Expose CurveID

Expose getter to retrieve ID for a curve given an element.

Fixes #16

Signed-off-by: Alessandro Sorniotti <aso@zurich.ibm.com>

Author: ale-linux

math.go

@@ -177,6 +177,10 @@ type Zr struct {
 	curveID CurveID
 }
 
+func (z *Zr) CurveID() CurveID {
+	return z.curveID
+}
+
 func (z *Zr) Plus(a *Zr) *Zr {
 	return &Zr{zr: z.zr.Plus(a.zr), curveID: z.curveID}
 }
@@ -244,6 +248,10 @@ type G1 struct {
 	curveID CurveID
 }
 
+func (g *G1) CurveID() CurveID {
+	return g.curveID
+}
+
 func (g *G1) Clone(a *G1) {
 	g.g1.Clone(a.g1)
 }
@@ -299,6 +307,10 @@ type G2 struct {
 	curveID CurveID
 }
 
+func (g *G2) CurveID() CurveID {
+	return g.curveID
+}
+
 func (g *G2) Clone(a *G2) {
 	g.g2.Clone(a.g2)
 }
@@ -346,6 +358,10 @@ type Gt struct {
 	curveID CurveID
 }
 
+func (g *Gt) CurveID() CurveID {
+	return g.curveID
+}
+
 func (g *Gt) Equals(a *Gt) bool {
 	return g.gt.Equals(a.gt)
 }

math_test.go

@@ -32,6 +32,24 @@ func TestImmutability(t *testing.T) {
 	}
 }
 
+func TestCurveId(t *testing.T) {
+	for _, curve := range Curves {
+		rng, err := curve.Rand()
+		assert.NoError(t, err)
+
+		runCurveIdTest(t, curve, rng)
+	}
+}
+
+func runCurveIdTest(t *testing.T, c *Curve, rng io.Reader) {
+	r := c.NewRandomZr(rng)
+
+	assert.Equal(t, r.CurveID(), c.curveID)
+	assert.Equal(t, c.GenG1.Mul(r).CurveID(), c.curveID)
+	assert.Equal(t, c.GenG2.Mul(r).CurveID(), c.curveID)
+	assert.Equal(t, c.GenGt.Exp(r).CurveID(), c.curveID)
+}
+
 var r *Zr
 var g1 *G1
 var g2 *G2