vendor HEAD main

1 files changed, 427 insertions, 0 deletions

diff --git a/vendor/filippo.io/edwards25519/edwards25519.go b/vendor/filippo.io/edwards25519/edwards25519.go
new file mode 100644
index 0000000..a744da2
--- /dev/null
+++ b/vendor/filippo.io/edwards25519/edwards25519.go
@@ -0,0 +1,427 @@
+// Copyright (c) 2017 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 (
+	"errors"
+
+	"filippo.io/edwards25519/field"
+)
+
+// Point types.
+
+type projP1xP1 struct {
+	X, Y, Z, T field.Element
+}
+
+type projP2 struct {
+	X, Y, Z field.Element
+}
+
+// Point represents a point on the edwards25519 curve.
+//
+// This type works similarly to math/big.Int, and all arguments and receivers
+// are allowed to alias.
+//
+// The zero value is NOT valid, and it may be used only as a receiver.
+type Point struct {
+	// Make the type not comparable (i.e. used with == or as a map key), as
+	// equivalent points can be represented by different Go values.
+	_ incomparable
+
+	// The point is internally represented in extended coordinates (X, Y, Z, T)
+	// where x = X/Z, y = Y/Z, and xy = T/Z per https://eprint.iacr.org/2008/522.
+	x, y, z, t field.Element
+}
+
+type incomparable [0]func()
+
+func checkInitialized(points ...*Point) {
+	for _, p := range points {
+		if p.x == (field.Element{}) && p.y == (field.Element{}) {
+			panic("edwards25519: use of uninitialized Point")
+		}
+	}
+}
+
+type projCached struct {
+	YplusX, YminusX, Z, T2d field.Element
+}
+
+type affineCached struct {
+	YplusX, YminusX, T2d field.Element
+}
+
+// Constructors.
+
+func (v *projP2) Zero() *projP2 {
+	v.X.Zero()
+	v.Y.One()
+	v.Z.One()
+	return v
+}
+
+// identity is the point at infinity.
+var identity, _ = new(Point).SetBytes([]byte{
+	1, 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})
+
+// NewIdentityPoint returns a new Point set to the identity.
+func NewIdentityPoint() *Point {
+	return new(Point).Set(identity)
+}
+
+// generator is the canonical curve basepoint. See TestGenerator for the
+// correspondence of this encoding with the values in RFC 8032.
+var generator, _ = new(Point).SetBytes([]byte{
+	0x58, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66,
+	0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66,
+	0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66,
+	0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66})
+
+// NewGeneratorPoint returns a new Point set to the canonical generator.
+func NewGeneratorPoint() *Point {
+	return new(Point).Set(generator)
+}
+
+func (v *projCached) Zero() *projCached {
+	v.YplusX.One()
+	v.YminusX.One()
+	v.Z.One()
+	v.T2d.Zero()
+	return v
+}
+
+func (v *affineCached) Zero() *affineCached {
+	v.YplusX.One()
+	v.YminusX.One()
+	v.T2d.Zero()
+	return v
+}
+
+// Assignments.
+
+// Set sets v = u, and returns v.
+func (v *Point) Set(u *Point) *Point {
+	*v = *u
+	return v
+}
+
+// Encoding.
+
+// Bytes returns the canonical 32-byte encoding of v, according to RFC 8032,
+// Section 5.1.2.
+func (v *Point) Bytes() []byte {
+	// This function is outlined to make the allocations inline in the caller
+	// rather than happen on the heap.
+	var buf [32]byte
+	return v.bytes(&buf)
+}
+
+func (v *Point) bytes(buf *[32]byte) []byte {
+	checkInitialized(v)
+
+	var zInv, x, y field.Element
+	zInv.Invert(&v.z)       // zInv = 1 / Z
+	x.Multiply(&v.x, &zInv) // x = X / Z
+	y.Multiply(&v.y, &zInv) // y = Y / Z
+
+	out := copyFieldElement(buf, &y)
+	out[31] |= byte(x.IsNegative() << 7)
+	return out
+}
+
+var feOne = new(field.Element).One()
+
+// SetBytes sets v = x, where x is a 32-byte encoding of v. If x does not
+// represent a valid point on the curve, SetBytes returns nil and an error and
+// the receiver is unchanged. Otherwise, SetBytes returns v.
+//
+// Note that SetBytes accepts all non-canonical encodings of valid points.
+// That is, it follows decoding rules that match most implementations in
+// the ecosystem rather than RFC 8032.
+func (v *Point) SetBytes(x []byte) (*Point, error) {
+	// Specifically, the non-canonical encodings that are accepted are
+	//   1) the ones where the field element is not reduced (see the
+	//      (*field.Element).SetBytes docs) and
+	//   2) the ones where the x-coordinate is zero and the sign bit is set.
+	//
+	// Read more at https://hdevalence.ca/blog/2020-10-04-its-25519am,
+	// specifically the "Canonical A, R" section.
+
+	y, err := new(field.Element).SetBytes(x)
+	if err != nil {
+		return nil, errors.New("edwards25519: invalid point encoding length")
+	}
+
+	// -x² + y² = 1 + dx²y²
+	// x² + dx²y² = x²(dy² + 1) = y² - 1
+	// x² = (y² - 1) / (dy² + 1)
+
+	// u = y² - 1
+	y2 := new(field.Element).Square(y)
+	u := new(field.Element).Subtract(y2, feOne)
+
+	// v = dy² + 1
+	vv := new(field.Element).Multiply(y2, d)
+	vv = vv.Add(vv, feOne)
+
+	// x = +√(u/v)
+	xx, wasSquare := new(field.Element).SqrtRatio(u, vv)
+	if wasSquare == 0 {
+		return nil, errors.New("edwards25519: invalid point encoding")
+	}
+
+	// Select the negative square root if the sign bit is set.
+	xxNeg := new(field.Element).Negate(xx)
+	xx = xx.Select(xxNeg, xx, int(x[31]>>7))
+
+	v.x.Set(xx)
+	v.y.Set(y)
+	v.z.One()
+	v.t.Multiply(xx, y) // xy = T / Z
+
+	return v, nil
+}
+
+func copyFieldElement(buf *[32]byte, v *field.Element) []byte {
+	copy(buf[:], v.Bytes())
+	return buf[:]
+}
+
+// Conversions.
+
+func (v *projP2) FromP1xP1(p *projP1xP1) *projP2 {
+	v.X.Multiply(&p.X, &p.T)
+	v.Y.Multiply(&p.Y, &p.Z)
+	v.Z.Multiply(&p.Z, &p.T)
+	return v
+}
+
+func (v *projP2) FromP3(p *Point) *projP2 {
+	v.X.Set(&p.x)
+	v.Y.Set(&p.y)
+	v.Z.Set(&p.z)
+	return v
+}
+
+func (v *Point) fromP1xP1(p *projP1xP1) *Point {
+	v.x.Multiply(&p.X, &p.T)
+	v.y.Multiply(&p.Y, &p.Z)
+	v.z.Multiply(&p.Z, &p.T)
+	v.t.Multiply(&p.X, &p.Y)
+	return v
+}
+
+func (v *Point) fromP2(p *projP2) *Point {
+	v.x.Multiply(&p.X, &p.Z)
+	v.y.Multiply(&p.Y, &p.Z)
+	v.z.Square(&p.Z)
+	v.t.Multiply(&p.X, &p.Y)
+	return v
+}
+
+// d is a constant in the curve equation.
+var d, _ = new(field.Element).SetBytes([]byte{
+	0xa3, 0x78, 0x59, 0x13, 0xca, 0x4d, 0xeb, 0x75,
+	0xab, 0xd8, 0x41, 0x41, 0x4d, 0x0a, 0x70, 0x00,
+	0x98, 0xe8, 0x79, 0x77, 0x79, 0x40, 0xc7, 0x8c,
+	0x73, 0xfe, 0x6f, 0x2b, 0xee, 0x6c, 0x03, 0x52})
+var d2 = new(field.Element).Add(d, d)
+
+func (v *projCached) FromP3(p *Point) *projCached {
+	v.YplusX.Add(&p.y, &p.x)
+	v.YminusX.Subtract(&p.y, &p.x)
+	v.Z.Set(&p.z)
+	v.T2d.Multiply(&p.t, d2)
+	return v
+}
+
+func (v *affineCached) FromP3(p *Point) *affineCached {
+	v.YplusX.Add(&p.y, &p.x)
+	v.YminusX.Subtract(&p.y, &p.x)
+	v.T2d.Multiply(&p.t, d2)
+
+	var invZ field.Element
+	invZ.Invert(&p.z)
+	v.YplusX.Multiply(&v.YplusX, &invZ)
+	v.YminusX.Multiply(&v.YminusX, &invZ)
+	v.T2d.Multiply(&v.T2d, &invZ)
+	return v
+}
+
+// (Re)addition and subtraction.
+
+// Add sets v = p + q, and returns v.
+func (v *Point) Add(p, q *Point) *Point {
+	checkInitialized(p, q)
+	qCached := new(projCached).FromP3(q)
+	result := new(projP1xP1).Add(p, qCached)
+	return v.fromP1xP1(result)
+}
+
+// Subtract sets v = p - q, and returns v.
+func (v *Point) Subtract(p, q *Point) *Point {
+	checkInitialized(p, q)
+	qCached := new(projCached).FromP3(q)
+	result := new(projP1xP1).Sub(p, qCached)
+	return v.fromP1xP1(result)
+}
+
+func (v *projP1xP1) Add(p *Point, q *projCached) *projP1xP1 {
+	var YplusX, YminusX, PP, MM, TT2d, ZZ2 field.Element
+
+	YplusX.Add(&p.y, &p.x)
+	YminusX.Subtract(&p.y, &p.x)
+
+	PP.Multiply(&YplusX, &q.YplusX)
+	MM.Multiply(&YminusX, &q.YminusX)
+	TT2d.Multiply(&p.t, &q.T2d)
+	ZZ2.Multiply(&p.z, &q.Z)
+
+	ZZ2.Add(&ZZ2, &ZZ2)
+
+	v.X.Subtract(&PP, &MM)
+	v.Y.Add(&PP, &MM)
+	v.Z.Add(&ZZ2, &TT2d)
+	v.T.Subtract(&ZZ2, &TT2d)
+	return v
+}
+
+func (v *projP1xP1) Sub(p *Point, q *projCached) *projP1xP1 {
+	var YplusX, YminusX, PP, MM, TT2d, ZZ2 field.Element
+
+	YplusX.Add(&p.y, &p.x)
+	YminusX.Subtract(&p.y, &p.x)
+
+	PP.Multiply(&YplusX, &q.YminusX) // flipped sign
+	MM.Multiply(&YminusX, &q.YplusX) // flipped sign
+	TT2d.Multiply(&p.t, &q.T2d)
+	ZZ2.Multiply(&p.z, &q.Z)
+
+	ZZ2.Add(&ZZ2, &ZZ2)
+
+	v.X.Subtract(&PP, &MM)
+	v.Y.Add(&PP, &MM)
+	v.Z.Subtract(&ZZ2, &TT2d) // flipped sign
+	v.T.Add(&ZZ2, &TT2d)      // flipped sign
+	return v
+}
+
+func (v *projP1xP1) AddAffine(p *Point, q *affineCached) *projP1xP1 {
+	var YplusX, YminusX, PP, MM, TT2d, Z2 field.Element
+
+	YplusX.Add(&p.y, &p.x)
+	YminusX.Subtract(&p.y, &p.x)
+
+	PP.Multiply(&YplusX, &q.YplusX)
+	MM.Multiply(&YminusX, &q.YminusX)
+	TT2d.Multiply(&p.t, &q.T2d)
+
+	Z2.Add(&p.z, &p.z)
+
+	v.X.Subtract(&PP, &MM)
+	v.Y.Add(&PP, &MM)
+	v.Z.Add(&Z2, &TT2d)
+	v.T.Subtract(&Z2, &TT2d)
+	return v
+}
+
+func (v *projP1xP1) SubAffine(p *Point, q *affineCached) *projP1xP1 {
+	var YplusX, YminusX, PP, MM, TT2d, Z2 field.Element
+
+	YplusX.Add(&p.y, &p.x)
+	YminusX.Subtract(&p.y, &p.x)
+
+	PP.Multiply(&YplusX, &q.YminusX) // flipped sign
+	MM.Multiply(&YminusX, &q.YplusX) // flipped sign
+	TT2d.Multiply(&p.t, &q.T2d)
+
+	Z2.Add(&p.z, &p.z)
+
+	v.X.Subtract(&PP, &MM)
+	v.Y.Add(&PP, &MM)
+	v.Z.Subtract(&Z2, &TT2d) // flipped sign
+	v.T.Add(&Z2, &TT2d)      // flipped sign
+	return v
+}
+
+// Doubling.
+
+func (v *projP1xP1) Double(p *projP2) *projP1xP1 {
+	var XX, YY, ZZ2, XplusYsq field.Element
+
+	XX.Square(&p.X)
+	YY.Square(&p.Y)
+	ZZ2.Square(&p.Z)
+	ZZ2.Add(&ZZ2, &ZZ2)
+	XplusYsq.Add(&p.X, &p.Y)
+	XplusYsq.Square(&XplusYsq)
+
+	v.Y.Add(&YY, &XX)
+	v.Z.Subtract(&YY, &XX)
+
+	v.X.Subtract(&XplusYsq, &v.Y)
+	v.T.Subtract(&ZZ2, &v.Z)
+	return v
+}
+
+// Negation.
+
+// Negate sets v = -p, and returns v.
+func (v *Point) Negate(p *Point) *Point {
+	checkInitialized(p)
+	v.x.Negate(&p.x)
+	v.y.Set(&p.y)
+	v.z.Set(&p.z)
+	v.t.Negate(&p.t)
+	return v
+}
+
+// Equal returns 1 if v is equivalent to u, and 0 otherwise.
+func (v *Point) Equal(u *Point) int {
+	checkInitialized(v, u)
+
+	var t1, t2, t3, t4 field.Element
+	t1.Multiply(&v.x, &u.z)
+	t2.Multiply(&u.x, &v.z)
+	t3.Multiply(&v.y, &u.z)
+	t4.Multiply(&u.y, &v.z)
+
+	return t1.Equal(&t2) & t3.Equal(&t4)
+}
+
+// Constant-time operations
+
+// Select sets v to a if cond == 1 and to b if cond == 0.
+func (v *projCached) Select(a, b *projCached, cond int) *projCached {
+	v.YplusX.Select(&a.YplusX, &b.YplusX, cond)
+	v.YminusX.Select(&a.YminusX, &b.YminusX, cond)
+	v.Z.Select(&a.Z, &b.Z, cond)
+	v.T2d.Select(&a.T2d, &b.T2d, cond)
+	return v
+}
+
+// Select sets v to a if cond == 1 and to b if cond == 0.
+func (v *affineCached) Select(a, b *affineCached, cond int) *affineCached {
+	v.YplusX.Select(&a.YplusX, &b.YplusX, cond)
+	v.YminusX.Select(&a.YminusX, &b.YminusX, cond)
+	v.T2d.Select(&a.T2d, &b.T2d, cond)
+	return v
+}
+
+// CondNeg negates v if cond == 1 and leaves it unchanged if cond == 0.
+func (v *projCached) CondNeg(cond int) *projCached {
+	v.YplusX.Swap(&v.YminusX, cond)
+	v.T2d.Select(new(field.Element).Negate(&v.T2d), &v.T2d, cond)
+	return v
+}
+
+// CondNeg negates v if cond == 1 and leaves it unchanged if cond == 0.
+func (v *affineCached) CondNeg(cond int) *affineCached {
+	v.YplusX.Swap(&v.YminusX, cond)
+	v.T2d.Select(new(field.Element).Negate(&v.T2d), &v.T2d, cond)
+	return v
+}