aes support (unfinished)

Originally committed as revision 7460 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/aes.c

+/*
+ * 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