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1 | /* -*-c-*- |
2 | * |
383e235b |
3 | * $Id: limlee.c,v 1.8 2001/02/03 11:59:07 mdw Exp $ |
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4 | * |
5 | * Generate Lim-Lee primes |
6 | * |
7 | * (c) 2000 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: limlee.c,v $ |
383e235b |
33 | * Revision 1.8 2001/02/03 11:59:07 mdw |
34 | * Don't use the @pgen@ random number generator for generating primes: it's |
35 | * only for testing them. Use a caller-supplied one instead. |
36 | * |
d50e18d7 |
37 | * Revision 1.7 2001/01/25 21:40:44 mdw |
38 | * Remove dead code now that the new stepper structure is trustworthy. |
39 | * |
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40 | * Revision 1.6 2001/01/25 21:16:20 mdw |
41 | * Boring cosmetic stuff. |
42 | * |
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43 | * Revision 1.5 2000/08/18 19:16:51 mdw |
44 | * New stepper interface for constructing Lim-Lee primes. |
45 | * |
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46 | * Revision 1.4 2000/08/15 21:45:05 mdw |
47 | * Use the new trial division equipment in pfilt. This gives a 10% |
48 | * performance improvement in dsa-gen.t. |
49 | * |
2f627546 |
50 | * Revision 1.3 2000/07/29 09:58:32 mdw |
51 | * (limlee): Bug fix. Old versions didn't set the filter step if @ql@ was |
52 | * an exact divisor of @pl@. |
53 | * |
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54 | * Revision 1.2 2000/07/26 18:00:00 mdw |
55 | * No footer line! |
56 | * |
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57 | * Revision 1.1 2000/07/09 21:30:58 mdw |
58 | * Lim-Lee prime generation. |
59 | * |
60 | */ |
61 | |
62 | /*----- Header files ------------------------------------------------------*/ |
63 | |
64 | #include <mLib/alloc.h> |
65 | #include <mLib/dstr.h> |
66 | |
67 | #include "limlee.h" |
68 | #include "mpmul.h" |
69 | #include "mprand.h" |
70 | #include "pgen.h" |
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71 | #include "rabin.h" |
72 | |
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73 | /*----- Stepping through combinations -------------------------------------*/ |
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74 | |
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75 | /* --- @comb_init@ --- * |
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76 | * |
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77 | * Arguments: @octet *c@ = pointer to byte-flag array |
78 | * @unsigned n@ = number of items in the array |
79 | * @unsigned r@ = number of desired items |
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80 | * |
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81 | * Returns: --- |
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82 | * |
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83 | * Use: Initializes a byte-flag array which, under the control of |
84 | * @comb_next@, will step through all combinations of @r@ chosen |
85 | * elements. |
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86 | */ |
87 | |
88 | static void comb_init(octet *c, unsigned n, unsigned r) |
89 | { |
90 | memset(c, 0, n - r); |
91 | memset(c + (n - r), 1, r); |
92 | } |
93 | |
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94 | /* --- @comb_next@ --- * |
95 | * |
96 | * Arguments: @octet *c@ = pointer to byte-flag array |
97 | * @unsigned n@ = number of items in the array |
98 | * @unsigned r@ = number of desired items |
99 | * |
100 | * Returns: Nonzero if another combination was returned, zero if we've |
101 | * reached the end. |
102 | * |
103 | * Use: Steps on to the next combination in sequence. |
104 | */ |
105 | |
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106 | static int comb_next(octet *c, unsigned n, unsigned r) |
107 | { |
108 | unsigned g = 0; |
109 | |
110 | /* --- How the algorithm works --- * |
111 | * |
112 | * Set bits start at the end and work their way towards the start. |
113 | * Excepting bits already at the start, we scan for the lowest set bit, and |
114 | * move it one place nearer the start. A group of bits at the start are |
115 | * counted and reset just below the `moved' bit. If there is no moved bit |
116 | * then we're done. |
117 | */ |
118 | |
119 | /* --- Count the group at the start --- */ |
120 | |
121 | for (; *c; c++) { |
122 | g++; |
123 | *c = 0; |
124 | } |
125 | if (g == r) |
126 | return (0); |
127 | |
128 | /* --- Move the next bit down one --- * |
129 | * |
130 | * There must be one, because otherwise we'd have counted %$r$% bits |
131 | * earlier. |
132 | */ |
133 | |
134 | for (; !*c; c++) |
135 | ; |
136 | *c = 0; |
137 | g++; |
138 | for (; g; g--) |
139 | *--c = 1; |
140 | return (1); |
141 | } |
142 | |
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143 | /*----- Default prime generator -------------------------------------------*/ |
144 | |
145 | static void llgen(limlee_factor *f, unsigned pl, limlee_stepctx *l) |
146 | { |
147 | pgen_filterctx pf; |
148 | rabin r; |
149 | mp *p; |
150 | |
151 | again: |
152 | p = mprand(l->newp, pl, l->r, 1); |
153 | pf.step = 2; |
154 | p = pgen(l->d.buf, p, p, l->iev, l->iec, 0, pgen_filter, &pf, |
155 | rabin_iters(pl), pgen_test, &r); |
156 | if (!p) |
157 | goto again; |
158 | f->p = p; |
159 | } |
160 | |
161 | static void llfree(limlee_factor *f, limlee_stepctx *l) |
162 | { |
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163 | mp_drop(f->p); |
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164 | } |
165 | |
166 | static const limlee_primeops primeops_simple = { llgen, llfree }; |
167 | |
168 | /*----- Lim-Lee stepper ---------------------------------------------------*/ |
169 | |
170 | /* --- @init@ --- * |
171 | * |
172 | * Arguments: @pgen_event *ev@ = pointer to event block |
173 | * @limlee_stepctx *l@ = pointer to Lim-Lee context |
174 | * |
175 | * Returns: A @PGEN@ result code. |
176 | * |
177 | * Use: Initializes the stepper. |
178 | */ |
179 | |
180 | static int init(pgen_event *ev, limlee_stepctx *l) |
181 | { |
182 | size_t i; |
183 | unsigned qql; |
184 | |
185 | /* --- First of all, decide on a number of factors to make --- */ |
186 | |
187 | l->nf = l->pl / l->ql; |
188 | qql = l->pl % l->ql; |
189 | if (!l->nf) |
190 | return (PGEN_ABORT); |
191 | else if (qql && l->nf > 1) { |
192 | l->nf--; |
193 | qql += l->ql; |
194 | } |
195 | |
196 | /* --- Now decide on how many primes I'll actually generate --- * |
197 | * |
198 | * The formula %$m = \max(3 n + 5, 25)$% comes from GPG's prime generation |
199 | * library. |
200 | */ |
201 | |
202 | l->poolsz = l->nf * 3 + 5; |
203 | if (l->poolsz < 25) |
204 | l->poolsz = 25; |
205 | |
206 | /* --- Allocate and initialize the various tables --- */ |
207 | |
208 | l->c = xmalloc(l->poolsz); |
209 | l->v = xmalloc(l->poolsz * sizeof(limlee_factor)); |
210 | comb_init(l->c, l->poolsz, l->nf); |
211 | for (i = 0; i < l->poolsz; i++) |
212 | l->v[i].p = 0; |
213 | |
214 | /* --- Other bits of initialization --- */ |
215 | |
216 | l->seq = 0; |
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217 | dstr_create(&l->d); |
218 | if (!l->pops) { |
219 | l->pops = &primeops_simple; |
220 | l->pc = 0; |
221 | } |
222 | |
223 | /* --- Find a big prime --- */ |
224 | |
225 | if (!qql) |
226 | l->qq.p = 0; |
227 | else { |
228 | dstr_putf(&l->d, "%s*", ev->name); |
229 | l->pops->pgen(&l->qq, qql, l); |
230 | } |
231 | |
232 | return (PGEN_TRY); |
233 | } |
234 | |
235 | /* --- @next@ --- * |
236 | * |
237 | * Arguments: @int rq@ = request which triggered this call |
238 | * @pgen_event *ev@ = pointer to event block |
239 | * @limlee_stepctx *l@ = pointer to Lim-Lee context |
240 | * |
241 | * Returns: A @PGEN@ result code. |
242 | * |
243 | * Use: Initializes the stepper. |
244 | */ |
245 | |
246 | static int next(int rq, pgen_event *ev, limlee_stepctx *l) |
247 | { |
248 | mp *p; |
249 | int rc; |
250 | |
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251 | mp_drop(ev->m); |
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252 | |
253 | for (;;) { |
254 | size_t i; |
255 | mpmul mm = MPMUL_INIT; |
256 | |
257 | /* --- Step on to next combination --- */ |
258 | |
259 | if (rq == PGEN_TRY && !comb_next(l->c, l->poolsz, l->nf)) { |
260 | for (i = 0; i < l->poolsz; i++) { |
261 | l->pops->pfree(&l->v[i], l); |
262 | l->v[i].p = 0; |
263 | } |
264 | } |
265 | rq = PGEN_TRY; /* For next time through */ |
266 | |
267 | /* --- Gather up some factors --- */ |
268 | |
269 | if (l->qq.p) |
270 | mpmul_add(&mm, l->qq.p); |
271 | for (i = 0; i < l->poolsz; i++) { |
272 | if (!l->c[i]) |
273 | continue; |
274 | if (!l->v[i].p) { |
275 | DRESET(&l->d); |
276 | dstr_putf(&l->d, "%s_%lu", ev->name, l->seq++); |
277 | l->pops->pgen(&l->v[i], l->ql, l); |
278 | } |
279 | mpmul_add(&mm, l->v[i].p); |
280 | } |
281 | |
282 | /* --- Check it for small factors --- */ |
283 | |
284 | p = mpmul_done(&mm); |
285 | p = mp_lsl(p, p, 1); |
286 | p->v[0] |= 1; |
287 | if ((rc = pfilt_smallfactor(p)) != PGEN_FAIL) |
288 | break; |
289 | mp_drop(p); |
290 | } |
291 | |
292 | ev->m = p; |
293 | return (rc); |
294 | } |
295 | |
296 | /* --- @done@ --- * |
297 | * |
298 | * Arguments: @pgen_event *ev@ = pointer to event block |
299 | * @limlee_stepctx *l@ = pointer to Lim-Lee context |
300 | * |
301 | * Returns: A @PGEN@ result code. |
302 | * |
303 | * Use: Finalizes the stepper. The output values in the context |
304 | * take on their final results; other resources are discarded. |
305 | */ |
306 | |
307 | static int done(pgen_event *ev, limlee_stepctx *l) |
308 | { |
309 | size_t i, j; |
310 | limlee_factor *v; |
311 | |
312 | /* --- If an output vector of factors is wanted, produce one --- */ |
313 | |
314 | if (!(l->f & LIMLEE_KEEPFACTORS)) |
315 | v = 0; |
316 | else { |
317 | if (l->qq.p) |
318 | l->nf++; |
319 | v = xmalloc(l->nf * sizeof(limlee_factor)); |
320 | } |
321 | |
322 | for (i = 0, j = 0; i < l->poolsz; i++) { |
323 | if (v && l->c[i]) |
324 | v[j++] = l->v[i]; |
325 | else if (l->v[i].p) |
326 | l->pops->pfree(&l->v[i], l); |
327 | } |
328 | |
329 | if (l->qq.p) { |
330 | if (v) |
331 | v[j++] = l->qq; |
332 | else |
333 | l->pops->pfree(&l->qq, l); |
334 | } |
335 | |
336 | xfree(l->v); |
337 | l->v = v; |
338 | |
339 | /* --- Free other resources --- */ |
340 | |
341 | xfree(l->c); |
342 | dstr_destroy(&l->d); |
343 | |
344 | /* --- Done --- */ |
345 | |
346 | return (PGEN_DONE); |
347 | } |
348 | |
349 | /* --- @limlee_step@ --- */ |
350 | |
351 | int limlee_step(int rq, pgen_event *ev, void *p) |
352 | { |
353 | limlee_stepctx *l = p; |
354 | int rc; |
355 | |
356 | switch (rq) { |
357 | case PGEN_BEGIN: |
358 | if ((rc = init(ev, l)) != PGEN_TRY) |
359 | return (rc); |
360 | case PGEN_TRY: |
361 | return (next(rq, ev, l)); |
362 | case PGEN_DONE: |
363 | return (done(ev, l)); |
364 | } |
365 | return (PGEN_ABORT); |
366 | } |
367 | |
368 | /*----- Main code ---------------------------------------------------------*/ |
369 | |
370 | /* --- @limlee@ --- * |
371 | * |
372 | * Arguments: @const char *name@ = pointer to name root |
373 | * @mp *d@ = pointer to destination integer |
374 | * @mp *newp@ = how to generate factor primes |
375 | * @unsigned ql@ = size of individual factors |
376 | * @unsigned pl@ = size of large prime |
377 | * @grand *r@ = a random number source |
378 | * @unsigned on@ = number of outer attempts to make |
379 | * @pgen_proc *oev@ = outer event handler function |
380 | * @void *oec@ = argument for the outer event handler |
381 | * @pgen_proc *iev@ = inner event handler function |
382 | * @void *iec@ = argument for the inner event handler |
383 | * @size_t *nf@, @mp ***f@ = output array for factors |
384 | * |
385 | * Returns: A Lim-Lee prime, or null if generation failed. |
386 | * |
387 | * Use: Generates Lim-Lee primes. A Lim-Lee prime %$p$% is one which |
388 | * satisfies %$p = 2 \prod_i q_i + 1$%, where all of the %$q_i$% |
389 | * are large enough to resist square-root discrete log |
390 | * algorithms. |
391 | * |
392 | * If we succeed, and @f@ is non-null, we write the array of |
393 | * factors chosen to @f@ for the benefit of the caller. |
394 | */ |
395 | |
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396 | mp *limlee(const char *name, mp *d, mp *newp, |
397 | unsigned ql, unsigned pl, grand *r, |
398 | unsigned on, pgen_proc *oev, void *oec, |
399 | pgen_proc *iev, void *iec, |
400 | size_t *nf, mp ***f) |
401 | { |
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402 | limlee_stepctx l; |
403 | rabin rr; |
404 | |
405 | l.f = 0; if (f) l.f |= LIMLEE_KEEPFACTORS; |
406 | l.newp = newp; |
407 | l.pl = pl; l.ql = ql; |
408 | l.pops = 0; |
409 | l.iev = iev; |
410 | l.iec = iec; |
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411 | l.r = r; |
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412 | |
413 | d = pgen(name, d, 0, oev, oec, on, limlee_step, &l, |
414 | rabin_iters(pl), pgen_test, &rr); |
415 | |
416 | if (f) { |
417 | mp **v; |
418 | size_t i; |
419 | v = xmalloc(l.nf * sizeof(mp *)); |
420 | for (i = 0; i < l.nf; i++) |
421 | v[i] = l.v[i].p; |
422 | xfree(l.v); |
423 | *f = v; |
424 | *nf = l.nf; |
425 | } |
426 | |
427 | return (d); |
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428 | } |
429 | |
d28d625a |
430 | /*----- That's all, folks -------------------------------------------------*/ |