Merge pull request #182 from ConsenSys/std/pairing

Pairing + Groth16 verifier std gadgets

std/algebra/fields/e12.go

@@ -330,18 +330,18 @@ func (e *E12) Conjugate(api frontend.API, e1 E12) *E12 {
 }
 
 // MulBy034 multiplication by sparse element
-func (e *E12) MulBy034(api frontend.API, c0, c3, c4 E2, ext Extension) *E12 {
+func (e *E12) MulBy034(api frontend.API, c3, c4 E2, ext Extension) *E12 {
 
-	var a, b, d E6
+	var d E6
 
-	a.MulByE2(api, e.C0, c0, ext)
+	a := e.C0
+	b := e.C1
 
-	b = e.C1
 	b.MulBy01(api, c3, c4, ext)
 
-	c0.Add(api, c0, c3)
+	c3.Add(api, E2{A0: 1, A1: 0}, c3)
 	d.Add(api, e.C0, e.C1)
-	d.MulBy01(api, c0, c4, ext)
+	d.MulBy01(api, c3, c4, ext)
 
 	e.C1.Add(api, a, b).Neg(api, e.C1).Add(api, e.C1, d)
 	e.C0.MulByNonResidue(api, b, ext).Add(api, e.C0, a)

std/algebra/fields/e12_test.go

@@ -364,14 +364,14 @@ func TestExpFinalExpoFp12(t *testing.T) {
 }
 
 type fp12MulBy034 struct {
-	A       E12 `gnark:",public"`
-	W       E12
-	B, C, D E2
+	A    E12 `gnark:",public"`
+	W    E12
+	B, C E2
 }
 
 func (circuit *fp12MulBy034) Define(api frontend.API) error {
 	ext := GetBLS377ExtensionFp12(api)
-	circuit.A.MulBy034(api, circuit.B, circuit.C, circuit.D, ext)
+	circuit.A.MulBy034(api, circuit.B, circuit.C, ext)
 	circuit.A.MustBeEqual(api, circuit.W)
 	return nil
 }
@@ -381,7 +381,8 @@ func TestFp12MulBy034(t *testing.T) {
 	var circuit, witness fp12MulBy034
 
 	var a bls12377.E12
-	var b, c, d bls12377.E2
+	var b, c, one bls12377.E2
+	one.SetOne()
 	a.SetRandom()
 	witness.A.Assign(&a)
 
@@ -391,10 +392,7 @@ func TestFp12MulBy034(t *testing.T) {
 	c.SetRandom()
 	witness.C.Assign(&c)
 
-	d.SetRandom()
-	witness.D.Assign(&d)
-
-	a.MulBy034(&b, &c, &d)
+	a.MulBy034(&one, &b, &c)
 
 	witness.W.Assign(&a)
 

std/algebra/sw/g1.go

@@ -252,3 +252,36 @@ func (p *G1Affine) MustBeEqual(api frontend.API, other G1Affine) {
 	api.AssertIsEqual(p.X, other.X)
 	api.AssertIsEqual(p.Y, other.Y)
 }
+
+// DoubleAndAdd computes 2*p1+p in affine coords
+func (p *G1Affine) DoubleAndAdd(api frontend.API, p1, p2 *G1Affine) *G1Affine {
+
+	// compute lambda1 = (y2-y1)/(x2-x1)
+	l1 := api.DivUnchecked(api.Sub(p1.Y, p2.Y), api.Sub(p1.X, p2.X))
+
+	// compute x3 = lambda1**2-x1-x2
+	x3 := api.Mul(l1, l1)
+	x3 = api.Sub(x3, p1.X)
+	x3 = api.Sub(x3, p2.X)
+
+	// omit y3 computation
+	// compute lambda2 = -lambda1-2*y1/(x3-x1)
+	l2 := api.DivUnchecked(api.Add(p1.Y, p1.Y), api.Sub(x3, p1.X))
+	l2 = api.Add(l2, l1)
+	l2 = api.Neg(l2)
+
+	// compute x4 =lambda2**2-x1-x3
+	x4 := api.Mul(l2, l2)
+	x4 = api.Sub(x4, p1.X)
+	x4 = api.Sub(x4, x3)
+
+	// compute y4 = lambda2*(x1 - x4)-y1
+	y4 := api.Sub(p1.X, x4)
+	y4 = api.Mul(l2, y4)
+	y4 = api.Sub(y4, p1.Y)
+
+	p.X = x4
+	p.Y = y4
+
+	return p
+}

std/algebra/sw/g1_test.go

@@ -177,6 +177,47 @@ func TestDoubleAffineG1(t *testing.T) {
 
 }
 
+// -------------------------------------------------------------------------------------------------
+// DoubleAndAdd affine
+
+type g1DoubleAndAddAffine struct {
+	A, B G1Affine
+	C    G1Affine `gnark:",public"`
+}
+
+func (circuit *g1DoubleAndAddAffine) Define(api frontend.API) error {
+	expected := circuit.A
+	expected.DoubleAndAdd(api, &circuit.A, &circuit.B)
+	expected.MustBeEqual(api, circuit.C)
+	return nil
+}
+
+func TestDoubleAndAddAffineG1(t *testing.T) {
+
+	// sample 2 random points
+	_a := randomPointG1()
+	_b := randomPointG1()
+	var a, b, c bls12377.G1Affine
+	a.FromJacobian(&_a)
+	b.FromJacobian(&_b)
+
+	// create the cs
+	var circuit, witness g1DoubleAndAddAffine
+
+	// assign the inputs
+	witness.A.Assign(&a)
+	witness.B.Assign(&b)
+
+	// compute the result
+	_a.Double(&_a).AddAssign(&_b)
+	c.FromJacobian(&_a)
+	witness.C.Assign(&c)
+
+	assert := test.NewAssert(t)
+	assert.SolvingSucceeded(&circuit, &witness, test.WithCurves(ecc.BW6_761))
+
+}
+
 // -------------------------------------------------------------------------------------------------
 // Neg
 

std/algebra/sw/g2.go

@@ -224,3 +224,41 @@ func (p *G2Affine) MustBeEqual(api frontend.API, other G2Affine) {
 	p.X.MustBeEqual(api, other.X)
 	p.Y.MustBeEqual(api, other.Y)
 }
+
+// DoubleAndAdd computes 2*p1+p2 in affine coords
+func (p *G2Affine) DoubleAndAdd(api frontend.API, p1, p2 *G2Affine, ext fields.Extension) *G2Affine {
+
+	var n, d, l1, l2, x3, x4, y4 fields.E2
+
+	// compute lambda1 = (y2-y1)/(x2-x1)
+	n.Sub(api, p1.Y, p2.Y)
+	d.Sub(api, p1.X, p2.X)
+	l1.Inverse(api, d, ext).Mul(api, l1, n, ext)
+
+	// compute x3 = lambda1**2-x1-x2
+	x3.Square(api, l1, ext).
+		Sub(api, x3, p1.X).
+		Sub(api, x3, p2.X)
+
+	// omit y3 computation
+	// compute lambda2 = -lambda1-2*y1/(x3-x1)
+	n.Double(api, p1.Y)
+	d.Sub(api, x3, p1.X)
+	l2.Inverse(api, d, ext).Mul(api, l2, n, ext)
+	l2.Add(api, l2, l1).Neg(api, l2)
+
+	// compute x4 =lambda2**2-x1-x3
+	x4.Square(api, l2, ext).
+		Sub(api, x4, p1.X).
+		Sub(api, x4, x3)
+
+	// compute y4 = lambda2*(x1 - x4)-y1
+	y4.Sub(api, p1.X, x4).
+		Mul(api, l2, y4, ext).
+		Sub(api, y4, p1.Y)
+
+	p.X = x4
+	p.Y = y4
+
+	return p
+}

std/algebra/sw/g2_test.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/consensys/gnark-crypto/ecc"
 	"github.com/consensys/gnark-crypto/ecc/bls12-377/fr"
+	"github.com/consensys/gnark/backend"
 	"github.com/consensys/gnark/frontend"
 	"github.com/consensys/gnark/std/algebra/fields"
 	"github.com/consensys/gnark/test"
@@ -142,6 +143,47 @@ func TestDoubleAssignG2(t *testing.T) {
 
 }
 
+// -------------------------------------------------------------------------------------------------
+// DoubleAndAdd affine
+
+type g2DoubleAndAddAffine struct {
+	A, B G2Affine
+	C    G2Affine `gnark:",public"`
+}
+
+func (circuit *g2DoubleAndAddAffine) Define(api frontend.API) error {
+	expected := circuit.A
+	expected.DoubleAndAdd(api, &circuit.A, &circuit.B, fields.GetBLS377ExtensionFp12(api))
+	expected.MustBeEqual(api, circuit.C)
+	return nil
+}
+
+func TestDoubleAndAddAffineG2(t *testing.T) {
+
+	// sample 2 random points
+	_a := randomPointG2()
+	_b := randomPointG2()
+	var a, b, c bls12377.G2Affine
+	a.FromJacobian(&_a)
+	b.FromJacobian(&_b)
+
+	// create the cs
+	var circuit, witness g2DoubleAndAddAffine
+
+	// assign the inputs
+	witness.A.Assign(&a)
+	witness.B.Assign(&b)
+
+	// compute the result
+	_a.Double(&_a).AddAssign(&_b)
+	c.FromJacobian(&_a)
+	witness.C.Assign(&c)
+
+	assert := test.NewAssert(t)
+	assert.SolvingSucceeded(&circuit, &witness, test.WithCurves(ecc.BW6_761))
+
+}
+
 // -------------------------------------------------------------------------------------------------
 // Double affine
 
@@ -224,3 +266,37 @@ func randomPointG2() bls12377.G2Jac {
 	p2.ScalarMultiplication(&p2, r1.ToBigIntRegular(&b))
 	return p2
 }
+
+// benches
+func BenchmarkDoubleAffineG2(b *testing.B) {
+	var c g2DoubleAffine
+	b.Run("groth16", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			ccsBench, _ = frontend.Compile(ecc.BW6_761, backend.GROTH16, &c)
+		}
+
+	})
+	b.Log("groth16", ccsBench.GetNbConstraints())
+}
+
+func BenchmarkAddAssignAffineG2(b *testing.B) {
+	var c g2AddAssignAffine
+	b.Run("groth16", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			ccsBench, _ = frontend.Compile(ecc.BW6_761, backend.GROTH16, &c)
+		}
+
+	})
+	b.Log("groth16", ccsBench.GetNbConstraints())
+}
+
+func BenchmarkDoubleAndAddAffineG2(b *testing.B) {
+	var c g2DoubleAndAddAffine
+	b.Run("groth16", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			ccsBench, _ = frontend.Compile(ecc.BW6_761, backend.GROTH16, &c)
+		}
+
+	})
+	b.Log("groth16", ccsBench.GetNbConstraints())
+}