| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Generate Blum integers |
| 4 | * |
| 5 | * (c) 1999 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Catacomb. |
| 11 | * |
| 12 | * Catacomb is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU Library General Public License as |
| 14 | * published by the Free Software Foundation; either version 2 of the |
| 15 | * License, or (at your option) any later version. |
| 16 | * |
| 17 | * Catacomb is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU Library General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU Library General Public |
| 23 | * License along with Catacomb; if not, write to the Free |
| 24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 25 | * MA 02111-1307, USA. |
| 26 | */ |
| 27 | |
| 28 | /*----- Header files ------------------------------------------------------*/ |
| 29 | |
| 30 | #include <stdio.h> |
| 31 | #include <stdlib.h> |
| 32 | #include <string.h> |
| 33 | |
| 34 | #include "bbs.h" |
| 35 | #include "mp.h" |
| 36 | #include "mprand.h" |
| 37 | #include "pgen.h" |
| 38 | #include "strongprime.h" |
| 39 | |
| 40 | /*----- Main code ---------------------------------------------------------*/ |
| 41 | |
| 42 | /* --- @bbs_gen@ --- * |
| 43 | * |
| 44 | * Arguments: @bbs_priv *bp@ = pointer to parameter block |
| 45 | * @unsigned nbits@ = number of bits in the modulus |
| 46 | * @grand *r@ = pointer to random number source |
| 47 | * @unsigned n@ = number of attempts to make |
| 48 | * @pgen_proc *event@ = event handler function |
| 49 | * @void *ectx@ = argument for event handler |
| 50 | * |
| 51 | * Returns: If it worked OK, @PGEN_DONE@, otherwise @PGEN_ABORT@. |
| 52 | * |
| 53 | * Use: Finds two prime numbers %$p'$% and %$q'$% such that both are |
| 54 | * congruent to %$3 \bmod 4$%, and $(p - 1)/2$% and |
| 55 | * %$(q - 1)/2$% have no common factors. The product %$n = pq$% |
| 56 | * is eminently suitable for use as a modulus in a Blum-Blum- |
| 57 | * Shub pseudorandom bit generator. |
| 58 | */ |
| 59 | |
| 60 | int bbs_gen(bbs_priv *bp, unsigned nbits, grand *r, unsigned n, |
| 61 | pgen_proc *event, void *ectx) |
| 62 | { |
| 63 | rabin rb; |
| 64 | pfilt jp; |
| 65 | pgen_jumpctx j; |
| 66 | pgen_gcdstepctx g; |
| 67 | unsigned nb = nbits/2; |
| 68 | mp *x = MP_NEWSEC; |
| 69 | |
| 70 | /* --- Generate @p@ --- */ |
| 71 | |
| 72 | if ((x = strongprime_setup("p", x, &jp, nb, r, n, event, ectx)) == 0) |
| 73 | goto fail_x; |
| 74 | j.j = &jp; |
| 75 | bp->p = pgen("p", MP_NEWSEC, x, event, ectx, n, pgen_jump, &j, |
| 76 | rabin_iters(nb), pgen_test, &rb); |
| 77 | pfilt_destroy(&jp); |
| 78 | if (!bp->p) goto fail_p; |
| 79 | |
| 80 | /* --- Generate @q@ --- */ |
| 81 | |
| 82 | nb = nbits - nb; |
| 83 | if ((x = strongprime_setup("q", x, &g.jp, nb, r, n, event, ectx)) == 0) |
| 84 | goto fail_q; |
| 85 | if ((x->v[0] & 3) != 3) |
| 86 | x = mp_add(x, x, g.jp.m); |
| 87 | pfilt_muladd(&g.jp, &g.jp, 2, 0); |
| 88 | g.r = mp_lsr(MP_NEW, bp->p, 1); |
| 89 | g.g = MP_NEW; |
| 90 | g.max = MP_ONE; |
| 91 | bp->q = pgen("q", MP_NEWSEC, x, event, ectx, n, pgen_gcdstep, &g, |
| 92 | rabin_iters(nb), pgen_test, &rb); |
| 93 | pfilt_destroy(&g.jp); |
| 94 | mp_drop(g.r); |
| 95 | mp_drop(g.g); |
| 96 | if (!bp->q) goto fail_q; |
| 97 | |
| 98 | /* --- Compute @n@ --- */ |
| 99 | |
| 100 | bp->n = mp_mul(MP_NEW, bp->p, bp->q); |
| 101 | if (mp_bits(bp->n) != nbits) goto fail_n; |
| 102 | mp_drop(x); |
| 103 | return (PGEN_DONE); |
| 104 | |
| 105 | /* --- Tidy up if things went wrong --- */ |
| 106 | |
| 107 | fail_n: |
| 108 | mp_drop(bp->n); |
| 109 | fail_q: |
| 110 | mp_drop(bp->p); |
| 111 | fail_p: |
| 112 | mp_drop(x); |
| 113 | fail_x: |
| 114 | return (PGEN_ABORT); |
| 115 | } |
| 116 | |
| 117 | /*----- That's all, folks -------------------------------------------------*/ |