release/src/router/nettle/aes-set-encrypt-key.c

   1 /* aes-set-encrypt-key.c
   2  *
   3  * Key setup for the aes/rijndael block cipher.
   4  */
   5
   6 /* nettle, low-level cryptographics library
   7  *
   8  * Copyright (C) 2000, 2001, 2002 Rafael R. Sevilla, Niels Möller
   9  *
  10  * The nettle library is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU Lesser General Public License as published by
  12  * the Free Software Foundation; either version 2.1 of the License, or (at your
  13  * option) any later version.
  14  *
  15  * The nettle library is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  17  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  18  * License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public License
  21  * along with the nettle library; see the file COPYING.LIB.  If not, write to
  22  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  23  * MA 02111-1301, USA.
  24  */
  25
  26 /* Originally written by Rafael R. Sevilla <dido@pacific.net.ph> */
  27
  28 #if HAVE_CONFIG_H
  29 # include "config.h"
  30 #endif
  31
  32 #include <assert.h>
  33
  34 #include "aes-internal.h"
  35 #include "macros.h"
  36
  37 void
  38 aes_set_encrypt_key(struct aes_ctx *ctx,
  39                     unsigned keysize, const uint8_t *key)
  40 {
  41   static const uint8_t rcon[10] = {
  42     0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80,0x1b,0x36,
  43   };
  44   unsigned nk, nr, i, lastkey;
  45   uint32_t temp;
  46   const uint8_t *rp;
  47
  48   assert(keysize >= AES_MIN_KEY_SIZE);
  49   assert(keysize <= AES_MAX_KEY_SIZE);
  50
  51   /* Truncate keysizes to the valid key sizes provided by Rijndael */
  52   if (keysize == 32) {
  53     nk = 8;
  54     nr = 14;
  55   } else if (keysize >= 24) {
  56     nk = 6;
  57     nr = 12;
  58   } else { /* must be 16 or more */
  59     nk = 4;
  60     nr = 10;
  61   }
  62
  63   lastkey = (AES_BLOCK_SIZE/4) * (nr + 1);
  64   ctx->nrounds = nr;
  65
  66   for (i=0, rp = rcon; i<nk; i++)
  67     ctx->keys[i] = LE_READ_UINT32(key + i*4);
  68
  69   for (i=nk; i<lastkey; i++)
  70     {
  71       temp = ctx->keys[i-1];
  72       if (i % nk == 0)
  73         temp = SUBBYTE(ROTL32(24, temp), aes_sbox) ^ *rp++;
  74
  75       else if (nk > 6 && (i%nk) == 4)
  76         temp = SUBBYTE(temp, aes_sbox);
  77
  78       ctx->keys[i] = ctx->keys[i-nk] ^ temp;
  79     }
  80 }
  81