echo/aes_enc_round.c

   1 /* aes-round.c */
   2 /*
   3     This file is part of the ARM-Crypto-Lib.
   4     Copyright (C) 2006-2010  Daniel Otte (daniel.otte@rub.de)
   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 3 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License
  17     along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include <stdint.h>
  21 #include "aes_enc_round.h"
  22 #include "gf256mul.h"
  23 #include "aes_sbox.h"
  24
  25 static
  26 void aes_shiftcol(void* data, uint8_t shift){
  27         uint8_t tmp[4];
  28         tmp[0] = ((uint8_t*)data)[ 0];
  29         tmp[1] = ((uint8_t*)data)[ 4];
  30         tmp[2] = ((uint8_t*)data)[ 8];
  31         tmp[3] = ((uint8_t*)data)[12];
  32         ((uint8_t*)data)[ 0] = tmp[(shift+0)&3];
  33         ((uint8_t*)data)[ 4] = tmp[(shift+1)&3];
  34         ((uint8_t*)data)[ 8] = tmp[(shift+2)&3];
  35         ((uint8_t*)data)[12] = tmp[(shift+3)&3];
  36 }
  37
  38 #define GF256MUL_1(a) (a)
  39 #define GF256MUL_2(a) (gf256mul(2, (a), 0x1b))
  40 #define GF256MUL_3(a) (gf256mul(3, (a), 0x1b))
  41
  42 void aes_enc_round(aes_cipher_state_t* state, const aes_roundkey_t* k){
  43         uint8_t tmp[16], t;
  44         uint8_t i;
  45         /* subBytes */
  46         for(i=0; i<16; ++i){
  47                 tmp[i] = aes_sbox[state->s[i]];
  48         }
  49         /* shiftRows */
  50         aes_shiftcol(tmp+1, 1);
  51         aes_shiftcol(tmp+2, 2);
  52         aes_shiftcol(tmp+3, 3);
  53         /* mixColums */
  54         for(i=0; i<4; ++i){
  55                 t = tmp[4*i+0] ^ tmp[4*i+1] ^ tmp[4*i+2] ^ tmp[4*i+3];
  56                 state->s[4*i+0] =
  57                           GF256MUL_2(tmp[4*i+0]^tmp[4*i+1])
  58                         ^ tmp[4*i+0]
  59                         ^ t;
  60                 state->s[4*i+1] =
  61                           GF256MUL_2(tmp[4*i+1]^tmp[4*i+2])
  62                         ^ tmp[4*i+1]
  63                         ^ t;
  64                 state->s[4*i+2] =
  65                           GF256MUL_2(tmp[4*i+2]^tmp[4*i+3])
  66                         ^ tmp[4*i+2]
  67                         ^ t;
  68                 state->s[4*i+3] =
  69                           GF256MUL_2(tmp[4*i+3]^tmp[4*i+0])
  70                         ^ tmp[4*i+3]
  71                         ^ t;
  72         }
  73
  74         /* addKey */
  75         for(i=0; i<16; ++i){
  76                 state->s[i] ^= k->ks[i];
  77         }
  78 }