3 * $Id: dh-limlee.c,v 1.2 2000/07/29 17:02:00 mdw Exp $
5 * Generate Diffie-Hellman parameters from Lim-Lee primes
7 * (c) 2000 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 --------------------------------------------------*
32 * $Log: dh-limlee.c,v $
33 * Revision 1.2 2000/07/29 17:02:00 mdw
34 * (dh_limlee): Bug fix. Return @dp->q@ as the subgroup order, which isn't
35 * necessarily the first factor.
37 * Revision 1.1 2000/07/29 10:01:31 mdw
38 * Diffie-Hellman parameter generation based on Lim-Lee primes.
42 /*----- Header files ------------------------------------------------------*/
49 /*----- Main code ---------------------------------------------------------*/
51 /* --- @dh_limlee@ --- *
53 * Arguments: @dh_param *dp@ = pointer to output parameter block
54 * @unsigned ql@ = length of smallest factor of %$(p - 1)/2$%
55 * @unsigned pl@ = length of %$p$% in bits
56 * @unsigned flags@ = other generation flags
57 * @unsigned steps@ = number of steps to go
58 * @grand *r@ = random number source
59 * @pgen_proc *oev@ = outer event handler function
60 * @void *oec@ = argument for the outer event handler
61 * @pgen_proc *iev@ = inner event handler function
62 * @void *iec@ = argument for the inner event handler
63 * @size_t *nf@, @mp ***f@ = output array for factors
65 * Returns: @PGEN_DONE@ if it worked, @PGEN_ABORT@ if it didn't.
67 * Use: Generates Diffie-Hellman parameters based on a Lim-Lee prime.
69 * The modulus is a large prime %$p = 2 \prod q_i + 1$%, @pl@
70 * bits long, where the %$q_i$% are smaller primes each at least
71 * @ql@ bits long. It is safe to set @nf@ and @f@ to zero if
72 * you're not interested in the factor values.
74 * The returned %$g$% generates a subgroup of order %$q_0$% (the
75 * first factor, returned as @f[0]@), if the flag @DH_SUBGROUP@
76 * is set on entry; otherwise %$g$% will have order
80 int dh_limlee(dh_param
*dp
, unsigned ql
, unsigned pl
,
81 unsigned flags
, unsigned steps
, grand
*r
,
82 pgen_proc
*oev
, void *oec
, pgen_proc
*iev
,
83 void *iec
, size_t *nf
, mp
***f
)
92 /* --- Generate the Lim-Lee prime --- */
94 if ((dp
->p
= limlee("p", MP_NEW
, MP_NEW
, ql
, pl
,
95 r
, steps
, oev
, oec
, iev
, iec
, &nff
, &ff
)) == 0)
98 /* --- Now find a primitive element --- */
100 mpmont_create(&pc
.mm
, dp
->p
);
101 pp
= mp_sub(MP_NEW
, dp
->p
, MP_ONE
);
102 if (flags
& DH_SUBGROUP
) {
103 dp
->q
= mp_copy(ff
[0]);
105 mp_div(&pc
.exp
, 0, pp
, dp
->q
);
109 dp
->q
= mp_lsr(MP_NEW
, dp
->p
, 1);
112 pc
.f
= xmalloc(nff
* sizeof(mp
*));
113 for (i
= 0; i
< nff
; i
++) {
115 mp_div(&pc
.f
[i
], 0, pp
, ff
[i
]);
120 dp
->g
= pgen("g", MP_NEW
, MP_NEW
, oev
, oec
,
121 0, prim_step
, &j
, 1, prim_test
, &pc
);
125 for (i
= 0; i
< pc
.n
; i
++)
129 mpmont_destroy(&pc
.mm
);
131 /* --- Do something sensible with the list of primes --- */
137 for (i
= 0; i
< nff
; i
++)
142 /* --- Tidy up and return --- */
152 /*----- That's all, folks -------------------------------------------------*/