3 * Generate Diffie-Hellman parameters from Lim-Lee primes
5 * (c) 2000 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Catacomb.
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.
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.
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,
28 /*----- Header files ------------------------------------------------------*/
35 /*----- Main code ---------------------------------------------------------*/
37 /* --- @dh_limlee@ --- *
39 * Arguments: @dh_param *dp@ = pointer to output parameter block
40 * @unsigned ql@ = length of smallest factor of %$(p - 1)/2$%
41 * @unsigned pl@ = length of %$p$% in bits
42 * @unsigned flags@ = other generation flags
43 * @unsigned steps@ = number of steps to go
44 * @grand *r@ = random number source
45 * @pgen_proc *oev@ = outer event handler function
46 * @void *oec@ = argument for the outer event handler
47 * @pgen_proc *iev@ = inner event handler function
48 * @void *iec@ = argument for the inner event handler
49 * @size_t *nf@, @mp ***f@ = output array for factors
51 * Returns: @PGEN_DONE@ if it worked, @PGEN_ABORT@ if it didn't.
53 * Use: Generates Diffie-Hellman parameters based on a Lim-Lee prime.
55 * The modulus is a large prime %$p = 2 \prod q_i + 1$%, @pl@
56 * bits long, where the %$q_i$% are smaller primes each at least
57 * @ql@ bits long. It is safe to set @nf@ and @f@ to zero if
58 * you're not interested in the factor values.
60 * The returned %$g$% generates a subgroup of order %$q_0$% (the
61 * first factor, returned as @f[0]@), if the flag @DH_SUBGROUP@
62 * is set on entry; otherwise %$g$% will have order
66 int dh_limlee(dh_param
*dp
, unsigned ql
, unsigned pl
,
67 unsigned flags
, unsigned steps
, grand
*r
,
68 pgen_proc
*oev
, void *oec
, pgen_proc
*iev
,
69 void *iec
, size_t *nf
, mp
***f
)
78 /* --- Generate the Lim-Lee prime --- */
80 if ((dp
->p
= limlee("p", MP_NEW
, MP_NEW
, ql
, pl
,
81 r
, steps
, oev
, oec
, iev
, iec
, &nff
, &ff
)) == 0)
84 /* --- Now find a primitive element --- */
86 mpmont_create(&pc
.mm
, dp
->p
);
87 pp
= mp_sub(MP_NEW
, dp
->p
, MP_ONE
);
88 if (flags
& DH_SUBGROUP
) {
89 dp
->q
= mp_copy(ff
[0]);
91 mp_div(&pc
.exp
, 0, pp
, dp
->q
);
95 dp
->q
= mp_lsr(MP_NEW
, dp
->p
, 1);
98 pc
.f
= xmalloc(nff
* sizeof(mp
*));
99 for (i
= 0; i
< nff
; i
++) {
101 mp_div(&pc
.f
[i
], 0, pp
, ff
[i
]);
106 dp
->g
= pgen("g", MP_NEW
, MP_NEW
, oev
, oec
,
107 0, prim_step
, &j
, 1, prim_test
, &pc
);
111 for (i
= 0; i
< pc
.n
; i
++)
115 mpmont_destroy(&pc
.mm
);
117 /* --- Do something sensible with the list of primes --- */
123 for (i
= 0; i
< nff
; i
++)
128 /* --- Tidy up and return --- */
138 /*----- That's all, folks -------------------------------------------------*/