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// Copyright (c) 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package edwards25519
import (
"crypto/rand"
"encoding/hex"
"testing"
"testing/quick"
)
// TestBytesMontgomery tests the SetBytesWithClamping+BytesMontgomery path
// equivalence to curve25519.X25519 for basepoint scalar multiplications.
//
// Note that you can't actually implement X25519 with this package because
// there is no SetBytesMontgomery, and it would not be possible to implement
// it properly: points on the twist would get rejected, and the Scalar returned
// by SetBytesWithClamping does not preserve its cofactor-clearing properties.
//
// Disabled to avoid the golang.org/x/crypto module dependency.
/* func TestBytesMontgomery(t *testing.T) {
f := func(scalar [32]byte) bool {
s := NewScalar().SetBytesWithClamping(scalar[:])
p := (&Point{}).ScalarBaseMult(s)
got := p.BytesMontgomery()
want, _ := curve25519.X25519(scalar[:], curve25519.Basepoint)
return bytes.Equal(got, want)
}
if err := quick.Check(f, nil); err != nil {
t.Error(err)
}
} */
func TestBytesMontgomerySodium(t *testing.T) {
// Generated with libsodium.js 1.0.18
// crypto_sign_keypair().publicKey
publicKey := "3bf918ffc2c955dc895bf145f566fb96623c1cadbe040091175764b5fde322c0"
p, err := (&Point{}).SetBytes(decodeHex(publicKey))
if err != nil {
t.Fatal(err)
}
// crypto_sign_ed25519_pk_to_curve25519(publicKey)
want := "efc6c9d0738e9ea18d738ad4a2653631558931b0f1fde4dd58c436d19686dc28"
if got := hex.EncodeToString(p.BytesMontgomery()); got != want {
t.Errorf("got %q, want %q", got, want)
}
}
func TestBytesMontgomeryInfinity(t *testing.T) {
p := NewIdentityPoint()
want := "0000000000000000000000000000000000000000000000000000000000000000"
if got := hex.EncodeToString(p.BytesMontgomery()); got != want {
t.Errorf("got %q, want %q", got, want)
}
}
func TestMultByCofactor(t *testing.T) {
lowOrderBytes := "26e8958fc2b227b045c3f489f2ef98f0d5dfac05d3c63339b13802886d53fc85"
lowOrder, err := (&Point{}).SetBytes(decodeHex(lowOrderBytes))
if err != nil {
t.Fatal(err)
}
if p := (&Point{}).MultByCofactor(lowOrder); p.Equal(NewIdentityPoint()) != 1 {
t.Errorf("expected low order point * cofactor to be the identity")
}
f := func(scalar [64]byte) bool {
s, _ := NewScalar().SetUniformBytes(scalar[:])
p := (&Point{}).ScalarBaseMult(s)
p8 := (&Point{}).MultByCofactor(p)
checkOnCurve(t, p8)
// 8 * p == (8 * s) * B
reprEight := [32]byte{8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
scEight, _ := (&Scalar{}).SetCanonicalBytes(reprEight[:])
s.Multiply(s, scEight)
pp := (&Point{}).ScalarBaseMult(s)
if p8.Equal(pp) != 1 {
return false
}
// 8 * p == 8 * (lowOrder + p)
pp.Add(p, lowOrder)
pp.MultByCofactor(pp)
if p8.Equal(pp) != 1 {
return false
}
// 8 * p == p + p + p + p + p + p + p + p
pp.Set(NewIdentityPoint())
for i := 0; i < 8; i++ {
pp.Add(pp, p)
}
return p8.Equal(pp) == 1
}
if err := quick.Check(f, nil); err != nil {
t.Error(err)
}
}
func TestScalarInvert(t *testing.T) {
invertWorks := func(xInv Scalar, x notZeroScalar) bool {
xInv.Invert((*Scalar)(&x))
var check Scalar
check.Multiply((*Scalar)(&x), &xInv)
return check.Equal(scOne) == 1 && isReduced(xInv.Bytes())
}
if err := quick.Check(invertWorks, quickCheckConfig(32)); err != nil {
t.Error(err)
}
randomScalar := *dalekScalar
randomInverse := NewScalar().Invert(&randomScalar)
var check Scalar
check.Multiply(&randomScalar, randomInverse)
if check.Equal(scOne) == 0 || !isReduced(randomInverse.Bytes()) {
t.Error("inversion did not work")
}
zero := NewScalar()
if xx := NewScalar().Invert(zero); xx.Equal(zero) != 1 {
t.Errorf("inverting zero did not return zero")
}
}
func TestMultiScalarMultMatchesBaseMult(t *testing.T) {
multiScalarMultMatchesBaseMult := func(x, y, z Scalar) bool {
var p, q1, q2, q3, check Point
p.MultiScalarMult([]*Scalar{&x, &y, &z}, []*Point{B, B, B})
q1.ScalarBaseMult(&x)
q2.ScalarBaseMult(&y)
q3.ScalarBaseMult(&z)
check.Add(&q1, &q2).Add(&check, &q3)
checkOnCurve(t, &p, &check, &q1, &q2, &q3)
return p.Equal(&check) == 1
}
if err := quick.Check(multiScalarMultMatchesBaseMult, quickCheckConfig(32)); err != nil {
t.Error(err)
}
}
func TestVarTimeMultiScalarMultMatchesBaseMult(t *testing.T) {
varTimeMultiScalarMultMatchesBaseMult := func(x, y, z Scalar) bool {
var p, q1, q2, q3, check Point
p.VarTimeMultiScalarMult([]*Scalar{&x, &y, &z}, []*Point{B, B, B})
q1.ScalarBaseMult(&x)
q2.ScalarBaseMult(&y)
q3.ScalarBaseMult(&z)
check.Add(&q1, &q2).Add(&check, &q3)
checkOnCurve(t, &p, &check, &q1, &q2, &q3)
return p.Equal(&check) == 1
}
if err := quick.Check(varTimeMultiScalarMultMatchesBaseMult, quickCheckConfig(32)); err != nil {
t.Error(err)
}
}
func BenchmarkMultiScalarMultSize8(t *testing.B) {
var p Point
x := dalekScalar
for i := 0; i < t.N; i++ {
p.MultiScalarMult([]*Scalar{x, x, x, x, x, x, x, x},
[]*Point{B, B, B, B, B, B, B, B})
}
}
func BenchmarkScalarAddition(b *testing.B) {
var rnd [128]byte
rand.Read(rnd[:])
s1, _ := (&Scalar{}).SetUniformBytes(rnd[0:64])
s2, _ := (&Scalar{}).SetUniformBytes(rnd[64:128])
t := &Scalar{}
b.ResetTimer()
for i := 0; i < b.N; i++ {
t.Add(s1, s2)
}
}
func BenchmarkScalarMultiplication(b *testing.B) {
var rnd [128]byte
rand.Read(rnd[:])
s1, _ := (&Scalar{}).SetUniformBytes(rnd[0:64])
s2, _ := (&Scalar{}).SetUniformBytes(rnd[64:128])
t := &Scalar{}
b.ResetTimer()
for i := 0; i < b.N; i++ {
t.Multiply(s1, s2)
}
}
func BenchmarkScalarInversion(b *testing.B) {
var rnd [64]byte
rand.Read(rnd[:])
s1, _ := (&Scalar{}).SetUniformBytes(rnd[0:64])
b.ResetTimer()
for i := 0; i < b.N; i++ {
s1.Invert(s1)
}
}
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