From 157c9ead5c2e0c49adc90c0227fb7d400350c6b1 Mon Sep 17 00:00:00 2001
From: Arya Tabaie <15056835+Tabaie@users.noreply.github.com>
Date: Mon, 16 Dec 2024 22:03:57 -0600
Subject: [PATCH] fix another shifted case

---
 backend/groth16/bn254/mpcsetup/unit_test.go | 8 ++++++++
 backend/groth16/bn254/mpcsetup/utils.go     | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/backend/groth16/bn254/mpcsetup/unit_test.go b/backend/groth16/bn254/mpcsetup/unit_test.go
index 93b28fcc3..e22dcfbad 100644
--- a/backend/groth16/bn254/mpcsetup/unit_test.go
+++ b/backend/groth16/bn254/mpcsetup/unit_test.go
@@ -313,6 +313,14 @@ func TestLinearCombinationsG1(t *testing.T) {
 		acc.Add(&acc, &g1)
 	}
 
+	testLinearCombinationsG1(
+		[]int{3},
+		frs(1, 1, 1),
+		frs(1, 1, 0),
+		frs(0, 1, 1),
+		infty, g1, infty,
+	)
+
 	testLinearCombinationsG1(
 		[]int{3},
 		frs(1, 1, 1),
diff --git a/backend/groth16/bn254/mpcsetup/utils.go b/backend/groth16/bn254/mpcsetup/utils.go
index f45481f53..19549f324 100644
--- a/backend/groth16/bn254/mpcsetup/utils.go
+++ b/backend/groth16/bn254/mpcsetup/utils.go
@@ -156,7 +156,7 @@ func linearCombinationsG1(A []curve.G1Affine, powers []fr.Element, ends []int) (
 		A[2*i+1] = A[ends[i]-1]
 	}
 	powers[2*len(ends)].Neg(&rInvNeg) // r⁻¹: coefficient for truncated
-	A[2*len(ends)] = A[prevEnd]
+	A[2*len(ends)] = truncated
 
 	// TODO @Tabaie O(1) MSM worth it?
 	if _, err := shifted.MultiExp(A[:2*len(ends)+1], powers[:2*len(ends)+1], msmCfg); err != nil {