--- /dev/null
+/* -*-c-*-
+ *
+ * Generate Diffie-Hellman parameters from Lim-Lee primes
+ *
+ * (c) 2000 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * Catacomb is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "dh.h"
+#include "limlee.h"
+#include "mpmont.h"
+#include "prim.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @dh_limlee@ --- *
+ *
+ * Arguments: @dh_param *dp@ = pointer to output parameter block
+ * @unsigned ql@ = length of smallest factor of %$(p - 1)/2$%
+ * @unsigned pl@ = length of %$p$% in bits
+ * @unsigned flags@ = other generation flags
+ * @unsigned steps@ = number of steps to go
+ * @grand *r@ = random number source
+ * @pgen_proc *oev@ = outer event handler function
+ * @void *oec@ = argument for the outer event handler
+ * @pgen_proc *iev@ = inner event handler function
+ * @void *iec@ = argument for the inner event handler
+ * @size_t *nf@, @mp ***f@ = output array for factors
+ *
+ * Returns: @PGEN_DONE@ if it worked, @PGEN_ABORT@ if it didn't.
+ *
+ * Use: Generates Diffie-Hellman parameters based on a Lim-Lee prime.
+ *
+ * The modulus is a large prime %$p = 2 \prod q_i + 1$%, @pl@
+ * bits long, where the %$q_i$% are smaller primes each at least
+ * @ql@ bits long. It is safe to set @nf@ and @f@ to zero if
+ * you're not interested in the factor values.
+ *
+ * The returned %$g$% generates a subgroup of order %$q_0$% (the
+ * first factor, returned as @f[0]@), if the flag @DH_SUBGROUP@
+ * is set on entry; otherwise %$g$% will have order
+ * %$(p - 1)/2$%.
+ */
+
+int dh_limlee(dh_param *dp, unsigned ql, unsigned pl,
+ unsigned flags, unsigned steps, grand *r,
+ pgen_proc *oev, void *oec, pgen_proc *iev,
+ void *iec, size_t *nf, mp ***f)
+{
+ mp **ff;
+ size_t nff;
+ prim_ctx pc;
+ size_t i;
+ int j;
+ mp *pp;
+
+ /* --- Generate the Lim-Lee prime --- */
+
+ if ((dp->p = limlee("p", MP_NEW, MP_NEW, ql, pl,
+ r, steps, oev, oec, iev, iec, &nff, &ff)) == 0)
+ return (PGEN_ABORT);
+
+ /* --- Now find a primitive element --- */
+
+ mpmont_create(&pc.mm, dp->p);
+ pp = mp_sub(MP_NEW, dp->p, MP_ONE);
+ if (flags & DH_SUBGROUP) {
+ dp->q = mp_copy(ff[0]);
+ pc.exp = MP_NEW;
+ mp_div(&pc.exp, 0, pp, dp->q);
+ pc.n = 0;
+ pc.f = 0;
+ } else {
+ dp->q = mp_lsr(MP_NEW, dp->p, 1);
+ pc.exp = MP_TWO;
+ pc.n = nff;
+ pc.f = xmalloc(nff * sizeof(mp *));
+ for (i = 0; i < nff; i++) {
+ pc.f[i] = MP_NEW;
+ mp_div(&pc.f[i], 0, pp, ff[i]);
+ }
+ }
+
+ j = 0;
+ dp->g = pgen("g", MP_NEW, MP_NEW, oev, oec,
+ 0, prim_step, &j, 1, prim_test, &pc);
+
+ mp_drop(pp);
+ if (pc.f) {
+ for (i = 0; i < pc.n; i++)
+ mp_drop(pc.f[i]);
+ xfree(pc.f);
+ }
+ mpmont_destroy(&pc.mm);
+
+ /* --- Do something sensible with the list of primes --- */
+
+ if (dp->g && f) {
+ *f = ff;
+ *nf = nff;
+ } else {
+ for (i = 0; i < nff; i++)
+ mp_drop(ff[i]);
+ xfree(ff);
+ }
+
+ /* --- Tidy up and return --- */
+
+ if (!dp->g) {
+ mp_drop(dp->p);
+ mp_drop(dp->q);
+ return (PGEN_ABORT);
+ }
+ return (PGEN_DONE);
+}
+
+/*----- That's all, folks -------------------------------------------------*/