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