simplify
[libav.git] / libavutil / aes.c
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1/*
2 * copyright (c) 2007 Michael Niedermayer <michaelni@gmx.at>
3 *
4 * This file is part of FFmpeg.
5 *
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21#include "common.h"
22#include "log.h"
23#include "aes.h"
24
25typedef struct AVAES{
26 uint8_t state[4][4];
27 uint8_t round_key[15][4][4];
28 int rounds;
29}AVAES;
30
31static const uint8_t rcon[30] = {
32 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80,
33 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f,
34 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4,
35 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91
36};
37
38static uint8_t log8[256];
39static uint8_t alog8[512];
40static uint8_t sbox[256];
41static uint8_t inv_sbox[256];
42
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43static inline void addkey(uint64_t state[2], uint64_t round_key[2]){
44 state[0] ^= round_key[0];
45 state[1] ^= round_key[1];
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46}
47
48#define SUBSHIFT0(s, box) s[0]=box[s[ 0]]; s[ 4]=box[s[ 4]]; s[ 8]=box[s[ 8]]; s[12]=box[s[12]];
49#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];
50#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];
51#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];
52
53static inline int mul(int a, int b){
54 if(a==255) return 0;
55 else return alog8[a+b];
56}
57
58static inline void mix(uint8_t state[4][4], int c0, int c1, int c2, int c3){
59 uint8_t tmp[4][4];
60 int i, j;
61
62 for(i=0; i<16; i++)
63 tmp[0][i]= log8[ state[0][i] ];
64 for(j=0; j<4; j++)
65 for(i=0; i<4; i++)
66 state[j][i]= mul( tmp[j][ i ], c0 )
67 ^mul( tmp[j][(i+ 1)&3], c1 )
68 ^mul( tmp[j][(i+ 2)&3], c2 )
69 ^mul( tmp[j][(i+ 3)&3], c3 );
70}
71
72
73void av_aes_decrypt(AVAES *a){
74 int t, r;
75
76 for(r=a->rounds-1; r>=0; r--){
77 if(r==a->rounds-1)
78 addkey(a->state, a->round_key[r+1]);
79 else
80 mix(a->state, log8[0xe], log8[0xb], log8[0xd], log8[9]); //FIXME replace log8 by const
81 SUBSHIFT0((a->state[0]+0), inv_sbox)
82 SUBSHIFT3((a->state[0]+1), inv_sbox)
83 SUBSHIFT2((a->state[0]+2), inv_sbox)
84 SUBSHIFT1((a->state[0]+3), inv_sbox)
85 addkey(a->state, a->round_key[r]);
86 }
87}
88
89void av_aes_encrypt(AVAES *a){
90 int r, t;
91
92 for(r=0; r<a->rounds; r++){
93 addkey(a->state, a->round_key[r]);
94 SUBSHIFT0((a->state[0]+0), sbox)
95 SUBSHIFT1((a->state[0]+1), sbox)
96 SUBSHIFT2((a->state[0]+2), sbox)
97 SUBSHIFT3((a->state[0]+3), sbox)
98 if(r==a->rounds-1)
99 addkey(a->state, a->round_key[r+1]);
100 else
101 mix(a->state, log8[2], log8[3], 0, 0); //FIXME replace log8 by const / optimze mix as this can be simplified alot
102 }
103}
104
105// this is based on the reference AES code by Paulo Barreto and Vincent Rijmen
d43a2975 106AVAES *av_aes_init(uint8_t *key, int key_bits) {
eade86e2 107 AVAES *a;
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108 int i, j, t, rconpointer = 0;
109 uint8_t tk[8][4];
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110 int KC= key_bits/32;
111 int rounds= KC + 6;
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112
113 if(!sbox[255]){
114 j=1;
115 for(i=0; i<255; i++){
116 alog8[i]=
117 alog8[i+255]= j;
118 log8[j]= i;
119 j^= j+j;
120 if(j>255) j^= 0x11B;
121 }
122 log8[0]= 255;
123 for(i=0; i<256; i++){
124 j= i ? alog8[255-log8[i]] : 0;
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125 j ^= (j<<1) ^ (j<<2) ^ (j<<3) ^ (j<<4);
126 j = (j ^ (j>>8) ^ 99) & 255;
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127 inv_sbox[j]= i;
128 sbox [i]= j;
129// av_log(NULL, AV_LOG_ERROR, "%d, ", log8[i]);
130 }
131 }
132
d43a2975 133 if(key_bits!=128 && key_bits!=192 && key_bits!=256)
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134 return NULL;
135
eade86e2 136 a= av_malloc(sizeof(AVAES));
d43a2975 137 a->rounds= rounds;
eade86e2 138
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139 memcpy(tk, key, KC*4);
140
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141 for(t= 0; t < (rounds+1)*4; ) {
142 for(j = 0; (j < KC) && (t < (rounds+1)*4); j++, t++)
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143 for(i = 0; i < 4; i++)
144 a->round_key[0][t][i] = tk[j][i];
145
146 for(i = 0; i < 4; i++)
147 tk[0][i] ^= sbox[tk[KC-1][(i+1)&3]];
148 tk[0][0] ^= rcon[rconpointer++];
149
150 for(j = 1; j < KC; j++){
151 if(KC != 8 || j != KC/2)
152 for(i = 0; i < 4; i++) tk[j][i] ^= tk[j-1][i];
153 else
154 for(i = 0; i < 4; i++)
155 tk[KC/2][i] ^= sbox[tk[KC/2 - 1][i]];
156 }
157 }
158 return a;
159}
160
161#ifdef TEST
162
163int main(){
164 int i,j,k;
165 AVAES *a= av_aes_init("PI=3.141592654..", 128);
166
167 for(i=0; i<10000; i++){
168 }
169 return 0;
170}
171#endif