homomorphic: fix package name, add new method AddPair

homomorphic/add.go

@@ -1,11 +1,16 @@
-package hadd
+package homomorphic
 
 import (
 	ecc_tweds "github.com/consensys/gnark-crypto/ecc/twistededwards"
 	"github.com/consensys/gnark/frontend"
 	"github.com/consensys/gnark/std/algebra/native/twistededwards"
 )
 
+type Pair struct {
+	P1 twistededwards.Point
+	P2 twistededwards.Point
+}
+
 func Add(api frontend.API, a, b twistededwards.Point) (twistededwards.Point, error) {
 	curve, err := twistededwards.NewEdCurve(api, ecc_tweds.BN254)
 	if err != nil {
@@ -15,3 +20,18 @@ func Add(api frontend.API, a, b twistededwards.Point) (twistededwards.Point, err
 	curve.AssertIsOnCurve(b)
 	return curve.Add(a, b), nil
 }
+
+// AddPair returns the result (a.P1 + b.P1), (a.P2, b.P2) as a Pair
+func AddPair(api frontend.API, a, b Pair) (Pair, error) {
+	curve, err := twistededwards.NewEdCurve(api, ecc_tweds.BN254)
+	if err != nil {
+		return Pair{}, err
+	}
+	for _, p := range []twistededwards.Point{a.P1, a.P2, b.P1, b.P2} {
+		curve.AssertIsOnCurve(p)
+	}
+	return Pair{
+		curve.Add(a.P1, b.P1),
+		curve.Add(a.P2, b.P2),
+	}, nil
+}

homomorphic/add_test.go

@@ -1,4 +1,4 @@
-package hadd
+package homomorphic
 
 import (
 	"crypto/rand"