impl Add for FeldmanCommitment and leverage batch_norm

Author: alxiong

timeboost-crypto/src/feldman.rs

@@ -9,7 +9,7 @@ use derive_more::{Deref, From, IntoIterator};
 use rayon::prelude::*;
 use serde::{Deserialize, Serialize};
 use serde_with::serde_as;
-use std::{iter::successors, num::NonZeroUsize};
+use std::{iter::successors, num::NonZeroUsize, ops::Add};
 
 use crate::{
     interpolation::{interpolate, interpolate_in_exponent},
@@ -211,6 +211,30 @@ impl<C: CurveGroup> FeldmanCommitment<C> {
     }
 }
 
+// Implementation of Add trait for FeldmanCommitment + &FeldmanCommitment
+impl<C: CurveGroup> Add<&FeldmanCommitment<C>> for FeldmanCommitment<C> {
+    type Output = FeldmanCommitment<C>;
+
+    fn add(self, other: &FeldmanCommitment<C>) -> Self::Output {
+        &self + other
+    }
+}
+
+// Implementation of Add trait for &FeldmanCommitment + &FeldmanCommitment
+impl<C: CurveGroup> Add<&FeldmanCommitment<C>> for &FeldmanCommitment<C> {
+    type Output = FeldmanCommitment<C>;
+
+    fn add(self, other: &FeldmanCommitment<C>) -> Self::Output {
+        let combined: Vec<C> = self
+            .comm
+            .iter()
+            .zip(other.comm.iter())
+            .map(|(x, y)| *x + y)
+            .collect();
+        C::normalize_batch(&combined).into()
+    }
+}
+
 impl<C: CurveGroup> KeyResharing<Self> for FeldmanVss<C> {
     fn reshare<R: Rng>(
         new_pp: &FeldmanVssPublicParam,

timeboost-types/src/decryption.rs

@@ -1,7 +1,7 @@
 use std::collections::{BTreeMap, btree_map};
 
 use anyhow::anyhow;
-use ark_ec::{AffineRepr, CurveGroup};
+use ark_ec::AffineRepr;
 use multisig::{Committee, CommitteeId, KeyId};
 use rayon::prelude::*;
 use serde::{Deserialize, Serialize};
@@ -60,16 +60,7 @@ impl DecryptionKey {
         let agg_comm = commitments
             .par_iter()
             .cloned()
-            .reduce_with(|a, b| {
-                let combined: Vec<_> = a
-                    .into_iter()
-                    .zip(b.into_iter())
-                    // NOTE: ideally we can use C::normalize_batch(), but C is not exposed,
-                    // minor optimization, so ignore for now.
-                    .map(|(x, y)| (x + y).into_affine())
-                    .collect();
-                combined.into()
-            })
+            .reduce_with(|a, b| a + &b)
             .ok_or_else(|| anyhow!("no commitments provided"))?;
         let agg_key_share = key_shares.iter().sum();