3 * $Id: bbs-gen.c,v 1.4 2000/06/17 10:43:57 mdw Exp $
5 * Generate Blum integers
7 * (c) 1999 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of Catacomb.
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.
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.
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,
30 /*----- Revision history --------------------------------------------------*
33 * Revision 1.4 2000/06/17 10:43:57 mdw
34 * Move GCD filter to separate file. Handle failures from pgen_jump.
36 * Revision 1.3 2000/02/12 18:21:02 mdw
37 * Overhaul of key management (again).
39 * Revision 1.2 1999/12/22 15:52:28 mdw
40 * Reworking for new prime-search system.
42 * Revision 1.1 1999/12/10 23:14:59 mdw
43 * Blum-Blum-Shub generator, and Blum-Goldwasser encryption.
47 /*----- Header files ------------------------------------------------------*/
57 #include "strongprime.h"
59 /*----- Main code ---------------------------------------------------------*/
61 /* --- @bbs_gen@ --- *
63 * Arguments: @bbs_param *bp@ = pointer to parameter block
64 * @unsigned nbits@ = number of bits in the modulus
65 * @grand *r@ = pointer to random number source
66 * @unsigned n@ = number of attempts to make
67 * @pgen_proc *event@ = event handler function
68 * @void *ectx@ = argument for event handler
70 * Returns: If it worked OK, @PGEN_DONE@, otherwise @PGEN_ABORT@.
72 * Use: Finds two prime numbers %$p'$% and %$q'$% such that both are
73 * congruent to %$3 \bmod 4$%, and $(p - 1)/2$% and
74 * %$(q - 1)/2$% have no common factors. The product %$n = pq$%
75 * is eminently suitable for use as a modulus in a Blum-Blum-
76 * Shub pseudorandom bit generator.
79 int bbs_gen(bbs_param *bp, unsigned nbits, grand *r, unsigned n,
80 pgen_proc *event, void *ectx)
85 unsigned nb = nbits/2;
88 /* --- Generate @p@ --- */
91 if ((x = strongprime_setup("p", x, &j.jq, nb, r, n, event, ectx)) == 0)
93 bp->p = pgen("p", MP_NEW, x, event, ectx, n, pgen_safejump, &j,
94 rabin_iters(nb), pgen_test, &rb);
102 /* --- Generate @q@ --- */
105 if ((x = strongprime_setup("q", x, &g.jp, nb, r, n, event, ectx)) == 0)
107 if ((x->v[0] & 3) != 3)
108 x = mp_add(x, x, g.jp.m);
109 pfilt_muladd(&g.jp, &g.jp, 2, 0);
110 g.r = mp_lsr(MP_NEW, bp->p, 1);
113 bp->q = pgen("q", MP_NEW, x, event, ectx, n, pgen_gcdstep, &g,
114 rabin_iters(nb), pgen_test, &rb);
115 pfilt_destroy(&g.jp);
125 /* --- Compute @n@ --- */
127 bp->n = mp_mul(MP_NEW, bp->p, bp->q);
131 /* --- Tidy up if things went wrong --- */
141 /*----- That's all, folks -------------------------------------------------*/