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ffmpeg/libavutil/aes.c

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/*
* copyright (c) 2007 Michael Niedermayer <michaelni@gmx.at> and Reimar Doeffinger
*
* 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 round_key[15][4][4];
uint8_t state[4][4];
int rounds;
}AVAES;
static const uint8_t rcon[11] = {
0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c
};
static uint8_t sbox[256];
static uint8_t inv_sbox[256];
#ifdef CONFIG_SMALL
static uint32_t enc_multbl[1][256];
static uint32_t dec_multbl[1][256];
#else
static uint32_t enc_multbl[4][256];
static uint32_t dec_multbl[4][256];
#endif
static inline void addkey(uint64_t state[2], uint64_t round_key[2]){
state[0] ^= round_key[0];
state[1] ^= round_key[1];
}
#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];
#define ROT(x,s) ((x>>s)|(x<<(32-s))
static inline void mix(uint8_t state[4][4], uint32_t multbl[4][256]){
int i;
for(i=0; i<4; i++)
#ifdef CONFIG_SMALL
((uint32_t *)(state))[i] = multbl[0][state[i][0]] ^ ROT(multbl[0][state[i][1]], 8)
^ROT(multbl[0][state[i][2]],16) ^ ROT(multbl[0][state[i][3]],24);
#else
((uint32_t *)(state))[i] = multbl[0][state[i][0]] ^ multbl[1][state[i][1]]
^multbl[2][state[i][2]] ^ multbl[3][state[i][3]];
#endif
}
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, dec_multbl);
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, enc_multbl); //FIXME replace log8 by const / optimze mix as this can be simplified alot
}
}
static init_multbl(uint8_t tbl[256], int c[4], uint8_t *log8, uint8_t *alog8){
int i;
for(i=4; i<1024; i++)
tbl[i]= alog8[ log8[i/4] + log8[c[i&3]] ];
}
// this is based on the reference AES code by Paulo Barreto and Vincent Rijmen
AVAES *av_aes_init(uint8_t *key, int key_bits) {
AVAES *a;
int i, j, t, rconpointer = 0;
uint8_t tk[8][4];
int KC= key_bits/32;
int rounds= KC + 6;
uint8_t log8[256];
uint8_t alog8[512];
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 = (j ^ (j>>8) ^ 99) & 255;
inv_sbox[j]= i;
sbox [i]= j;
// av_log(NULL, AV_LOG_ERROR, "%d, ", log8[i]);
}
init_multbl(dec_multbl[0], (int[4]){0xe, 0x9, 0xd, 0xb}, log8, alog8);
init_multbl(dec_multbl[1], (int[4]){0xb, 0xe, 0x9, 0xd}, log8, alog8);
init_multbl(dec_multbl[2], (int[4]){0xd, 0xb, 0xe, 0x9}, log8, alog8);
init_multbl(dec_multbl[3], (int[4]){0x9, 0xd, 0xb, 0xe}, log8, alog8);
init_multbl(enc_multbl[0], (int[4]){0x2, 0x1, 0x1, 0x3}, log8, alog8);
init_multbl(enc_multbl[1], (int[4]){0x3, 0x2, 0x1, 0x1}, log8, alog8);
init_multbl(enc_multbl[2], (int[4]){0x1, 0x3, 0x2, 0x1}, log8, alog8);
init_multbl(enc_multbl[3], (int[4]){0x1, 0x1, 0x3, 0x2}, log8, alog8);
}
if(key_bits!=128 && key_bits!=192 && key_bits!=256)
return NULL;
a= av_malloc(sizeof(AVAES));
a->rounds= rounds;
memcpy(tk, key, KC*4);
for(t= 0; t < (rounds+1)*4;) {
memcpy(a->round_key[0][t], tk, KC*4);
t+= KC;
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[j][i] ^= sbox[tk[j-1][i]];
}
}
return a;
}
#ifdef TEST
int main(){
int i,j,k;
AVAES *a= av_aes_init("PI=3.141592654..", 128);
uint8_t ct[16], pt[16], key[32];
for(i=0; i<10000; i++){
for(j=0; j<16; j++){
pt[j]= random();
}
memcpy(a->state, pt, 16);
av_aes_encrypt(a);
if(!(i&(i-1)))
av_log(NULL, AV_LOG_ERROR, "%02X %02X %02X %02X\n", a->state[0][0], a->state[1][1], a->state[2][2], a->state[3][3]);
av_aes_decrypt(a);
for(j=0; j<16; j++){
if(pt[j] != a->state[0][j]){
av_log(NULL, AV_LOG_ERROR, "%d %d %02X %02X\n", i,j, pt[j], a->state[0][j]);
}
}
}
return 0;
}
#endif
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