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