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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: bbs-rand.c,v 1.4 2001/02/03 12:00:29 mdw Exp $ |
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4 | * |
5 | * Blum-Blum-Shub secure random number generator |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
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. |
18 | * |
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. |
23 | * |
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 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: bbs-rand.c,v $ |
f1140c41 |
33 | * Revision 1.4 2001/02/03 12:00:29 mdw |
34 | * Now @mp_drop@ checks its argument is non-NULL before attempting to free |
35 | * it. Note that the macro version @MP_DROP@ doesn't do this. |
36 | * |
fbdfd34e |
37 | * Revision 1.3 2000/06/17 10:45:21 mdw |
38 | * Typesetting fixes. Advertise random number generator strength. Use |
39 | * secure arena for memory allocation. |
40 | * |
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41 | * Revision 1.2 1999/12/13 15:34:01 mdw |
42 | * Add support for seeding from a generic pseudorandom source. |
43 | * |
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44 | * Revision 1.1 1999/12/10 23:14:59 mdw |
45 | * Blum-Blum-Shub generator, and Blum-Goldwasser encryption. |
46 | * |
47 | */ |
48 | |
49 | /*----- Header files ------------------------------------------------------*/ |
50 | |
51 | #include <stdarg.h> |
52 | #include <stdlib.h> |
53 | #include <string.h> |
54 | |
55 | #include <mLib/bits.h> |
56 | #include <mLib/sub.h> |
57 | |
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58 | #include "arena.h" |
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59 | #include "bbs.h" |
60 | #include "grand.h" |
61 | #include "mp.h" |
62 | #include "mpbarrett.h" |
63 | #include "mpint.h" |
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64 | #include "mprand.h" |
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65 | #include "paranoia.h" |
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66 | |
67 | /*----- Main code ---------------------------------------------------------*/ |
68 | |
69 | /* --- @bbs_create@ --- * |
70 | * |
71 | * Arguments: @bbs *b@ = pointer to BBS generator state to initialize |
72 | * @mp *m@ = modulus (must be a Blum integer) |
73 | * @mp *x@ = initial seed for generator |
74 | * |
75 | * Returns: --- |
76 | * |
77 | * Use: Initializes a BBS generator. The generator is stepped once |
78 | * after initialization, as for @bbs_seed@. |
79 | */ |
80 | |
81 | void bbs_create(bbs *b, mp *m, mp *x) |
82 | { |
83 | mpw kw; |
84 | mp k; |
85 | |
86 | mpbarrett_create(&b->mb, m); |
87 | kw = mp_bits(m) - 1; |
88 | mp_build(&k, &kw, &kw + 1); |
89 | b->k = mp_bits(&k) - 1; |
90 | b->x = 0; |
91 | bbs_seed(b, x); |
92 | } |
93 | |
94 | /* --- @bbs_destroy@ --- * |
95 | * |
96 | * Arguments: @bbs *b@ = pointer to BBS generator state |
97 | * |
98 | * Returns: --- |
99 | * |
100 | * Use: Destroys a generator state when it's no longer wanted. |
101 | */ |
102 | |
103 | void bbs_destroy(bbs *b) |
104 | { |
105 | mp_drop(b->x); |
106 | mpbarrett_destroy(&b->mb); |
107 | } |
108 | |
109 | /* --- @bbs_step@ --- * |
110 | * |
111 | * Arguments: @bbs *b@ = pointer to BBS generator state |
112 | * |
113 | * Returns: --- |
114 | * |
115 | * Use: Steps the generator once. This isn't too useful in client |
116 | * code. |
117 | */ |
118 | |
119 | void bbs_step(bbs *b) |
120 | { |
121 | mp *x = b->x; |
122 | x = mp_sqr(x, x); |
123 | x = mpbarrett_reduce(&b->mb, x, x); |
124 | b->x = x; |
125 | b->b = b->k; |
126 | b->r = b->x->v[0]; |
127 | } |
128 | |
129 | /* --- @bbs_set@ --- * |
130 | * |
131 | * Arguments: @bbs *b@ = pointer to BBS generator state |
132 | * @mp *x@ = new residue to set |
133 | * |
134 | * Returns: --- |
135 | * |
136 | * Use: Sets a new quadratic residue. The generator is stepped once. |
137 | */ |
138 | |
139 | void bbs_set(bbs *b, mp *x) |
140 | { |
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141 | mp_drop(b->x); |
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142 | b->x = MP_COPY(x); |
143 | bbs_step(b); |
144 | } |
145 | |
146 | /* --- @bbs_seed@ --- * |
147 | * |
148 | * Arguments: @bbs *b@ = pointer to BBS generator state |
149 | * @mp *x@ = new seed to set |
150 | * |
151 | * Returns --- |
152 | * |
153 | * Use: Sets a new seed. The generator is stepped until the residue |
154 | * has clearly wrapped around. |
155 | */ |
156 | |
157 | void bbs_seed(bbs *b, mp *x) |
158 | { |
159 | mp *y; |
160 | x = MP_COPY(x); |
161 | for (;;) { |
162 | y = mp_sqr(MP_NEW, x); |
163 | y = mpbarrett_reduce(&b->mb, y, y); |
164 | if (MP_CMP(y, <, x)) |
165 | break; |
166 | mp_drop(x); |
167 | x = y; |
168 | } |
169 | mp_drop(x); |
170 | bbs_set(b, y); |
171 | mp_drop(y); |
172 | } |
173 | |
174 | /* --- @bbs_bits@ --- * |
175 | * |
176 | * Arguments: @bbs *b@ = pointer to BBS generator state |
177 | * @unsigned bits@ = number of bits wanted |
178 | * |
179 | * Returns: Bits extracted from the BBS generator. |
180 | * |
181 | * Use: Extracts a requested number of bits from the BBS generator. |
182 | */ |
183 | |
184 | uint32 bbs_bits(bbs *b, unsigned bits) |
185 | { |
186 | uint32 x = 0; |
187 | mpw m; |
188 | |
189 | /* --- Keep turning the handle until there's enough in the reservoir --- */ |
190 | |
191 | while (bits >= b->b) { |
192 | bits -= b->b; |
193 | m = (1 << b->b) - 1; |
194 | x |= (b->r & m) << bits; |
195 | bbs_step(b); |
196 | } |
197 | |
198 | /* --- Extract the last few bits needed --- */ |
199 | |
200 | if (bits) { |
201 | m = (1 << bits) - 1; |
202 | b->b -= bits; |
203 | x |= (b->r >> b->b) & m; |
204 | } |
205 | |
206 | /* --- Done --- */ |
207 | |
208 | return (x); |
209 | } |
210 | |
211 | /* --- @bbs_wrap@ --- * |
212 | * |
213 | * Arguments: @bbs *b@ = pointer to BBS generator state |
214 | * |
215 | * Returns: --- |
216 | * |
217 | * Use: Steps the generator if any of the reservoir bits are used. |
218 | * This can be used to `wrap up' after a Blum-Goldwasser |
219 | * encryption, for example, producing the final value to be sent |
220 | * along with the ciphertext. |
221 | * |
222 | * If a generator is seeded, %$b$% bits are extracted, and then |
223 | * @bbs_wrap@ is called, the generator will have been stepped |
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224 | * %$\lceil b/k \rceil$% times. |
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225 | */ |
226 | |
227 | void bbs_wrap(bbs *b) |
228 | { |
229 | if (b->b < b->k) |
230 | bbs_step(b); |
231 | } |
232 | |
233 | /*----- Generic random number generator interface -------------------------*/ |
234 | |
235 | typedef struct gctx { |
236 | grand r; |
237 | bbs b; |
238 | } gctx; |
239 | |
240 | static void gdestroy(grand *r) |
241 | { |
242 | gctx *g = (gctx *)r; |
243 | bbs_destroy(&g->b); |
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244 | BURN(*g); |
245 | S_DESTROY(g); |
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246 | } |
247 | |
248 | static int gmisc(grand *r, unsigned op, ...) |
249 | { |
250 | gctx *g = (gctx *)r; |
251 | va_list ap; |
252 | int rc = 0; |
253 | va_start(ap, op); |
254 | |
255 | switch (op) { |
256 | case GRAND_CHECK: |
257 | switch (va_arg(ap, unsigned)) { |
258 | case GRAND_CHECK: |
259 | case GRAND_SEEDINT: |
260 | case GRAND_SEEDUINT32: |
261 | case GRAND_SEEDMP: |
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262 | case GRAND_SEEDRAND: |
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263 | case BBS_SET: |
264 | rc = 1; |
265 | break; |
266 | default: |
267 | rc = 0; |
268 | break; |
269 | } |
270 | break; |
271 | case GRAND_SEEDINT: { |
272 | mp *x = mp_fromuint(MP_NEW, va_arg(ap, unsigned)); |
273 | bbs_seed(&g->b, x); |
274 | mp_drop(x); |
275 | } break; |
276 | case GRAND_SEEDUINT32: { |
277 | mp *x = mp_fromuint32(MP_NEW, va_arg(ap, uint32)); |
278 | bbs_seed(&g->b, x); |
279 | mp_drop(x); |
280 | } break; |
281 | case GRAND_SEEDMP: |
282 | bbs_seed(&g->b, va_arg(ap, mp *)); |
283 | break; |
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284 | case GRAND_SEEDRAND: { |
285 | grand *rr = va_arg(ap, grand *); |
286 | mp *m = mprand(MP_NEW, mp_bits(g->b.mb.m) - 1, rr, 0); |
287 | bbs_seed(&g->b, m); |
288 | mp_drop(m); |
289 | } break; |
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290 | case BBS_SET: |
291 | bbs_set(&g->b, va_arg(ap, mp *)); |
292 | break; |
293 | default: |
294 | GRAND_BADOP; |
295 | break; |
296 | } |
297 | |
298 | va_end(ap); |
299 | return (rc); |
300 | } |
301 | |
302 | static octet gbyte(grand *r) |
303 | { |
304 | gctx *g = (gctx *)r; |
305 | return (bbs_bits(&g->b, 8)); |
306 | } |
307 | |
308 | static uint32 gword(grand *r) |
309 | { |
310 | gctx *g = (gctx *)r; |
311 | return (bbs_bits(&g->b, 32)); |
312 | } |
313 | |
314 | static const grand_ops gops = { |
315 | "bbs", |
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316 | GRAND_CRYPTO, 0, |
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317 | gmisc, gdestroy, |
318 | gword, gbyte, gword, grand_range, grand_fill |
319 | }; |
320 | |
321 | /* --- @bbs_rand@ --- * |
322 | * |
323 | * Arguments: @mp *m@ = modulus |
324 | * @mp *x@ = initial seed |
325 | * |
326 | * Returns: Pointer to a generic generator. |
327 | * |
328 | * Use: Constructs a generic generator interface over a |
329 | * Blum-Blum-Shub generator. |
330 | */ |
331 | |
332 | grand *bbs_rand(mp *m, mp *x) |
333 | { |
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334 | gctx *g = S_CREATE(gctx); |
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335 | g->r.ops = &gops; |
336 | bbs_create(&g->b, m, x); |
337 | return (&g->r); |
338 | } |
339 | |
340 | /*----- Test rig ----------------------------------------------------------*/ |
341 | |
342 | #ifdef TEST_RIG |
343 | |
344 | static int verify(dstr *v) |
345 | { |
346 | mp *n = *(mp **)v[0].buf; |
347 | mp *x = *(mp **)v[1].buf; |
348 | grand *b = bbs_rand(n, x); |
349 | dstr d = DSTR_INIT; |
350 | int ok = 1; |
351 | |
352 | dstr_ensure(&d, v[2].len); |
353 | b->ops->fill(b, d.buf, v[2].len); |
354 | d.len = v[2].len; |
355 | if (memcmp(d.buf, v[2].buf, v[2].len) != 0) { |
356 | fputs("\n*** bbs failure\n", stderr); |
357 | fputs("n = ", stderr); mp_writefile(n, stderr, 10); fputc('\n', stderr); |
358 | fputs("x = ", stderr); mp_writefile(x, stderr, 10); fputc('\n', stderr); |
359 | fputs("expected = ", stderr); type_hex.dump(&v[2], stderr); |
360 | fputc('\n', stderr); |
361 | fputs(" found = ", stderr); type_hex.dump(&d, stderr); |
362 | fputc('\n', stderr); |
363 | fprintf(stderr, "k = %u\n", ((gctx *)b)->b.k); |
364 | ok = 0; |
365 | } |
366 | b->ops->destroy(b); |
367 | mp_drop(x); |
368 | mp_drop(n); |
369 | dstr_destroy(&d); |
370 | assert(mparena_count(MPARENA_GLOBAL) == 0); |
371 | return (ok); |
372 | } |
373 | |
374 | static test_chunk tests[] = { |
375 | { "bbs", verify, { &type_mp, &type_mp, &type_hex, 0 } }, |
376 | { 0, 0, { 0 } } |
377 | }; |
378 | |
379 | int main(int argc, char *argv[]) |
380 | { |
381 | sub_init(); |
382 | test_run(argc, argv, tests, SRCDIR "/tests/bbs"); |
383 | return (0); |
384 | } |
385 | |
386 | #endif |
387 | |
388 | /*----- That's all, folks -------------------------------------------------*/ |