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2c52abe6 | 1 | /* -*-c-*- |
2 | * | |
2cc3d1d0 | 3 | * $Id$ |
2c52abe6 | 4 | * |
5 | * Blum-Blum-Shub secure random number generator | |
6 | * | |
7 | * (c) 1999 Straylight/Edgeware | |
8 | */ | |
9 | ||
45c0fd36 | 10 | /*----- Licensing notice --------------------------------------------------* |
2c52abe6 | 11 | * |
12 | * This file is part of Catacomb. | |
13 | * | |
14 | * Catacomb is free software; you can redistribute it and/or modify | |
15 | * it under the terms of the GNU Library General Public License as | |
16 | * published by the Free Software Foundation; either version 2 of the | |
17 | * License, or (at your option) any later version. | |
45c0fd36 | 18 | * |
2c52abe6 | 19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
22 | * GNU Library General Public License for more details. | |
45c0fd36 | 23 | * |
2c52abe6 | 24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free | |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
27 | * MA 02111-1307, USA. | |
28 | */ | |
29 | ||
2c52abe6 | 30 | /*----- Header files ------------------------------------------------------*/ |
31 | ||
32 | #include <stdarg.h> | |
33 | #include <stdlib.h> | |
34 | #include <string.h> | |
35 | ||
36 | #include <mLib/bits.h> | |
37 | #include <mLib/sub.h> | |
38 | ||
fbdfd34e | 39 | #include "arena.h" |
2c52abe6 | 40 | #include "bbs.h" |
41 | #include "grand.h" | |
42 | #include "mp.h" | |
43 | #include "mpbarrett.h" | |
44 | #include "mpint.h" | |
4ab1268f | 45 | #include "mprand.h" |
fbdfd34e | 46 | #include "paranoia.h" |
2c52abe6 | 47 | |
48 | /*----- Main code ---------------------------------------------------------*/ | |
49 | ||
50 | /* --- @bbs_create@ --- * | |
51 | * | |
52 | * Arguments: @bbs *b@ = pointer to BBS generator state to initialize | |
53 | * @mp *m@ = modulus (must be a Blum integer) | |
54 | * @mp *x@ = initial seed for generator | |
55 | * | |
56 | * Returns: --- | |
57 | * | |
58 | * Use: Initializes a BBS generator. The generator is stepped once | |
59 | * after initialization, as for @bbs_seed@. | |
60 | */ | |
61 | ||
62 | void bbs_create(bbs *b, mp *m, mp *x) | |
63 | { | |
64 | mpw kw; | |
65 | mp k; | |
66 | ||
67 | mpbarrett_create(&b->mb, m); | |
68 | kw = mp_bits(m) - 1; | |
69 | mp_build(&k, &kw, &kw + 1); | |
70 | b->k = mp_bits(&k) - 1; | |
71 | b->x = 0; | |
72 | bbs_seed(b, x); | |
73 | } | |
74 | ||
75 | /* --- @bbs_destroy@ --- * | |
76 | * | |
77 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
78 | * | |
79 | * Returns: --- | |
80 | * | |
81 | * Use: Destroys a generator state when it's no longer wanted. | |
82 | */ | |
83 | ||
84 | void bbs_destroy(bbs *b) | |
85 | { | |
86 | mp_drop(b->x); | |
87 | mpbarrett_destroy(&b->mb); | |
88 | } | |
89 | ||
90 | /* --- @bbs_step@ --- * | |
91 | * | |
92 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
93 | * | |
94 | * Returns: --- | |
95 | * | |
96 | * Use: Steps the generator once. This isn't too useful in client | |
97 | * code. | |
98 | */ | |
99 | ||
100 | void bbs_step(bbs *b) | |
101 | { | |
102 | mp *x = b->x; | |
103 | x = mp_sqr(x, x); | |
104 | x = mpbarrett_reduce(&b->mb, x, x); | |
105 | b->x = x; | |
106 | b->b = b->k; | |
107 | b->r = b->x->v[0]; | |
108 | } | |
109 | ||
110 | /* --- @bbs_set@ --- * | |
111 | * | |
112 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
113 | * @mp *x@ = new residue to set | |
114 | * | |
115 | * Returns: --- | |
116 | * | |
117 | * Use: Sets a new quadratic residue. The generator is stepped once. | |
118 | */ | |
119 | ||
120 | void bbs_set(bbs *b, mp *x) | |
121 | { | |
f1140c41 | 122 | mp_drop(b->x); |
2c52abe6 | 123 | b->x = MP_COPY(x); |
124 | bbs_step(b); | |
125 | } | |
126 | ||
127 | /* --- @bbs_seed@ --- * | |
128 | * | |
129 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
130 | * @mp *x@ = new seed to set | |
131 | * | |
132 | * Returns --- | |
133 | * | |
134 | * Use: Sets a new seed. The generator is stepped until the residue | |
135 | * has clearly wrapped around. | |
136 | */ | |
137 | ||
138 | void bbs_seed(bbs *b, mp *x) | |
139 | { | |
140 | mp *y; | |
141 | x = MP_COPY(x); | |
142 | for (;;) { | |
143 | y = mp_sqr(MP_NEW, x); | |
144 | y = mpbarrett_reduce(&b->mb, y, y); | |
145 | if (MP_CMP(y, <, x)) | |
146 | break; | |
147 | mp_drop(x); | |
148 | x = y; | |
149 | } | |
150 | mp_drop(x); | |
151 | bbs_set(b, y); | |
152 | mp_drop(y); | |
153 | } | |
154 | ||
155 | /* --- @bbs_bits@ --- * | |
156 | * | |
157 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
158 | * @unsigned bits@ = number of bits wanted | |
159 | * | |
160 | * Returns: Bits extracted from the BBS generator. | |
161 | * | |
162 | * Use: Extracts a requested number of bits from the BBS generator. | |
163 | */ | |
164 | ||
165 | uint32 bbs_bits(bbs *b, unsigned bits) | |
166 | { | |
167 | uint32 x = 0; | |
168 | mpw m; | |
169 | ||
170 | /* --- Keep turning the handle until there's enough in the reservoir --- */ | |
171 | ||
172 | while (bits >= b->b) { | |
173 | bits -= b->b; | |
174 | m = (1 << b->b) - 1; | |
175 | x |= (b->r & m) << bits; | |
176 | bbs_step(b); | |
177 | } | |
178 | ||
179 | /* --- Extract the last few bits needed --- */ | |
180 | ||
181 | if (bits) { | |
182 | m = (1 << bits) - 1; | |
183 | b->b -= bits; | |
184 | x |= (b->r >> b->b) & m; | |
185 | } | |
186 | ||
187 | /* --- Done --- */ | |
188 | ||
189 | return (x); | |
190 | } | |
191 | ||
192 | /* --- @bbs_wrap@ --- * | |
193 | * | |
194 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
195 | * | |
196 | * Returns: --- | |
197 | * | |
198 | * Use: Steps the generator if any of the reservoir bits are used. | |
199 | * This can be used to `wrap up' after a Blum-Goldwasser | |
200 | * encryption, for example, producing the final value to be sent | |
201 | * along with the ciphertext. | |
202 | * | |
203 | * If a generator is seeded, %$b$% bits are extracted, and then | |
204 | * @bbs_wrap@ is called, the generator will have been stepped | |
fbdfd34e | 205 | * %$\lceil b/k \rceil$% times. |
2c52abe6 | 206 | */ |
207 | ||
208 | void bbs_wrap(bbs *b) | |
209 | { | |
210 | if (b->b < b->k) | |
211 | bbs_step(b); | |
212 | } | |
213 | ||
214 | /*----- Generic random number generator interface -------------------------*/ | |
215 | ||
216 | typedef struct gctx { | |
217 | grand r; | |
218 | bbs b; | |
219 | } gctx; | |
220 | ||
221 | static void gdestroy(grand *r) | |
222 | { | |
223 | gctx *g = (gctx *)r; | |
224 | bbs_destroy(&g->b); | |
fbdfd34e | 225 | BURN(*g); |
226 | S_DESTROY(g); | |
2c52abe6 | 227 | } |
228 | ||
229 | static int gmisc(grand *r, unsigned op, ...) | |
230 | { | |
231 | gctx *g = (gctx *)r; | |
232 | va_list ap; | |
233 | int rc = 0; | |
234 | va_start(ap, op); | |
235 | ||
236 | switch (op) { | |
237 | case GRAND_CHECK: | |
238 | switch (va_arg(ap, unsigned)) { | |
45c0fd36 MW |
239 | case GRAND_CHECK: |
240 | case GRAND_SEEDINT: | |
241 | case GRAND_SEEDUINT32: | |
242 | case GRAND_SEEDMP: | |
4ab1268f | 243 | case GRAND_SEEDRAND: |
2c52abe6 | 244 | case BBS_SET: |
2cc3d1d0 | 245 | case BBS_STEP: |
246 | case BBS_STEPSZ: | |
247 | case BBS_BITS: | |
248 | case BBS_WRAP: | |
249 | case BBS_FF: | |
250 | case BBS_FFN: | |
251 | case BBS_REW: | |
252 | case BBS_REWN: | |
253 | case BBS_MOD: | |
254 | case BBS_STATE: | |
45c0fd36 MW |
255 | rc = 1; |
256 | break; | |
257 | default: | |
258 | rc = 0; | |
259 | break; | |
2c52abe6 | 260 | } |
261 | break; | |
262 | case GRAND_SEEDINT: { | |
263 | mp *x = mp_fromuint(MP_NEW, va_arg(ap, unsigned)); | |
264 | bbs_seed(&g->b, x); | |
265 | mp_drop(x); | |
266 | } break; | |
267 | case GRAND_SEEDUINT32: { | |
268 | mp *x = mp_fromuint32(MP_NEW, va_arg(ap, uint32)); | |
269 | bbs_seed(&g->b, x); | |
270 | mp_drop(x); | |
271 | } break; | |
272 | case GRAND_SEEDMP: | |
273 | bbs_seed(&g->b, va_arg(ap, mp *)); | |
274 | break; | |
4ab1268f | 275 | case GRAND_SEEDRAND: { |
276 | grand *rr = va_arg(ap, grand *); | |
277 | mp *m = mprand(MP_NEW, mp_bits(g->b.mb.m) - 1, rr, 0); | |
278 | bbs_seed(&g->b, m); | |
279 | mp_drop(m); | |
280 | } break; | |
2c52abe6 | 281 | case BBS_SET: |
282 | bbs_set(&g->b, va_arg(ap, mp *)); | |
283 | break; | |
2cc3d1d0 | 284 | case BBS_STEP: |
285 | bbs_step(&g->b); | |
286 | break; | |
287 | case BBS_STEPSZ: | |
288 | rc = g->b.k; | |
289 | break; | |
290 | case BBS_BITS: { | |
291 | unsigned nb = va_arg(ap, unsigned); | |
292 | uint32 *w = va_arg(ap, uint32 *); | |
293 | *w = bbs_bits(&g->b, nb); | |
294 | } break; | |
295 | case BBS_WRAP: | |
296 | bbs_wrap(&g->b); | |
297 | break; | |
298 | case BBS_FF: { | |
299 | const bbs_priv *bp = va_arg(ap, const bbs_priv *); | |
300 | mp *n = va_arg(ap, mp *); | |
301 | bbs_ff(&g->b, bp, n); | |
302 | } break; | |
303 | case BBS_FFN: { | |
304 | const bbs_priv *bp = va_arg(ap, const bbs_priv *); | |
305 | unsigned long n = va_arg(ap, unsigned long); | |
306 | bbs_ffn(&g->b, bp, n); | |
307 | } break; | |
308 | case BBS_REW: { | |
309 | const bbs_priv *bp = va_arg(ap, const bbs_priv *); | |
310 | mp *n = va_arg(ap, mp *); | |
311 | bbs_rew(&g->b, bp, n); | |
312 | } break; | |
313 | case BBS_REWN: { | |
314 | const bbs_priv *bp = va_arg(ap, const bbs_priv *); | |
315 | unsigned long n = va_arg(ap, unsigned long); | |
316 | bbs_rewn(&g->b, bp, n); | |
317 | } break; | |
318 | case BBS_MOD: { | |
319 | mp **n = va_arg(ap, mp **); | |
320 | if (*n) MP_DROP(*n); | |
321 | *n = MP_COPY(g->b.mb.m); | |
322 | } break; | |
323 | case BBS_STATE: { | |
324 | mp **n = va_arg(ap, mp **); | |
325 | if (*n) MP_DROP(*n); | |
326 | *n = MP_COPY(g->b.x); | |
327 | } break; | |
2c52abe6 | 328 | default: |
329 | GRAND_BADOP; | |
330 | break; | |
331 | } | |
332 | ||
333 | va_end(ap); | |
334 | return (rc); | |
335 | } | |
336 | ||
337 | static octet gbyte(grand *r) | |
338 | { | |
339 | gctx *g = (gctx *)r; | |
340 | return (bbs_bits(&g->b, 8)); | |
341 | } | |
342 | ||
343 | static uint32 gword(grand *r) | |
344 | { | |
345 | gctx *g = (gctx *)r; | |
346 | return (bbs_bits(&g->b, 32)); | |
347 | } | |
348 | ||
349 | static const grand_ops gops = { | |
350 | "bbs", | |
fbdfd34e | 351 | GRAND_CRYPTO, 0, |
2c52abe6 | 352 | gmisc, gdestroy, |
353 | gword, gbyte, gword, grand_range, grand_fill | |
354 | }; | |
355 | ||
356 | /* --- @bbs_rand@ --- * | |
357 | * | |
45c0fd36 | 358 | * Arguments: @mp *m@ = modulus |
2c52abe6 | 359 | * @mp *x@ = initial seed |
360 | * | |
45c0fd36 | 361 | * Returns: Pointer to a generic generator. |
2c52abe6 | 362 | * |
45c0fd36 | 363 | * Use: Constructs a generic generator interface over a |
2c52abe6 | 364 | * Blum-Blum-Shub generator. |
365 | */ | |
366 | ||
367 | grand *bbs_rand(mp *m, mp *x) | |
368 | { | |
fbdfd34e | 369 | gctx *g = S_CREATE(gctx); |
2c52abe6 | 370 | g->r.ops = &gops; |
371 | bbs_create(&g->b, m, x); | |
372 | return (&g->r); | |
373 | } | |
374 | ||
375 | /*----- Test rig ----------------------------------------------------------*/ | |
376 | ||
377 | #ifdef TEST_RIG | |
378 | ||
379 | static int verify(dstr *v) | |
380 | { | |
381 | mp *n = *(mp **)v[0].buf; | |
382 | mp *x = *(mp **)v[1].buf; | |
383 | grand *b = bbs_rand(n, x); | |
384 | dstr d = DSTR_INIT; | |
385 | int ok = 1; | |
386 | ||
387 | dstr_ensure(&d, v[2].len); | |
388 | b->ops->fill(b, d.buf, v[2].len); | |
389 | d.len = v[2].len; | |
390 | if (memcmp(d.buf, v[2].buf, v[2].len) != 0) { | |
391 | fputs("\n*** bbs failure\n", stderr); | |
392 | fputs("n = ", stderr); mp_writefile(n, stderr, 10); fputc('\n', stderr); | |
393 | fputs("x = ", stderr); mp_writefile(x, stderr, 10); fputc('\n', stderr); | |
394 | fputs("expected = ", stderr); type_hex.dump(&v[2], stderr); | |
395 | fputc('\n', stderr); | |
396 | fputs(" found = ", stderr); type_hex.dump(&d, stderr); | |
397 | fputc('\n', stderr); | |
398 | fprintf(stderr, "k = %u\n", ((gctx *)b)->b.k); | |
399 | ok = 0; | |
400 | } | |
401 | b->ops->destroy(b); | |
402 | mp_drop(x); | |
403 | mp_drop(n); | |
404 | dstr_destroy(&d); | |
405 | assert(mparena_count(MPARENA_GLOBAL) == 0); | |
406 | return (ok); | |
407 | } | |
408 | ||
409 | static test_chunk tests[] = { | |
410 | { "bbs", verify, { &type_mp, &type_mp, &type_hex, 0 } }, | |
411 | { 0, 0, { 0 } } | |
412 | }; | |
413 | ||
414 | int main(int argc, char *argv[]) | |
415 | { | |
416 | sub_init(); | |
417 | test_run(argc, argv, tests, SRCDIR "/tests/bbs"); | |
418 | return (0); | |
419 | } | |
420 | ||
421 | #endif | |
422 | ||
423 | /*----- That's all, folks -------------------------------------------------*/ |