From a9969b161f7b98eaa5cd984409b1c426a7ca0bf4 Mon Sep 17 00:00:00 2001
From: Zack Scholl <zack.scholl@gmail.com>
Date: Sat, 30 Jun 2018 14:45:44 -0700
Subject: [PATCH] use elliptic curve interface

---
 src/pake/pake.go      | 12 +++++++++---
 src/pake/pake_test.go |  9 +++++----
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/pake/pake.go b/src/pake/pake.go
index 0cb62b2..daa6801 100644
--- a/src/pake/pake.go
+++ b/src/pake/pake.go
@@ -1,7 +1,6 @@
 package pake
 
 import (
-	"crypto/elliptic"
 	"crypto/rand"
 	"crypto/sha256"
 	"encoding/json"
@@ -20,6 +19,13 @@ import (
 // http://www.lothar.com/~warner/MagicWormhole-PyCon2016.pdf
 // Slide 11
 
+type EllipticCurve interface {
+	Add(x1, y1, x2, y2 *big.Int) (*big.Int, *big.Int)
+	ScalarBaseMult(k []byte) (*big.Int, *big.Int)
+	ScalarMult(Bx, By *big.Int, k []byte) (*big.Int, *big.Int)
+	IsOnCurve(x, y *big.Int) bool
+}
+
 type Pake struct {
 	// Public variables
 	Role     int
@@ -30,7 +36,7 @@ type Pake struct {
 	HkA, HkB []byte
 
 	// Private variables
-	curve      elliptic.Curve
+	curve      EllipticCurve
 	pw         []byte
 	vpwᵤ, vpwᵥ *big.Int
 	upwᵤ, upwᵥ *big.Int
@@ -42,7 +48,7 @@ type Pake struct {
 	isVerified bool
 }
 
-func Init(pw []byte, role int, curve elliptic.Curve) (p *Pake, err error) {
+func Init(pw []byte, role int, curve EllipticCurve) (p *Pake, err error) {
 	p = new(Pake)
 	if role == 1 {
 		p.Role = 1
diff --git a/src/pake/pake_test.go b/src/pake/pake_test.go
index 104b065..a4bd02a 100644
--- a/src/pake/pake_test.go
+++ b/src/pake/pake_test.go
@@ -8,13 +8,14 @@ import (
 )
 
 func TestPake(t *testing.T) {
+	curve := elliptic.P521() //siec.SIEC255()
 	// successful (both have same k)
 	// initialize A
-	A, err := Init([]byte{1, 2, 3}, 0, elliptic.P256())
+	A, err := Init([]byte{1, 2, 3}, 0, curve)
 	assert.Nil(t, err)
 	assert.False(t, A.IsVerified())
 	// initialize B
-	B, err := Init([]byte{1, 2, 3}, 1, elliptic.P256())
+	B, err := Init([]byte{1, 2, 3}, 1, curve)
 	assert.Nil(t, err)
 	assert.False(t, B.IsVerified())
 	// send A's stuff to B
@@ -32,11 +33,11 @@ func TestPake(t *testing.T) {
 
 	// failure (both have different k)
 	// initialize A
-	A, err = Init([]byte{1, 2, 3}, 0, elliptic.P256())
+	A, err = Init([]byte{1, 2, 3}, 0, curve)
 	assert.Nil(t, err)
 	assert.False(t, A.IsVerified())
 	// initialize B
-	B, err = Init([]byte{4, 5, 6}, 1, elliptic.P256())
+	B, err = Init([]byte{4, 5, 6}, 1, curve)
 	assert.Nil(t, err)
 	assert.False(t, B.IsVerified())
 	// send A's stuff to B