Do not alter ukm in gost3410.KEK*

[gogost.git] / gost3410 / vko.go

diff --git a/gost3410/vko.go b/gost3410/vko.go
index fdf3a2f5cb191312f678297696745d75964049f6..a6df7f402b415ddfca6126c265a2973ecb2004be 100644 (file)
--- a/gost3410/vko.go
+++ b/gost3410/vko.go
@@ -24,9 +24,9 @@ func (prv *PrivateKey) KEK(pub *PublicKey, ukm *big.Int) ([]byte, error) {
        if err != nil {
                return nil, err
        }
-       ukm = ukm.Mul(ukm, prv.C.Co)
-       if ukm.Cmp(bigInt1) != 0 {
-               keyX, keyY, err = prv.C.Exp(ukm, keyX, keyY)
+       u := big.NewInt(0).Set(ukm).Mul(ukm, prv.C.Co)
+       if u.Cmp(bigInt1) != 0 {
+               keyX, keyY, err = prv.C.Exp(u, keyX, keyY)
                if err != nil {
                        return nil, err
                }