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, either version 3 of the License, or
7 // (at your option) any later version.
9 // This program is distributed in the hope that it will be useful,
10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 // GNU General Public License for more details.
14 // You should have received a copy of the GNU General Public License
15 // along with this program. If not, see <http://www.gnu.org/licenses/>.
25 func (c *Cipher) NewCTR(iv []byte) *CTR {
26 if len(iv) != BlockSize {
27 panic("iv length is not equal to blocksize")
29 n1, n2 := block2nvs(iv)
30 n2, n1 = c.xcrypt(SeqEncrypt, n1, n2)
31 return &CTR{c, n1, n2}
34 func (c *CTR) XORKeyStream(dst, src []byte) {
37 block := make([]byte, BlockSize)
42 c.n1 += 0x01010101 // C2
43 c.n2 += 0x01010104 // C1
47 n1t, n2t = c.c.xcrypt(SeqEncrypt, c.n1, c.n2)
48 nvs2block(n1t, n2t, block)
49 for n = 0; n < BlockSize; n++ {
50 if i*BlockSize+n == len(src) {
53 dst[i*BlockSize+n] = src[i*BlockSize+n] ^ block[n]