| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: bbs-rand.c,v 1.5 2004/04/08 01:36:15 mdw Exp $ |
| 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 | /*----- Header files ------------------------------------------------------*/ |
| 31 | |
| 32 | #include <stdarg.h> |
| 33 | #include <stdlib.h> |
| 34 | #include <string.h> |
| 35 | |
| 36 | #include <mLib/bits.h> |
| 37 | #include <mLib/sub.h> |
| 38 | |
| 39 | #include "arena.h" |
| 40 | #include "bbs.h" |
| 41 | #include "grand.h" |
| 42 | #include "mp.h" |
| 43 | #include "mpbarrett.h" |
| 44 | #include "mpint.h" |
| 45 | #include "mprand.h" |
| 46 | #include "paranoia.h" |
| 47 | |
| 48 | /*----- Main code ---------------------------------------------------------*/ |
| 49 | |
| 50 | /* --- @bbs_create@ --- * |
| 51 | * |
| 52 | * Arguments: @bbs *b@ = pointer to BBS generator state to initialize |
| 53 | * @mp *m@ = modulus (must be a Blum integer) |
| 54 | * @mp *x@ = initial seed for generator |
| 55 | * |
| 56 | * Returns: --- |
| 57 | * |
| 58 | * Use: Initializes a BBS generator. The generator is stepped once |
| 59 | * after initialization, as for @bbs_seed@. |
| 60 | */ |
| 61 | |
| 62 | void bbs_create(bbs *b, mp *m, mp *x) |
| 63 | { |
| 64 | mpw kw; |
| 65 | mp k; |
| 66 | |
| 67 | mpbarrett_create(&b->mb, m); |
| 68 | kw = mp_bits(m) - 1; |
| 69 | mp_build(&k, &kw, &kw + 1); |
| 70 | b->k = mp_bits(&k) - 1; |
| 71 | b->x = 0; |
| 72 | bbs_seed(b, x); |
| 73 | } |
| 74 | |
| 75 | /* --- @bbs_destroy@ --- * |
| 76 | * |
| 77 | * Arguments: @bbs *b@ = pointer to BBS generator state |
| 78 | * |
| 79 | * Returns: --- |
| 80 | * |
| 81 | * Use: Destroys a generator state when it's no longer wanted. |
| 82 | */ |
| 83 | |
| 84 | void bbs_destroy(bbs *b) |
| 85 | { |
| 86 | mp_drop(b->x); |
| 87 | mpbarrett_destroy(&b->mb); |
| 88 | } |
| 89 | |
| 90 | /* --- @bbs_step@ --- * |
| 91 | * |
| 92 | * Arguments: @bbs *b@ = pointer to BBS generator state |
| 93 | * |
| 94 | * Returns: --- |
| 95 | * |
| 96 | * Use: Steps the generator once. This isn't too useful in client |
| 97 | * code. |
| 98 | */ |
| 99 | |
| 100 | void bbs_step(bbs *b) |
| 101 | { |
| 102 | mp *x = b->x; |
| 103 | x = mp_sqr(x, x); |
| 104 | x = mpbarrett_reduce(&b->mb, x, x); |
| 105 | b->x = x; |
| 106 | b->b = b->k; |
| 107 | b->r = b->x->v[0]; |
| 108 | } |
| 109 | |
| 110 | /* --- @bbs_set@ --- * |
| 111 | * |
| 112 | * Arguments: @bbs *b@ = pointer to BBS generator state |
| 113 | * @mp *x@ = new residue to set |
| 114 | * |
| 115 | * Returns: --- |
| 116 | * |
| 117 | * Use: Sets a new quadratic residue. The generator is stepped once. |
| 118 | */ |
| 119 | |
| 120 | void bbs_set(bbs *b, mp *x) |
| 121 | { |
| 122 | mp_drop(b->x); |
| 123 | b->x = MP_COPY(x); |
| 124 | bbs_step(b); |
| 125 | } |
| 126 | |
| 127 | /* --- @bbs_seed@ --- * |
| 128 | * |
| 129 | * Arguments: @bbs *b@ = pointer to BBS generator state |
| 130 | * @mp *x@ = new seed to set |
| 131 | * |
| 132 | * Returns --- |
| 133 | * |
| 134 | * Use: Sets a new seed. The generator is stepped until the residue |
| 135 | * has clearly wrapped around. |
| 136 | */ |
| 137 | |
| 138 | void bbs_seed(bbs *b, mp *x) |
| 139 | { |
| 140 | mp *y; |
| 141 | x = MP_COPY(x); |
| 142 | for (;;) { |
| 143 | y = mp_sqr(MP_NEW, x); |
| 144 | y = mpbarrett_reduce(&b->mb, y, y); |
| 145 | if (MP_CMP(y, <, x)) |
| 146 | break; |
| 147 | mp_drop(x); |
| 148 | x = y; |
| 149 | } |
| 150 | mp_drop(x); |
| 151 | bbs_set(b, y); |
| 152 | mp_drop(y); |
| 153 | } |
| 154 | |
| 155 | /* --- @bbs_bits@ --- * |
| 156 | * |
| 157 | * Arguments: @bbs *b@ = pointer to BBS generator state |
| 158 | * @unsigned bits@ = number of bits wanted |
| 159 | * |
| 160 | * Returns: Bits extracted from the BBS generator. |
| 161 | * |
| 162 | * Use: Extracts a requested number of bits from the BBS generator. |
| 163 | */ |
| 164 | |
| 165 | uint32 bbs_bits(bbs *b, unsigned bits) |
| 166 | { |
| 167 | uint32 x = 0; |
| 168 | mpw m; |
| 169 | |
| 170 | /* --- Keep turning the handle until there's enough in the reservoir --- */ |
| 171 | |
| 172 | while (bits >= b->b) { |
| 173 | bits -= b->b; |
| 174 | m = (1 << b->b) - 1; |
| 175 | x |= (b->r & m) << bits; |
| 176 | bbs_step(b); |
| 177 | } |
| 178 | |
| 179 | /* --- Extract the last few bits needed --- */ |
| 180 | |
| 181 | if (bits) { |
| 182 | m = (1 << bits) - 1; |
| 183 | b->b -= bits; |
| 184 | x |= (b->r >> b->b) & m; |
| 185 | } |
| 186 | |
| 187 | /* --- Done --- */ |
| 188 | |
| 189 | return (x); |
| 190 | } |
| 191 | |
| 192 | /* --- @bbs_wrap@ --- * |
| 193 | * |
| 194 | * Arguments: @bbs *b@ = pointer to BBS generator state |
| 195 | * |
| 196 | * Returns: --- |
| 197 | * |
| 198 | * Use: Steps the generator if any of the reservoir bits are used. |
| 199 | * This can be used to `wrap up' after a Blum-Goldwasser |
| 200 | * encryption, for example, producing the final value to be sent |
| 201 | * along with the ciphertext. |
| 202 | * |
| 203 | * If a generator is seeded, %$b$% bits are extracted, and then |
| 204 | * @bbs_wrap@ is called, the generator will have been stepped |
| 205 | * %$\lceil b/k \rceil$% times. |
| 206 | */ |
| 207 | |
| 208 | void bbs_wrap(bbs *b) |
| 209 | { |
| 210 | if (b->b < b->k) |
| 211 | bbs_step(b); |
| 212 | } |
| 213 | |
| 214 | /*----- Generic random number generator interface -------------------------*/ |
| 215 | |
| 216 | typedef struct gctx { |
| 217 | grand r; |
| 218 | bbs b; |
| 219 | } gctx; |
| 220 | |
| 221 | static void gdestroy(grand *r) |
| 222 | { |
| 223 | gctx *g = (gctx *)r; |
| 224 | bbs_destroy(&g->b); |
| 225 | BURN(*g); |
| 226 | S_DESTROY(g); |
| 227 | } |
| 228 | |
| 229 | static int gmisc(grand *r, unsigned op, ...) |
| 230 | { |
| 231 | gctx *g = (gctx *)r; |
| 232 | va_list ap; |
| 233 | int rc = 0; |
| 234 | va_start(ap, op); |
| 235 | |
| 236 | switch (op) { |
| 237 | case GRAND_CHECK: |
| 238 | switch (va_arg(ap, unsigned)) { |
| 239 | case GRAND_CHECK: |
| 240 | case GRAND_SEEDINT: |
| 241 | case GRAND_SEEDUINT32: |
| 242 | case GRAND_SEEDMP: |
| 243 | case GRAND_SEEDRAND: |
| 244 | case BBS_SET: |
| 245 | rc = 1; |
| 246 | break; |
| 247 | default: |
| 248 | rc = 0; |
| 249 | break; |
| 250 | } |
| 251 | break; |
| 252 | case GRAND_SEEDINT: { |
| 253 | mp *x = mp_fromuint(MP_NEW, va_arg(ap, unsigned)); |
| 254 | bbs_seed(&g->b, x); |
| 255 | mp_drop(x); |
| 256 | } break; |
| 257 | case GRAND_SEEDUINT32: { |
| 258 | mp *x = mp_fromuint32(MP_NEW, va_arg(ap, uint32)); |
| 259 | bbs_seed(&g->b, x); |
| 260 | mp_drop(x); |
| 261 | } break; |
| 262 | case GRAND_SEEDMP: |
| 263 | bbs_seed(&g->b, va_arg(ap, mp *)); |
| 264 | break; |
| 265 | case GRAND_SEEDRAND: { |
| 266 | grand *rr = va_arg(ap, grand *); |
| 267 | mp *m = mprand(MP_NEW, mp_bits(g->b.mb.m) - 1, rr, 0); |
| 268 | bbs_seed(&g->b, m); |
| 269 | mp_drop(m); |
| 270 | } break; |
| 271 | case BBS_SET: |
| 272 | bbs_set(&g->b, va_arg(ap, mp *)); |
| 273 | break; |
| 274 | default: |
| 275 | GRAND_BADOP; |
| 276 | break; |
| 277 | } |
| 278 | |
| 279 | va_end(ap); |
| 280 | return (rc); |
| 281 | } |
| 282 | |
| 283 | static octet gbyte(grand *r) |
| 284 | { |
| 285 | gctx *g = (gctx *)r; |
| 286 | return (bbs_bits(&g->b, 8)); |
| 287 | } |
| 288 | |
| 289 | static uint32 gword(grand *r) |
| 290 | { |
| 291 | gctx *g = (gctx *)r; |
| 292 | return (bbs_bits(&g->b, 32)); |
| 293 | } |
| 294 | |
| 295 | static const grand_ops gops = { |
| 296 | "bbs", |
| 297 | GRAND_CRYPTO, 0, |
| 298 | gmisc, gdestroy, |
| 299 | gword, gbyte, gword, grand_range, grand_fill |
| 300 | }; |
| 301 | |
| 302 | /* --- @bbs_rand@ --- * |
| 303 | * |
| 304 | * Arguments: @mp *m@ = modulus |
| 305 | * @mp *x@ = initial seed |
| 306 | * |
| 307 | * Returns: Pointer to a generic generator. |
| 308 | * |
| 309 | * Use: Constructs a generic generator interface over a |
| 310 | * Blum-Blum-Shub generator. |
| 311 | */ |
| 312 | |
| 313 | grand *bbs_rand(mp *m, mp *x) |
| 314 | { |
| 315 | gctx *g = S_CREATE(gctx); |
| 316 | g->r.ops = &gops; |
| 317 | bbs_create(&g->b, m, x); |
| 318 | return (&g->r); |
| 319 | } |
| 320 | |
| 321 | /*----- Test rig ----------------------------------------------------------*/ |
| 322 | |
| 323 | #ifdef TEST_RIG |
| 324 | |
| 325 | static int verify(dstr *v) |
| 326 | { |
| 327 | mp *n = *(mp **)v[0].buf; |
| 328 | mp *x = *(mp **)v[1].buf; |
| 329 | grand *b = bbs_rand(n, x); |
| 330 | dstr d = DSTR_INIT; |
| 331 | int ok = 1; |
| 332 | |
| 333 | dstr_ensure(&d, v[2].len); |
| 334 | b->ops->fill(b, d.buf, v[2].len); |
| 335 | d.len = v[2].len; |
| 336 | if (memcmp(d.buf, v[2].buf, v[2].len) != 0) { |
| 337 | fputs("\n*** bbs failure\n", stderr); |
| 338 | fputs("n = ", stderr); mp_writefile(n, stderr, 10); fputc('\n', stderr); |
| 339 | fputs("x = ", stderr); mp_writefile(x, stderr, 10); fputc('\n', stderr); |
| 340 | fputs("expected = ", stderr); type_hex.dump(&v[2], stderr); |
| 341 | fputc('\n', stderr); |
| 342 | fputs(" found = ", stderr); type_hex.dump(&d, stderr); |
| 343 | fputc('\n', stderr); |
| 344 | fprintf(stderr, "k = %u\n", ((gctx *)b)->b.k); |
| 345 | ok = 0; |
| 346 | } |
| 347 | b->ops->destroy(b); |
| 348 | mp_drop(x); |
| 349 | mp_drop(n); |
| 350 | dstr_destroy(&d); |
| 351 | assert(mparena_count(MPARENA_GLOBAL) == 0); |
| 352 | return (ok); |
| 353 | } |
| 354 | |
| 355 | static test_chunk tests[] = { |
| 356 | { "bbs", verify, { &type_mp, &type_mp, &type_hex, 0 } }, |
| 357 | { 0, 0, { 0 } } |
| 358 | }; |
| 359 | |
| 360 | int main(int argc, char *argv[]) |
| 361 | { |
| 362 | sub_init(); |
| 363 | test_run(argc, argv, tests, SRCDIR "/tests/bbs"); |
| 364 | return (0); |
| 365 | } |
| 366 | |
| 367 | #endif |
| 368 | |
| 369 | /*----- That's all, folks -------------------------------------------------*/ |