simplify commitmentengine (#149)

src/provider/ipa_pc.rs

@@ -5,7 +5,7 @@ use crate::{
   provider::pedersen::CommitmentKeyExtTrait,
   spartan::polynomial::EqPolynomial,
   traits::{
-    commitment::{CommitmentEngineTrait, CommitmentKeyTrait, CommitmentTrait},
+    commitment::{CommitmentEngineTrait, CommitmentTrait},
     evaluation::EvaluationEngineTrait,
     Group, TranscriptEngineTrait, TranscriptReprTrait,
   },
@@ -59,12 +59,12 @@ where
     ck: &<Self::CE as CommitmentEngineTrait<G>>::CommitmentKey,
   ) -> (Self::ProverKey, Self::VerifierKey) {
     let pk = ProverKey {
-      ck_s: CommitmentKey::<G>::new(b"ipa", 1),
+      ck_s: G::CE::setup(b"ipa", 1),
     };
 
     let vk = VerifierKey {
       ck_v: ck.clone(),
-      ck_s: CommitmentKey::<G>::new(b"ipa", 1),
+      ck_s: G::CE::setup(b"ipa", 1),
     };
 
     (pk, vk)

src/provider/pedersen.rs

@@ -2,7 +2,7 @@
 use crate::{
   errors::NovaError,
   traits::{
-    commitment::{CommitmentEngineTrait, CommitmentKeyTrait, CommitmentTrait},
+    commitment::{CommitmentEngineTrait, CommitmentTrait},
     AbsorbInROTrait, CompressedGroup, Group, ROTrait, TranscriptReprTrait,
   },
 };
@@ -36,28 +36,6 @@ pub struct CompressedCommitment<G: Group> {
   comm: G::CompressedGroupElement,
 }
 
-impl<G: Group> CommitmentKeyTrait<G> for CommitmentKey<G> {
-  type Commitment = Commitment<G>;
-
-  fn new(label: &'static [u8], n: usize) -> Self {
-    CommitmentKey {
-      ck: G::from_label(label, n.next_power_of_two()),
-      _p: Default::default(),
-    }
-  }
-
-  fn len(&self) -> usize {
-    self.ck.len()
-  }
-
-  fn commit(&self, v: &[G::Scalar]) -> Self::Commitment {
-    assert!(self.ck.len() >= v.len());
-    Commitment {
-      comm: G::vartime_multiscalar_mul(v, &self.ck[..v.len()]),
-    }
-  }
-}
-
 impl<G: Group> CommitmentTrait<G> for Commitment<G> {
   type CompressedCommitment = CompressedCommitment<G>;
 
@@ -210,12 +188,22 @@ impl<G: Group> CommitmentEngineTrait<G> for CommitmentEngine<G> {
   type CommitmentKey = CommitmentKey<G>;
   type Commitment = Commitment<G>;
 
+  fn setup(label: &'static [u8], n: usize) -> Self::CommitmentKey {
+    Self::CommitmentKey {
+      ck: G::from_label(label, n.next_power_of_two()),
+      _p: Default::default(),
+    }
+  }
+
   fn commit(ck: &Self::CommitmentKey, v: &[G::Scalar]) -> Self::Commitment {
-    ck.commit(v)
+    assert!(ck.ck.len() >= v.len());
+    Commitment {
+      comm: G::vartime_multiscalar_mul(v, &ck.ck[..v.len()]),
+    }
   }
 }
 
-pub(crate) trait CommitmentKeyExtTrait<G: Group>: CommitmentKeyTrait<G> {
+pub(crate) trait CommitmentKeyExtTrait<G: Group> {
   type CE: CommitmentEngineTrait<G>;
 
   /// Splits the commitment key into two pieces at a specified point
@@ -271,9 +259,9 @@ impl<G: Group> CommitmentKeyExtTrait<G> for CommitmentKey<G> {
   // combines the left and right halves of `self` using `w1` and `w2` as the weights
   fn fold(&self, w1: &G::Scalar, w2: &G::Scalar) -> CommitmentKey<G> {
     let w = vec![*w1, *w2];
-    let (L, R) = self.split_at(self.len() / 2);
+    let (L, R) = self.split_at(self.ck.len() / 2);
 
-    let ck = (0..self.len() / 2)
+    let ck = (0..self.ck.len() / 2)
       .into_par_iter()
       .map(|i| {
         let bases = [L.ck[i].clone(), R.ck[i].clone()].to_vec();

src/r1cs.rs

@@ -8,8 +8,7 @@ use crate::{
     utils::scalar_as_base,
   },
   traits::{
-    commitment::{CommitmentEngineTrait, CommitmentKeyTrait},
+    commitment::CommitmentEngineTrait, AbsorbInROTrait, Group, ROTrait, TranscriptReprTrait,
-    AbsorbInROTrait, Group, ROTrait, TranscriptReprTrait,
   },
   Commitment, CommitmentKey, CE,
 };
@@ -74,7 +73,7 @@ pub struct RelaxedR1CSInstance<G: Group> {
 impl<G: Group> R1CS<G> {
   /// Samples public parameters for the specified number of constraints and variables in an R1CS
   pub fn commitment_key(num_cons: usize, num_vars: usize) -> CommitmentKey<G> {
-    CommitmentKey::<G>::new(b"ck", max(num_vars, num_cons))
+    G::CE::setup(b"ck", max(num_vars, num_cons))
   }
 }
 

src/traits/commitment.rs

@@ -10,24 +10,6 @@ use core::{
 };
 use serde::{Deserialize, Serialize};
 
-/// This trait defines the behavior of commitment key
-#[allow(clippy::len_without_is_empty)]
-pub trait CommitmentKeyTrait<G: Group>:
-  Clone + Debug + Send + Sync + Serialize + for<'de> Deserialize<'de>
-{
-  /// Holds the type of the commitment that can be produced
-  type Commitment;
-
-  /// Samples a new commitment key of a specified size
-  fn new(label: &'static [u8], n: usize) -> Self;
-
-  /// Returns the vector length that can be committed
-  fn len(&self) -> usize;
-
-  /// Commits to a vector using the commitment key
-  fn commit(&self, v: &[G::Scalar]) -> Self::Commitment;
-}
-
 /// Defines basic operations on commitments
 pub trait CommitmentOps<Rhs = Self, Output = Self>:
   Add<Rhs, Output = Output> + AddAssign<Rhs>
@@ -99,11 +81,14 @@ pub trait CommitmentEngineTrait<G: Group>:
   Clone + Send + Sync + Serialize + for<'de> Deserialize<'de>
 {
   /// Holds the type of the commitment key
-  type CommitmentKey: CommitmentKeyTrait<G, Commitment = Self::Commitment>;
+  type CommitmentKey: Clone + Debug + Send + Sync + Serialize + for<'de> Deserialize<'de>;
 
   /// Holds the type of the commitment
   type Commitment: CommitmentTrait<G>;
 
+  /// Samples a new commitment key of a specified size
+  fn setup(label: &'static [u8], n: usize) -> Self::CommitmentKey;
+
   /// Commits to the provided vector using the provided generators
   fn commit(ck: &Self::CommitmentKey, v: &[G::Scalar]) -> Self::Commitment;
 }