From ceff23fc6ba2033dc9d48d88fdd81fc39c5a11fb Mon Sep 17 00:00:00 2001
From: thelitfire <jiaxingzhao@mail.ustc.edu.cn>
Date: Wed, 15 Apr 2026 22:25:14 +0800
Subject: [PATCH] commit_sparse implementation

---
 src/provider/hyperkzg.rs | 19 +++++++++++++++++++
 src/provider/pedersen.rs | 19 +++++++++++++++++++
 src/traits/commitment.rs |  9 +++++++++
 3 files changed, 47 insertions(+)

diff --git a/src/provider/hyperkzg.rs b/src/provider/hyperkzg.rs
index fe13c6c8..b1ba3639 100644
--- a/src/provider/hyperkzg.rs
+++ b/src/provider/hyperkzg.rs
@@ -744,6 +744,25 @@ where
 
     Commitment { comm }
   }
+
+  fn commit_sparse(
+    ck: &Self::CommitmentKey,
+    indices: &[usize],
+    scalars: &[E::Scalar],
+    r: &E::Scalar,
+  ) -> Self::Commitment {
+    assert_eq!(indices.len(), scalars.len());
+
+    let bases: Vec<_> = indices.par_iter().map(|&i| ck.ck[i]).collect();
+
+    let mut comm = E::GE::vartime_multiscalar_mul(scalars, &bases);
+
+    if r != &E::Scalar::ZERO {
+      comm += <E::GE as DlogGroup>::group(&ck.h) * r;
+    }
+
+    Commitment { comm }
+  }
 }
 
 /// Provides an implementation of generators for proving evaluations
diff --git a/src/provider/pedersen.rs b/src/provider/pedersen.rs
index e4c7e915..acb55536 100644
--- a/src/provider/pedersen.rs
+++ b/src/provider/pedersen.rs
@@ -428,6 +428,25 @@ where
 
     Commitment { comm }
   }
+
+  fn commit_sparse(
+    ck: &Self::CommitmentKey,
+    indices: &[usize],
+    scalars: &[E::Scalar],
+    r: &E::Scalar,
+  ) -> Self::Commitment {
+    assert_eq!(indices.len(), scalars.len());
+
+    let bases: Vec<_> = indices.par_iter().map(|&i| ck.ck[i]).collect();
+
+    let mut comm = E::GE::vartime_multiscalar_mul(scalars, &bases);
+
+    if r != &E::Scalar::ZERO {
+      comm += <E::GE as DlogGroup>::group(&ck.h) * r;
+    }
+
+    Commitment { comm }
+  }
 }
 
 /// A trait listing properties of a commitment key that can be managed in a divide-and-conquer fashion
diff --git a/src/traits/commitment.rs b/src/traits/commitment.rs
index e983617e..988acef4 100644
--- a/src/traits/commitment.rs
+++ b/src/traits/commitment.rs
@@ -110,6 +110,15 @@ pub trait CommitmentEngineTrait<E: Engine>: Clone + Send + Sync {
     r: &E::Scalar,
   ) -> Self::Commitment;
 
+  /// Commits to the provided vector of sparse scalars given by (indices, scalars),
+  /// using the provided generators and random blind
+  fn commit_sparse(
+    ck: &Self::CommitmentKey,
+    indices: &[usize],
+    scalars: &[E::Scalar],
+    r: &E::Scalar,
+  ) -> Self::Commitment;
+
   /// Commits to the provided vector of "small" scalars (at most 64 bits) using the provided generators and random blind
   fn commit_small<T: Integer + Into<u64> + Copy + Sync + ToPrimitive>(
     ck: &Self::CommitmentKey,