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103 lines
3.0 KiB
103 lines
3.0 KiB
package main
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type WCurve struct {
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p, r, a, b, h bigint
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g *JacobiPoint
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montA, conversionFromM bigint
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conversion bigint
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}
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func NewWCurve() *WCurve {
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curve := WCurve{}
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curve.p = NewBigintFromString("7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed", 16)
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curve.r = NewBigintFromString("1000000000000000000000000000000014def9dea2f79cd65812631a5cf5d3ed", 16)
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curve.montA = NewBigintFromString("486662", 10)
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curve.a = NewBigintFromString("2aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa984914a144", 16)
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curve.b = NewBigintFromString("7b425ed097b425ed097b425ed097b425ed097b425ed097b4260b5e9c7710c864", 16)
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curve.h = NewBigintFromString("8", 10)
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curve.conversionFromM = curve.montA.Mul(modinv(NewBigint(3), curve.p)).Mod(curve.p)
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curve.conversion = curve.p.Sub(curve.montA.Mul(modinv(NewBigint(3), curve.p))).Mod(curve.p)
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curve.g = curve.liftX(NewBigint(9), false)
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return &curve
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}
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func (curve *WCurve) Eq(other *WCurve) bool {
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return curve.p.Eq(other.p) &&
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curve.a.Mod(curve.p).Eq(other.a.Mod(curve.p)) &&
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curve.b.Mod(curve.p).Eq(other.b.Mod(curve.p))
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}
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func (curve *WCurve) containsPoint(x, y bigint) bool {
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p1 := x.Mul(x).Add(curve.a).Mul(x).Add(curve.b)
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return y.Mul(y).Sub(p1).Mod(curve.p).EqInt(0)
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}
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func (curve *WCurve) genPublicKey(priv []byte) (pub []byte, parity bool) {
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if len(priv) != 32 {
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panic("invalid private key length")
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}
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p := NewBigintFromBytes(priv)
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pt := curve.g.Mul(p)
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return curve.toMontgomery(pt)
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}
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func (self *WCurve) toMontgomery(pt *JacobiPoint) (bytes []byte, parity bool) {
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x := pt.AffineX().Add(self.conversion).Mod(self.p)
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return x.ToBytes(32), pt.AffineY().AndInt(1).EqInt(1)
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}
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func (self *WCurve) liftX(x bigint, parity bool) *JacobiPoint {
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x = x.Mod(self.p)
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ySquared := x.Mul(x).Mul(x).Add(self.montA.Mul(x).Mul(x).Add(x)).Mod(self.p)
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x = x.Add(self.conversionFromM).Mod(self.p)
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ys0, ys1 := primeModSqrt(ySquared, self.p)
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if ys0.Empty() && ys1.Empty() {
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return nil
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} else {
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pt1 := NewJacobiPoint(self, x, ys0, NewBigint(1), self.r)
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pt2 := NewJacobiPoint(self, x, ys1, NewBigint(1), self.r)
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if pt1.AffineY().AndInt(1).EqInt(1) && parity {
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return pt1
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} else if pt2.AffineY().AndInt(1).EqInt(1) && parity {
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return pt2
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} else if pt1.AffineY().AndInt(1).EqInt(0) && !parity {
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return pt1
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} else {
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return pt2
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}
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}
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}
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func (self *WCurve) redp1(bytes []byte, parity bool) *JacobiPoint {
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x := getSHA2Digest(bytes)
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for {
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x2 := getSHA2Digest(x)
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pt := self.liftX(NewBigintFromBytes(x2), parity)
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if pt == nil {
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x = NewBigintFromBytes(x).AddInt(1).ToBytes(32)
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} else {
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return pt
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}
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}
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}
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func (self *WCurve) check(a *JacobiPoint) bool {
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ax := a.AffineX()
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ay := a.AffineY()
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left := ay.Mul(ay).Mod(self.p)
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right := ax.Mul(ax).Mul(ax).Add(self.a.Mul(ax)).Add(self.b).Mod(self.p)
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return left.Eq(right)
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}
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func (self *WCurve) multiplyByG(a bigint) *JacobiPoint {
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return self.g.Mul(a)
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}
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func (self *WCurve) finiteFieldValue(a bigint) bigint {
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return a.Mod(self.r)
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}
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