1 // GoGOST -- Pure Go GOST cryptographic functions library
2 // Copyright (C) 2015-2021 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/>.
22 const Mul128MaxBit = 128 - 1
24 var R128 = big.NewInt(0).SetBytes([]byte{
25 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
26 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x87,
36 func newMul128() *mul128 {
44 func (mul *mul128) Mul(x, y []byte) []byte {
48 for mul.y.BitLen() != 0 {
49 if mul.y.Bit(0) == 1 {
50 mul.z.Xor(mul.z, mul.x)
52 if mul.x.Bit(Mul128MaxBit) == 1 {
53 mul.x.SetBit(mul.x, Mul128MaxBit, 0)
55 mul.x.Xor(mul.x, R128)
61 zBytes := mul.z.Bytes()
62 rem := len(x) - len(zBytes)
63 for i := 0; i < rem; i++ {
66 copy(mul.buf[rem:], zBytes)