aes/aes_enc.c

   1 /* aes_enc.c */
   2 /*
   3     This file is part of the AVR-Crypto-Lib.
   4     Copyright (C) 2008  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  * \file     aes_enc.c
  21  * \email    daniel.otte@rub.de
  22  * \author   Daniel Otte
  23  * \date     2008-12-30
  24  * \license  GPLv3 or later
  25  *
  26  */
  27
  28 #include <stdint.h>
  29 #include <string.h>
  30 #include "aes.h"
  31 #include "gf256mul.h"
  32 #include "aes_sbox.h"
  33 #include "aes_enc.h"
  34 #include <avr/pgmspace.h>
  35
  36 void aes_shiftcol(void *data, uint8_t shift){
  37         uint8_t tmp[4];
  38         tmp[0] = ((uint8_t*)data)[ 0];
  39         tmp[1] = ((uint8_t*)data)[ 4];
  40         tmp[2] = ((uint8_t*)data)[ 8];
  41         tmp[3] = ((uint8_t*)data)[12];
  42         ((uint8_t*)data)[ 0] = tmp[(shift+0)&3];
  43         ((uint8_t*)data)[ 4] = tmp[(shift+1)&3];
  44         ((uint8_t*)data)[ 8] = tmp[(shift+2)&3];
  45         ((uint8_t*)data)[12] = tmp[(shift+3)&3];
  46 }
  47
  48 #define GF256MUL_1(a) (a)
  49 #define GF256MUL_2(a) (gf256mul(2, (a), 0x1b))
  50 #define GF256MUL_3(a) (gf256mul(3, (a), 0x1b))
  51
  52 static
  53 void aes_enc_round(aes_cipher_state_t *state, const aes_roundkey_t *k){
  54         uint8_t tmp[16], t;
  55         uint8_t i;
  56         /* subBytes */
  57         for(i=0; i<16; ++i){
  58                 tmp[i] = pgm_read_byte(aes_sbox+state->s[i]);
  59         }
  60         /* shiftRows */
  61         aes_shiftcol(tmp+1, 1);
  62         aes_shiftcol(tmp+2, 2);
  63         aes_shiftcol(tmp+3, 3);
  64         /* mixColums */
  65         for(i=0; i<4; ++i){
  66                 t = tmp[4*i+0] ^ tmp[4*i+1] ^ tmp[4*i+2] ^ tmp[4*i+3];
  67                 state->s[4*i+0] =
  68                           GF256MUL_2(tmp[4*i+0]^tmp[4*i+1])
  69                         ^ tmp[4*i+0]
  70                         ^ t;
  71                 state->s[4*i+1] =
  72                           GF256MUL_2(tmp[4*i+1]^tmp[4*i+2])
  73                         ^ tmp[4*i+1]
  74                         ^ t;
  75                 state->s[4*i+2] =
  76                           GF256MUL_2(tmp[4*i+2]^tmp[4*i+3])
  77                         ^ tmp[4*i+2]
  78                         ^ t;
  79                 state->s[4*i+3] =
  80                           GF256MUL_2(tmp[4*i+3]^tmp[4*i+0])
  81                         ^ tmp[4*i+3]
  82                         ^ t;
  83         }
  84
  85         /* addKey */
  86         for(i=0; i<16; ++i){
  87                 state->s[i] ^= k->ks[i];
  88         }
  89 }
  90
  91
  92 static
  93 void aes_enc_lastround(aes_cipher_state_t *state,const aes_roundkey_t *k){
  94         uint8_t i;
  95         /* subBytes */
  96         for(i=0; i<16; ++i){
  97                 state->s[i] = pgm_read_byte(aes_sbox+state->s[i]);
  98         }
  99         /* shiftRows */
 100         aes_shiftcol(state->s+1, 1);
 101         aes_shiftcol(state->s+2, 2);
 102         aes_shiftcol(state->s+3, 3);
 103         /* keyAdd */
 104         for(i=0; i<16; ++i){
 105                 state->s[i] ^= k->ks[i];
 106         }
 107 }
 108
 109 void aes_encrypt_core(aes_cipher_state_t *state, const aes_genctx_t *ks, uint8_t rounds){
 110         uint8_t i;
 111         for(i=0; i<16; ++i){
 112                 state->s[i] ^= ks->key[0].ks[i];
 113         }
 114         i=1;
 115         for(;rounds>1;--rounds){
 116                 aes_enc_round(state, &(ks->key[i]));
 117                 ++i;
 118         }
 119         aes_enc_lastround(state, &(ks->key[i]));
 120 }