From bdc420be66832e8d1ecd3dc6688ddf99d9e06172 Mon Sep 17 00:00:00 2001
From: Henry de Valence <hdevalence@hdevalence.ca>
Date: Tue, 7 May 2019 22:55:29 -0700
Subject: [PATCH] internal/ed25519: add addition for Edwards points

---
 internal/edwards25519/edwards25519.go | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/internal/edwards25519/edwards25519.go b/internal/edwards25519/edwards25519.go
index 3dd7089..6f06378 100644
--- a/internal/edwards25519/edwards25519.go
+++ b/internal/edwards25519/edwards25519.go
@@ -138,6 +138,24 @@ func (v *AffineCached) FromP3(p *ProjP3) *AffineCached {
 
 // (Re)addition and subtraction.
 
+func (v *ProjP3) Add(p, q *ProjP3) *ProjP3 {
+	result := ProjP1xP1{}
+	qCached := ProjCached{}
+	qCached.FromP3(q)
+	result.Add(p, &qCached)
+	v.FromP1xP1(&result)
+	return v
+}
+
+func (v *ProjP3) Sub(p, q *ProjP3) *ProjP3 {
+	result := ProjP1xP1{}
+	qCached := ProjCached{}
+	qCached.FromP3(q)
+	result.Sub(p, &qCached)
+	v.FromP1xP1(&result)
+	return v
+}
+
 func (v *ProjP1xP1) Add(p *ProjP3, q *ProjCached) *ProjP1xP1 {
 	var YplusX, YminusX, PP, MM, TT2d, ZZ2 radix51.FieldElement
 
@@ -236,6 +254,8 @@ func (v *ProjP1xP1) Double(p *ProjP2) *ProjP1xP1 {
 	return v
 }
 
+// Negation.
+
 func (v *ProjP3) Neg(p *ProjP3) *ProjP3 {
 	v.X.Neg(&p.X)
 	v.Y.Set(&p.Y)