move IPA-specific methods to the provider (#138)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "nova-snark"
-version = "0.13.0"
+version = "0.14.0"
 authors = ["Srinath Setty <srinath@microsoft.com>"]
 edition = "2021"
 description = "Recursive zkSNARKs without trusted setup"

src/bellperson/solver.rs

@@ -32,7 +32,7 @@ impl fmt::Debug for SatisfyingAssignment
 where
   G::Scalar: PrimeField,
 {
-  fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+  fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
     fmt
       .debug_struct("SatisfyingAssignment")
       .field("a_aux_density", &self.a_aux_density)

src/lib.rs

@@ -1,7 +1,15 @@
 //! This library implements Nova, a high-speed recursive SNARK.
+#![deny(
+  warnings,
+  unused,
+  future_incompatible,
+  nonstandard_style,
+  rust_2018_idioms,
+  missing_docs
+)]
 #![allow(non_snake_case)]
 #![allow(clippy::type_complexity)]
-#![deny(missing_docs)]
+#![forbid(unsafe_code)]
 
 // private modules
 mod bellperson;

src/provider/ipa_pc.rs

@@ -2,6 +2,7 @@
 #![allow(clippy::too_many_arguments)]
 use crate::{
   errors::NovaError,
+  provider::pedersen::CommitmentGensExtTrait,
   spartan::polynomial::EqPolynomial,
   traits::{
     commitment::{CommitmentEngineTrait, CommitmentGensTrait, CommitmentTrait},
@@ -39,7 +40,11 @@ pub struct EvaluationEngine {
   _p: PhantomData<G>,
 }
 
-impl<G: Group> EvaluationEngineTrait<G> for EvaluationEngine<G> {
+impl<G> EvaluationEngineTrait<G> for EvaluationEngine<G>
+where
+  G: Group,
+  CommitmentGens<G>: CommitmentGensExtTrait<G, CE = G::CE>,
+{
   type CE = G::CE;
   type EvaluationGens = EvaluationGens<G>;
   type EvaluationArgument = EvaluationArgument<G>;
@@ -99,7 +104,7 @@ impl EvaluationEngineTrait for EvaluationEngine {
   fn verify_batch(
     gens: &Self::EvaluationGens,
     transcript: &mut Transcript,
-    comms: &[<Self::CE as CommitmentEngineTrait<G>>::Commitment],
+    comms: &[Commitment<G>],
     points: &[Vec<G::Scalar>],
     evals: &[G::Scalar],
     arg: &Self::EvaluationArgument,
@@ -324,7 +329,11 @@ struct InnerProductArgument {
   _p: PhantomData<G>,
 }
 
-impl<G: Group> InnerProductArgument<G> {
+impl<G> InnerProductArgument<G>
+where
+  G: Group,
+  CommitmentGens<G>: CommitmentGensExtTrait<G, CE = G::CE>,
+{
   fn protocol_name() -> &'static [u8] {
     b"inner product argument"
   }

src/provider/pedersen.rs

@@ -60,92 +60,6 @@ impl CommitmentGensTrait for CommitmentGens {
       comm: G::vartime_multiscalar_mul(v, &self.gens[..v.len()]),
     }
   }
-
-  fn split_at(&self, n: usize) -> (CommitmentGens<G>, CommitmentGens<G>) {
-    (
-      CommitmentGens {
-        gens: self.gens[0..n].to_vec(),
-        _p: Default::default(),
-      },
-      CommitmentGens {
-        gens: self.gens[n..].to_vec(),
-        _p: Default::default(),
-      },
-    )
-  }
-
-  fn combine(&self, other: &CommitmentGens<G>) -> CommitmentGens<G> {
-    let gens = {
-      let mut c = self.gens.clone();
-      c.extend(other.gens.clone());
-      c
-    };
-    CommitmentGens {
-      gens,
-      _p: Default::default(),
-    }
-  }
-
-  // combines the left and right halves of `self` using `w1` and `w2` as the weights
-  fn fold(&self, w1: &G::Scalar, w2: &G::Scalar) -> CommitmentGens<G> {
-    let w = vec![*w1, *w2];
-    let (L, R) = self.split_at(self.len() / 2);
-
-    let gens = (0..self.len() / 2)
-      .into_par_iter()
-      .map(|i| {
-        let gens = CommitmentGens::<G> {
-          gens: [L.gens[i].clone(), R.gens[i].clone()].to_vec(),
-          _p: Default::default(),
-        };
-        gens.commit(&w).comm.preprocessed()
-      })
-      .collect();
-
-    CommitmentGens {
-      gens,
-      _p: Default::default(),
-    }
-  }
-
-  /// Scales each element in `self` by `r`
-  fn scale(&self, r: &G::Scalar) -> Self {
-    let gens_scaled = self
-      .gens
-      .clone()
-      .into_par_iter()
-      .map(|g| {
-        let gens = CommitmentGens::<G> {
-          gens: vec![g],
-          _p: Default::default(),
-        };
-        gens.commit(&[*r]).comm.preprocessed()
-      })
-      .collect();
-
-    CommitmentGens {
-      gens: gens_scaled,
-      _p: Default::default(),
-    }
-  }
-
-  /// reinterprets a vector of commitments as a set of generators
-  fn reinterpret_commitments_as_gens(
-    c: &[CompressedCommitment<G::CompressedGroupElement>],
-  ) -> Result<Self, NovaError> {
-    let d = (0..c.len())
-      .into_par_iter()
-      .map(|i| c[i].decompress())
-      .collect::<Result<Vec<Commitment<G>>, NovaError>>()?;
-    let gens = (0..d.len())
-      .into_par_iter()
-      .map(|i| d[i].comm.preprocessed())
-      .collect();
-    Ok(CommitmentGens {
-      gens,
-      _p: Default::default(),
-    })
-  }
 }
 
 impl<G: Group> CommitmentTrait<G> for Commitment<G> {
@@ -302,3 +216,109 @@ impl CommitmentEngineTrait for CommitmentEngine {
     gens.commit(v)
   }
 }
+
+pub(crate) trait CommitmentGensExtTrait<G: Group>: CommitmentGensTrait<G> {
+  type CE: CommitmentEngineTrait<G>;
+
+  /// Splits the commitment key into two pieces at a specified point
+  fn split_at(&self, n: usize) -> (Self, Self)
+  where
+    Self: Sized;
+
+  /// Combines two commitment keys into one
+  fn combine(&self, other: &Self) -> Self;
+
+  /// Folds the two commitment keys into one using the provided weights
+  fn fold(&self, w1: &G::Scalar, w2: &G::Scalar) -> Self;
+
+  /// Scales the commitment key using the provided scalar
+  fn scale(&self, r: &G::Scalar) -> Self;
+
+  /// Reinterprets commitments as commitment keys
+  fn reinterpret_commitments_as_gens(
+    c: &[<<Self as CommitmentGensExtTrait<G>>::CE as CommitmentEngineTrait<G>>::CompressedCommitment],
+  ) -> Result<Self, NovaError>
+  where
+    Self: Sized;
+}
+
+impl<G: Group> CommitmentGensExtTrait<G> for CommitmentGens<G> {
+  type CE = CommitmentEngine<G>;
+
+  fn split_at(&self, n: usize) -> (CommitmentGens<G>, CommitmentGens<G>) {
+    (
+      CommitmentGens {
+        gens: self.gens[0..n].to_vec(),
+        _p: Default::default(),
+      },
+      CommitmentGens {
+        gens: self.gens[n..].to_vec(),
+        _p: Default::default(),
+      },
+    )
+  }
+
+  fn combine(&self, other: &CommitmentGens<G>) -> CommitmentGens<G> {
+    let gens = {
+      let mut c = self.gens.clone();
+      c.extend(other.gens.clone());
+      c
+    };
+    CommitmentGens {
+      gens,
+      _p: Default::default(),
+    }
+  }
+
+  // combines the left and right halves of `self` using `w1` and `w2` as the weights
+  fn fold(&self, w1: &G::Scalar, w2: &G::Scalar) -> CommitmentGens<G> {
+    let w = vec![*w1, *w2];
+    let (L, R) = self.split_at(self.len() / 2);
+
+    let gens = (0..self.len() / 2)
+      .into_par_iter()
+      .map(|i| {
+        let bases = [L.gens[i].clone(), R.gens[i].clone()].to_vec();
+        G::vartime_multiscalar_mul(&w, &bases).preprocessed()
+      })
+      .collect();
+
+    CommitmentGens {
+      gens,
+      _p: Default::default(),
+    }
+  }
+
+  /// Scales each element in `self` by `r`
+  fn scale(&self, r: &G::Scalar) -> Self {
+    let gens_scaled = self
+      .gens
+      .clone()
+      .into_par_iter()
+      .map(|g| G::vartime_multiscalar_mul(&[*r], &[g]).preprocessed())
+      .collect();
+
+    CommitmentGens {
+      gens: gens_scaled,
+      _p: Default::default(),
+    }
+  }
+
+  /// reinterprets a vector of commitments as a set of generators
+  fn reinterpret_commitments_as_gens(
+    c: &[CompressedCommitment<G::CompressedGroupElement>],
+  ) -> Result<Self, NovaError> {
+    let d = (0..c.len())
+      .into_par_iter()
+      .map(|i| c[i].decompress())
+      .collect::<Result<Vec<Commitment<G>>, NovaError>>()?;
+    let gens = (0..d.len())
+      .into_par_iter()
+      .map(|i| d[i].comm.preprocessed())
+      .collect();
+    Ok(CommitmentGens {
+      gens,
+      _p: Default::default(),
+    })
+  }
+}

src/r1cs.rs

@@ -247,7 +247,7 @@ impl R1CSShape {
     };
 
     // verify if comm_W is a commitment to W
-    let res_comm: bool = U.comm_W == gens.gens.commit(&W.W);
+    let res_comm: bool = U.comm_W == CE::<G>::commit(&gens.gens, &W.W);
 
     if res_eq && res_comm {
       Ok(())
@@ -301,7 +301,7 @@ impl R1CSShape {
       .map(|(((a, b), c), d)| *a + *b - *c - *d)
       .collect::<Vec<G::Scalar>>();
 
-    let comm_T = gens.gens.commit(&T);
+    let comm_T = CE::<G>::commit(&gens.gens, &T);
 
     Ok((T, comm_T))
   }
@@ -466,7 +466,7 @@ impl R1CSWitness {
 
   /// Commits to the witness using the supplied generators
   pub fn commit(&self, gens: &R1CSGens<G>) -> Commitment<G> {
-    gens.gens.commit(&self.W)
+    CE::<G>::commit(&gens.gens, &self.W)
   }
 }
 

src/traits/commitment.rs

@@ -29,25 +29,6 @@ pub trait CommitmentGensTrait:
 
   /// Commits to a vector using the commitment key
   fn commit(&self, v: &[G::Scalar]) -> Self::Commitment;
-
-  /// Splits the commitment key into two pieces at a specified point
-  fn split_at(&self, n: usize) -> (Self, Self)
-  where
-    Self: Sized;
-
-  /// Combines two commitment keys into one
-  fn combine(&self, other: &Self) -> Self;
-
-  /// Folds the two commitment keys into one using the provided weights
-  fn fold(&self, w1: &G::Scalar, w2: &G::Scalar) -> Self;
-
-  /// Scales the commitment key using the provided scalar
-  fn scale(&self, r: &G::Scalar) -> Self;
-
-  /// Reinterprets commitments as commitment keys
-  fn reinterpret_commitments_as_gens(c: &[Self::CompressedCommitment]) -> Result<Self, NovaError>
-  where
-    Self: Sized;
 }
 
 /// Defines basic operations on commitments