1 // GoGOST -- Pure Go GOST cryptographic functions library
2 // Copyright (C) 2015-2019 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/>.
24 func (c *Cipher) NewCTR(iv []byte) *CTR {
25 if len(iv) != BlockSize {
26 panic("iv length is not equal to blocksize")
28 n1, n2 := block2nvs(iv)
29 n2, n1 = c.xcrypt(SeqEncrypt, n1, n2)
30 return &CTR{c, n1, n2}
33 func (c *CTR) XORKeyStream(dst, src []byte) {
36 block := make([]byte, BlockSize)
41 c.n1 += 0x01010101 // C2
42 c.n2 += 0x01010104 // C1
46 n1t, n2t = c.c.xcrypt(SeqEncrypt, c.n1, c.n2)
47 nvs2block(n1t, n2t, block)
48 for n = 0; n < BlockSize; n++ {
49 if i*BlockSize+n == len(src) {
52 dst[i*BlockSize+n] = src[i*BlockSize+n] ^ block[n]