X-Git-Url: http://www.git.cypherpunks.ru/?a=blobdiff_plain;f=gost3410%2Fcurve.go;h=a5f8d5125fe48da5d0f5573527e3a2a359da42f2;hb=7bed9561c7c09958ad1268b397058431fd3362bc;hp=47f964b583a66bf9b735b73c671b0ca0e97873e3;hpb=c07494bbd559b9d00f391e28cfd070e18afe9900;p=gogost.git

diff --git a/gost3410/curve.go b/gost3410/curve.go
index 47f964b..a5f8d51 100644
--- a/gost3410/curve.go
+++ b/gost3410/curve.go
@@ -1,5 +1,5 @@
 // GoGOST -- Pure Go GOST cryptographic functions library
-// Copyright (C) 2015-2019 Sergey Matveev <stargrave@stargrave.org>
+// Copyright (C) 2015-2021 Sergey Matveev <stargrave@stargrave.org>
 //
 // This program is free software: you can redistribute it and/or modify
 // it under the terms of the GNU General Public License as published by
@@ -25,6 +25,7 @@ var (
 	bigInt1 *big.Int = big.NewInt(1)
 	bigInt2 *big.Int = big.NewInt(2)
 	bigInt3 *big.Int = big.NewInt(3)
+	bigInt4 *big.Int = big.NewInt(4)
 )
 
 type Curve struct {
@@ -33,6 +34,8 @@ type Curve struct {
 	P *big.Int // Characteristic of the underlying prime field
 	Q *big.Int // Elliptic curve subgroup order
 
+	Co *big.Int // Cofactor
+
 	// Equation coefficients of the elliptic curve in canonical form
 	A *big.Int
 	B *big.Int
@@ -45,17 +48,12 @@ type Curve struct {
 	X *big.Int
 	Y *big.Int
 
-	// Temporary variable for the add method
-	t  *big.Int
-	tx *big.Int
-	ty *big.Int
-
 	// Cached s/t parameters for Edwards curve points conversion
 	edS *big.Int
 	edT *big.Int
 }
 
-func NewCurve(p, q, a, b, x, y, e, d *big.Int) (*Curve, error) {
+func NewCurve(p, q, a, b, x, y, e, d, co *big.Int) (*Curve, error) {
 	c := Curve{
 		Name: "unknown",
 		P:    p,
@@ -64,9 +62,6 @@ func NewCurve(p, q, a, b, x, y, e, d *big.Int) (*Curve, error) {
 		B:    b,
 		X:    x,
 		Y:    y,
-		t:    big.NewInt(0),
-		tx:   big.NewInt(0),
-		ty:   big.NewInt(0),
 	}
 	r1 := big.NewInt(0)
 	r2 := big.NewInt(0)
@@ -79,15 +74,24 @@ func NewCurve(p, q, a, b, x, y, e, d *big.Int) (*Curve, error) {
 	r2.Mod(r2, c.P)
 	c.pos(r2)
 	if r1.Cmp(r2) != 0 {
-		return nil, errors.New("Invalid curve parameters")
+		return nil, errors.New("gogost/gost3410: invalid curve parameters")
 	}
 	if e != nil && d != nil {
 		c.E = e
 		c.D = d
 	}
+	if co == nil {
+		c.Co = bigInt1
+	} else {
+		c.Co = co
+	}
 	return &c, nil
 }
 
+func (c *Curve) PointSize() int {
+	return PointSize(c.P)
+}
+
 func (c *Curve) pos(v *big.Int) {
 	if v.Cmp(zero) < 0 {
 		v.Add(v, c.P)
@@ -95,43 +99,44 @@ func (c *Curve) pos(v *big.Int) {
 }
 
 func (c *Curve) add(p1x, p1y, p2x, p2y *big.Int) {
+	var t, tx, ty big.Int
 	if p1x.Cmp(p2x) == 0 && p1y.Cmp(p2y) == 0 {
 		// double
-		c.t.Mul(p1x, p1x)
-		c.t.Mul(c.t, bigInt3)
-		c.t.Add(c.t, c.A)
-		c.tx.Mul(bigInt2, p1y)
-		c.tx.ModInverse(c.tx, c.P)
-		c.t.Mul(c.t, c.tx)
-		c.t.Mod(c.t, c.P)
+		t.Mul(p1x, p1x)
+		t.Mul(&t, bigInt3)
+		t.Add(&t, c.A)
+		tx.Mul(bigInt2, p1y)
+		tx.ModInverse(&tx, c.P)
+		t.Mul(&t, &tx)
+		t.Mod(&t, c.P)
 	} else {
-		c.tx.Sub(p2x, p1x)
-		c.tx.Mod(c.tx, c.P)
-		c.pos(c.tx)
-		c.ty.Sub(p2y, p1y)
-		c.ty.Mod(c.ty, c.P)
-		c.pos(c.ty)
-		c.t.ModInverse(c.tx, c.P)
-		c.t.Mul(c.t, c.ty)
-		c.t.Mod(c.t, c.P)
+		tx.Sub(p2x, p1x)
+		tx.Mod(&tx, c.P)
+		c.pos(&tx)
+		ty.Sub(p2y, p1y)
+		ty.Mod(&ty, c.P)
+		c.pos(&ty)
+		t.ModInverse(&tx, c.P)
+		t.Mul(&t, &ty)
+		t.Mod(&t, c.P)
 	}
-	c.tx.Mul(c.t, c.t)
-	c.tx.Sub(c.tx, p1x)
-	c.tx.Sub(c.tx, p2x)
-	c.tx.Mod(c.tx, c.P)
-	c.pos(c.tx)
-	c.ty.Sub(p1x, c.tx)
-	c.ty.Mul(c.ty, c.t)
-	c.ty.Sub(c.ty, p1y)
-	c.ty.Mod(c.ty, c.P)
-	c.pos(c.ty)
-	p1x.Set(c.tx)
-	p1y.Set(c.ty)
+	tx.Mul(&t, &t)
+	tx.Sub(&tx, p1x)
+	tx.Sub(&tx, p2x)
+	tx.Mod(&tx, c.P)
+	c.pos(&tx)
+	ty.Sub(p1x, &tx)
+	ty.Mul(&ty, &t)
+	ty.Sub(&ty, p1y)
+	ty.Mod(&ty, c.P)
+	c.pos(&ty)
+	p1x.Set(&tx)
+	p1y.Set(&ty)
 }
 
 func (c *Curve) Exp(degree, xS, yS *big.Int) (*big.Int, *big.Int, error) {
 	if degree.Cmp(zero) == 0 {
-		return nil, nil, errors.New("Bad degree value")
+		return nil, nil, errors.New("gogost/gost3410: zero degree value")
 	}
 	dg := big.NewInt(0).Sub(degree, bigInt1)
 	tx := big.NewInt(0).Set(xS)
@@ -147,3 +152,15 @@ func (c *Curve) Exp(degree, xS, yS *big.Int) (*big.Int, *big.Int, error) {
 	}
 	return tx, ty, nil
 }
+
+func (our *Curve) Equal(their *Curve) bool {
+	return our.P.Cmp(their.P) == 0 &&
+		our.Q.Cmp(their.Q) == 0 &&
+		our.A.Cmp(their.A) == 0 &&
+		our.B.Cmp(their.B) == 0 &&
+		our.X.Cmp(their.X) == 0 &&
+		our.Y.Cmp(their.Y) == 0 &&
+		((our.E == nil && their.E == nil) || our.E.Cmp(their.E) == 0) &&
+		((our.D == nil && their.D == nil) || our.D.Cmp(their.D) == 0) &&
+		our.Co.Cmp(their.Co) == 0
+}