19d1256d |
1 | /* -*-c-*- |
2 | * |
3 | * $Id: dh-limlee.c,v 1.1 2000/07/29 10:01:31 mdw Exp $ |
4 | * |
5 | * Generate Diffie-Hellman parameters from Lim-Lee primes |
6 | * |
7 | * (c) 2000 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
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. |
18 | * |
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. |
23 | * |
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 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: dh-limlee.c,v $ |
33 | * Revision 1.1 2000/07/29 10:01:31 mdw |
34 | * Diffie-Hellman parameter generation based on Lim-Lee primes. |
35 | * |
36 | */ |
37 | |
38 | /*----- Header files ------------------------------------------------------*/ |
39 | |
40 | #include "dh.h" |
41 | #include "limlee.h" |
42 | #include "mpmont.h" |
43 | #include "prim.h" |
44 | |
45 | /*----- Main code ---------------------------------------------------------*/ |
46 | |
47 | /* --- @dh_limlee@ --- * |
48 | * |
49 | * Arguments: @dh_param *dp@ = pointer to output parameter block |
50 | * @unsigned ql@ = length of smallest factor of %$(p - 1)/2$% |
51 | * @unsigned pl@ = length of %$p$% in bits |
52 | * @unsigned flags@ = other generation flags |
53 | * @unsigned steps@ = number of steps to go |
54 | * @grand *r@ = random number source |
55 | * @pgen_proc *oev@ = outer event handler function |
56 | * @void *oec@ = argument for the outer event handler |
57 | * @pgen_proc *iev@ = inner event handler function |
58 | * @void *iec@ = argument for the inner event handler |
59 | * @size_t *nf@, @mp ***f@ = output array for factors |
60 | * |
61 | * Returns: @PGEN_DONE@ if it worked, @PGEN_ABORT@ if it didn't. |
62 | * |
63 | * Use: Generates Diffie-Hellman parameters based on a Lim-Lee prime. |
64 | * |
65 | * The modulus is a large prime %$p = 2 \prod q_i + 1$%, @pl@ |
66 | * bits long, where the %$q_i$% are smaller primes each at least |
67 | * @ql@ bits long. It is safe to set @nf@ and @f@ to zero if |
68 | * you're not interested in the factor values. |
69 | * |
70 | * The returned %$g$% generates a subgroup of order %$q_0$% (the |
71 | * first factor, returned as @f[0]@), if the flag @DH_SUBGROUP@ |
72 | * is set on entry; otherwise %$g$% will have order |
73 | * %$(p - 1)/2$%. |
74 | */ |
75 | |
76 | int dh_limlee(dh_param *dp, unsigned ql, unsigned pl, |
77 | unsigned flags, unsigned steps, grand *r, |
78 | pgen_proc *oev, void *oec, pgen_proc *iev, |
79 | void *iec, size_t *nf, mp ***f) |
80 | { |
81 | mp **ff; |
82 | size_t nff; |
83 | prim_ctx pc; |
84 | size_t i; |
85 | int j; |
86 | mp *pp; |
87 | |
88 | /* --- Generate the Lim-Lee prime --- */ |
89 | |
90 | if ((dp->p = limlee("p", MP_NEW, MP_NEW, ql, pl, |
91 | r, steps, oev, oec, iev, iec, &nff, &ff)) == 0) |
92 | return (PGEN_FAIL); |
93 | dp->q = mp_copy(ff[0]); |
94 | |
95 | /* --- Now find a primitive element --- */ |
96 | |
97 | mpmont_create(&pc.mm, dp->p); |
98 | pp = mp_sub(MP_NEW, dp->p, MP_ONE); |
99 | if (flags & DH_SUBGROUP) { |
100 | pc.exp = MP_NEW; |
101 | mp_div(&pc.exp, 0, pp, dp->q); |
102 | pc.n = 0; |
103 | pc.f = 0; |
104 | } else { |
105 | pc.exp = MP_TWO; |
106 | pc.n = nff; |
107 | pc.f = xmalloc(nff * sizeof(mp *)); |
108 | for (i = 0; i < nff; i++) { |
109 | pc.f[i] = MP_NEW; |
110 | mp_div(&pc.f[i], 0, pp, ff[i]); |
111 | } |
112 | } |
113 | |
114 | j = 0; |
115 | dp->g = pgen("g", MP_NEW, MP_NEW, oev, oec, |
116 | 0, prim_step, &j, 1, prim_test, &pc); |
117 | |
118 | mp_drop(pp); |
119 | if (pc.f) { |
120 | for (i = 0; i < pc.n; i++) |
121 | mp_drop(pc.f[i]); |
122 | xfree(pc.f); |
123 | } |
124 | mpmont_destroy(&pc.mm); |
125 | |
126 | /* --- Do something sensible with the list of primes --- */ |
127 | |
128 | if (dp->g && f) { |
129 | *f = ff; |
130 | *nf = nff; |
131 | } else { |
132 | for (i = 0; i < nff; i++) |
133 | mp_drop(ff[i]); |
134 | xfree(ff); |
135 | } |
136 | |
137 | /* --- Tidy up and return --- */ |
138 | |
139 | if (!dp->g) { |
140 | mp_drop(dp->p); |
141 | mp_drop(dp->q); |
142 | return (PGEN_FAIL); |
143 | } |
144 | return (PGEN_DONE); |
145 | } |
146 | |
147 | /*----- That's all, folks -------------------------------------------------*/ |