X-Git-Url: http://www.git.cypherpunks.ru/?a=blobdiff_plain;f=src%2Fcypherpunks.ru%2Fgogost%2Fgost3410%2Fcurve.go;h=0ad10c9ff747dcc4d3b3b5087f735d4bf2ee98a8;hb=cc6addfa724ba7b7d3119e9171c65298f0711ac4;hp=70f5a66c3596f11b89df39fea74ee1a0a4119da1;hpb=0c90f3181c01f68c4f2c986b02cda16dba85521b;p=gogost.git

diff --git a/src/cypherpunks.ru/gogost/gost3410/curve.go b/src/cypherpunks.ru/gogost/gost3410/curve.go
index 70f5a66..0ad10c9 100644
--- a/src/cypherpunks.ru/gogost/gost3410/curve.go
+++ b/src/cypherpunks.ru/gogost/gost3410/curve.go
@@ -1,5 +1,5 @@
 // GoGOST -- Pure Go GOST cryptographic functions library
-// Copyright (C) 2015-2016 Sergey Matveev <stargrave@stargrave.org>
+// Copyright (C) 2015-2019 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
@@ -29,14 +29,16 @@ var (
 )
 
 type Curve struct {
-	P *big.Int
-	Q *big.Int
+	P *big.Int // Characteristic of the underlying prime field
+	Q *big.Int // Elliptic curve subgroup order
+
+	// Equation coefficients of the elliptic curve in canonical form
 	A *big.Int
 	B *big.Int
 
 	// Basic point X and Y coordinates
-	Bx *big.Int
-	By *big.Int
+	X *big.Int
+	Y *big.Int
 
 	// Temporary variable for the add method
 	t  *big.Int
@@ -58,19 +60,18 @@ func NewCurve(p, q, a, b, bx, by []byte) (*Curve, error) {
 	}
 	r1 := big.NewInt(0)
 	r2 := big.NewInt(0)
-	r1.Mul(c.By, c.By)
+	r1.Mul(c.Y, c.Y)
 	r1.Mod(r1, c.P)
-	r2.Mul(c.Bx, c.Bx)
+	r2.Mul(c.X, c.X)
 	r2.Add(r2, c.A)
-	r2.Mul(r2, c.Bx)
+	r2.Mul(r2, c.X)
 	r2.Add(r2, c.B)
 	r2.Mod(r2, c.P)
-	if r2.Cmp(big.NewInt(0)) == -1 {
-		r2.Add(r2, c.P)
-	}
+	c.pos(r2)
 	if r1.Cmp(r2) != 0 {
 		return nil, errors.New("Invalid curve parameters")
 	}
+	}
 	return &c, nil
 }
 
@@ -116,14 +117,14 @@ func (c *Curve) add(p1x, p1y, p2x, p2y *big.Int) {
 }
 
 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")
+	}
 	dg := big.NewInt(0).Sub(degree, bigInt1)
 	tx := big.NewInt(0).Set(xS)
 	ty := big.NewInt(0).Set(yS)
 	cx := big.NewInt(0).Set(xS)
 	cy := big.NewInt(0).Set(yS)
-	if dg.Cmp(zero) == 0 {
-		return nil, nil, errors.New("Bad degree value")
-	}
 	for dg.Cmp(zero) != 0 {
 		if dg.Bit(0) == 1 {
 			c.add(tx, ty, cx, cy)