| 1 | /* crapto1.c\r |
| 2 | \r |
| 3 | This program is free software; you can redistribute it and/or\r |
| 4 | modify it under the terms of the GNU General Public License\r |
| 5 | as published by the Free Software Foundation; either version 2\r |
| 6 | of the License, or (at your option) any later version.\r |
| 7 | \r |
| 8 | This program is distributed in the hope that it will be useful,\r |
| 9 | but WITHOUT ANY WARRANTY; without even the implied warranty of\r |
| 10 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the\r |
| 11 | GNU General Public License for more details.\r |
| 12 | \r |
| 13 | You should have received a copy of the GNU General Public License\r |
| 14 | along with this program; if not, write to the Free Software\r |
| 15 | Foundation, Inc., 51 Franklin Street, Fifth Floor,\r |
| 16 | Boston, MA 02110-1301, US$\r |
| 17 | \r |
| 18 | Copyright (C) 2008-2008 bla <blapost@gmail.com>\r |
| 19 | */\r |
| 20 | #include "crapto1.h"\r |
| 21 | #include <stdlib.h>\r |
| 22 | \r |
| 23 | #if !defined LOWMEM && defined __GNUC__\r |
| 24 | static uint8_t filterlut[1 << 20];\r |
| 25 | static void __attribute__((constructor)) fill_lut()\r |
| 26 | {\r |
| 27 | uint32_t i;\r |
| 28 | for(i = 0; i < 1 << 20; ++i)\r |
| 29 | filterlut[i] = filter(i);\r |
| 30 | }\r |
| 31 | #define filter(x) (filterlut[(x) & 0xfffff])\r |
| 32 | #endif\r |
| 33 | \r |
| 34 | static void quicksort(uint32_t* const start, uint32_t* const stop)\r |
| 35 | {\r |
| 36 | uint32_t *it = start + 1, *rit = stop;\r |
| 37 | \r |
| 38 | if(it > rit)\r |
| 39 | return;\r |
| 40 | \r |
| 41 | while(it < rit)\r |
| 42 | if(*it <= *start)\r |
| 43 | ++it;\r |
| 44 | else if(*rit > *start)\r |
| 45 | --rit;\r |
| 46 | else\r |
| 47 | *it ^= (*it ^= *rit, *rit ^= *it);\r |
| 48 | \r |
| 49 | if(*rit >= *start)\r |
| 50 | --rit;\r |
| 51 | if(rit != start)\r |
| 52 | *rit ^= (*rit ^= *start, *start ^= *rit);\r |
| 53 | \r |
| 54 | quicksort(start, rit - 1);\r |
| 55 | quicksort(rit + 1, stop);\r |
| 56 | }\r |
| 57 | /** binsearch\r |
| 58 | * Binary search for the first occurence of *stop's MSB in sorted [start,stop]\r |
| 59 | */\r |
| 60 | static inline uint32_t*\r |
| 61 | binsearch(uint32_t *start, uint32_t *stop)\r |
| 62 | {\r |
| 63 | uint32_t mid, val = *stop & 0xff000000;\r |
| 64 | while(start != stop)\r |
| 65 | if(start[mid = (stop - start) >> 1] > val)\r |
| 66 | stop = &start[mid];\r |
| 67 | else\r |
| 68 | start += mid + 1;\r |
| 69 | \r |
| 70 | return start;\r |
| 71 | }\r |
| 72 | \r |
| 73 | /** update_contribution\r |
| 74 | * helper, calculates the partial linear feedback contributions and puts in MSB\r |
| 75 | */\r |
| 76 | static inline void\r |
| 77 | update_contribution(uint32_t *item, const uint32_t mask1, const uint32_t mask2)\r |
| 78 | {\r |
| 79 | uint32_t p = *item >> 25;\r |
| 80 | \r |
| 81 | p = p << 1 | parity(*item & mask1);\r |
| 82 | p = p << 1 | parity(*item & mask2);\r |
| 83 | *item = p << 24 | (*item & 0xffffff);\r |
| 84 | }\r |
| 85 | \r |
| 86 | /** extend_table\r |
| 87 | * using a bit of the keystream extend the table of possible lfsr states\r |
| 88 | */\r |
| 89 | static inline void\r |
| 90 | extend_table(uint32_t *tbl, uint32_t **end, int bit, int m1, int m2, uint32_t in)\r |
| 91 | {\r |
| 92 | in <<= 24;\r |
| 93 | for(*tbl <<= 1; tbl <= *end; *++tbl <<= 1)\r |
| 94 | if(filter(*tbl) ^ filter(*tbl | 1)) {\r |
| 95 | *tbl |= filter(*tbl) ^ bit;\r |
| 96 | update_contribution(tbl, m1, m2);\r |
| 97 | *tbl ^= in;\r |
| 98 | } else if(filter(*tbl) == bit) {\r |
| 99 | *++*end = tbl[1];\r |
| 100 | tbl[1] = tbl[0] | 1;\r |
| 101 | update_contribution(tbl, m1, m2);\r |
| 102 | *tbl++ ^= in;\r |
| 103 | update_contribution(tbl, m1, m2);\r |
| 104 | *tbl ^= in;\r |
| 105 | } else\r |
| 106 | *tbl-- = *(*end)--;\r |
| 107 | }\r |
| 108 | /** extend_table_simple\r |
| 109 | * using a bit of the keystream extend the table of possible lfsr states\r |
| 110 | */\r |
| 111 | static inline void\r |
| 112 | extend_table_simple(uint32_t *tbl, uint32_t **end, int bit)\r |
| 113 | {\r |
| 114 | for(*tbl <<= 1; tbl <= *end; *++tbl <<= 1)\r |
| 115 | if(filter(*tbl) ^ filter(*tbl | 1)) {\r |
| 116 | *tbl |= filter(*tbl) ^ bit;\r |
| 117 | } else if(filter(*tbl) == bit) {\r |
| 118 | *++*end = *++tbl;\r |
| 119 | *tbl = tbl[-1] | 1;\r |
| 120 | } else\r |
| 121 | *tbl-- = *(*end)--;\r |
| 122 | }\r |
| 123 | /** recover\r |
| 124 | * recursively narrow down the search space, 4 bits of keystream at a time\r |
| 125 | */\r |
| 126 | static struct Crypto1State*\r |
| 127 | recover(uint32_t *o_head, uint32_t *o_tail, uint32_t oks,\r |
| 128 | uint32_t *e_head, uint32_t *e_tail, uint32_t eks, int rem,\r |
| 129 | struct Crypto1State *sl, uint32_t in)\r |
| 130 | {\r |
| 131 | uint32_t *o, *e, i;\r |
| 132 | \r |
| 133 | if(rem == -1) {\r |
| 134 | for(e = e_head; e <= e_tail; ++e) {\r |
| 135 | *e = *e << 1 ^ parity(*e & LF_POLY_EVEN) ^ !!(in & 4);\r |
| 136 | for(o = o_head; o <= o_tail; ++o, ++sl) {\r |
| 137 | sl->even = *o;\r |
| 138 | sl->odd = *e ^ parity(*o & LF_POLY_ODD);\r |
| 139 | sl[1].odd = sl[1].even = 0;\r |
| 140 | }\r |
| 141 | }\r |
| 142 | return sl;\r |
| 143 | }\r |
| 144 | \r |
| 145 | for(i = 0; i < 4 && rem--; i++) {\r |
| 146 | extend_table(o_head, &o_tail, (oks >>= 1) & 1,\r |
| 147 | LF_POLY_EVEN << 1 | 1, LF_POLY_ODD << 1, 0);\r |
| 148 | if(o_head > o_tail)\r |
| 149 | return sl;\r |
| 150 | \r |
| 151 | extend_table(e_head, &e_tail, (eks >>= 1) & 1,\r |
| 152 | LF_POLY_ODD, LF_POLY_EVEN << 1 | 1, (in >>= 2) & 3);\r |
| 153 | if(e_head > e_tail)\r |
| 154 | return sl;\r |
| 155 | }\r |
| 156 | \r |
| 157 | quicksort(o_head, o_tail);\r |
| 158 | quicksort(e_head, e_tail);\r |
| 159 | \r |
| 160 | while(o_tail >= o_head && e_tail >= e_head)\r |
| 161 | if(((*o_tail ^ *e_tail) >> 24) == 0) {\r |
| 162 | o_tail = binsearch(o_head, o = o_tail);\r |
| 163 | e_tail = binsearch(e_head, e = e_tail);\r |
| 164 | sl = recover(o_tail--, o, oks,\r |
| 165 | e_tail--, e, eks, rem, sl, in);\r |
| 166 | }\r |
| 167 | else if(*o_tail > *e_tail)\r |
| 168 | o_tail = binsearch(o_head, o_tail) - 1;\r |
| 169 | else\r |
| 170 | e_tail = binsearch(e_head, e_tail) - 1;\r |
| 171 | \r |
| 172 | return sl;\r |
| 173 | }\r |
| 174 | /** lfsr_recovery\r |
| 175 | * recover the state of the lfsr given 32 bits of the keystream\r |
| 176 | * additionally you can use the in parameter to specify the value\r |
| 177 | * that was fed into the lfsr at the time the keystream was generated\r |
| 178 | */\r |
| 179 | struct Crypto1State* lfsr_recovery32(uint32_t ks2, uint32_t in)\r |
| 180 | {\r |
| 181 | struct Crypto1State *statelist;\r |
| 182 | uint32_t *odd_head = 0, *odd_tail = 0, oks = 0;\r |
| 183 | uint32_t *even_head = 0, *even_tail = 0, eks = 0;\r |
| 184 | int i;\r |
| 185 | \r |
| 186 | for(i = 31; i >= 0; i -= 2)\r |
| 187 | oks = oks << 1 | BEBIT(ks2, i);\r |
| 188 | for(i = 30; i >= 0; i -= 2)\r |
| 189 | eks = eks << 1 | BEBIT(ks2, i);\r |
| 190 | \r |
| 191 | odd_head = odd_tail = malloc(sizeof(uint32_t) << 21);\r |
| 192 | even_head = even_tail = malloc(sizeof(uint32_t) << 21);\r |
| 193 | statelist = malloc(sizeof(struct Crypto1State) << 18);\r |
| 194 | if(!odd_tail-- || !even_tail-- || !statelist)\r |
| 195 | goto out;\r |
| 196 | \r |
| 197 | statelist->odd = statelist->even = 0;\r |
| 198 | \r |
| 199 | for(i = 1 << 20; i >= 0; --i) {\r |
| 200 | if(filter(i) == (oks & 1))\r |
| 201 | *++odd_tail = i;\r |
| 202 | if(filter(i) == (eks & 1))\r |
| 203 | *++even_tail = i;\r |
| 204 | }\r |
| 205 | \r |
| 206 | for(i = 0; i < 4; i++) {\r |
| 207 | extend_table_simple(odd_head, &odd_tail, (oks >>= 1) & 1);\r |
| 208 | extend_table_simple(even_head, &even_tail, (eks >>= 1) & 1);\r |
| 209 | }\r |
| 210 | \r |
| 211 | in = (in >> 16 & 0xff) | (in << 16) | (in & 0xff00);\r |
| 212 | recover(odd_head, odd_tail, oks,\r |
| 213 | even_head, even_tail, eks, 11, statelist, in << 1);\r |
| 214 | \r |
| 215 | out:\r |
| 216 | free(odd_head);\r |
| 217 | free(even_head);\r |
| 218 | return statelist;\r |
| 219 | }\r |
| 220 | \r |
| 221 | static const uint32_t S1[] = { 0x62141, 0x310A0, 0x18850, 0x0C428, 0x06214,\r |
| 222 | 0x0310A, 0x85E30, 0xC69AD, 0x634D6, 0xB5CDE, 0xDE8DA, 0x6F46D, 0xB3C83,\r |
| 223 | 0x59E41, 0xA8995, 0xD027F, 0x6813F, 0x3409F, 0x9E6FA};\r |
| 224 | static const uint32_t S2[] = { 0x3A557B00, 0x5D2ABD80, 0x2E955EC0, 0x174AAF60,\r |
| 225 | 0x0BA557B0, 0x05D2ABD8, 0x0449DE68, 0x048464B0, 0x42423258, 0x278192A8,\r |
| 226 | 0x156042D0, 0x0AB02168, 0x43F89B30, 0x61FC4D98, 0x765EAD48, 0x7D8FDD20,\r |
| 227 | 0x7EC7EE90, 0x7F63F748, 0x79117020};\r |
| 228 | static const uint32_t T1[] = {\r |
| 229 | 0x4F37D, 0x279BE, 0x97A6A, 0x4BD35, 0x25E9A, 0x12F4D, 0x097A6, 0x80D66,\r |
| 230 | 0xC4006, 0x62003, 0xB56B4, 0x5AB5A, 0xA9318, 0xD0F39, 0x6879C, 0xB057B,\r |
| 231 | 0x582BD, 0x2C15E, 0x160AF, 0x8F6E2, 0xC3DC4, 0xE5857, 0x72C2B, 0x39615,\r |
| 232 | 0x98DBF, 0xC806A, 0xE0680, 0x70340, 0x381A0, 0x98665, 0x4C332, 0xA272C};\r |
| 233 | static const uint32_t T2[] = { 0x3C88B810, 0x5E445C08, 0x2982A580, 0x14C152C0,\r |
| 234 | 0x4A60A960, 0x253054B0, 0x52982A58, 0x2FEC9EA8, 0x1156C4D0, 0x08AB6268,\r |
| 235 | 0x42F53AB0, 0x217A9D58, 0x161DC528, 0x0DAE6910, 0x46D73488, 0x25CB11C0,\r |
| 236 | 0x52E588E0, 0x6972C470, 0x34B96238, 0x5CFC3A98, 0x28DE96C8, 0x12CFC0E0,\r |
| 237 | 0x4967E070, 0x64B3F038, 0x74F97398, 0x7CDC3248, 0x38CE92A0, 0x1C674950,\r |
| 238 | 0x0E33A4A8, 0x01B959D0, 0x40DCACE8, 0x26CEDDF0};\r |
| 239 | static const uint32_t C1[] = { 0x846B5, 0x4235A, 0x211AD};\r |
| 240 | static const uint32_t C2[] = { 0x1A822E0, 0x21A822E0, 0x21A822E0};\r |
| 241 | /** Reverse 64 bits of keystream into possible cipher states\r |
| 242 | * Variation mentioned in the paper. Somewhat optimized version\r |
| 243 | */\r |
| 244 | struct Crypto1State* lfsr_recovery64(uint32_t ks2, uint32_t ks3)\r |
| 245 | {\r |
| 246 | struct Crypto1State *statelist, *sl;\r |
| 247 | uint8_t oks[32], eks[32], hi[32];\r |
| 248 | uint32_t low = 0, win = 0;\r |
| 249 | uint32_t *tail, table[1 << 16];\r |
| 250 | int i, j;\r |
| 251 | \r |
| 252 | sl = statelist = malloc(sizeof(struct Crypto1State) << 4);\r |
| 253 | if(!sl)\r |
| 254 | return 0;\r |
| 255 | sl->odd = sl->even = 0;\r |
| 256 | \r |
| 257 | for(i = 30; i >= 0; i -= 2) {\r |
| 258 | oks[i >> 1] = BIT(ks2, i ^ 24);\r |
| 259 | oks[16 + (i >> 1)] = BIT(ks3, i ^ 24);\r |
| 260 | }\r |
| 261 | for(i = 31; i >= 0; i -= 2) {\r |
| 262 | eks[i >> 1] = BIT(ks2, i ^ 24);\r |
| 263 | eks[16 + (i >> 1)] = BIT(ks3, i ^ 24);\r |
| 264 | }\r |
| 265 | \r |
| 266 | for(i = 0xfffff; i >= 0; --i) {\r |
| 267 | if (filter(i) != oks[0])\r |
| 268 | continue;\r |
| 269 | \r |
| 270 | *(tail = table) = i;\r |
| 271 | for(j = 1; tail >= table && j < 29; ++j)\r |
| 272 | extend_table_simple(table, &tail, oks[j]);\r |
| 273 | \r |
| 274 | if(tail < table)\r |
| 275 | continue;\r |
| 276 | \r |
| 277 | for(j = 0; j < 19; ++j)\r |
| 278 | low = low << 1 | parity(i & S1[j]);\r |
| 279 | for(j = 0; j < 32; ++j)\r |
| 280 | hi[j] = parity(i & T1[j]);\r |
| 281 | \r |
| 282 | for(; tail >= table; --tail) {\r |
| 283 | for(j = 0; j < 3; ++j) {\r |
| 284 | *tail = *tail << 1;\r |
| 285 | *tail |= parity((i & C1[j]) ^ (*tail & C2[j]));\r |
| 286 | if(filter(*tail) != oks[29 + j])\r |
| 287 | goto continue2;\r |
| 288 | }\r |
| 289 | \r |
| 290 | for(j = 0; j < 19; ++j)\r |
| 291 | win = win << 1 | parity(*tail & S2[j]);\r |
| 292 | \r |
| 293 | win ^= low;\r |
| 294 | for(j = 0; j < 32; ++j) {\r |
| 295 | win = win << 1 ^ hi[j] ^ parity(*tail & T2[j]);\r |
| 296 | if(filter(win) != eks[j])\r |
| 297 | goto continue2;\r |
| 298 | }\r |
| 299 | \r |
| 300 | *tail = *tail << 1 | parity(LF_POLY_EVEN & *tail);\r |
| 301 | sl->odd = *tail ^ parity(LF_POLY_ODD & win);\r |
| 302 | sl->even = win;\r |
| 303 | ++sl;\r |
| 304 | sl->odd = sl->even = 0;\r |
| 305 | continue2:;\r |
| 306 | }\r |
| 307 | }\r |
| 308 | return statelist;\r |
| 309 | }\r |
| 310 | \r |
| 311 | /** lfsr_rollback_bit\r |
| 312 | * Rollback the shift register in order to get previous states\r |
| 313 | */\r |
| 314 | void lfsr_rollback_bit(struct Crypto1State *s, uint32_t in, int fb)\r |
| 315 | {\r |
| 316 | int out;\r |
| 317 | \r |
| 318 | s->odd &= 0xffffff;\r |
| 319 | s->odd ^= (s->odd ^= s->even, s->even ^= s->odd);\r |
| 320 | \r |
| 321 | out = s->even & 1;\r |
| 322 | out ^= LF_POLY_EVEN & (s->even >>= 1);\r |
| 323 | out ^= LF_POLY_ODD & s->odd;\r |
| 324 | out ^= !!in;\r |
| 325 | out ^= filter(s->odd) & !!fb;\r |
| 326 | \r |
| 327 | s->even |= parity(out) << 23;\r |
| 328 | }\r |
| 329 | /** lfsr_rollback_byte\r |
| 330 | * Rollback the shift register in order to get previous states\r |
| 331 | */\r |
| 332 | void lfsr_rollback_byte(struct Crypto1State *s, uint32_t in, int fb)\r |
| 333 | {\r |
| 334 | int i;\r |
| 335 | for (i = 7; i >= 0; --i)\r |
| 336 | lfsr_rollback_bit(s, BEBIT(in, i), fb);\r |
| 337 | }\r |
| 338 | /** lfsr_rollback_word\r |
| 339 | * Rollback the shift register in order to get previous states\r |
| 340 | */\r |
| 341 | void lfsr_rollback_word(struct Crypto1State *s, uint32_t in, int fb)\r |
| 342 | {\r |
| 343 | int i;\r |
| 344 | for (i = 31; i >= 0; --i)\r |
| 345 | lfsr_rollback_bit(s, BEBIT(in, i), fb);\r |
| 346 | }\r |
| 347 | \r |
| 348 | /** nonce_distance\r |
| 349 | * x,y valid tag nonces, then prng_successor(x, nonce_distance(x, y)) = y\r |
| 350 | */\r |
| 351 | static uint16_t *dist = 0;\r |
| 352 | int nonce_distance(uint32_t from, uint32_t to)\r |
| 353 | {\r |
| 354 | uint16_t x, i;\r |
| 355 | if(!dist) {\r |
| 356 | dist = malloc(2 << 16);\r |
| 357 | if(!dist)\r |
| 358 | return -1;\r |
| 359 | for (x = i = 1; i; ++i) {\r |
| 360 | dist[(x & 0xff) << 8 | x >> 8] = i;\r |
| 361 | x = x >> 1 | (x ^ x >> 2 ^ x >> 3 ^ x >> 5) << 15;\r |
| 362 | }\r |
| 363 | }\r |
| 364 | return (65535 + dist[to >> 16] - dist[from >> 16]) % 65535;\r |
| 365 | }\r |
| 366 | \r |
| 367 | \r |
| 368 | static uint32_t fastfwd[2][8] = {\r |
| 369 | { 0, 0x4BC53, 0xECB1, 0x450E2, 0x25E29, 0x6E27A, 0x2B298, 0x60ECB},\r |
| 370 | { 0, 0x1D962, 0x4BC53, 0x56531, 0xECB1, 0x135D3, 0x450E2, 0x58980}};\r |
| 371 | \r |
| 372 | \r |
| 373 | /** lfsr_prefix_ks\r |
| 374 | *\r |
| 375 | * Is an exported helper function from the common prefix attack\r |
| 376 | * Described in the "dark side" paper. It returns an -1 terminated array\r |
| 377 | * of possible partial(21 bit) secret state.\r |
| 378 | * The required keystream(ks) needs to contain the keystream that was used to\r |
| 379 | * encrypt the NACK which is observed when varying only the 4 last bits of Nr\r |
| 380 | * only correct iff [NR_3] ^ NR_3 does not depend on Nr_3\r |
| 381 | */\r |
| 382 | uint32_t *lfsr_prefix_ks(uint8_t ks[8], int isodd)\r |
| 383 | {\r |
| 384 | uint32_t *candidates = malloc(4 << 21);\r |
| 385 | uint32_t c, entry;\r |
| 386 | int size, i;\r |
| 387 | \r |
| 388 | if(!candidates)\r |
| 389 | return 0;\r |
| 390 | \r |
| 391 | size = (1 << 21) - 1;\r |
| 392 | for(i = 0; i <= size; ++i)\r |
| 393 | candidates[i] = i;\r |
| 394 | \r |
| 395 | for(c = 0; c < 8; ++c)\r |
| 396 | for(i = 0;i <= size; ++i) {\r |
| 397 | entry = candidates[i] ^ fastfwd[isodd][c];\r |
| 398 | \r |
| 399 | if(filter(entry >> 1) == BIT(ks[c], isodd))\r |
| 400 | if(filter(entry) == BIT(ks[c], isodd + 2))\r |
| 401 | continue;\r |
| 402 | \r |
| 403 | candidates[i--] = candidates[size--];\r |
| 404 | }\r |
| 405 | \r |
| 406 | candidates[size + 1] = -1;\r |
| 407 | \r |
| 408 | return candidates;\r |
| 409 | }\r |
| 410 | \r |
| 411 | /** brute_top\r |
| 412 | * helper function which eliminates possible secret states using parity bits\r |
| 413 | */\r |
| 414 | static struct Crypto1State*\r |
| 415 | brute_top(uint32_t prefix, uint32_t rresp, unsigned char parities[8][8],\r |
| 416 | uint32_t odd, uint32_t even, struct Crypto1State* sl)\r |
| 417 | {\r |
| 418 | struct Crypto1State s;\r |
| 419 | uint32_t ks1, nr, ks2, rr, ks3, good, c;\r |
| 420 | \r |
| 421 | for(c = 0; c < 8; ++c) {\r |
| 422 | s.odd = odd ^ fastfwd[1][c];\r |
| 423 | s.even = even ^ fastfwd[0][c];\r |
| 424 | \r |
| 425 | lfsr_rollback_bit(&s, 0, 0);\r |
| 426 | lfsr_rollback_bit(&s, 0, 0);\r |
| 427 | lfsr_rollback_bit(&s, 0, 0);\r |
| 428 | \r |
| 429 | lfsr_rollback_word(&s, 0, 0);\r |
| 430 | lfsr_rollback_word(&s, prefix | c << 5, 1);\r |
| 431 | \r |
| 432 | sl->odd = s.odd;\r |
| 433 | sl->even = s.even;\r |
| 434 | \r |
| 435 | ks1 = crypto1_word(&s, prefix | c << 5, 1);\r |
| 436 | ks2 = crypto1_word(&s,0,0);\r |
| 437 | ks3 = crypto1_word(&s, 0,0);\r |
| 438 | nr = ks1 ^ (prefix | c << 5);\r |
| 439 | rr = ks2 ^ rresp;\r |
| 440 | \r |
| 441 | good = 1;\r |
| 442 | good &= parity(nr & 0x000000ff) ^ parities[c][3] ^ BIT(ks2, 24);\r |
| 443 | good &= parity(rr & 0xff000000) ^ parities[c][4] ^ BIT(ks2, 16);\r |
| 444 | good &= parity(rr & 0x00ff0000) ^ parities[c][5] ^ BIT(ks2, 8);\r |
| 445 | good &= parity(rr & 0x0000ff00) ^ parities[c][6] ^ BIT(ks2, 0);\r |
| 446 | good &= parity(rr & 0x000000ff) ^ parities[c][7] ^ BIT(ks3, 24);\r |
| 447 | \r |
| 448 | if(!good)\r |
| 449 | return sl;\r |
| 450 | }\r |
| 451 | \r |
| 452 | return ++sl;\r |
| 453 | } \r |
| 454 | \r |
| 455 | \r |
| 456 | /** lfsr_common_prefix\r |
| 457 | * Implentation of the common prefix attack.\r |
| 458 | * Requires the 28 bit constant prefix used as reader nonce (pfx)\r |
| 459 | * The reader response used (rr)\r |
| 460 | * The keystream used to encrypt the observed NACK's (ks)\r |
| 461 | * The parity bits (par)\r |
| 462 | * It returns a zero terminated list of possible cipher states after the\r |
| 463 | * tag nonce was fed in\r |
| 464 | */\r |
| 465 | struct Crypto1State*\r |
| 466 | lfsr_common_prefix(uint32_t pfx, uint32_t rr, uint8_t ks[8], uint8_t par[8][8])\r |
| 467 | {\r |
| 468 | struct Crypto1State *statelist, *s;\r |
| 469 | uint32_t *odd, *even, *o, *e, top;\r |
| 470 | \r |
| 471 | odd = lfsr_prefix_ks(ks, 1);\r |
| 472 | even = lfsr_prefix_ks(ks, 0);\r |
| 473 | \r |
| 474 | statelist = malloc((sizeof *statelist) << 20);\r |
| 475 | if(!statelist || !odd || !even)\r |
| 476 | return 0;\r |
| 477 | \r |
| 478 | \r |
| 479 | s = statelist;\r |
| 480 | for(o = odd; *o != 0xffffffff; ++o)\r |
| 481 | for(e = even; *e != 0xffffffff; ++e)\r |
| 482 | for(top = 0; top < 64; ++top) {\r |
| 483 | *o = (*o & 0x1fffff) | (top << 21);\r |
| 484 | *e = (*e & 0x1fffff) | (top >> 3) << 21;\r |
| 485 | s = brute_top(pfx, rr, par, *o, *e, s);\r |
| 486 | }\r |
| 487 | \r |
| 488 | s->odd = s->even = 0;\r |
| 489 | \r |
| 490 | free(odd);\r |
| 491 | free(even);\r |
| 492 | \r |
| 493 | return statelist;\r |
| 494 | }\r |