107 lines
2.9 KiB
C
107 lines
2.9 KiB
C
/* aes.c */
|
|
/*
|
|
This file is part of the Crypto-avr-lib/microcrypt-lib.
|
|
Copyright (C) 2008, 2009 Daniel Otte (daniel.otte@rub.de)
|
|
|
|
This program is free software: you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation, either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
This program 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 General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
#include <stdint.h>
|
|
#include <string.h>
|
|
#include "gf256mul.h"
|
|
#include "aes.h"
|
|
#include "aes_invsbox.h"
|
|
#include "aes_dec.h"
|
|
#include <avr/pgmspace.h>
|
|
|
|
void aes_invshiftrow(void* data, uint8_t shift){
|
|
uint8_t tmp[4];
|
|
tmp[0] = ((uint8_t*)data)[(4+0-shift)&3];
|
|
tmp[1] = ((uint8_t*)data)[(4+1-shift)&3];
|
|
tmp[2] = ((uint8_t*)data)[(4+2-shift)&3];
|
|
tmp[3] = ((uint8_t*)data)[(4+3-shift)&3];
|
|
memcpy(data, tmp, 4);
|
|
}
|
|
|
|
static
|
|
void aes_dec_round(aes_cipher_state_t* state, const aes_roundkey_t* k){
|
|
uint8_t tmp[16];
|
|
uint8_t i;
|
|
/* keyAdd */
|
|
for(i=0; i<16; ++i){
|
|
tmp[i] = state->s[i] ^ k->ks[i];
|
|
}
|
|
/* mixColums */
|
|
for(i=0; i<4; ++i){
|
|
state->s[4*0+i] =
|
|
gf256mul(0xe, tmp[4*0+i], 0x1b)
|
|
^ gf256mul(0xb, tmp[4*1+i], 0x1b)
|
|
^ gf256mul(0xd, tmp[4*2+i], 0x1b)
|
|
^ gf256mul(0x9, tmp[4*3+i], 0x1b);
|
|
state->s[4*1+i] =
|
|
gf256mul(0x9, tmp[4*0+i], 0x1b)
|
|
^ gf256mul(0xe, tmp[4*1+i], 0x1b)
|
|
^ gf256mul(0xb, tmp[4*2+i], 0x1b)
|
|
^ gf256mul(0xd, tmp[4*3+i], 0x1b);
|
|
state->s[4*2+i] =
|
|
gf256mul(0xd, tmp[4*0+i], 0x1b)
|
|
^ gf256mul(0x9, tmp[4*1+i], 0x1b)
|
|
^ gf256mul(0xe, tmp[4*2+i], 0x1b)
|
|
^ gf256mul(0xb, tmp[4*3+i], 0x1b);
|
|
state->s[4*3+i] =
|
|
gf256mul(0xb, tmp[4*0+i], 0x1b)
|
|
^ gf256mul(0xd, tmp[4*1+i], 0x1b)
|
|
^ gf256mul(0x9, tmp[4*2+i], 0x1b)
|
|
^ gf256mul(0xe, tmp[4*3+i], 0x1b);
|
|
}
|
|
/* shiftRows */
|
|
aes_invshiftrow(state->s+4, 1);
|
|
aes_invshiftrow(state->s+8, 2);
|
|
aes_invshiftrow(state->s+12, 3);
|
|
/* subBytes */
|
|
for(i=0; i<16; ++i){
|
|
state->s[i] = pgm_read_byte(aes_invsbox+state->s[i]);
|
|
}
|
|
}
|
|
|
|
|
|
static
|
|
void aes_dec_firstround(aes_cipher_state_t* state, const aes_roundkey_t* k){
|
|
uint8_t i;
|
|
/* keyAdd */
|
|
for(i=0; i<16; ++i){
|
|
state->s[i] ^= k->ks[i];
|
|
}
|
|
/* shiftRows */
|
|
aes_invshiftrow(state->s+4, 1);
|
|
aes_invshiftrow(state->s+8, 2);
|
|
aes_invshiftrow(state->s+12, 3);
|
|
/* subBytes */
|
|
for(i=0; i<16; ++i){
|
|
state->s[i] = pgm_read_byte(aes_invsbox+state->s[i]);
|
|
}
|
|
}
|
|
|
|
void aes_decrypt_core(aes_cipher_state_t* state, const aes_genctx_t* ks, uint8_t rounds){
|
|
uint8_t i;
|
|
aes_dec_firstround(state, &(ks->key[i=rounds]));
|
|
for(;rounds>1;--rounds){
|
|
--i;
|
|
aes_dec_round(state, &(ks->key[i]));
|
|
}
|
|
for(i=0; i<16; ++i){
|
|
state->s[i] ^= ks->key[0].ks[i];
|
|
}
|
|
}
|