lib/chacha20.c

   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
  19 static inline u32 rotl32(u32 v, u8 n)
  20 {
  21         return (v << n) | (v >> (sizeof(v) * 8 - n));
  22 }
  23
  24 extern 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 }
  79 EXPORT_SYMBOL(chacha20_block);