| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: dh-limlee.c,v 1.3 2004/04/08 01:36:15 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 | /*----- 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 |
| 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 |
| 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) |
| 84 | return (PGEN_ABORT); |
| 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) { |
| 91 | dp->q = mp_copy(ff[0]); |
| 92 | pc.exp = MP_NEW; |
| 93 | mp_div(&pc.exp, 0, pp, dp->q); |
| 94 | pc.n = 0; |
| 95 | pc.f = 0; |
| 96 | } else { |
| 97 | dp->q = mp_lsr(MP_NEW, dp->p, 1); |
| 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); |
| 135 | return (PGEN_ABORT); |
| 136 | } |
| 137 | return (PGEN_DONE); |
| 138 | } |
| 139 | |
| 140 | /*----- That's all, folks -------------------------------------------------*/ |