From 91b2ed32a51aef0c23d12ac037f6614f6144f9b7 Mon Sep 17 00:00:00 2001
From: Jimmy Song <jaejoon@gmail.com>
Date: Thu, 25 May 2017 17:04:59 -0400
Subject: [PATCH] more efficient pubkey generation

---
 internal_test.go      | 15 +++++++++++++++
 ringct.go             |  2 +-
 ringsignature_test.go |  3 +--
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/internal_test.go b/internal_test.go
index d33debc..f25c741 100644
--- a/internal_test.go
+++ b/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
+}
diff --git a/ringct.go b/ringct.go
index 2f53232..158ebbd 100644
--- a/ringct.go
+++ b/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)
diff --git a/ringsignature_test.go b/ringsignature_test.go
index ead55f0..431b20d 100644
--- a/ringsignature_test.go
+++ b/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) {