Do not perform exponentiation if UKM=1, optimization

[gogost.git] / src / cypherpunks.ru / gogost / gost3410 / vko.go

diff --git a/src/cypherpunks.ru/gogost/gost3410/vko.go b/src/cypherpunks.ru/gogost/gost3410/vko.go
index dfb9610880d8f1e8049cb35b1e0d590cd9b1dca2..aad430b139413de793ce3121e4b8d1d2467a6f99 100644 (file)
--- a/src/cypherpunks.ru/gogost/gost3410/vko.go
+++ b/src/cypherpunks.ru/gogost/gost3410/vko.go
@@ -1,5 +1,5 @@
 // GoGOST -- Pure Go GOST cryptographic functions library
-// Copyright (C) 2015-2018 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
@@ -21,14 +21,16 @@ import (
 )
 
 func (prv *PrivateKey) KEK(pub *PublicKey, ukm *big.Int) ([]byte, error) {
-       keyX, keyY, err := prv.c.Exp(prv.key, pub.x, pub.y)
+       keyX, keyY, err := prv.C.Exp(prv.Key, pub.X, pub.Y)
        if err != nil {
                return nil, err
        }
-       keyX, keyY, err = prv.c.Exp(ukm, keyX, keyY)
-       if err != nil {
-               return nil, err
+       if ukm.Cmp(bigInt1) != 0 {
+               keyX, keyY, err = prv.C.Exp(ukm, keyX, keyY)
+               if err != nil {
+                       return nil, err
+               }
        }
-       pk := PublicKey{prv.c, prv.mode, keyX, keyY}
+       pk := PublicKey{prv.C, prv.Mode, keyX, keyY}
        return pk.Raw(), nil
 }