| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: idea.c,v 1.2 1997/08/04 10:24:22 mdw Exp $ |
| 4 | * |
| 5 | * IDEA encryption routines |
| 6 | * Based on Straylight ARM assembler routines |
| 7 | * |
| 8 | * (c) 1996, 1997 Mark Wooding |
| 9 | */ |
| 10 | |
| 11 | /*----- Licensing notice --------------------------------------------------* |
| 12 | * |
| 13 | * This file is part of `become' |
| 14 | * |
| 15 | * `Become' is free software; you can redistribute it and/or modify |
| 16 | * it under the terms of the GNU General Public License as published by |
| 17 | * the Free Software Foundation; either version 2 of the License, or |
| 18 | * (at your option) any later version. |
| 19 | * |
| 20 | * `Become' is distributed in the hope that it will be useful, |
| 21 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 22 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 23 | * GNU General Public License for more details. |
| 24 | * |
| 25 | * You should have received a copy of the GNU General Public License |
| 26 | * along with `become'; if not, write to the Free Software Foundation, |
| 27 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 28 | */ |
| 29 | |
| 30 | /*----- Revision history --------------------------------------------------* |
| 31 | * |
| 32 | * $Log: idea.c,v $ |
| 33 | * Revision 1.2 1997/08/04 10:24:22 mdw |
| 34 | * Sources placed under CVS control. |
| 35 | * |
| 36 | * Revision 1.1 1997/07/21 13:47:49 mdw |
| 37 | * Initial revision |
| 38 | * |
| 39 | */ |
| 40 | |
| 41 | /*----- Notes -------------------------------------------------------------* |
| 42 | * |
| 43 | * This code is optimised for 32-bit processors with reasonable numbers of |
| 44 | * registers. Hopefully it should still work on a Spectrum, although rather |
| 45 | * slowly. I do assume two's complement arithmetic. |
| 46 | * |
| 47 | * Since this is actually /decompiled/, by hand, from some existing assembler |
| 48 | * code, you can expect some parts to be a little strange. |
| 49 | */ |
| 50 | |
| 51 | /*----- Header files ------------------------------------------------------*/ |
| 52 | |
| 53 | #include <stdio.h> |
| 54 | #include <string.h> |
| 55 | |
| 56 | #include "config.h" |
| 57 | #include "idea.h" |
| 58 | #include "utils.h" |
| 59 | |
| 60 | /*----- Low-level support functions ---------------------------------------*/ |
| 61 | |
| 62 | /* --- @idea__inv@ --- * |
| 63 | * |
| 64 | * Arguments: @int n@ = number to invert |
| 65 | * |
| 66 | * Returns: Multiplicative inverse of n, mod 2^{16} + 1 |
| 67 | */ |
| 68 | |
| 69 | static int idea__inv(int n) |
| 70 | { |
| 71 | long m, a, b, q, r, t; |
| 72 | |
| 73 | /* --- Check the easy case --- */ |
| 74 | |
| 75 | if (!n) |
| 76 | return (0); |
| 77 | |
| 78 | /* --- Start off the loop --- */ |
| 79 | |
| 80 | m = 0x10001L; |
| 81 | a = 1; |
| 82 | b = 0; |
| 83 | for (;;) { |
| 84 | q = m / n, r = m % n; |
| 85 | if (!r) |
| 86 | break; |
| 87 | m = n, n = r; |
| 88 | t = a, a = b - q * a, b = t; |
| 89 | } |
| 90 | |
| 91 | /* --- Get return value in range --- */ |
| 92 | |
| 93 | if (a < 0) |
| 94 | a += 1; |
| 95 | return ((int) a & 0xFFFF); |
| 96 | } |
| 97 | |
| 98 | /* --- @_mul@ --- * |
| 99 | * |
| 100 | * An evil macro to do multiplication. Satan lives here. |
| 101 | */ |
| 102 | |
| 103 | #define _mul(x, y) \ |
| 104 | (void)( \ |
| 105 | x &= ffff, x ? \ |
| 106 | ( y &= ffff, y ? \ |
| 107 | ((y = x * y), x = y & ffff, y = y >> 16, x < y ? \ |
| 108 | (x = x - y + 1) : (x = x - y)) : \ |
| 109 | (x = 1 - x)) : \ |
| 110 | (x = 1 - y) \ |
| 111 | ) |
| 112 | |
| 113 | /*----- Key unpacking functions -------------------------------------------*/ |
| 114 | |
| 115 | /* --- @idea_ekeys@ --- * |
| 116 | * |
| 117 | * Arguments: @idea_key *k@ = the expanded key buffer |
| 118 | * @const unsigned char *key@ = the user's key encryption key |
| 119 | * |
| 120 | * Returns: --- |
| 121 | * |
| 122 | * Use: Unpacks an encryption key. |
| 123 | */ |
| 124 | |
| 125 | void idea_ekeys(idea_key *k, const unsigned char *key) |
| 126 | { |
| 127 | /* --- Convince compiler to do this properly --- */ |
| 128 | |
| 129 | register const int ffff = 0xFFFF; |
| 130 | |
| 131 | uint_32 ka, kb, kc, kd; |
| 132 | int count; |
| 133 | int *p = k->k; |
| 134 | |
| 135 | /* --- Load the 4 words from the block --- * |
| 136 | * |
| 137 | * Don't ask. |
| 138 | */ |
| 139 | |
| 140 | ka = load32(key + 0); |
| 141 | kb = load32(key + 4); |
| 142 | kc = load32(key + 8); |
| 143 | kd = load32(key + 12); |
| 144 | |
| 145 | for (count = 48; count > 0; count -= 8) { |
| 146 | |
| 147 | /* --- Unpack halfwords into the block --- */ |
| 148 | |
| 149 | *p++ = (ka >> 16) & ffff; |
| 150 | *p++ = ka & ffff; |
| 151 | *p++ = (kb >> 16) & ffff; |
| 152 | *p++ = kb & ffff; |
| 153 | *p++ = (kc >> 16) & ffff; |
| 154 | *p++ = kc & ffff; |
| 155 | *p++ = (kd >> 16) & ffff; |
| 156 | *p++ = kd & ffff; |
| 157 | |
| 158 | /* --- Now rotate the 128-bit key --- */ |
| 159 | |
| 160 | { |
| 161 | uint_32 kx = ka; |
| 162 | ka = ((ka << 25) | (kb >> 7)) & 0xffffffffu; |
| 163 | kb = ((kb << 25) | (kc >> 7)) & 0xffffffffu; |
| 164 | kc = ((kc << 25) | (kd >> 7)) & 0xffffffffu; |
| 165 | kd = ((kd << 25) | (kx >> 7)) & 0xffffffffu; |
| 166 | } |
| 167 | } |
| 168 | |
| 169 | /* --- Write the tail-enders over --- */ |
| 170 | |
| 171 | *p++ = (ka >> 16) & ffff; |
| 172 | *p++ = ka & ffff; |
| 173 | *p++ = (kb >> 16) & ffff; |
| 174 | *p++ = kb & ffff; |
| 175 | } |
| 176 | |
| 177 | /* --- @idea_invertKey@ --- * |
| 178 | * |
| 179 | * Arguments: @const idea_key *in@ = pointer to input expanded key buffer |
| 180 | * @idea_key *out@ = pointer to output expanded key buffer |
| 181 | * |
| 182 | * Returns: --- |
| 183 | * |
| 184 | * Use: Computes the inverse (decryption) key given an expanded |
| 185 | * IDEA encryption key. |
| 186 | */ |
| 187 | |
| 188 | void idea_invertKey(const idea_key *in, idea_key *out) |
| 189 | { |
| 190 | int i; |
| 191 | unsigned a, b, c, d, e, f; |
| 192 | int *ibuf = in->k, *obuf = out->k; |
| 193 | |
| 194 | /* --- Deal with identical input and output buffers --- */ |
| 195 | |
| 196 | if (in == out) { |
| 197 | idea_key t; |
| 198 | memcpy(&t, in, sizeof(t)); |
| 199 | idea_invertKey(&t, out); |
| 200 | return; |
| 201 | } |
| 202 | |
| 203 | /* --- Do the real work --- */ |
| 204 | |
| 205 | ibuf += IDEA_EXPKEYSIZE; |
| 206 | for (i = 8; i; i--) { |
| 207 | ibuf -= 6; |
| 208 | a = ibuf[0]; |
| 209 | b = ibuf[1]; |
| 210 | c = ibuf[2]; |
| 211 | d = ibuf[3]; |
| 212 | e = ibuf[4]; |
| 213 | f = ibuf[5]; |
| 214 | |
| 215 | c = idea__inv(c); |
| 216 | f = idea__inv(f); |
| 217 | d = 0x10000 - d; |
| 218 | e = 0x10000 - e; |
| 219 | |
| 220 | if (i < 8) |
| 221 | d ^= e, e ^= d, d ^= e; |
| 222 | |
| 223 | obuf[0] = c; |
| 224 | obuf[1] = d; |
| 225 | obuf[2] = e; |
| 226 | obuf[3] = f; |
| 227 | obuf[4] = a; |
| 228 | obuf[5] = b; |
| 229 | obuf += 6; |
| 230 | } |
| 231 | |
| 232 | /* --- Deal with the tail-enders --- */ |
| 233 | |
| 234 | ibuf -= 4; |
| 235 | c = ibuf[0]; |
| 236 | d = ibuf[1]; |
| 237 | e = ibuf[2]; |
| 238 | f = ibuf[3]; |
| 239 | |
| 240 | c = idea__inv(c); |
| 241 | f = idea__inv(f); |
| 242 | d = 0x10000 - d; |
| 243 | e = 0x10000 - e; |
| 244 | |
| 245 | obuf[0] = c; |
| 246 | obuf[1] = d; |
| 247 | obuf[2] = e; |
| 248 | obuf[3] = f; |
| 249 | } |
| 250 | |
| 251 | /* --- @idea_dkeys@ --- * |
| 252 | * |
| 253 | * Arguments: @idea_key *k@ = the expanded key buffer |
| 254 | * @const unsigned char *key@ = the user's key encryption key |
| 255 | * |
| 256 | * Returns: --- |
| 257 | * |
| 258 | * Use: Unpacks a decryption key. |
| 259 | */ |
| 260 | |
| 261 | void idea_dkeys(idea_key *k, const unsigned char *key) |
| 262 | { |
| 263 | idea_key t; |
| 264 | idea_ekeys(&t, key); |
| 265 | idea_invertKey(&t, k); |
| 266 | } |
| 267 | |
| 268 | /*----- Main IDEA cipher --------------------------------------------------*/ |
| 269 | |
| 270 | /* --- @idea_encrypt@ --- * |
| 271 | * |
| 272 | * Arguments: @const idea_key *k@ = key to use |
| 273 | * @const void *src@ = block to encrypt |
| 274 | * @void *dest@ = where to store the result |
| 275 | * |
| 276 | * Returns: --- |
| 277 | * |
| 278 | * Use: Encrypts (or decrypts) a block, using the IDEA cryptosystem. |
| 279 | * Since the decryption operation is the same as encryption |
| 280 | * except that a different key buffer is used, this is all we |
| 281 | * need to complete the simple bits. |
| 282 | * |
| 283 | * For people following this at home: I've been very sloppy |
| 284 | * about chopping off excess bits from the ints here. Most of |
| 285 | * the time it doesn't matter, and when it does, in the |
| 286 | * multiplication stage, the macro does this for us. |
| 287 | * |
| 288 | * Our @register const int ffff@ makes another appearance. This |
| 289 | * might suggest to compilers that having this constant |
| 290 | * available would be beneficial. |
| 291 | * |
| 292 | * Registers are in short supply here. So is legibility. |
| 293 | */ |
| 294 | |
| 295 | #if defined(TEST_RIG) && defined(DUMPROUNDS) |
| 296 | # define _dump(a,b,c,d) \ |
| 297 | printf(" %5lu %5lu %5lu %5lu\n", \ |
| 298 | a & ffff, b & ffff, c & ffff, d & ffff) |
| 299 | #else |
| 300 | # define _dump(a,b,c,d) ((void)0) |
| 301 | #endif |
| 302 | |
| 303 | #define _round(a, b, c, d) do { \ |
| 304 | _dump(a, b, c, d); \ |
| 305 | u = kp[0]; v = kp[1]; w = kp[2]; x = kp[3]; y = kp[4]; z = kp[5]; \ |
| 306 | kp += 6; \ |
| 307 | _mul(a, u); b += v; c += w; _mul(d, x); \ |
| 308 | u = a ^ c; v = b ^ d; _mul(u, y); v += u; _mul(v, z); u += v; \ |
| 309 | a ^= v; b ^= u; c ^= v; d ^= u; \ |
| 310 | _dump(a, b, c, d); \ |
| 311 | } while (0) \ |
| 312 | |
| 313 | void idea_encrypt(const idea_key *k, const void *src, void *dest) |
| 314 | { |
| 315 | register const int ffff = 0xFFFF; |
| 316 | const unsigned char *usrc = src; |
| 317 | unsigned char *udest = dest; |
| 318 | int *kp = k->k; |
| 319 | |
| 320 | uint_32 a, b, c, d; |
| 321 | uint_32 u, v, w, x, y, z; |
| 322 | |
| 323 | /* --- Unpack next block into registers --- */ |
| 324 | |
| 325 | a = (usrc[0] << 8) | usrc[1]; |
| 326 | b = (usrc[2] << 8) | usrc[3]; |
| 327 | c = (usrc[4] << 8) | usrc[5]; |
| 328 | d = (usrc[6] << 8) | usrc[7]; |
| 329 | |
| 330 | /* --- Now run the block through the eight rounds --- * |
| 331 | * |
| 332 | * Notice how the arguments swap around so as I don't have to move the |
| 333 | * values about. |
| 334 | */ |
| 335 | |
| 336 | _round(a, b, c, d); |
| 337 | _round(a, c, b, d); |
| 338 | _round(a, b, c, d); |
| 339 | _round(a, c, b, d); |
| 340 | |
| 341 | _round(a, b, c, d); |
| 342 | _round(a, c, b, d); |
| 343 | _round(a, b, c, d); |
| 344 | _round(a, c, b, d); |
| 345 | |
| 346 | /* --- Do the output transformation --- */ |
| 347 | |
| 348 | u = kp[0]; |
| 349 | v = kp[1]; |
| 350 | w = kp[2]; |
| 351 | x = kp[3]; |
| 352 | _mul(a, u); |
| 353 | b += w; |
| 354 | c += v; |
| 355 | _mul(d, x); |
| 356 | |
| 357 | /* --- Repack and store the block --- */ |
| 358 | |
| 359 | udest[0] = (a >> 8) & 0xFF; udest[1] = a & 0xFF; |
| 360 | udest[2] = (c >> 8) & 0xFF; udest[3] = c & 0xFF; |
| 361 | udest[4] = (b >> 8) & 0xFF; udest[5] = b & 0xFF; |
| 362 | udest[6] = (d >> 8) & 0xFF; udest[7] = d & 0xFF; |
| 363 | } |
| 364 | |
| 365 | /*----- Debugging driver --------------------------------------------------*/ |
| 366 | |
| 367 | #ifdef TEST_RIG |
| 368 | |
| 369 | #define TESTENCRYPTION |
| 370 | |
| 371 | void dumpbuf(int *k) |
| 372 | { |
| 373 | int i; |
| 374 | printf("Round "); |
| 375 | for (i = 1; i <= 6; i++) |
| 376 | printf("%5i ", i); |
| 377 | for (i = 0; i < 52; i++) { |
| 378 | if (i % 6 == 0) |
| 379 | printf("\n %i ", i / 6 + 1); |
| 380 | printf("%5i ", *k++); |
| 381 | } |
| 382 | printf("\n\n"); |
| 383 | } |
| 384 | |
| 385 | void dumpblk(char *bb) |
| 386 | { |
| 387 | unsigned char *b = (unsigned char *)bb; |
| 388 | printf("++ %5u %5u %5u %5u\n", |
| 389 | (b[0]<<8)|b[1], |
| 390 | (b[2]<<8)|b[3], |
| 391 | (b[4]<<8)|b[5], |
| 392 | (b[6]<<8)|b[7]); |
| 393 | } |
| 394 | |
| 395 | int main(void) |
| 396 | { |
| 397 | |
| 398 | #ifdef TESTMULTIPLY |
| 399 | { |
| 400 | unsigned int i, j; |
| 401 | char buf[256]; |
| 402 | int ffff = 0xFFFF; |
| 403 | for (;;) { |
| 404 | gets(buf); |
| 405 | if (!buf[0]) |
| 406 | break; |
| 407 | sscanf(buf, "%u%u", &i, &j); |
| 408 | _mul(i, j); |
| 409 | printf("%u\n", i); |
| 410 | } |
| 411 | } |
| 412 | #endif |
| 413 | |
| 414 | #ifdef TESTENCRYPTION |
| 415 | { |
| 416 | int i; |
| 417 | int f; |
| 418 | |
| 419 | unsigned char k[] = { 0, 1, 0, 2, 0, 3, 0, 4, 0, 5, 0, 6, 0, 7, 0, 8 }; |
| 420 | idea_key e, d; |
| 421 | unsigned char b[] = { 0, 0, 0, 1, 0, 2, 0, 3 }; |
| 422 | |
| 423 | static idea_key correct_e = { { |
| 424 | 1, 2, 3, 4, 5, 6, |
| 425 | 7, 8, 1024, 1536, 2048, 2560, |
| 426 | 3072, 3584, 4096, 512, 16, 20, |
| 427 | 24, 28, 32, 4, 8, 12, |
| 428 | 10240, 12288, 14336, 16384, 2048, 4096, |
| 429 | 6144, 8192, 112, 128, 16, 32, |
| 430 | 48, 64, 80, 96, 0, 8192, |
| 431 | 16384, 24576, 32768, 40960, 49152, 57345, |
| 432 | 128, 192, 256, 320 |
| 433 | } }; |
| 434 | |
| 435 | static idea_key correct_d = { { |
| 436 | 65025, 65344, 65280, 26010, 49152, 57345, |
| 437 | 65533, 32768, 40960, 52428, 0, 8192, |
| 438 | 42326, 65456, 65472, 21163, 16, 32, |
| 439 | 21835, 65424, 57344, 65025, 2048, 4096, |
| 440 | 13101, 51200, 53248, 65533, 8, 12, |
| 441 | 19115, 65504, 65508, 49153, 16, 20, |
| 442 | 43670, 61440, 61952, 65409, 2048, 2560, |
| 443 | 18725, 64512, 65528, 21803, 5, 6, |
| 444 | 1, 65534, 65533, 49153 |
| 445 | } }; |
| 446 | |
| 447 | static unsigned char correct_encrypt[] = { |
| 448 | 4603 / 256, 4603 % 256, |
| 449 | 60715 / 256, 60715 % 256, |
| 450 | 408 / 256, 408 % 256, |
| 451 | 28133 / 256, 28133 % 256 |
| 452 | }; |
| 453 | |
| 454 | static unsigned char correct_decrypt[] = { |
| 455 | 0, 0, 0, 1, 0, 2, 0, 3 |
| 456 | }; |
| 457 | |
| 458 | idea_ekeys(&e, k); |
| 459 | dumpbuf(e.k); |
| 460 | |
| 461 | f = 1; |
| 462 | for (i = 0; i < IDEA_EXPKEYSIZE; i++) { |
| 463 | if (e.k[i] != correct_e.k[i]) { |
| 464 | f = 0; |
| 465 | printf("!!! bad encryption key values!\n\n"); |
| 466 | } |
| 467 | } |
| 468 | if (f) |
| 469 | printf("*** expanded encryption key correct\n\n"); |
| 470 | |
| 471 | idea_dkeys(&d, k); |
| 472 | dumpbuf(d.k); |
| 473 | |
| 474 | f = 1; |
| 475 | for (i = 0; i < IDEA_EXPKEYSIZE; i++) { |
| 476 | if (d.k[i] != correct_d.k[i]) { |
| 477 | f = 0; |
| 478 | printf("!!! bad decryption key values!\n\n"); |
| 479 | } |
| 480 | } |
| 481 | if (f) |
| 482 | printf("*** expanded decryption key correct\n\n"); |
| 483 | |
| 484 | idea_encrypt(&e, b, b); |
| 485 | dumpblk(b); |
| 486 | if (memcmp(b, correct_encrypt, 8) == 0) |
| 487 | printf("*** correct encipherment\n\n"); |
| 488 | else |
| 489 | printf("!!! bad encipherment\n\n"); |
| 490 | |
| 491 | idea_encrypt(&d, b, b); |
| 492 | dumpblk(b); |
| 493 | if (memcmp(b, correct_decrypt, 8) == 0) |
| 494 | printf("*** correct decipherment\n"); |
| 495 | else |
| 496 | printf("!!! bad decipherment\n"); |
| 497 | } |
| 498 | #endif |
| 499 | |
| 500 | return (0); |
| 501 | } |
| 502 | |
| 503 | #endif |
| 504 | |
| 505 | /*----- That's all, folks -------------------------------------------------*/ |