aes_enc.cpp

/* aes_enc.c */
/*
    This file is part of the AVR-Crypto-Lib.
    Copyright (C) 2008  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/>.
*/
/**
 * \file     aes_enc.c
 * \email    daniel.otte@rub.de
 * \author   Daniel Otte 
 * \date     2008-12-30
 * \license  GPLv3 or later
 * 
 */

#include <stdint.h>
#include <string.h>
#include "aes.h"
#include "gf256mul.h"
#include "aes_sbox.h"
#include "aes_enc.h"
#include <avr/pgmspace.h>

void aes_shiftcol(void *data, uint8_t shift){
	uint8_t tmp[4];
	tmp[0] = ((uint8_t*)data)[ 0];
	tmp[1] = ((uint8_t*)data)[ 4];
	tmp[2] = ((uint8_t*)data)[ 8];
	tmp[3] = ((uint8_t*)data)[12];
	((uint8_t*)data)[ 0] = tmp[(shift+0)&3];
	((uint8_t*)data)[ 4] = tmp[(shift+1)&3];
	((uint8_t*)data)[ 8] = tmp[(shift+2)&3];
	((uint8_t*)data)[12] = tmp[(shift+3)&3];
}

#define GF256MUL_1(a) (a)
#define GF256MUL_2(a) (gf256mul(2, (a), 0x1b))
#define GF256MUL_3(a) (gf256mul(3, (a), 0x1b))

static
void aes_enc_round(aes_cipher_state_t *state, const aes_roundkey_t *k){
	uint8_t tmp[16], t;
	uint8_t i;
	/* subBytes */
	for(i=0; i<16; ++i){
		tmp[i] = pgm_read_byte(aes_sbox+state->s[i]);
	}
	/* shiftRows */
	aes_shiftcol(tmp+1, 1);
	aes_shiftcol(tmp+2, 2);
	aes_shiftcol(tmp+3, 3);
	/* mixColums */
	for(i=0; i<4; ++i){
		t = tmp[4*i+0] ^ tmp[4*i+1] ^ tmp[4*i+2] ^ tmp[4*i+3];
		state->s[4*i+0] =
			  GF256MUL_2(tmp[4*i+0]^tmp[4*i+1])
			^ tmp[4*i+0]
			^ t;
		state->s[4*i+1] =
			  GF256MUL_2(tmp[4*i+1]^tmp[4*i+2])
			^ tmp[4*i+1]
			^ t;
		state->s[4*i+2] =
			  GF256MUL_2(tmp[4*i+2]^tmp[4*i+3])
			^ tmp[4*i+2]
			^ t;
		state->s[4*i+3] =
			  GF256MUL_2(tmp[4*i+3]^tmp[4*i+0])
			^ tmp[4*i+3]
			^ t;
	}

	/* addKey */
	for(i=0; i<16; ++i){
		state->s[i] ^= k->ks[i];
	}
}


static
void aes_enc_lastround(aes_cipher_state_t *state,const aes_roundkey_t *k){
	uint8_t i;
	/* subBytes */
	for(i=0; i<16; ++i){
		state->s[i] = pgm_read_byte(aes_sbox+state->s[i]);
	}
	/* shiftRows */
	aes_shiftcol(state->s+1, 1);
	aes_shiftcol(state->s+2, 2);
	aes_shiftcol(state->s+3, 3);
	/* keyAdd */
	for(i=0; i<16; ++i){
		state->s[i] ^= k->ks[i];
	}
}

void aes_encrypt_core(aes_cipher_state_t *state, const aes_genctx_t *ks, uint8_t rounds){
	uint8_t i;
	for(i=0; i<16; ++i){
		state->s[i] ^= ks->key[0].ks[i];
	}
	i=1;
	for(;rounds>1;--rounds){
		aes_enc_round(state, &(ks->key[i]));
		++i;
	}
	aes_enc_lastround(state, &(ks->key[i]));
}