_of_g && self.powers_of_h == other.powers_of_h
+  }
+}
+// for the purpose of the Len trait, we count commitment bases, i.e. G1 elements
+impl<E: Engine> Len for UniversalKZGParam<E> {
+  fn length(&self) -> usize {
+    self.powers_of_g.len()
+  }
+}
+
+/// `UnivariateProverKey` is used to generate a proof
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct KZGProverKey<E: Engine> {
+  /// generators from the universal parameters
+  uv_params: Arc<UniversalKZGParam<E>>,
+  /// offset at which we start reading into the SRS
+  offset: usize,
+  /// maximum supported size
+  supported_size: usize,
+}
+
+impl<E: Engine> KZGProverKey<E> {
+  pub(in crate::provider) fn new(
+    uv_params: Arc<UniversalKZGParam<E>>,
+    offset: usize,
+    supported_size: usize,
+  ) -> Self {
+    assert!(
+      uv_params.max_degree() >= offset + supported_size,
+      "not enough bases (req: {} from offset {}) in the UVKZGParams (length: {})",
+      supported_size,
+      offset,
+      uv_params.max_degree()
+    );
+    Self {
+      uv_params,
+      offset,
+      supported_size,
+    }
+  }
+
+  pub fn powers_of_g(&self) -> &[E::G1Affine] {
+    &self.uv_params.powers_of_g[self.offset..self.offset + self.supported_size]
+  }
+}
+
+/// `UVKZGVerifierKey` is used to check evaluation proofs for a given
+/// commitment.
+#[derive(Clone, Debug, Eq, PartialEq, Serialize)]
+#[serde(bound(serialize = "E::G1Affine: Serialize, E::G2Affine: Serialize",))]
+pub struct KZGVerifierKey<E: Engine> {
+  /// The generator of G1.
+  pub g: E::G1Affine,
+  /// The generator of G2.
+  pub h: E::G2Affine,
+  /// β times the above generator of G2.
+  pub beta_h: E::G2Affine,
+}
+
+impl<E: Engine> SimpleDigestible for KZGVerifierKey<E>
+where
+  E::G1Affine: Serialize,
+  E::G2Affine: Serialize,
+{
+}
+
+impl<E: Engine> UniversalKZGParam<E> {
+  /// Returns the maximum supported degree
+  pub fn max_degree(&self) -> usize {
+    self.powers_of_g.len()
+  }
+
+  /// Trim the universal parameters to specialize the public parameters
+  /// for univariate polynomials to the given `supported_size`, and
+  /// returns prover key and verifier key. `supported_size` should
+  /// be in range `1..params.len()`
+  ///
+  /// # Panics
+  /// If `supported_size` is greater than `self.max_degree()`, or `self.max_degree()` is zero.
+  pub fn trim(
+    ukzg: Arc<UniversalKZGParam<E>>,
+    supported_size: usize,
+  ) -> (KZGProverKey<E>, KZGVerifierKey<E>) {
+    assert!(ukzg.max_degree() > 0, "max_degree is zero");
+    let g = ukzg.powers_of_g[0];
+    let h = ukzg.powers_of_h[0];
+    let beta_h = ukzg.powers_of_h[1];
+    let pk = KZGProverKey::new(ukzg, 0, supported_size + 1);
+    let vk = KZGVerifierKey { g, h, beta_h };
+    (pk, vk)
+  }  
+}
+
+impl<E: Engine> UniversalKZGParam<E> 
+  where
+  E::Fr: PrimeFieldBits,
+{
+  /// Build SRS for testing.
+  /// WARNING: THIS FUNCTION IS FOR TESTING PURPOSE ONLY.
+  /// THE OUTPUT SRS SHOULD NOT BE USED IN PRODUCTION.
+  pub fn gen_srs_for_testing<R: RngCore + CryptoRng>(mut rng: &mut R, max_degree: usize) -> Self {
+    let beta = E::Fr::random(&mut rng);
+    let g = E::G1::random(&mut rng);
+    let h = E::G2::random(rng);
+
+    let nz_powers_of_beta = (0..=max_degree)
+      .scan(beta, |acc, _| {
+        let val = *acc;
+        *acc *= beta;
+        Some(val)
+      })
+      .collect::<Vec<E::Fr>>();
+
+    let window_size = fb_msm::get_mul_window_size(max_degree);
+    let scalar_bits = E::Fr::NUM_BITS as usize;
+
+    let (powers_of_g_projective, powers_of_h_projective) = rayon::join(
+      || {
+        let g_table = fb_msm::get_window_table(scalar_bits, window_size, g);
+        fb_msm::multi_scalar_mul::<E::G1>(scalar_bits, window_size, &g_table, &nz_powers_of_beta)
+      },
+      || {
+        let h_table = fb_msm::get_window_table(scalar_bits, window_size, h);
+        fb_msm::multi_scalar_mul::<E::G2>(scalar_bits, window_size, &h_table, &nz_powers_of_beta)
+      },
+    );
+
+    let mut powers_of_g = vec![E::G1Affine::identity(); powers_of_g_projective.len()];
+    let mut powers_of_h = vec![E::G2Affine::identity(); powers_of_h_projective.len()];
+
+    rayon::join(
+      || E::G1::batch_normalize(&powers_of_g_projective, &mut powers_of_g),
+      || E::G2::batch_normalize(&powers_of_h_projective, &mut powers_of_h),
+    );
+
+    Self {
+      powers_of_g,
+      powers_of_h,
+    }
+  }
+
+}
+
+/// Commitments
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Default, Serialize, Deserialize)]
+#[serde(bound(
+  serialize = "E::G1Affine: Serialize",
+  deserialize = "E::G1Affine: Deserialize<'de>"
+))]
+pub struct UVKZGCommitment<E: Engine>(
+  /// the actual commitment is an affine point.
+  pub E::G1Affine,
+);
+
+impl<E: Engine> TranscriptReprTrait<E::G1> for UVKZGCommitment<E>
+where
+  E::G1: DlogGroup,
+  // Note: due to the move of the bound TranscriptReprTrait<G> on G::Base from Group to Engine
+  <E::G1 as Group>::Base: TranscriptReprTrait<E::G1>,
+{
+  fn to_transcript_bytes(&self) -> Vec<u8> {
+    // TODO: avoid the round-trip through the group (to_curve .. to_coordinates)
+    let (x, y, is_infinity) = self.0.to_curve().to_coordinates();
+    let is_infinity_byte = (!is_infinity).into();
+    [
+      x.to_transcript_bytes(),
+      y.to_transcript_bytes(),
+      [is_infinity_byte].to_vec(),
+    ]
+    .concat()
+  }
+}
 
 /// Provides a commitment engine
 #[derive(Clone, Debug, PartialEq, Eq)]

src/provider/mod.rs

@@ -15,7 +15,6 @@ pub(crate) mod secp_secq;
 pub(crate) mod traits;
 // a non-hiding variant of {kzg, zeromorph}
 mod kzg_commitment;
-mod non_hiding_kzg;
 pub(crate) mod util;
 
 // crate-private modules