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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: idea.c,v 1.2 1997/08/04 10:24:22 mdw Exp $ |
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4 | * |
5 | * IDEA encryption routines |
6 | * Based on Straylight ARM assembler routines |
7 | * |
8 | * (c) 1996, 1997 Mark Wooding |
9 | */ |
10 | |
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11 | /*----- Licensing notice --------------------------------------------------* |
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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 |
03f996bd |
26 | * along with `become'; if not, write to the Free Software Foundation, |
27 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: idea.c,v $ |
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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 |
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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> |
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54 | #include <string.h> |
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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 -------------------------------------------------*/ |