| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: dh-gen.c,v 1.1 2000/02/12 18:21:02 mdw Exp $ |
| 4 | * |
| 5 | * Generate Diffie-Hellman parameters |
| 6 | * |
| 7 | * (c) 1999 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-gen.c,v $ |
| 33 | * Revision 1.1 2000/02/12 18:21:02 mdw |
| 34 | * Overhaul of key management (again). |
| 35 | * |
| 36 | */ |
| 37 | |
| 38 | /*----- Header files ------------------------------------------------------*/ |
| 39 | |
| 40 | #include "dh.h" |
| 41 | #include "grand.h" |
| 42 | #include "mp.h" |
| 43 | #include "mpmont.h" |
| 44 | #include "mprand.h" |
| 45 | #include "pfilt.h" |
| 46 | #include "pgen.h" |
| 47 | #include "prim.h" |
| 48 | #include "rabin.h" |
| 49 | |
| 50 | /*----- Main code ---------------------------------------------------------*/ |
| 51 | |
| 52 | /* --- @dh_gen@ --- * |
| 53 | * |
| 54 | * Arguments: @dh_param *dp@ = pointer to output parameter block |
| 55 | * @unsigned ql@ = length of %$q$% in bits, or zero |
| 56 | * @unsigned pl@ = length of %$p$% in bits |
| 57 | * @unsigned steps@ = number of steps to go |
| 58 | * @grand *r@ = random number source |
| 59 | * @pgen_proc *event@ = event handler function |
| 60 | * @void *ectx@ = argument for the event handler |
| 61 | * |
| 62 | * Returns: @PGEN_DONE@ if it worked, @PGEN_ABORT@ if it didn't. |
| 63 | * |
| 64 | * Use: Generates Diffie-Hellman parameters. |
| 65 | * |
| 66 | * The parameters are a prime %$q$%, relatively small, and a |
| 67 | * large prime %$p = kq + 1$% for some %$k$%, together with a |
| 68 | * generator %$g$% of the cyclic subgroup of order %$q$%. These |
| 69 | * are actually the same as the DSA parameter set, but the |
| 70 | * generation algorithm is different. Also, if @ql@ is zero, |
| 71 | * this algorithm forces %$k = 2$%, and chooses %$g = 4$%. Make |
| 72 | * sure you have something interesting to do if you choose this |
| 73 | * option. |
| 74 | */ |
| 75 | |
| 76 | int dh_gen(dh_param *dp, unsigned ql, unsigned pl, unsigned steps, grand *r, |
| 77 | pgen_proc *event, void *ectx) |
| 78 | { |
| 79 | /* --- If @ql@ is zero, do the time consuming safe-prime thing --- */ |
| 80 | |
| 81 | if (!ql) { |
| 82 | pgen_safetestctx c; |
| 83 | |
| 84 | mp *m = mprand(MP_NEW, pl, r, 3); |
| 85 | dp->p = pgen("p", MP_NEW, m, event, ectx, steps, pgen_safestep, &c.c, |
| 86 | rabin_iters(pl), pgen_safetest, &c); |
| 87 | mp_drop(m); |
| 88 | if (!dp->p) |
| 89 | return (PGEN_ABORT); |
| 90 | dp->q = mp_lsr(MP_NEW, dp->p, 1); |
| 91 | dp->g = MP_FOUR; |
| 92 | return (PGEN_DONE); |
| 93 | } |
| 94 | |
| 95 | /* --- Otherwise the job is much simpler --- * |
| 96 | * |
| 97 | * But doesn't look it... |
| 98 | */ |
| 99 | |
| 100 | else { |
| 101 | pgen_filterctx c; |
| 102 | pgen_jumpctx j; |
| 103 | rabin rb; |
| 104 | prim_ctx p; |
| 105 | int i; |
| 106 | mp *m = MP_NEW; |
| 107 | mp *x, *y; |
| 108 | |
| 109 | /* --- Generate @q@ first --- */ |
| 110 | |
| 111 | c.step = 2; |
| 112 | m = mprand(MP_NEW, ql, r, 1); |
| 113 | dp->q = pgen("q", MP_NEW, m, event, ectx, steps, pgen_filter, &c, |
| 114 | rabin_iters(ql), pgen_test, &rb); |
| 115 | if (!dp->q) |
| 116 | goto fail_q; |
| 117 | |
| 118 | /* --- Now pick a suitable @p@ --- */ |
| 119 | |
| 120 | m = mp_lsl(m, dp->q, 1); |
| 121 | x = mprand(MP_NEW, pl, r, 0); |
| 122 | y = MP_NEW; mp_div(0, &y, x, m); |
| 123 | x = mp_sub(x, x, y); |
| 124 | x = mp_add(x, x, MP_ONE); |
| 125 | mp_drop(y); |
| 126 | pfilt_create(&c.f, m); |
| 127 | j.j = &c.f; |
| 128 | dp->p = pgen("p", MP_NEW, x, event, ectx, steps, pgen_jump, &j, |
| 129 | rabin_iters(pl), pgen_test, &rb); |
| 130 | pfilt_destroy(&c.f); |
| 131 | mp_drop(x); |
| 132 | if (!dp->p) |
| 133 | goto fail_p; |
| 134 | |
| 135 | /* --- And finally a suitable @g@ --- */ |
| 136 | |
| 137 | mpmont_create(&p.mm, dp->p); |
| 138 | mp_div(&m, 0, dp->p, dp->q); |
| 139 | i = 0; |
| 140 | p.f = m; |
| 141 | p.n = 0; |
| 142 | dp->g = pgen("g", MP_NEW, MP_NEW, event, ectx, 0, prim_step, &i, |
| 143 | 1, prim_test, &p); |
| 144 | mpmont_destroy(&p.mm); |
| 145 | if (!dp->g) |
| 146 | goto fail_g; |
| 147 | mp_drop(m); |
| 148 | return (PGEN_DONE); |
| 149 | |
| 150 | /* --- Tidy up --- */ |
| 151 | |
| 152 | fail_g: |
| 153 | mp_drop(dp->q); |
| 154 | fail_q: |
| 155 | mp_drop(dp->p); |
| 156 | fail_p: |
| 157 | mp_drop(m); |
| 158 | return (PGEN_ABORT); |
| 159 | } |
| 160 | } |
| 161 | |
| 162 | /*----- That's all, folks -------------------------------------------------*/ |