| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: pgen-safe.c,v 1.4 2000/07/03 18:09:27 mdw Exp $ |
| 4 | * |
| 5 | * Safe prime generation |
| 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: pgen-safe.c,v $ |
| 33 | * Revision 1.4 2000/07/03 18:09:27 mdw |
| 34 | * Bug fix to the GCD check. With any luck, this is the last of these to |
| 35 | * need nailing to the wall. |
| 36 | * |
| 37 | * Revision 1.3 2000/06/17 11:52:36 mdw |
| 38 | * Signal a pgen abort if the jump and base share a common factor. |
| 39 | * |
| 40 | * Revision 1.2 2000/02/12 18:21:03 mdw |
| 41 | * Overhaul of key management (again). |
| 42 | * |
| 43 | * Revision 1.1 1999/12/22 16:01:34 mdw |
| 44 | * Find `safe' primes (i.e., %$p = 2q + 1$%). |
| 45 | * |
| 46 | */ |
| 47 | |
| 48 | /*----- Header files ------------------------------------------------------*/ |
| 49 | |
| 50 | #include "mp.h" |
| 51 | #include "mprand.h" |
| 52 | #include "pgen.h" |
| 53 | |
| 54 | /*----- Main code ---------------------------------------------------------*/ |
| 55 | |
| 56 | /* --- @pgen_safestep@ --- * |
| 57 | * |
| 58 | * Steps two numbers, %$q$% and %$p = 2q + 1$%, such that neither has any |
| 59 | * small factors. %$p$% is put in the event block. |
| 60 | */ |
| 61 | |
| 62 | int pgen_safestep(int rq, pgen_event *ev, void *p) |
| 63 | { |
| 64 | pgen_safestepctx *c = p; |
| 65 | int rc = PGEN_ABORT, qrc = 0; |
| 66 | |
| 67 | switch (rq) { |
| 68 | |
| 69 | /* --- Set up the contexts --- */ |
| 70 | |
| 71 | case PGEN_BEGIN: { |
| 72 | mp *p = mp_split(MP_COPY(ev->m)); |
| 73 | mp *q; |
| 74 | p->v[0] |= 3; |
| 75 | q = mp_lsr(MP_NEW, p, 1); |
| 76 | rc = pfilt_create(&c->p, p); |
| 77 | qrc = pfilt_create(&c->q, q); |
| 78 | mp_drop(p); mp_drop(q); |
| 79 | } break; |
| 80 | |
| 81 | /* --- Step along --- */ |
| 82 | |
| 83 | case PGEN_TRY: |
| 84 | mp_drop(ev->m); |
| 85 | rc = pfilt_step(&c->p, 4); |
| 86 | qrc = pfilt_step(&c->q, 2); |
| 87 | break; |
| 88 | |
| 89 | break; |
| 90 | |
| 91 | /* --- Tidy the toys away --- */ |
| 92 | |
| 93 | case PGEN_DONE: |
| 94 | pfilt_destroy(&c->q); |
| 95 | pfilt_destroy(&c->p); |
| 96 | return (PGEN_DONE); |
| 97 | } |
| 98 | |
| 99 | /* --- Continue stepping if necessary --- */ |
| 100 | |
| 101 | while (rc == PGEN_FAIL || qrc == PGEN_FAIL) { |
| 102 | rc = pfilt_step(&c->p, 4); |
| 103 | qrc = pfilt_step(&c->q, 2); |
| 104 | } |
| 105 | |
| 106 | ev->m = MP_COPY(c->p.m); |
| 107 | if (qrc == PGEN_TRY) |
| 108 | rc = PGEN_TRY; |
| 109 | return (rc); |
| 110 | } |
| 111 | |
| 112 | /* --- @pgen_safejump@ --- * |
| 113 | * |
| 114 | * Jumps two numbers, %$q$% and %$p = 2q + 1$% such that neither has any |
| 115 | * small factors. |
| 116 | */ |
| 117 | |
| 118 | int pgen_safejump(int rq, pgen_event *ev, void *p) |
| 119 | { |
| 120 | pgen_safejumpctx *j = p; |
| 121 | int rc = PGEN_ABORT, qrc = 0; |
| 122 | |
| 123 | switch (rq) { |
| 124 | |
| 125 | /* --- Set up the jump contexts --- * |
| 126 | * |
| 127 | * The jump in @j.q@ is congruent to 2 (mod 4); see @strongprime_setup@. |
| 128 | * If @p@ is initially 1 (mod 4) then add @j.q@. Then double @j.q@ to |
| 129 | * ensure that the step is 0 (mod 4). Ensure that @jq@ and @q@ don't |
| 130 | * have any common factors. |
| 131 | */ |
| 132 | |
| 133 | case PGEN_BEGIN: { |
| 134 | mp *p = ev->m; |
| 135 | mp *q; |
| 136 | mp *g = MP_NEW; |
| 137 | if ((p->v[0] & 3) != 3) |
| 138 | p = mp_add(p, p, j->jq.m); |
| 139 | q = mp_lsr(MP_NEW, p, 1); |
| 140 | mp_gcd(&g, 0, 0, p, j->jq.m); |
| 141 | if (MP_CMP(g, >, MP_ONE)) { |
| 142 | ev->m = p; |
| 143 | mp_drop(q); |
| 144 | mp_drop(g); |
| 145 | return (PGEN_ABORT); |
| 146 | } |
| 147 | mp_drop(g); |
| 148 | rc = pfilt_create(&j->p, p); |
| 149 | pfilt_muladd(&j->jp, &j->jq, 2, 0); |
| 150 | qrc = pfilt_create(&j->q, q); |
| 151 | mp_drop(p); |
| 152 | mp_drop(q); |
| 153 | } break; |
| 154 | |
| 155 | /* --- Step on one place --- */ |
| 156 | |
| 157 | case PGEN_TRY: |
| 158 | mp_drop(ev->m); |
| 159 | rc = pfilt_jump(&j->p, &j->jp); |
| 160 | qrc = pfilt_jump(&j->q, &j->jq); |
| 161 | break; |
| 162 | |
| 163 | /* --- Tidy everything up --- */ |
| 164 | |
| 165 | case PGEN_DONE: |
| 166 | pfilt_destroy(&j->jp); |
| 167 | pfilt_destroy(&j->p); |
| 168 | pfilt_destroy(&j->q); |
| 169 | return (PGEN_DONE); |
| 170 | } |
| 171 | |
| 172 | /* --- Step on while @p@ or @q@ have small factors --- */ |
| 173 | |
| 174 | while (rc == PGEN_FAIL || qrc == PGEN_FAIL) { |
| 175 | rc = pfilt_jump(&j->p, &j->jp); |
| 176 | qrc = pfilt_jump(&j->q, &j->jq); |
| 177 | } |
| 178 | ev->m = MP_COPY(j->p.m); |
| 179 | if (qrc == PGEN_TRY) |
| 180 | rc = PGEN_TRY; |
| 181 | return (rc); |
| 182 | } |
| 183 | |
| 184 | /* --- @pgen_safetest@ --- * |
| 185 | * |
| 186 | * Applies Rabin-Miller tests to %$p$% and %$q$%. |
| 187 | */ |
| 188 | |
| 189 | int pgen_safetest(int rq, pgen_event *ev, void *p) |
| 190 | { |
| 191 | pgen_safetestctx *c = p; |
| 192 | int rc = PGEN_ABORT; |
| 193 | |
| 194 | switch (rq) { |
| 195 | case PGEN_BEGIN: |
| 196 | rabin_create(&c->q, c->c.q.m); |
| 197 | rabin_create(&c->p, c->c.p.m); |
| 198 | rc = PGEN_TRY; |
| 199 | break; |
| 200 | case PGEN_TRY: { |
| 201 | mp *m = mprand_range(MP_NEW, c->c.q.m, ev->r, 0); |
| 202 | rc = rabin_test(&c->p, m); |
| 203 | if (rc == PGEN_PASS) |
| 204 | rc = rabin_test(&c->q, m); |
| 205 | mp_drop(m); |
| 206 | } break; |
| 207 | case PGEN_DONE: |
| 208 | rabin_destroy(&c->q); |
| 209 | rabin_destroy(&c->p); |
| 210 | break; |
| 211 | } |
| 212 | return (rc); |
| 213 | } |
| 214 | |
| 215 | /*----- That's all, folks -------------------------------------------------*/ |