more efficient pubkey generation

internal_test.go

@@ -15,3 +15,18 @@ func HexToHash(h string) (result Hash) {
 	copy(result[:], byteSlice)
 	return
 }
+
+// RandomPubKey takes a random scalar, interprets it as a point on the curve
+// and then multiplies by 8 to make it a point in the Group
+func RandomPubKey() (result *Key) {
+	result = new(Key)
+	p3 := new(ExtendedGroupElement)
+	var p1 ProjectiveGroupElement
+	var p2 CompletedGroupElement
+	h := RandomScalar()
+	p1.FromBytes(h)
+	GeMul8(&p2, &p1)
+	p2.ToExtended(p3)
+	p3.ToBytes(result)
+	return
+}

ringct.go

@@ -133,7 +133,7 @@ func AddKeys2(result, a, b, B *Key) {
 	return
 }
 
-// subtract two points together
+// subtract two points A - B
 func SubKeys(diff, k1, k2 *Key) {
 	a := k1.ToExtended()
 	b := new(CachedGroupElement)

ringsignature_test.go

@@ -1819,8 +1819,7 @@ func TestCreateSignature(t *testing.T) {
 		privKey, _ := NewKeyPair()
 		mixins := make([]Key, numMixins)
 		for j := 0; j < numMixins; j++ {
-			_, pk := NewKeyPair()
-			mixins[j] = *pk
+			mixins[j] = *RandomPubKey()
 		}
 		keyImage, pubKeys, sig := CreateSignature(&hash, mixins, privKey)
 		if !VerifySignature(&hash, &keyImage, pubKeys, sig) {