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linux
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
19static inline u32 rotl32(u32 v, u8 n)
20{
21 return (v << n) | (v >> (sizeof(v) * 8 - n));
22}
23
24extern void chacha20_block(u32 *state, void *stream)
25{
26 u32 x[16], *out = stream;
27 int i;
28
29 for (i = 0; i < ARRAY_SIZE(x); i++)
30 x[i] = state[i];
31
32 for (i = 0; i < 20; i += 2) {
33 x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 16);
34 x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 16);
35 x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 16);
36 x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 16);
37
38 x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 12);
39 x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 12);
40 x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 12);
41 x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 12);
42
43 x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 8);
44 x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 8);
45 x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 8);
46 x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 8);
47
48 x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 7);
49 x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 7);
50 x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 7);
51 x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 7);
52
53 x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 16);
54 x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 16);
55 x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 16);
56 x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 16);
57
58 x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 12);
59 x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 12);
60 x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 12);
61 x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 12);
62
63 x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 8);
64 x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 8);
65 x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 8);
66 x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 8);
67
68 x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 7);
69 x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 7);
70 x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 7);
71 x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 7);
72 }
73
74 for (i = 0; i < ARRAY_SIZE(x); i++)
75 out[i] = cpu_to_le32(x[i] + state[i]);
76
77 state[12]++;
78}
79EXPORT_SYMBOL(chacha20_block);