aes-set-key-internal.c 1.77 KB
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/* aes-set-key-internal.c
 *
 * Key setup for the aes/rijndael block cipher.
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2000, 2001, 2002 Rafael R. Sevilla, Niels Möller
 * Copyright (C) 2013 Niels Möller
 * 
 * The nettle library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 * 
 * The nettle library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 * License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with the nettle library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02111-1301, USA.
 */

/* Originally written by Rafael R. Sevilla <dido@pacific.net.ph> */

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include "aes-internal.h"
#include "macros.h"

void
_aes_set_key(unsigned nr, unsigned nk,
	     uint32_t *subkeys, const uint8_t *key)
{
  static const uint8_t rcon[10] = {
    0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80,0x1b,0x36,
  };
  const uint8_t *rp;
  unsigned lastkey, i;
  uint32_t t;

  lastkey = (AES_BLOCK_SIZE/4) * (nr + 1);
  
  for (i=0, rp = rcon; i<nk; i++)
    subkeys[i] = LE_READ_UINT32(key + i*4);

  for (i=nk; i<lastkey; i++)
    {
      t = subkeys[i-1];
      if (i % nk == 0)
	t = SUBBYTE(ROTL32(24, t), aes_sbox) ^ *rp++;

      else if (nk > 6 && (i%nk) == 4)
	t = SUBBYTE(t, aes_sbox);

      subkeys[i] = subkeys[i-nk] ^ t;
    }  
}