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2c52abe6 | 1 | /* -*-c-*- |
2c52abe6 | 2 | * |
3 | * Blum-Blum-Shub secure random number generator | |
4 | * | |
5 | * (c) 1999 Straylight/Edgeware | |
6 | */ | |
7 | ||
45c0fd36 | 8 | /*----- Licensing notice --------------------------------------------------* |
2c52abe6 | 9 | * |
10 | * This file is part of Catacomb. | |
11 | * | |
12 | * Catacomb is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU Library General Public License as | |
14 | * published by the Free Software Foundation; either version 2 of the | |
15 | * License, or (at your option) any later version. | |
45c0fd36 | 16 | * |
2c52abe6 | 17 | * Catacomb is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU Library General Public License for more details. | |
45c0fd36 | 21 | * |
2c52abe6 | 22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with Catacomb; if not, write to the Free | |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
25 | * MA 02111-1307, USA. | |
26 | */ | |
27 | ||
2c52abe6 | 28 | /*----- Header files ------------------------------------------------------*/ |
29 | ||
30 | #include <stdarg.h> | |
31 | #include <stdlib.h> | |
32 | #include <string.h> | |
33 | ||
34 | #include <mLib/bits.h> | |
35 | #include <mLib/sub.h> | |
36 | ||
fbdfd34e | 37 | #include "arena.h" |
2c52abe6 | 38 | #include "bbs.h" |
39 | #include "grand.h" | |
40 | #include "mp.h" | |
41 | #include "mpbarrett.h" | |
42 | #include "mpint.h" | |
4ab1268f | 43 | #include "mprand.h" |
fbdfd34e | 44 | #include "paranoia.h" |
2c52abe6 | 45 | |
46 | /*----- Main code ---------------------------------------------------------*/ | |
47 | ||
48 | /* --- @bbs_create@ --- * | |
49 | * | |
50 | * Arguments: @bbs *b@ = pointer to BBS generator state to initialize | |
51 | * @mp *m@ = modulus (must be a Blum integer) | |
52 | * @mp *x@ = initial seed for generator | |
53 | * | |
54 | * Returns: --- | |
55 | * | |
56 | * Use: Initializes a BBS generator. The generator is stepped once | |
57 | * after initialization, as for @bbs_seed@. | |
58 | */ | |
59 | ||
60 | void bbs_create(bbs *b, mp *m, mp *x) | |
61 | { | |
62 | mpw kw; | |
63 | mp k; | |
64 | ||
65 | mpbarrett_create(&b->mb, m); | |
66 | kw = mp_bits(m) - 1; | |
67 | mp_build(&k, &kw, &kw + 1); | |
68 | b->k = mp_bits(&k) - 1; | |
69 | b->x = 0; | |
70 | bbs_seed(b, x); | |
71 | } | |
72 | ||
73 | /* --- @bbs_destroy@ --- * | |
74 | * | |
75 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
76 | * | |
77 | * Returns: --- | |
78 | * | |
79 | * Use: Destroys a generator state when it's no longer wanted. | |
80 | */ | |
81 | ||
82 | void bbs_destroy(bbs *b) | |
83 | { | |
84 | mp_drop(b->x); | |
85 | mpbarrett_destroy(&b->mb); | |
86 | } | |
87 | ||
88 | /* --- @bbs_step@ --- * | |
89 | * | |
90 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
91 | * | |
92 | * Returns: --- | |
93 | * | |
94 | * Use: Steps the generator once. This isn't too useful in client | |
95 | * code. | |
96 | */ | |
97 | ||
98 | void bbs_step(bbs *b) | |
99 | { | |
100 | mp *x = b->x; | |
101 | x = mp_sqr(x, x); | |
102 | x = mpbarrett_reduce(&b->mb, x, x); | |
103 | b->x = x; | |
104 | b->b = b->k; | |
105 | b->r = b->x->v[0]; | |
106 | } | |
107 | ||
108 | /* --- @bbs_set@ --- * | |
109 | * | |
110 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
111 | * @mp *x@ = new residue to set | |
112 | * | |
113 | * Returns: --- | |
114 | * | |
115 | * Use: Sets a new quadratic residue. The generator is stepped once. | |
116 | */ | |
117 | ||
118 | void bbs_set(bbs *b, mp *x) | |
119 | { | |
f1140c41 | 120 | mp_drop(b->x); |
2c52abe6 | 121 | b->x = MP_COPY(x); |
122 | bbs_step(b); | |
123 | } | |
124 | ||
125 | /* --- @bbs_seed@ --- * | |
126 | * | |
127 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
128 | * @mp *x@ = new seed to set | |
129 | * | |
130 | * Returns --- | |
131 | * | |
132 | * Use: Sets a new seed. The generator is stepped until the residue | |
133 | * has clearly wrapped around. | |
134 | */ | |
135 | ||
136 | void bbs_seed(bbs *b, mp *x) | |
137 | { | |
138 | mp *y; | |
139 | x = MP_COPY(x); | |
140 | for (;;) { | |
141 | y = mp_sqr(MP_NEW, x); | |
142 | y = mpbarrett_reduce(&b->mb, y, y); | |
143 | if (MP_CMP(y, <, x)) | |
144 | break; | |
145 | mp_drop(x); | |
146 | x = y; | |
147 | } | |
148 | mp_drop(x); | |
149 | bbs_set(b, y); | |
150 | mp_drop(y); | |
151 | } | |
152 | ||
153 | /* --- @bbs_bits@ --- * | |
154 | * | |
155 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
156 | * @unsigned bits@ = number of bits wanted | |
157 | * | |
158 | * Returns: Bits extracted from the BBS generator. | |
159 | * | |
160 | * Use: Extracts a requested number of bits from the BBS generator. | |
161 | */ | |
162 | ||
163 | uint32 bbs_bits(bbs *b, unsigned bits) | |
164 | { | |
165 | uint32 x = 0; | |
166 | mpw m; | |
167 | ||
168 | /* --- Keep turning the handle until there's enough in the reservoir --- */ | |
169 | ||
170 | while (bits >= b->b) { | |
171 | bits -= b->b; | |
172 | m = (1 << b->b) - 1; | |
173 | x |= (b->r & m) << bits; | |
174 | bbs_step(b); | |
175 | } | |
176 | ||
177 | /* --- Extract the last few bits needed --- */ | |
178 | ||
179 | if (bits) { | |
180 | m = (1 << bits) - 1; | |
181 | b->b -= bits; | |
182 | x |= (b->r >> b->b) & m; | |
183 | } | |
184 | ||
185 | /* --- Done --- */ | |
186 | ||
187 | return (x); | |
188 | } | |
189 | ||
190 | /* --- @bbs_wrap@ --- * | |
191 | * | |
192 | * Arguments: @bbs *b@ = pointer to BBS generator state | |
193 | * | |
194 | * Returns: --- | |
195 | * | |
196 | * Use: Steps the generator if any of the reservoir bits are used. | |
197 | * This can be used to `wrap up' after a Blum-Goldwasser | |
198 | * encryption, for example, producing the final value to be sent | |
199 | * along with the ciphertext. | |
200 | * | |
201 | * If a generator is seeded, %$b$% bits are extracted, and then | |
202 | * @bbs_wrap@ is called, the generator will have been stepped | |
fbdfd34e | 203 | * %$\lceil b/k \rceil$% times. |
2c52abe6 | 204 | */ |
205 | ||
206 | void bbs_wrap(bbs *b) | |
207 | { | |
208 | if (b->b < b->k) | |
209 | bbs_step(b); | |
210 | } | |
211 | ||
212 | /*----- Generic random number generator interface -------------------------*/ | |
213 | ||
214 | typedef struct gctx { | |
215 | grand r; | |
216 | bbs b; | |
217 | } gctx; | |
218 | ||
219 | static void gdestroy(grand *r) | |
220 | { | |
221 | gctx *g = (gctx *)r; | |
222 | bbs_destroy(&g->b); | |
fbdfd34e | 223 | BURN(*g); |
224 | S_DESTROY(g); | |
2c52abe6 | 225 | } |
226 | ||
227 | static int gmisc(grand *r, unsigned op, ...) | |
228 | { | |
229 | gctx *g = (gctx *)r; | |
230 | va_list ap; | |
231 | int rc = 0; | |
232 | va_start(ap, op); | |
233 | ||
234 | switch (op) { | |
235 | case GRAND_CHECK: | |
236 | switch (va_arg(ap, unsigned)) { | |
45c0fd36 MW |
237 | case GRAND_CHECK: |
238 | case GRAND_SEEDINT: | |
239 | case GRAND_SEEDUINT32: | |
240 | case GRAND_SEEDMP: | |
4ab1268f | 241 | case GRAND_SEEDRAND: |
2c52abe6 | 242 | case BBS_SET: |
2cc3d1d0 | 243 | case BBS_STEP: |
244 | case BBS_STEPSZ: | |
245 | case BBS_BITS: | |
246 | case BBS_WRAP: | |
247 | case BBS_FF: | |
248 | case BBS_FFN: | |
249 | case BBS_REW: | |
250 | case BBS_REWN: | |
251 | case BBS_MOD: | |
252 | case BBS_STATE: | |
45c0fd36 MW |
253 | rc = 1; |
254 | break; | |
255 | default: | |
256 | rc = 0; | |
257 | break; | |
2c52abe6 | 258 | } |
259 | break; | |
260 | case GRAND_SEEDINT: { | |
261 | mp *x = mp_fromuint(MP_NEW, va_arg(ap, unsigned)); | |
262 | bbs_seed(&g->b, x); | |
263 | mp_drop(x); | |
264 | } break; | |
265 | case GRAND_SEEDUINT32: { | |
266 | mp *x = mp_fromuint32(MP_NEW, va_arg(ap, uint32)); | |
267 | bbs_seed(&g->b, x); | |
268 | mp_drop(x); | |
269 | } break; | |
270 | case GRAND_SEEDMP: | |
271 | bbs_seed(&g->b, va_arg(ap, mp *)); | |
272 | break; | |
4ab1268f | 273 | case GRAND_SEEDRAND: { |
274 | grand *rr = va_arg(ap, grand *); | |
275 | mp *m = mprand(MP_NEW, mp_bits(g->b.mb.m) - 1, rr, 0); | |
276 | bbs_seed(&g->b, m); | |
277 | mp_drop(m); | |
278 | } break; | |
2c52abe6 | 279 | case BBS_SET: |
280 | bbs_set(&g->b, va_arg(ap, mp *)); | |
281 | break; | |
2cc3d1d0 | 282 | case BBS_STEP: |
283 | bbs_step(&g->b); | |
284 | break; | |
285 | case BBS_STEPSZ: | |
286 | rc = g->b.k; | |
287 | break; | |
288 | case BBS_BITS: { | |
289 | unsigned nb = va_arg(ap, unsigned); | |
290 | uint32 *w = va_arg(ap, uint32 *); | |
291 | *w = bbs_bits(&g->b, nb); | |
292 | } break; | |
293 | case BBS_WRAP: | |
294 | bbs_wrap(&g->b); | |
295 | break; | |
296 | case BBS_FF: { | |
297 | const bbs_priv *bp = va_arg(ap, const bbs_priv *); | |
298 | mp *n = va_arg(ap, mp *); | |
299 | bbs_ff(&g->b, bp, n); | |
300 | } break; | |
301 | case BBS_FFN: { | |
302 | const bbs_priv *bp = va_arg(ap, const bbs_priv *); | |
303 | unsigned long n = va_arg(ap, unsigned long); | |
304 | bbs_ffn(&g->b, bp, n); | |
305 | } break; | |
306 | case BBS_REW: { | |
307 | const bbs_priv *bp = va_arg(ap, const bbs_priv *); | |
308 | mp *n = va_arg(ap, mp *); | |
309 | bbs_rew(&g->b, bp, n); | |
310 | } break; | |
311 | case BBS_REWN: { | |
312 | const bbs_priv *bp = va_arg(ap, const bbs_priv *); | |
313 | unsigned long n = va_arg(ap, unsigned long); | |
314 | bbs_rewn(&g->b, bp, n); | |
315 | } break; | |
316 | case BBS_MOD: { | |
317 | mp **n = va_arg(ap, mp **); | |
318 | if (*n) MP_DROP(*n); | |
319 | *n = MP_COPY(g->b.mb.m); | |
320 | } break; | |
321 | case BBS_STATE: { | |
322 | mp **n = va_arg(ap, mp **); | |
323 | if (*n) MP_DROP(*n); | |
324 | *n = MP_COPY(g->b.x); | |
325 | } break; | |
2c52abe6 | 326 | default: |
327 | GRAND_BADOP; | |
328 | break; | |
329 | } | |
330 | ||
331 | va_end(ap); | |
332 | return (rc); | |
333 | } | |
334 | ||
335 | static octet gbyte(grand *r) | |
336 | { | |
337 | gctx *g = (gctx *)r; | |
338 | return (bbs_bits(&g->b, 8)); | |
339 | } | |
340 | ||
341 | static uint32 gword(grand *r) | |
342 | { | |
343 | gctx *g = (gctx *)r; | |
344 | return (bbs_bits(&g->b, 32)); | |
345 | } | |
346 | ||
347 | static const grand_ops gops = { | |
348 | "bbs", | |
fbdfd34e | 349 | GRAND_CRYPTO, 0, |
2c52abe6 | 350 | gmisc, gdestroy, |
44ff6c11 | 351 | gword, gbyte, gword, grand_defaultrange, grand_defaultfill |
2c52abe6 | 352 | }; |
353 | ||
354 | /* --- @bbs_rand@ --- * | |
355 | * | |
45c0fd36 | 356 | * Arguments: @mp *m@ = modulus |
2c52abe6 | 357 | * @mp *x@ = initial seed |
358 | * | |
45c0fd36 | 359 | * Returns: Pointer to a generic generator. |
2c52abe6 | 360 | * |
45c0fd36 | 361 | * Use: Constructs a generic generator interface over a |
2c52abe6 | 362 | * Blum-Blum-Shub generator. |
363 | */ | |
364 | ||
365 | grand *bbs_rand(mp *m, mp *x) | |
366 | { | |
fbdfd34e | 367 | gctx *g = S_CREATE(gctx); |
2c52abe6 | 368 | g->r.ops = &gops; |
369 | bbs_create(&g->b, m, x); | |
370 | return (&g->r); | |
371 | } | |
372 | ||
373 | /*----- Test rig ----------------------------------------------------------*/ | |
374 | ||
375 | #ifdef TEST_RIG | |
376 | ||
377 | static int verify(dstr *v) | |
378 | { | |
379 | mp *n = *(mp **)v[0].buf; | |
380 | mp *x = *(mp **)v[1].buf; | |
381 | grand *b = bbs_rand(n, x); | |
382 | dstr d = DSTR_INIT; | |
383 | int ok = 1; | |
384 | ||
385 | dstr_ensure(&d, v[2].len); | |
386 | b->ops->fill(b, d.buf, v[2].len); | |
387 | d.len = v[2].len; | |
388 | if (memcmp(d.buf, v[2].buf, v[2].len) != 0) { | |
389 | fputs("\n*** bbs failure\n", stderr); | |
390 | fputs("n = ", stderr); mp_writefile(n, stderr, 10); fputc('\n', stderr); | |
391 | fputs("x = ", stderr); mp_writefile(x, stderr, 10); fputc('\n', stderr); | |
392 | fputs("expected = ", stderr); type_hex.dump(&v[2], stderr); | |
393 | fputc('\n', stderr); | |
394 | fputs(" found = ", stderr); type_hex.dump(&d, stderr); | |
395 | fputc('\n', stderr); | |
396 | fprintf(stderr, "k = %u\n", ((gctx *)b)->b.k); | |
397 | ok = 0; | |
398 | } | |
399 | b->ops->destroy(b); | |
400 | mp_drop(x); | |
401 | mp_drop(n); | |
402 | dstr_destroy(&d); | |
403 | assert(mparena_count(MPARENA_GLOBAL) == 0); | |
404 | return (ok); | |
405 | } | |
406 | ||
407 | static test_chunk tests[] = { | |
408 | { "bbs", verify, { &type_mp, &type_mp, &type_hex, 0 } }, | |
409 | { 0, 0, { 0 } } | |
410 | }; | |
411 | ||
412 | int main(int argc, char *argv[]) | |
413 | { | |
414 | sub_init(); | |
0f00dc4c | 415 | test_run(argc, argv, tests, SRCDIR "/t/bbs"); |
2c52abe6 | 416 | return (0); |
417 | } | |
418 | ||
419 | #endif | |
420 | ||
421 | /*----- That's all, folks -------------------------------------------------*/ |