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19d1256d | 1 | /* -*-c-*- |
2 | * | |
b817bfc6 | 3 | * $Id: dh-limlee.c,v 1.3 2004/04/08 01:36:15 mdw Exp $ |
19d1256d | 4 | * |
5 | * Generate Diffie-Hellman parameters from Lim-Lee primes | |
6 | * | |
7 | * (c) 2000 Straylight/Edgeware | |
8 | */ | |
9 | ||
45c0fd36 | 10 | /*----- Licensing notice --------------------------------------------------* |
19d1256d | 11 | * |
12 | * This file is part of Catacomb. | |
13 | * | |
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. | |
45c0fd36 | 18 | * |
19d1256d | 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. | |
45c0fd36 | 23 | * |
19d1256d | 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, | |
27 | * MA 02111-1307, USA. | |
28 | */ | |
19d1256d | 29 | |
30 | /*----- Header files ------------------------------------------------------*/ | |
31 | ||
32 | #include "dh.h" | |
33 | #include "limlee.h" | |
34 | #include "mpmont.h" | |
35 | #include "prim.h" | |
36 | ||
37 | /*----- Main code ---------------------------------------------------------*/ | |
38 | ||
39 | /* --- @dh_limlee@ --- * | |
40 | * | |
41 | * Arguments: @dh_param *dp@ = pointer to output parameter block | |
42 | * @unsigned ql@ = length of smallest factor of %$(p - 1)/2$% | |
43 | * @unsigned pl@ = length of %$p$% in bits | |
44 | * @unsigned flags@ = other generation flags | |
45 | * @unsigned steps@ = number of steps to go | |
46 | * @grand *r@ = random number source | |
45c0fd36 MW |
47 | * @pgen_proc *oev@ = outer event handler function |
48 | * @void *oec@ = argument for the outer event handler | |
49 | * @pgen_proc *iev@ = inner event handler function | |
50 | * @void *iec@ = argument for the inner event handler | |
51 | * @size_t *nf@, @mp ***f@ = output array for factors | |
19d1256d | 52 | * |
53 | * Returns: @PGEN_DONE@ if it worked, @PGEN_ABORT@ if it didn't. | |
54 | * | |
55 | * Use: Generates Diffie-Hellman parameters based on a Lim-Lee prime. | |
56 | * | |
57 | * The modulus is a large prime %$p = 2 \prod q_i + 1$%, @pl@ | |
58 | * bits long, where the %$q_i$% are smaller primes each at least | |
59 | * @ql@ bits long. It is safe to set @nf@ and @f@ to zero if | |
60 | * you're not interested in the factor values. | |
61 | * | |
62 | * The returned %$g$% generates a subgroup of order %$q_0$% (the | |
63 | * first factor, returned as @f[0]@), if the flag @DH_SUBGROUP@ | |
64 | * is set on entry; otherwise %$g$% will have order | |
65 | * %$(p - 1)/2$%. | |
66 | */ | |
67 | ||
68 | int dh_limlee(dh_param *dp, unsigned ql, unsigned pl, | |
69 | unsigned flags, unsigned steps, grand *r, | |
70 | pgen_proc *oev, void *oec, pgen_proc *iev, | |
71 | void *iec, size_t *nf, mp ***f) | |
72 | { | |
73 | mp **ff; | |
74 | size_t nff; | |
75 | prim_ctx pc; | |
76 | size_t i; | |
77 | int j; | |
78 | mp *pp; | |
79 | ||
80 | /* --- Generate the Lim-Lee prime --- */ | |
81 | ||
82 | if ((dp->p = limlee("p", MP_NEW, MP_NEW, ql, pl, | |
83 | r, steps, oev, oec, iev, iec, &nff, &ff)) == 0) | |
9f05f5d8 | 84 | return (PGEN_ABORT); |
19d1256d | 85 | |
86 | /* --- Now find a primitive element --- */ | |
87 | ||
88 | mpmont_create(&pc.mm, dp->p); | |
89 | pp = mp_sub(MP_NEW, dp->p, MP_ONE); | |
90 | if (flags & DH_SUBGROUP) { | |
020e6360 | 91 | dp->q = mp_copy(ff[0]); |
19d1256d | 92 | pc.exp = MP_NEW; |
93 | mp_div(&pc.exp, 0, pp, dp->q); | |
94 | pc.n = 0; | |
95 | pc.f = 0; | |
96 | } else { | |
020e6360 | 97 | dp->q = mp_lsr(MP_NEW, dp->p, 1); |
19d1256d | 98 | pc.exp = MP_TWO; |
99 | pc.n = nff; | |
100 | pc.f = xmalloc(nff * sizeof(mp *)); | |
101 | for (i = 0; i < nff; i++) { | |
102 | pc.f[i] = MP_NEW; | |
103 | mp_div(&pc.f[i], 0, pp, ff[i]); | |
104 | } | |
105 | } | |
106 | ||
107 | j = 0; | |
108 | dp->g = pgen("g", MP_NEW, MP_NEW, oev, oec, | |
109 | 0, prim_step, &j, 1, prim_test, &pc); | |
110 | ||
111 | mp_drop(pp); | |
112 | if (pc.f) { | |
113 | for (i = 0; i < pc.n; i++) | |
114 | mp_drop(pc.f[i]); | |
115 | xfree(pc.f); | |
116 | } | |
117 | mpmont_destroy(&pc.mm); | |
118 | ||
119 | /* --- Do something sensible with the list of primes --- */ | |
120 | ||
121 | if (dp->g && f) { | |
122 | *f = ff; | |
123 | *nf = nff; | |
124 | } else { | |
125 | for (i = 0; i < nff; i++) | |
126 | mp_drop(ff[i]); | |
127 | xfree(ff); | |
128 | } | |
129 | ||
130 | /* --- Tidy up and return --- */ | |
131 | ||
132 | if (!dp->g) { | |
133 | mp_drop(dp->p); | |
134 | mp_drop(dp->q); | |
9f05f5d8 | 135 | return (PGEN_ABORT); |
19d1256d | 136 | } |
137 | return (PGEN_DONE); | |
138 | } | |
139 | ||
140 | /*----- That's all, folks -------------------------------------------------*/ |