Files
xgcl/sm/sm9/internal/bn256/bn256.go
T
2026-05-27 23:03:00 +08:00

619 lines
15 KiB
Go

// Package bn256 implements a particular bilinear group.
//
// Bilinear groups are the basis of many of the new cryptographic protocols that
// have been proposed over the past decade. They consist of a triplet of groups
// (G₁, G₂ and GT) such that there exists a function e(g₁ˣ,g₂ʸ)=gTˣʸ (where gₓ
// is a generator of the respective group). That function is called a pairing
// function.
//
// This package specifically implements the Optimal Ate pairing over a 256-bit
// Barreto-Naehrig curve as described in
// http://cryptojedi.org/papers/dclxvi-20100714.pdf. Its output is compatible
// with the implementation described in that paper.
//
// This package previously claimed to operate at a 128-bit security level.
// However, recent improvements in attacks mean that is no longer true. See
// https://moderncrypto.org/mail-archive/curves/2016/000740.html.
package bn256
import (
"io"
"math/big"
"xdx.jelly/xgcl/gerrors"
"xdx.jelly/xgcl/sm/sm9/errors"
)
var one = big.NewInt(1)
// randomK returns a random integer in [1, N-1].
func randomK(r io.Reader) (k *big.Int, err error) {
b := make([]byte, numBytes)
n, err := r.Read(b)
if err != nil {
return nil, errors.ErrGenerateRandomFailed
}
// it is possible that err != nil but n > 0.
// In this case, we also consider it succeed.
if n == 0 {
return nil, errors.ErrGenerateRandomFailed
}
// 0 <= k <= N-2
k = new(big.Int).SetBytes(b)
if k.Cmp(nMinusOne) >= 0 {
k.Sub(k, nMinusOne)
}
// 1 <= k <= N-1
k.Add(k, one)
return k, nil
}
// G1 is an abstract cyclic group. The zero value is suitable for use as the
// output of an operation, but cannot be used as an input.
type G1 struct {
p curvePoint
}
// UnmarshalCompressed restore e from x and the LSB of y.
func (e *G1) UnmarshalCompressed(x []byte, yBit0 byte) (*G1, error) {
ex := &gfP{}
ey := &gfP{}
ex.Unmarshal(x)
montEncode(ex, ex)
// y^2 = x^3 + B
gfpMul(ey, ex, ex)
gfpMul(ey, ey, ex)
gfpAdd(ey, ey, curveB)
if legendre(ey) != 1 {
return e, gerrors.WithAnnotating(errors.ErrInvalidInput, "sqrt failed, input bytes are not a valid compressed point")
}
ey.Sqrt(ey)
var temp gfP
montDecode(&temp, ey)
if yBit0 != byte(temp[0]&1) {
gfpNeg(ey, ey)
}
e.p.x = *ex
e.p.y = *ey
e.p.z = r
e.p.t = r
return e, nil
}
// RandomG1 returns x and g₁ˣ where x is a random, non-zero number read from r.
func RandomG1(r io.Reader) (*big.Int, *G1, error) {
k, err := randomK(r)
if err != nil {
return nil, nil, gerrors.WithMessage(err, "RandomG1 failed")
}
return k, new(G1).ScalarBaseMult(k), nil
}
// returns the montgemery domain of x
func (e *G1) X() *big.Int {
e.p.MakeAffine()
return e.p.x.toBigInt()
}
// returns the montgemery domain of x
func (e *G1) Y() *big.Int {
e.p.MakeAffine()
return e.p.y.toBigInt()
}
// returns the montgemery domain of x
func (e *G1) AffineX() *big.Int {
e.p.MakeAffine()
var x gfP
montDecode(&x, &e.p.x)
return x.toBigInt()
}
// returns the montgemery domain of x
func (e *G1) AffineY() *big.Int {
e.p.MakeAffine()
var y gfP
montDecode(&y, &e.p.y)
return y.toBigInt()
}
// String returns a readable string representation of e
func (e *G1) String() string {
return "G1" + e.p.String()
}
// IsInfinity returns if G1 is the infinity point
func (e *G1) IsInfinity() bool {
return e.p.IsInfinity()
}
// SetInfinity sets e to the infinity point
func (e *G1) SetInfinity() {
e.p.SetInfinity()
}
// Equal returns if e equals the other point
func (e *G1) Equal(other *G1) bool {
return e.p.Equal(&other.p)
}
// IsZero return true if e is infinity
func (e *G1) IsZero() bool {
return e.p.IsInfinity()
}
// IsValid return if e is a valid point of G1
func (e *G1) IsValid() bool {
return e.p.IsOnCurve()
}
// ScalarBaseMult sets e to [k]g1 where g1 is the generator of the group and returns e.
func (e *G1) ScalarBaseMult(k *big.Int) *G1 {
e.p.MulBase(k, curverBasePrecompted8)
return e
}
// ScalarMult sets e to [k]a and then returns e.
func (e *G1) ScalarMult(a *G1, k *big.Int) *G1 {
e.p.Mul(&a.p, k)
return e
}
// Add sets e to a+b and then returns e.
func (e *G1) Add(a, b *G1) *G1 {
e.p.Add(&a.p, &b.p)
return e
}
// Neg sets e to -a and then returns e.
func (e *G1) Neg(a *G1) *G1 {
e.p.Neg(&a.p)
return e
}
// Set sets e to a and then returns e.
func (e *G1) Set(a *G1) *G1 {
e.p.Set(&a.p)
return e
}
// FillBytes fills a point in G1 to a byte slice.
//
// The Input slice must be of exactly 64 bytes, i.e., len(b) == 64.
// Also assume the point is not infinity. But if so, then set b to 0s and return.
func (e *G1) FillBytes(b []byte) {
if e.IsInfinity() {
for i := 0; i < len(b); i++ {
b[i] = 0
}
return
}
e.p.MakeAffine()
temp := &gfP{}
montDecode(temp, &e.p.x)
temp.Marshal(b)
montDecode(temp, &e.p.y)
temp.Marshal(b[numBytes:])
}
// Marshal converts a point in G1 to a byte slice of length 64.
// The slice is filled with x || y.
func (e *G1) Marshal() []byte {
ret := make([]byte, numBytes*2)
if e.p.IsInfinity() {
return ret
}
e.FillBytes(ret)
return ret
}
// Unmarshal sets e to the result of converting the output of Marshal back into
// a group element and then returns e.
// The input byte slice m must at least 64 bytes long.
func (e *G1) Unmarshal(m []byte) ([]byte, error) {
if len(m) < 2*numBytes {
return m, gerrors.WithAnnotating(errors.ErrInvalidInput, "not enough data to unmarshal to G1")
}
e.p.x, e.p.y = gfP{0}, gfP{0}
e.p.x.Unmarshal(m)
e.p.y.Unmarshal(m[numBytes:])
montEncode(&e.p.x, &e.p.x)
montEncode(&e.p.y, &e.p.y)
zero := gfP{0}
if e.p.x == zero && e.p.y == zero {
// The point at infinity.
e.p.y = gfPOne
e.p.z = gfP{0}
e.p.t = gfP{0}
} else {
e.p.z = gfPOne
e.p.t = gfPOne
if !e.p.IsOnCurve() {
return nil, gerrors.WithAnnotating(errors.ErrInvalidPoint, "point is not a valid point on curve")
}
}
return m[2*numBytes:], nil
}
// G2 is an abstract cyclic group. The zero value is suitable for use as the
// output of an operation, but cannot be used as an input.
type G2 struct {
p twistPoint
}
// RandomG2 returns x and g₂ˣ where x is a random, non-zero number read from r.
func RandomG2(r io.Reader) (*big.Int, *G2, error) {
k, err := randomK(r)
if err != nil {
return nil, nil, gerrors.WithMessage(err, "RandomG2 failed")
}
return k, new(G2).ScalarBaseMult(k), nil
}
func (e *G2) X() (*big.Int, *big.Int) {
e.p.MakeAffine()
return e.p.x.x.toBigInt(), e.p.x.y.toBigInt()
}
func (e *G2) Y() (*big.Int, *big.Int) {
e.p.MakeAffine()
return e.p.y.x.toBigInt(), e.p.y.y.toBigInt()
}
func (e *G2) IsInfinity() bool {
return e.p.IsInfinity()
}
func (e *G2) SetInfinity() {
e.p.SetInfinity()
}
func (e *G2) Equal(other *G2) bool {
return e.p.Equal(&other.p)
}
// FromX restore e from x and the LSB of y. yBit0 can only be 0 or 1.
func (e *G2) UnmarshalCompressed(x0, x1 []byte, yBit0 byte) (*G2, error) {
if len(x0) < numBytes || len(x1) < numBytes {
return nil, gerrors.WithAnnotating(errors.ErrInvalidInput, "point is not a valid point on curve")
}
if yBit0&byte(0xfe) != 0 {
return nil, gerrors.WithAnnotatingf(errors.ErrInvalidInput, "yBit0 can only be 0 or 1, but it's %d", yBit0)
}
ex := &gfP2{}
ey := &gfP2{}
ex0 := &ex.x
ex1 := &ex.y
ex0.Unmarshal(x0)
montEncode(ex0, ex0)
ex1.Unmarshal(x1)
montEncode(ex1, ex1)
ey.Mul(ex, ex)
ey.Mul(ey, ex)
ey.Add(ey, twistB) // ey = x^3 + B
if !ey.Sqrt(ey) {
return e, gerrors.WithAnnotatingf(errors.ErrInvalidPoint, "sqrt failed, input bytes are not a valid compressed point")
}
tmp := &gfP{}
montDecode(tmp, &ey.y)
if yBit0 != byte(tmp[0]&1) {
ey.Neg(ey)
}
e.p.x = *ex
e.p.y = *ey
e.p.t = gfP2{y: r}
e.p.z = gfP2{y: r}
return e, nil
}
func (e *G2) String() string {
return "G2" + e.p.String()
}
// ScalarBaseMult sets e to [k]g where g is the generator of the group and then
// returns out.
func (e *G2) ScalarBaseMult(k *big.Int) *G2 {
e.p.MulBase(k, twistBasePrecomputed8)
return e
}
// ScalarMult sets e to [k]a and then returns e.
func (e *G2) ScalarMult(a *G2, k *big.Int) *G2 {
e.p.Mul(&a.p, k)
return e
}
// Add sets e to a+b and then returns e.
func (e *G2) Add(a, b *G2) *G2 {
e.p.Add(&a.p, &b.p)
return e
}
// Neg sets e to -a and then returns e.
func (e *G2) Neg(a *G2) *G2 {
e.p.Neg(&a.p)
return e
}
// Set sets e to a and then returns e.
func (e *G2) Set(a *G2) *G2 {
e.p.Set(&a.p)
return e
}
// FillBytes fills a point in G2 to a byte slice.
//
// The Input slice must be of exactly 128 bytes, i.e., len(b) == 128.
// Also assume the point is not infinity. But if so, then set b to 0s and return.
func (e *G2) FillBytes(b []byte) {
if e.IsInfinity() {
for i := 0; i < len(b); i++ {
b[i] = 0
}
return
}
e.p.MakeAffine()
temp := &gfP{}
montDecode(temp, &e.p.x.x)
temp.Marshal(b)
montDecode(temp, &e.p.x.y)
temp.Marshal(b[numBytes:])
montDecode(temp, &e.p.y.x)
temp.Marshal(b[2*numBytes:])
montDecode(temp, &e.p.y.y)
temp.Marshal(b[3*numBytes:])
}
// Marshal converts e into a byte slice.
func (e *G2) Marshal() []byte {
ret := make([]byte, numBytes*4)
if e.p.IsInfinity() {
return ret
}
e.FillBytes(ret)
return ret
}
// Unmarshal sets e to the result of converting the output of Marshal back into
// a group element and then returns e.
func (e *G2) Unmarshal(m []byte) ([]byte, error) {
if len(m) < 4*numBytes {
return m, gerrors.WithAnnotatingf(errors.ErrInvalidInput, "not enough data to unmarshal to G1")
}
e.p.x.x.Unmarshal(m)
e.p.x.y.Unmarshal(m[numBytes:])
e.p.y.x.Unmarshal(m[2*numBytes:])
e.p.y.y.Unmarshal(m[3*numBytes:])
montEncode(&e.p.x.x, &e.p.x.x)
montEncode(&e.p.x.y, &e.p.x.y)
montEncode(&e.p.y.x, &e.p.y.x)
montEncode(&e.p.y.y, &e.p.y.y)
if e.p.x.IsZero() && e.p.y.IsZero() {
// This is the point at infinity.
e.p.y.SetOne()
e.p.z.SetZero()
e.p.t.SetZero()
} else {
e.p.z.SetOne()
e.p.t.SetOne()
if !e.p.IsOnCurve() {
return m, gerrors.WithAnnotatingf(errors.ErrInvalidPoint, "unmarshaled point is not a valid point on curve")
}
}
return m[4*numBytes:], nil
}
// GT is an abstract cyclic group. The zero value is suitable for use as the
// output of an operation, but cannot be used as an input.
type GT struct {
p gfP12
}
func (e *GT) Equal(other *GT) bool {
return e.p.Equal(&other.p)
}
// Order12412 change e to 1-2-4-12 field extension represent
func (e *GT) Order12412() {
e.p.x.y.x, e.p.x.y.y, e.p.y.y.x, e.p.y.y.y, e.p.x.z.x, e.p.x.z.y, e.p.y.x.x, e.p.y.x.y =
e.p.y.y.x, e.p.y.y.y, e.p.x.y.x, e.p.x.y.y, e.p.y.x.x, e.p.y.x.y, e.p.x.z.x, e.p.x.z.y
}
// RandomGT returns x and e(g₁, g₂)ˣ where x is a random, non-zero number read
// from r.
func RandomGT(r io.Reader) (*big.Int, *GT, error) {
k, err := randomK(r)
if err != nil {
return nil, nil, gerrors.WithMessage(err, "RandomGT failed")
}
return k, new(GT).ScalarBaseMult(k), nil
}
// Pair calculates an Optimal Ate pairing.
func Pair(g1 *G1, g2 *G2) *GT {
var e GT
optimalAte(&e.p, &g2.p, &g1.p)
return &e
}
// Pair calculates an Optimal Ate pairing.
func PairLol(e *GT, g1 *G1, g2 *G2) {
optimalAte(&e.p, &g2.p, &g1.p)
}
// Miller applies Miller's algorithm, which is a bilinear function from the
// source groups to F_p^12. Miller(g1, g2).Finalize() is equivalent to Pair(g1,
// g2).
func Miller(g1 *G1, g2 *G2) *GT {
var e GT
miller(&e.p, &g2.p, &g1.p)
return &e
}
func (e *GT) String() string {
p := *e
p.Order12412()
return "GT" + gfP12Decode(&p.p).String()
}
// ScalarBaseMult sets e to g*k where g is the generator of the group and then
// returns out.
func (e *GT) ScalarBaseMult(k *big.Int) *GT {
if useLattice {
e.p.latticeExp(gfP12Gen, k)
return e
} else {
return e.ScalarMultSimple(&GT{*gfP12Gen}, k)
}
}
// ScalarMult sets e to a*k and then returns e. (If e is not guaranteed to be an element of the group because it is the
// output of Miller(), use ScalarMultSimple.)
func (e *GT) ScalarMult(a *GT, k *big.Int) *GT {
if useLattice {
e.p.latticeExp(&a.p, k)
return e
} else {
return e.ScalarMultSimple(a, k)
}
}
// ScalarMultSimple sets e to a*k and then returns e.
func (e *GT) ScalarMultSimple(a *GT, k *big.Int) *GT {
e.p.Exp(&a.p, k)
return e
}
func (e *GT) Mul(a, b *GT) *GT {
e.p.Mul(&a.p, &b.p)
return e
}
// Add sets e to a+b and then returns e.
func (e *GT) Add(a, b *GT) *GT {
e.p.Mul(&a.p, &b.p)
return e
}
// Neg sets e to -a and then returns e.
func (e *GT) Neg(a *GT) *GT {
e.p.Conjugate(&a.p)
return e
}
// Set sets e to a and then returns e.
func (e *GT) Set(a *GT) *GT {
e.p.Set(&a.p)
return e
}
// Set sets e to a and then returns e.
func (e *GT) SetOne() *GT {
e.p.SetOne()
return e
}
// Set sets e to a and then returns e.
func (e *GT) Invert(a *GT) *GT {
e.p.Invert(&a.p)
return e
}
// Finalize is a linear function from F_p^12 to GT.
// func (e *GT) Finalize() *GT {
// finalExponentiation(&e.p, &e.p)
// return e
// }
// Marshal converts e into a byte slice.
func (e *GT) Marshal() []byte {
p := *e
p.Order12412()
ret := make([]byte, numBytes*12)
temp := &gfP{}
montDecode(temp, &p.p.x.x.x)
temp.Marshal(ret)
montDecode(temp, &p.p.x.x.y)
temp.Marshal(ret[numBytes:])
montDecode(temp, &p.p.x.y.x)
temp.Marshal(ret[2*numBytes:])
montDecode(temp, &p.p.x.y.y)
temp.Marshal(ret[3*numBytes:])
montDecode(temp, &p.p.x.z.x)
temp.Marshal(ret[4*numBytes:])
montDecode(temp, &p.p.x.z.y)
temp.Marshal(ret[5*numBytes:])
montDecode(temp, &p.p.y.x.x)
temp.Marshal(ret[6*numBytes:])
montDecode(temp, &p.p.y.x.y)
temp.Marshal(ret[7*numBytes:])
montDecode(temp, &p.p.y.y.x)
temp.Marshal(ret[8*numBytes:])
montDecode(temp, &p.p.y.y.y)
temp.Marshal(ret[9*numBytes:])
montDecode(temp, &p.p.y.z.x)
temp.Marshal(ret[10*numBytes:])
montDecode(temp, &p.p.y.z.y)
temp.Marshal(ret[11*numBytes:])
return ret
}
// Unmarshal sets e to the result of converting the output of Marshal back into
// a group element and then returns e.
func (e *GT) Unmarshal(m []byte) ([]byte, error) {
if len(m) < 12*numBytes {
return m, gerrors.WithAnnotating(errors.ErrInvalidInput, "not enough data to unmarshal to GT")
}
e.p.x.x.x.Unmarshal(m)
e.p.x.x.y.Unmarshal(m[numBytes:])
e.p.x.y.x.Unmarshal(m[2*numBytes:])
e.p.x.y.y.Unmarshal(m[3*numBytes:])
e.p.x.z.x.Unmarshal(m[4*numBytes:])
e.p.x.z.y.Unmarshal(m[5*numBytes:])
e.p.y.x.x.Unmarshal(m[6*numBytes:])
e.p.y.x.y.Unmarshal(m[7*numBytes:])
e.p.y.y.x.Unmarshal(m[8*numBytes:])
e.p.y.y.y.Unmarshal(m[9*numBytes:])
e.p.y.z.x.Unmarshal(m[10*numBytes:])
e.p.y.z.y.Unmarshal(m[11*numBytes:])
montEncode(&e.p.x.x.x, &e.p.x.x.x)
montEncode(&e.p.x.x.y, &e.p.x.x.y)
montEncode(&e.p.x.y.x, &e.p.x.y.x)
montEncode(&e.p.x.y.y, &e.p.x.y.y)
montEncode(&e.p.x.z.x, &e.p.x.z.x)
montEncode(&e.p.x.z.y, &e.p.x.z.y)
montEncode(&e.p.y.x.x, &e.p.y.x.x)
montEncode(&e.p.y.x.y, &e.p.y.x.y)
montEncode(&e.p.y.y.x, &e.p.y.y.x)
montEncode(&e.p.y.y.y, &e.p.y.y.y)
montEncode(&e.p.y.z.x, &e.p.y.z.x)
montEncode(&e.p.y.z.y, &e.p.y.z.y)
e.Order12412()
return m[12*numBytes:], nil
}