| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: bbs-gen.c,v 1.2 1999/12/22 15:52:28 mdw Exp $ |
| 4 | * |
| 5 | * Generate Blum integers |
| 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-gen.c,v $ |
| 33 | * Revision 1.2 1999/12/22 15:52:28 mdw |
| 34 | * Reworking for new prime-search system. |
| 35 | * |
| 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 <stdio.h> |
| 44 | #include <stdlib.h> |
| 45 | #include <string.h> |
| 46 | |
| 47 | #include "bbs.h" |
| 48 | #include "mp.h" |
| 49 | #include "mprand.h" |
| 50 | #include "pgen.h" |
| 51 | |
| 52 | /*----- Data structures ---------------------------------------------------*/ |
| 53 | |
| 54 | typedef struct gcdctx { |
| 55 | mp *q; |
| 56 | mp *r; |
| 57 | pfilt p; |
| 58 | } gcdctx; |
| 59 | |
| 60 | /*----- Custom stepper ----------------------------------------------------*/ |
| 61 | |
| 62 | static int gcdstep(int rq, pgen_event *ev, void *p) |
| 63 | { |
| 64 | gcdctx *g = p; |
| 65 | int rc = PGEN_ABORT; |
| 66 | mp *z = MP_NEW; |
| 67 | |
| 68 | switch (rq) { |
| 69 | case PGEN_BEGIN: { |
| 70 | mp *p = ev->m = mp_split(ev->m); |
| 71 | p->v[0] |= 3; |
| 72 | g->q = mp_lsr(MP_NEW, p, 1); |
| 73 | rc = pfilt_create(&g->p, p); |
| 74 | } break; |
| 75 | case PGEN_TRY: |
| 76 | g->q = mp_add(g->q, g->q, MP_FOUR); |
| 77 | rc = pfilt_step(&g->p, 4); |
| 78 | break; |
| 79 | case PGEN_DONE: |
| 80 | pfilt_destroy(&g->p); |
| 81 | mp_drop(g->q); |
| 82 | return (PGEN_DONE); |
| 83 | } |
| 84 | for (;;) { |
| 85 | if (rc != PGEN_FAIL) { |
| 86 | mp_gcd(&z, 0, 0, g->r, g->q); |
| 87 | if (MP_CMP(z, !=, MP_ONE)) |
| 88 | rc = PGEN_FAIL; |
| 89 | } |
| 90 | if (rc != PGEN_FAIL) |
| 91 | break; |
| 92 | g->q = mp_add(g->q, g->q, MP_FOUR); |
| 93 | rc = pfilt_step(&g->p, 4); |
| 94 | } |
| 95 | |
| 96 | mp_drop(z); |
| 97 | mp_drop(ev->m); |
| 98 | ev->m = MP_COPY(g->p.m); |
| 99 | return (rc); |
| 100 | } |
| 101 | |
| 102 | /*----- Main code ---------------------------------------------------------*/ |
| 103 | |
| 104 | /* --- @bbs_gen@ --- * |
| 105 | * |
| 106 | * Arguments: @bbs_param *bp@ = pointer to parameter block |
| 107 | * @mp *p, *q@ = initial numbers to search from |
| 108 | * @size_t n@ = number of attempts to make |
| 109 | * @pgen_proc *event@ = event handler function |
| 110 | * @void *ectx@ = argument for event handler |
| 111 | * |
| 112 | * Returns: If it worked OK, @PGEN_DONE@, otherwise @PGEN_ABORT@. |
| 113 | * |
| 114 | * Use: Finds two prime numbers %$p'$% and %$q'$% such that both are |
| 115 | * congruent to %$3 \bmod 4$%, and $(p - 1)/2$% and |
| 116 | * %$(q - 1)/2$% have no common factors. The product %$n = pq$% |
| 117 | * is eminently suitable for use as a modulus in a Blum-Blum- |
| 118 | * Shub pseudorandom bit generator. |
| 119 | */ |
| 120 | |
| 121 | int bbs_gen(bbs_param *bp, mp *p, mp *q, size_t n, |
| 122 | pgen_proc *event, void *ectx) |
| 123 | { |
| 124 | rabin r; |
| 125 | pgen_safestepctx c; |
| 126 | gcdctx g; |
| 127 | |
| 128 | /* --- Generate @p@ --- */ |
| 129 | |
| 130 | if ((bp->p = pgen("p", MP_NEW, p, event, ectx, n, pgen_safestep, &c, |
| 131 | rabin_iters(mp_bits(p)), pgen_test, &r)) == 0) |
| 132 | goto fail_p; |
| 133 | |
| 134 | /* --- Generate @q@ --- */ |
| 135 | |
| 136 | g.r = mp_lsr(MP_NEW, bp->p, 1); |
| 137 | if ((bp->q = pgen("q", MP_NEW, q, event, ectx, n, gcdstep, &g, |
| 138 | rabin_iters(mp_bits(q)), pgen_test, &r)) == 0) |
| 139 | goto fail_q; |
| 140 | |
| 141 | /* --- Compute @n@ --- */ |
| 142 | |
| 143 | bp->n = mp_mul(MP_NEW, bp->p, bp->q); |
| 144 | mp_drop(g.r); |
| 145 | return (PGEN_DONE); |
| 146 | |
| 147 | /* --- Tidy up if things went wrong --- */ |
| 148 | |
| 149 | fail_q: |
| 150 | mp_drop(g.r); |
| 151 | mp_drop(bp->p); |
| 152 | fail_p: |
| 153 | return (PGEN_ABORT); |
| 154 | } |
| 155 | |
| 156 | /*----- That's all, folks -------------------------------------------------*/ |