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/*
* copyright (c) 2007 Michael Niedermayer <michaelni@gmx.at>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "common.h"
#include "log.h"
#include "aes.h"
typedef struct AVAES{
uint8_t state[4][4];
uint8_t round_key[15][4][4];
int rounds;
}AVAES;
static const uint8_t rcon[30] = {
0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80,
0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f,
0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4,
0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91
};
static uint8_t log8[256];
static uint8_t alog8[512];
static uint8_t sbox[256];
static uint8_t inv_sbox[256];
static inline void addkey(uint32_t state[4], uint32_t round_key[4]){
int i;
for(i=0; i<4; i++)
state[i] ^= round_key[i]; //partial memory stall? FIXME benchmark
}
#define SUBSHIFT0(s, box) s[0]=box[s[ 0]]; s[ 4]=box[s[ 4]]; s[ 8]=box[s[ 8]]; s[12]=box[s[12]];
#define SUBSHIFT1(s, box) t=s[0]; s[0]=box[s[ 4]]; s[ 4]=box[s[ 8]]; s[ 8]=box[s[12]]; s[12]=box[t];
#define SUBSHIFT2(s, box) t=s[0]; s[0]=box[s[ 8]]; s[ 8]=box[ t]; t=s[ 4]; s[ 4]=box[s[12]]; s[12]=box[t];
#define SUBSHIFT3(s, box) t=s[0]; s[0]=box[s[12]]; s[12]=box[s[ 8]]; s[ 8]=box[s[ 4]]; s[ 4]=box[t];
static inline int mul(int a, int b){
if(a==255) return 0;
else return alog8[a+b];
}
static inline void mix(uint8_t state[4][4], int c0, int c1, int c2, int c3){
uint8_t tmp[4][4];
int i, j;
for(i=0; i<16; i++)
tmp[0][i]= log8[ state[0][i] ];
for(j=0; j<4; j++)
for(i=0; i<4; i++)
state[j][i]= mul( tmp[j][ i ], c0 )
^mul( tmp[j][(i+ 1)&3], c1 )
^mul( tmp[j][(i+ 2)&3], c2 )
^mul( tmp[j][(i+ 3)&3], c3 );
}
void av_aes_decrypt(AVAES *a){
int t, r;
for(r=a->rounds-1; r>=0; r--){
if(r==a->rounds-1)
addkey(a->state, a->round_key[r+1]);
else
mix(a->state, log8[0xe], log8[0xb], log8[0xd], log8[9]); //FIXME replace log8 by const
SUBSHIFT0((a->state[0]+0), inv_sbox)
SUBSHIFT3((a->state[0]+1), inv_sbox)
SUBSHIFT2((a->state[0]+2), inv_sbox)
SUBSHIFT1((a->state[0]+3), inv_sbox)
addkey(a->state, a->round_key[r]);
}
}
void av_aes_encrypt(AVAES *a){
int r, t;
for(r=0; r<a->rounds; r++){
addkey(a->state, a->round_key[r]);
SUBSHIFT0((a->state[0]+0), sbox)
SUBSHIFT1((a->state[0]+1), sbox)
SUBSHIFT2((a->state[0]+2), sbox)
SUBSHIFT3((a->state[0]+3), sbox)
if(r==a->rounds-1)
addkey(a->state, a->round_key[r+1]);
else
mix(a->state, log8[2], log8[3], 0, 0); //FIXME replace log8 by const / optimze mix as this can be simplified alot
}
}
// this is based on the reference AES code by Paulo Barreto and Vincent Rijmen
AVAES *av_aes_init(uint8_t *key, int keyBits) {
AVAES *a= av_malloc(sizeof(AVAES));
int i, j, t, rconpointer = 0;
uint8_t tk[8][4];
int KC= keyBits/32;
int ROUNDS= KC + 6;
if(!sbox[255]){
j=1;
for(i=0; i<255; i++){
alog8[i]=
alog8[i+255]= j;
log8[j]= i;
j^= j+j;
if(j>255) j^= 0x11B;
}
log8[0]= 255;
for(i=0; i<256; i++){
j= i ? alog8[255-log8[i]] : 0;
j ^= (j<<1) ^ (j<<2) ^ (j<<3) ^ (j<<4)
^(j>>7) ^ (j>>6) ^ (j>>5) ^ (j>>4) ^ 99;
j&=255;
inv_sbox[j]= i;
sbox [i]= j;
// av_log(NULL, AV_LOG_ERROR, "%d, ", log8[i]);
}
}
a->rounds= ROUNDS;
if(keyBits!=128 && keyBits!=192 && keyBits!=256)
return NULL;
memcpy(tk, key, KC*4);
for(t= 0; t < (ROUNDS+1)*4; ) {
for(j = 0; (j < KC) && (t < (ROUNDS+1)*4); j++, t++)
for(i = 0; i < 4; i++)
a->round_key[0][t][i] = tk[j][i];
for(i = 0; i < 4; i++)
tk[0][i] ^= sbox[tk[KC-1][(i+1)&3]];
tk[0][0] ^= rcon[rconpointer++];
for(j = 1; j < KC; j++){
if(KC != 8 || j != KC/2)
for(i = 0; i < 4; i++) tk[j][i] ^= tk[j-1][i];
else
for(i = 0; i < 4; i++)
tk[KC/2][i] ^= sbox[tk[KC/2 - 1][i]];
}
}
return a;
}
#ifdef TEST
int main(){
int i,j,k;
AVAES *a= av_aes_init("PI=3.141592654..", 128);
for(i=0; i<10000; i++){
}
return 0;
}
#endif
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