132 lines
3.8 KiB
C
132 lines
3.8 KiB
C
/* aes.c */
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/*
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This file is part of the AVR-Crypto-Lib.
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Copyright (C) 2006-2015 Daniel Otte (bg@nerilex.org)
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdint.h>
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#include <string.h>
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#include "gf256mul.h"
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#include "aes.h"
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#include "aes_invsbox.h"
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#include "aes_dec.h"
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#include <avr/pgmspace.h>
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void aes_invshiftrow(void *data, uint8_t shift){
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uint8_t tmp[4];
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tmp[0] = ((uint8_t*)data)[(4+0-shift)&3];
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tmp[1] = ((uint8_t*)data)[(4+1-shift)&3];
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tmp[2] = ((uint8_t*)data)[(4+2-shift)&3];
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tmp[3] = ((uint8_t*)data)[(4+3-shift)&3];
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memcpy(data, tmp, 4);
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}
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void aes_invshiftcol(void *data, uint8_t shift){
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uint8_t tmp[4];
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tmp[0] = ((uint8_t*)data)[ 0];
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tmp[1] = ((uint8_t*)data)[ 4];
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tmp[2] = ((uint8_t*)data)[ 8];
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tmp[3] = ((uint8_t*)data)[12];
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((uint8_t*)data)[ 0] = tmp[(4-shift+0)&3];
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((uint8_t*)data)[ 4] = tmp[(4-shift+1)&3];
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((uint8_t*)data)[ 8] = tmp[(4-shift+2)&3];
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((uint8_t*)data)[12] = tmp[(4-shift+3)&3];
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}
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static
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void aes_dec_round(aes_cipher_state_t *state, const aes_roundkey_t *k){
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uint8_t tmp[16];
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uint8_t i;
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uint8_t t,u,v,w;
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/* keyAdd */
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for(i=0; i<16; ++i){
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tmp[i] = state->s[i] ^ k->ks[i];
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}
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/* mixColums */
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for(i=0; i<4; ++i){
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t = tmp[4*i+3] ^ tmp[4*i+2];
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u = tmp[4*i+1] ^ tmp[4*i+0];
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v = t ^ u;
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v = gf256mul(0x09, v, 0x1b);
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w = v ^ gf256mul(0x04, tmp[4*i+2] ^ tmp[4*i+0], 0x1b);
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v = v ^ gf256mul(0x04, tmp[4*i+3] ^ tmp[4*i+1], 0x1b);
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state->s[4*i+3] = tmp[4*i+3] ^ v ^ gf256mul(0x02, tmp[4*i+0] ^ tmp[4*i+3], 0x1b);
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state->s[4*i+2] = tmp[4*i+2] ^ w ^ gf256mul(0x02, t, 0x1b);
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state->s[4*i+1] = tmp[4*i+1] ^ v ^ gf256mul(0x02, tmp[4*i+2] ^ tmp[4*i+1], 0x1b);
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state->s[4*i+0] = tmp[4*i+0] ^ w ^ gf256mul(0x02, u, 0x1b);
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/*
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state->s[4*i+0] =
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gf256mul(0xe, tmp[4*i+0], 0x1b)
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^ gf256mul(0xb, tmp[4*i+1], 0x1b)
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^ gf256mul(0xd, tmp[4*i+2], 0x1b)
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^ gf256mul(0x9, tmp[4*i+3], 0x1b);
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state->s[4*i+1] =
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gf256mul(0x9, tmp[4*i+0], 0x1b)
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^ gf256mul(0xe, tmp[4*i+1], 0x1b)
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^ gf256mul(0xb, tmp[4*i+2], 0x1b)
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^ gf256mul(0xd, tmp[4*i+3], 0x1b);
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state->s[4*i+2] =
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gf256mul(0xd, tmp[4*i+0], 0x1b)
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^ gf256mul(0x9, tmp[4*i+1], 0x1b)
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^ gf256mul(0xe, tmp[4*i+2], 0x1b)
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^ gf256mul(0xb, tmp[4*i+3], 0x1b);
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state->s[4*i+3] =
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gf256mul(0xb, tmp[4*i+0], 0x1b)
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^ gf256mul(0xd, tmp[4*i+1], 0x1b)
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^ gf256mul(0x9, tmp[4*i+2], 0x1b)
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^ gf256mul(0xe, tmp[4*i+3], 0x1b);
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*/
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}
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/* shiftRows */
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aes_invshiftcol(state->s+1, 1);
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aes_invshiftcol(state->s+2, 2);
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aes_invshiftcol(state->s+3, 3);
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/* subBytes */
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for(i=0; i<16; ++i){
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state->s[i] = pgm_read_byte(aes_invsbox+state->s[i]);
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}
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}
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static
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void aes_dec_firstround(aes_cipher_state_t *state, const aes_roundkey_t *k){
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uint8_t i;
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/* keyAdd */
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for(i=0; i<16; ++i){
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state->s[i] ^= k->ks[i];
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}
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/* shiftRows */
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aes_invshiftcol(state->s+1, 1);
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aes_invshiftcol(state->s+2, 2);
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aes_invshiftcol(state->s+3, 3);
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/* subBytes */
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for(i=0; i<16; ++i){
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state->s[i] = pgm_read_byte(aes_invsbox+state->s[i]);
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}
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}
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void aes_decrypt_core(aes_cipher_state_t *state, const aes_genctx_t *ks, uint8_t rounds){
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uint8_t i;
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aes_dec_firstround(state, &(ks->key[i=rounds]));
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for(;rounds>1;--rounds){
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--i;
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aes_dec_round(state, &(ks->key[i]));
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}
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for(i=0; i<16; ++i){
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state->s[i] ^= ks->key[0].ks[i];
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}
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}
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