Rearrange the file tree.

[catacomb] / pub / bbs-gen.c

diff --git a/pub/bbs-gen.c b/pub/bbs-gen.c
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+/* -*-c-*-
+ *
+ * Generate Blum integers
+ *
+ * (c) 1999 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 <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "bbs.h"
+#include "mp.h"
+#include "mprand.h"
+#include "pgen.h"
+#include "strongprime.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @bbs_gen@ --- *
+ *
+ * Arguments:  @bbs_priv *bp@ = pointer to parameter block
+ *             @unsigned nbits@ = number of bits in the modulus
+ *             @grand *r@ = pointer to random number source
+ *             @unsigned n@ = number of attempts to make
+ *             @pgen_proc *event@ = event handler function
+ *             @void *ectx@ = argument for event handler
+ *
+ * Returns:    If it worked OK, @PGEN_DONE@, otherwise @PGEN_ABORT@.
+ *
+ * Use:                Finds two prime numbers %$p'$% and %$q'$% such that both are
+ *             congruent to %$3 \bmod 4$%, and  $(p - 1)/2$% and
+ *             %$(q - 1)/2$% have no common factors.  The product %$n = pq$%
+ *             is eminently suitable for use as a modulus in a Blum-Blum-
+ *             Shub pseudorandom bit generator.
+ */
+
+int bbs_gen(bbs_priv *bp, unsigned nbits, grand *r, unsigned n,
+           pgen_proc *event, void *ectx)
+{
+  rabin rb;
+  pfilt jp;
+  pgen_jumpctx j;
+  pgen_gcdstepctx g;
+  unsigned nb = nbits/2;
+  mp *x = MP_NEW;
+
+  /* --- Generate @p@ --- */
+
+again:
+  if ((x = strongprime_setup("p", x, &jp, nb, r, n, event, ectx)) == 0)
+    goto fail_x;
+  j.j = &jp;
+  bp->p = pgen("p", MP_NEW, x, event, ectx, n, pgen_jump, &j,
+              rabin_iters(nb), pgen_test, &rb);
+  pfilt_destroy(&jp);
+  if (!bp->p) {
+    if (n)
+      goto fail_p;
+    goto again;
+  }
+
+  /* --- Generate @q@ --- */
+
+  nb = nbits - nb;
+  if ((x = strongprime_setup("q", x, &g.jp, nb, r, n, event, ectx)) == 0)
+    goto fail_q;
+  if ((x->v[0] & 3) != 3)
+    x = mp_add(x, x, g.jp.m);
+  pfilt_muladd(&g.jp, &g.jp, 2, 0);
+  g.r = mp_lsr(MP_NEW, bp->p, 1);
+  g.g = MP_NEW;
+  g.max = MP_ONE;
+  bp->q = pgen("q", MP_NEW, x, event, ectx, n, pgen_gcdstep, &g,
+              rabin_iters(nb), pgen_test, &rb);
+  pfilt_destroy(&g.jp);
+  mp_drop(g.r);
+  mp_drop(g.g);
+  if (!bp->q) {
+    if (n)
+      goto fail_q;
+    mp_drop(bp->p);
+    goto again;
+  }
+
+  /* --- Compute @n@ --- */
+
+  bp->n = mp_mul(MP_NEW, bp->p, bp->q);
+  mp_drop(x);
+  return (PGEN_DONE);
+
+  /* --- Tidy up if things went wrong --- */
+
+fail_q:
+  mp_drop(bp->p);
+fail_p:
+  mp_drop(x);
+fail_x:
+  return (PGEN_ABORT);
+}
+
+/*----- That's all, folks -------------------------------------------------*/