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/>.
16 // GOST 28147-89 block cipher with ECB, CFB, CTR, MAC modes of operation.
25 // All 28147 operations are going with two 32-bit halves of the whole
26 // block. nv is representation of that one half.
29 // Cyclic 11-bit shift.
30 func (n nv) shift11() nv {
31 return ((n << 11) & (1<<32 - 1)) | ((n >> (32 - 11)) & (1<<32 - 1))
34 // Seq contains iteration numbers used in the encryption function
35 // itself. For example 28147 encryption and decryption process differs
36 // only with this sequence.
40 SeqEncrypt = Seq([]uint8{
41 0, 1, 2, 3, 4, 5, 6, 7,
42 0, 1, 2, 3, 4, 5, 6, 7,
43 0, 1, 2, 3, 4, 5, 6, 7,
44 7, 6, 5, 4, 3, 2, 1, 0,
46 SeqDecrypt = Seq([]uint8{
47 0, 1, 2, 3, 4, 5, 6, 7,
48 7, 6, 5, 4, 3, 2, 1, 0,
49 7, 6, 5, 4, 3, 2, 1, 0,
50 7, 6, 5, 4, 3, 2, 1, 0,
60 func NewCipher(key []byte, sbox *Sbox) *Cipher {
61 if len(key) != KeySize {
62 panic("invalid key size")
64 c := Cipher{sbox: sbox}
67 nv(key[0]) | nv(key[1])<<8 | nv(key[2])<<16 | nv(key[3])<<24,
68 nv(key[4]) | nv(key[5])<<8 | nv(key[6])<<16 | nv(key[7])<<24,
69 nv(key[8]) | nv(key[9])<<8 | nv(key[10])<<16 | nv(key[11])<<24,
70 nv(key[12]) | nv(key[13])<<8 | nv(key[14])<<16 | nv(key[15])<<24,
71 nv(key[16]) | nv(key[17])<<8 | nv(key[18])<<16 | nv(key[19])<<24,
72 nv(key[20]) | nv(key[21])<<8 | nv(key[22])<<16 | nv(key[23])<<24,
73 nv(key[24]) | nv(key[25])<<8 | nv(key[26])<<16 | nv(key[27])<<24,
74 nv(key[28]) | nv(key[29])<<8 | nv(key[30])<<16 | nv(key[31])<<24,
79 func (c *Cipher) BlockSize() int {
83 // Convert binary byte block to two 32-bit internal integers.
84 func block2nvs(b []byte) (n1, n2 nv) {
85 n1 = nv(b[0]) | nv(b[1])<<8 | nv(b[2])<<16 | nv(b[3])<<24
86 n2 = nv(b[4]) | nv(b[5])<<8 | nv(b[6])<<16 | nv(b[7])<<24
90 // Convert two 32-bit internal integers to binary byte block.
91 func nvs2block(n1, n2 nv, b []byte) {
92 b[0] = byte((n2 >> 0) & 255)
93 b[1] = byte((n2 >> 8) & 255)
94 b[2] = byte((n2 >> 16) & 255)
95 b[3] = byte((n2 >> 24) & 255)
96 b[4] = byte((n1 >> 0) & 255)
97 b[5] = byte((n1 >> 8) & 255)
98 b[6] = byte((n1 >> 16) & 255)
99 b[7] = byte((n1 >> 24) & 255)
102 func (c *Cipher) xcrypt(seq Seq, n1, n2 nv) (nv, nv) {
103 for _, i := range seq {
104 n1, n2 = c.sbox.k(n1+c.x[i]).shift11()^n2, n1
109 // Encrypt single block.
110 // If provided slices are shorter than the block size, then it will panic.
111 func (c *Cipher) Encrypt(dst, src []byte) {
112 n1, n2 := block2nvs(src)
113 n1, n2 = c.xcrypt(SeqEncrypt, n1, n2)
114 nvs2block(n1, n2, dst)
117 // Decrypt single block.
118 // If provided slices are shorter than the block size, then it will panic.
119 func (c *Cipher) Decrypt(dst, src []byte) {
120 n1, n2 := block2nvs(src)
121 n1, n2 = c.xcrypt(SeqDecrypt, n1, n2)
122 nvs2block(n1, n2, dst)