1 // GoGOST -- Pure Go GOST cryptographic functions library
2 // Copyright (C) 2015-2023 Sergey Matveev <stargrave@stargrave.org>
4 // This program is free software: you can redistribute it and/or modify
5 // it under the terms of the GNU General Public License as published by
6 // the Free Software Foundation, version 3 of the License.
8 // This program is distributed in the hope that it will be useful,
9 // but WITHOUT ANY WARRANTY; without even the implied warranty of
10 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 // GNU General Public License for more details.
13 // You should have received a copy of the GNU General Public License
14 // along with this program. If not, see <http://www.gnu.org/licenses/>.
23 func (prv *PrivateKey) KEK(pub *PublicKey, ukm *big.Int) ([]byte, error) {
24 keyX, keyY, err := prv.C.Exp(prv.Key, pub.X, pub.Y)
26 return nil, fmt.Errorf("gogost/gost3410.PrivateKey.KEK: %w", err)
28 u := big.NewInt(0).Set(ukm).Mul(ukm, prv.C.Co)
29 if u.Cmp(bigInt1) != 0 {
30 keyX, keyY, err = prv.C.Exp(u, keyX, keyY)
32 return nil, fmt.Errorf("gogost/gost3410.PrivateKey.KEK: %w", err)
35 pk := PublicKey{prv.C, keyX, keyY}