Commit | Line | Data |
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4e67e30b | 1 | /* -*-c-*- |
4e67e30b MW |
2 | * |
3 | * Generate KCDSA prime groups | |
4 | * | |
5 | * (c) 2006 Straylight/Edgeware | |
6 | */ | |
7 | ||
45c0fd36 | 8 | /*----- Licensing notice --------------------------------------------------* |
4e67e30b MW |
9 | * |
10 | * This file is part of Catacomb. | |
11 | * | |
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. | |
45c0fd36 | 16 | * |
4e67e30b MW |
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. | |
45c0fd36 | 21 | * |
4e67e30b MW |
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, | |
25 | * MA 02111-1307, USA. | |
26 | */ | |
27 | ||
28 | /*----- Header files ------------------------------------------------------*/ | |
29 | ||
30 | #include <mLib/macros.h> | |
31 | ||
32 | #include "dh.h" | |
33 | #include "mprand.h" | |
34 | #include "pgen.h" | |
35 | #include "prim.h" | |
36 | ||
37 | /*----- Main code ---------------------------------------------------------*/ | |
38 | ||
39 | /* --- @dh_kcdsagen@ --- * | |
40 | * | |
41 | * Arguments: @dh_param *dp@ = pointer to output parameter block | |
42 | * @unsigned ql@ = size of small factor of %$(p - 1)/2$% | |
43 | * @unsigned pl@ = size of %$p$% in bits | |
44 | * @unsigned flags@ = other generation flags | |
45 | * @unsigned steps@ = number of steps to go | |
46 | * @grand *r@ = random number source | |
47 | * @pgen_proc *ev@ = event handler function | |
48 | * @void *ec@ = context for the event handler | |
49 | * | |
50 | * Returns: @PGEN_DONE@ if it worked, @PGEN_ABORT@ if it failed. | |
51 | * | |
52 | * Use: Generates a KCDSA prime group. That is, it chooses a prime | |
53 | * %$p$%, such that $%p = 2 q v + 1$%, for primes %$q$% and | |
54 | * %$v$%. The actual group of interest is the subgroup of order | |
55 | * %$q$%. | |
56 | */ | |
57 | ||
58 | int dh_kcdsagen(dh_param *dp, unsigned ql, unsigned pl, | |
59 | unsigned flags, unsigned steps, grand *r, | |
60 | pgen_proc *ev, void *ec) | |
61 | { | |
62 | pgen_filterctx pf; | |
63 | pgen_simulprime sp[2]; | |
64 | pgen_simulctx ss; | |
65 | prim_ctx pc; | |
66 | rabin rb; | |
67 | int rc = PGEN_ABORT; | |
68 | int i; | |
69 | mp *x; | |
70 | ||
71 | /* --- First trick: find %$q$% --- */ | |
72 | ||
73 | pf.step = 2; | |
23aec1b4 MW |
74 | x = mprand(MP_NEW, pl - ql, r, 1); |
75 | x = pgen("v", x, x, ev, ec, | |
76 | steps, pgen_filter, &pf, | |
77 | rabin_iters(pl - ql), pgen_test, &rb); | |
78 | if (!x) | |
4e67e30b MW |
79 | goto fail_0; |
80 | ||
81 | /* --- Second trick: find %$p$% and %$v$% --- */ | |
82 | ||
23aec1b4 | 83 | x = mp_lsl(x, x, 1); |
4e67e30b MW |
84 | sp[0].add = MP_ZERO; sp[0].mul = MP_ONE; sp[0].f = 0; |
85 | sp[1].add = MP_ONE; sp[1].mul = x; sp[1].f = PGENF_KEEP; | |
86 | ss.step = MP_TWO; ss.v = sp; ss.n = N(sp); | |
23aec1b4 MW |
87 | x = mprand(MP_NEW, ql, r, 1); |
88 | dp->q = pgen("p", MP_NEW, x, ev, ec, | |
89 | steps, pgen_simulstep, &ss, | |
90 | rabin_iters(ql), pgen_simultest, &ss); | |
4e67e30b | 91 | mp_drop(sp[0].mul); |
23aec1b4 | 92 | if (!dp->q) |
4e67e30b MW |
93 | goto fail_1; |
94 | dp->p = sp[1].u.x; | |
95 | ||
96 | /* --- Third trick: find a generator --- */ | |
97 | ||
98 | mpmont_create(&pc.mm, dp->p); | |
99 | mp_div(&x, 0, dp->p, dp->q); | |
100 | i = 0; | |
101 | pc.exp = x; | |
102 | pc.n = 0; | |
103 | dp->g = pgen("g", MP_NEW, MP_NEW, ev, ec, | |
104 | 0, prim_step, &i, 1, prim_test, &pc); | |
105 | mpmont_destroy(&pc.mm); | |
106 | if (!dp->g) | |
107 | goto fail_2; | |
108 | ||
109 | rc = PGEN_DONE; | |
110 | goto done; | |
111 | ||
112 | /* --- Tidying up and going home --- */ | |
113 | ||
114 | fail_2: | |
115 | mp_drop(dp->p); | |
116 | fail_1: | |
4e67e30b MW |
117 | fail_0: |
118 | done: | |
119 | mp_drop(x); | |
120 | return (rc); | |
121 | } | |
122 | ||
123 | /*----- That's all, folks -------------------------------------------------*/ |