aes_enc.c

   1 /* aes_enc.c */
   2 /*
   3     This file is part of the Crypto-avr-lib/microcrypt-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
  37 void aes_shiftrow(void* data, uint8_t shift){
  38         uint8_t tmp[4];
  39         tmp[0] = ((uint8_t*)data)[(0+shift)&3];
  40         tmp[1] = ((uint8_t*)data)[(1+shift)&3];
  41         tmp[2] = ((uint8_t*)data)[(2+shift)&3];
  42         tmp[3] = ((uint8_t*)data)[(3+shift)&3];
  43         memcpy(data, tmp, 4);
  44 }
  45
  46 #define GF256MUL_1(a) (a)
  47 #define GF256MUL_2(a) (gf256mul(2, (a), 0x1b))
  48 #define GF256MUL_3(a) (gf256mul(3, (a), 0x1b))
  49
  50 static
  51 void aes_enc_round(aes_cipher_state_t* state, const aes_roundkey_t* k){
  52         uint8_t tmp[16];
  53         uint8_t i;
  54         /* subBytes */
  55         for(i=0; i<16; ++i){
  56                 tmp[i] = pgm_read_byte(aes_sbox+state->s[i]);
  57         }
  58         /* shiftRows */
  59         aes_shiftrow(tmp+4, 1);
  60         aes_shiftrow(tmp+8, 2);
  61         aes_shiftrow(tmp+12, 3);
  62         /* mixColums */
  63         for(i=0; i<4; ++i){
  64                 state->s[4*0+i] =
  65                           GF256MUL_2(tmp[4*0+i])
  66                         ^ GF256MUL_3(tmp[4*1+i])
  67                         ^ GF256MUL_1(tmp[4*2+i])
  68                         ^ GF256MUL_1(tmp[4*3+i]);
  69                 state->s[4*1+i] =
  70                           GF256MUL_1(tmp[4*0+i])
  71                         ^ GF256MUL_2(tmp[4*1+i])
  72                         ^ GF256MUL_3(tmp[4*2+i])
  73                         ^ GF256MUL_1(tmp[4*3+i]);
  74                 state->s[4*2+i] =
  75                           GF256MUL_1(tmp[4*0+i])
  76                         ^ GF256MUL_1(tmp[4*1+i])
  77                         ^ GF256MUL_2(tmp[4*2+i])
  78                         ^ GF256MUL_3(tmp[4*3+i]);
  79                 state->s[4*3+i] =
  80                           GF256MUL_3(tmp[4*0+i])
  81                         ^ GF256MUL_1(tmp[4*1+i])
  82                         ^ GF256MUL_1(tmp[4*2+i])
  83                         ^ GF256MUL_2(tmp[4*3+i]);
  84         }
  85
  86         /* addKey */
  87         for(i=0; i<16; ++i){
  88                 state->s[i] ^= k->ks[i];
  89         }
  90 }
  91
  92
  93 static
  94 void aes_enc_lastround(aes_cipher_state_t* state,const aes_roundkey_t* k){
  95         uint8_t i;
  96         /* subBytes */
  97         for(i=0; i<16; ++i){
  98                 state->s[i] = pgm_read_byte(aes_sbox+state->s[i]);
  99         }
 100         /* shiftRows */
 101         aes_shiftrow(state->s+4, 1);
 102         aes_shiftrow(state->s+8, 2);
 103         aes_shiftrow(state->s+12, 3);
 104         /* keyAdd */
 105         for(i=0; i<16; ++i){
 106                 state->s[i] ^= k->ks[i];
 107         }
 108 }
 109
 110 void aes_encrypt_core(aes_cipher_state_t* state, const aes_genctx_t* ks, uint8_t rounds){
 111         uint8_t i;
 112         for(i=0; i<16; ++i){
 113                 state->s[i] ^= ks->key[0].ks[i];
 114         }
 115         i=1;
 116         for(;rounds>1;--rounds){
 117                 aes_enc_round(state, &(ks->key[i]));
 118                 ++i;
 119         }
 120         aes_enc_lastround(state, &(ks->key[i]));
 121 }