1 /*
2 * ChaCha20 256-bit cipher algorithm, RFC7539
3 *
4 * Copyright (C) 2015 Martin Willi
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 */
11
12 #include <linux/kernel.h>
13 #include <linux/export.h>
14 #include <linux/bitops.h>
15 #include <linux/cryptohash.h>
16 #include <asm/unaligned.h>
17 #include <crypto/chacha20.h>
18
chacha20_block(u32 * state,u32 * stream)19 void chacha20_block(u32 *state, u32 *stream)
20 {
21 u32 x[16], *out = stream;
22 int i;
23
24 for (i = 0; i < ARRAY_SIZE(x); i++)
25 x[i] = state[i];
26
27 for (i = 0; i < 20; i += 2) {
28 x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 16);
29 x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 16);
30 x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 16);
31 x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 16);
32
33 x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 12);
34 x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 12);
35 x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 12);
36 x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 12);
37
38 x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 8);
39 x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 8);
40 x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 8);
41 x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 8);
42
43 x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 7);
44 x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 7);
45 x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 7);
46 x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 7);
47
48 x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 16);
49 x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 16);
50 x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 16);
51 x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 16);
52
53 x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 12);
54 x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 12);
55 x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 12);
56 x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 12);
57
58 x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 8);
59 x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 8);
60 x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 8);
61 x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 8);
62
63 x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 7);
64 x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 7);
65 x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7);
66 x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 7);
67 }
68
69 for (i = 0; i < ARRAY_SIZE(x); i++)
70 out[i] = cpu_to_le32(x[i] + state[i]);
71
72 state[12]++;
73 }
74 EXPORT_SYMBOL(chacha20_block);
75
