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