linux/lib/chacha20.c
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   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);
  80