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ffmpeg / libavutil / aes.c @ 7acc1a27

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/*
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 * copyright (c) 2007 Michael Niedermayer <michaelni@gmx.at> and Reimar D?ffinger
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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[11] = {
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  0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c
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};
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static uint8_t     sbox[256];
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static uint8_t inv_sbox[256];
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#ifdef CONFIG_SMALL
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static uint32_t enc_multbl[1][256];
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static uint32_t dec_multbl[1][256];
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#else
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static uint32_t enc_multbl[4][256];
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static uint32_t dec_multbl[4][256];
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#endif
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static inline void addkey(uint64_t state[2], uint64_t round_key[2]){
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    state[0] ^= round_key[0];
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    state[1] ^= round_key[1];
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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, uint8_t alog8[256]){
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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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#define ROT(x,s) ((x>>s)|(x<<(32-s))
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static inline void mix(uint8_t state[4][4], uint32_t multbl[4][256]){
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    int i;
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    for(i=0; i<4; i++)
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#ifdef CONFIG_SMALL
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        ((uint32_t *)(state))[i] =     multbl[0][state[i][0]]     ^ ROT(multbl[0][state[i][1]], 8)
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                                  ^ROT(multbl[0][state[i][2]],16) ^ ROT(multbl[0][state[i][3]],24);
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#else
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        ((uint32_t *)(state))[i] = multbl[0][state[i][0]] ^ multbl[1][state[i][1]]
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                                  ^multbl[2][state[i][2]] ^ multbl[3][state[i][3]];
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#endif
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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, dec_multbl);
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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, enc_multbl); //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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    uint8_t  log8[256];
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    uint8_t alog8[512];
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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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            //FIXME multbl init
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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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            memcpy(a->round_key[0][t],  tk[j], 4);
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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