3 * $Id: bbs-gen.c,v 1.6 2004/04/08 01:36:15 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 /*----- Header files ------------------------------------------------------*/
40 #include "strongprime.h"
42 /*----- Main code ---------------------------------------------------------*/
44 /* --- @bbs_gen@ --- *
46 * Arguments: @bbs_priv *bp@ = pointer to parameter block
47 * @unsigned nbits@ = number of bits in the modulus
48 * @grand *r@ = pointer to random number source
49 * @unsigned n@ = number of attempts to make
50 * @pgen_proc *event@ = event handler function
51 * @void *ectx@ = argument for event handler
53 * Returns: If it worked OK, @PGEN_DONE@, otherwise @PGEN_ABORT@.
55 * Use: Finds two prime numbers %$p'$% and %$q'$% such that both are
56 * congruent to %$3 \bmod 4$%, and $(p - 1)/2$% and
57 * %$(q - 1)/2$% have no common factors. The product %$n = pq$%
58 * is eminently suitable for use as a modulus in a Blum-Blum-
59 * Shub pseudorandom bit generator.
62 int bbs_gen(bbs_priv
*bp
, unsigned nbits
, grand
*r
, unsigned n
,
63 pgen_proc
*event
, void *ectx
)
68 unsigned nb
= nbits
/2;
71 /* --- Generate @p@ --- */
74 if ((x
= strongprime_setup("p", x
, &j
.jq
, nb
, r
, n
, event
, ectx
)) == 0)
76 bp
->p
= pgen("p", MP_NEW
, x
, event
, ectx
, n
, pgen_safejump
, &j
,
77 rabin_iters(nb
), pgen_test
, &rb
);
85 /* --- Generate @q@ --- */
88 if ((x
= strongprime_setup("q", x
, &g
.jp
, nb
, r
, n
, event
, ectx
)) == 0)
90 if ((x
->v
[0] & 3) != 3)
91 x
= mp_add(x
, x
, g
.jp
.m
);
92 pfilt_muladd(&g
.jp
, &g
.jp
, 2, 0);
93 g
.r
= mp_lsr(MP_NEW
, bp
->p
, 1);
96 bp
->q
= pgen("q", MP_NEW
, x
, event
, ectx
, n
, pgen_gcdstep
, &g
,
97 rabin_iters(nb
), pgen_test
, &rb
);
108 /* --- Compute @n@ --- */
110 bp
->n
= mp_mul(MP_NEW
, bp
->p
, bp
->q
);
114 /* --- Tidy up if things went wrong --- */
124 /*----- That's all, folks -------------------------------------------------*/