--- /dev/null
+/* -*-c-*-
+ *
+ * $Id: bbs-gen.c,v 1.1 1999/12/10 23:14:59 mdw Exp $
+ *
+ * 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.
+ */
+
+/*----- Revision history --------------------------------------------------*
+ *
+ * $Log: bbs-gen.c,v $
+ * Revision 1.1 1999/12/10 23:14:59 mdw
+ * Blum-Blum-Shub generator, and Blum-Goldwasser encryption.
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "bbs.h"
+#include "fibrand.h"
+#include "mp.h"
+#include "mprand.h"
+#include "pgen.h"
+#include "rabin.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @bbs_gen@ --- *
+ *
+ * Arguments: @bbs_params *bp@ = pointer to parameter block
+ * @mp *p, *q@ = initial numbers to search from
+ * @size_t n@ = number of attempts to make
+ * @void (*proc)(int ev, mp *m, void *p)@ = event handler
+ * @void *arg@ = argument for event handler
+ *
+ * Returns: Zero if all went well, otherwise an event code which explains
+ * the problem.
+ *
+ * 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_params *bp, mp *p, mp *q, size_t n,
+ int (*proc)(int /*ev*/, mp */*m*/, void */*p*/), void *arg)
+{
+ pgen px, py;
+ mp *pp;
+ mp *g = MP_NEW;
+ grand *gr = fibrand_create(0);
+ int rcx, rcy;
+ int fail = BBSEV_OK;
+ size_t sz;
+
+ /* --- Initialize @p@ and @q@ --- *
+ *
+ * Divide both by two, and make the results odd.
+ */
+
+ p = mp_lsr(MP_NEW, p, 1); p->v[0] |= 1;
+ q = mp_lsr(MP_NEW, q, 1); q->v[0] |= 1;
+
+ /* --- Set up the search for @p@ --- *
+ *
+ * I want a prime %$p$% such that %$(p - 1)/2$% has no small factors.
+ */
+
+ rcx = pgen_create(&px, p); mp_drop(p);
+ rcy = pgen_muladd(&py, &px, 2, 1);
+
+ if (proc && (fail = proc(BBSEV_FINDP, 0, arg)) != 0)
+ goto fail_0;
+
+ sz = mp_bits(py.m);
+ for (;;) {
+ if (rcx != PGEN_COMPOSITE && rcy != PGEN_COMPOSITE) {
+ if (rcy != PGEN_PRIME) {
+ rabin r;
+ int i;
+
+ if (proc && (fail = proc(BBSEV_TRYP, py.m, arg)) != 0)
+ break;
+ rabin_create(&r, py.m);
+ for (i = 0; i < 5; i++) {
+ g = mprand(g, sz, gr, 1);
+ if ((rcy = rabin_test(&r, g)) == PGEN_COMPOSITE)
+ break;
+ if (proc && (fail = proc(BBSEV_PASSP, py.m, arg)) != 0)
+ break;
+ }
+ rabin_destroy(&r);
+ if (fail)
+ goto fail_0;
+ if (i < 5) {
+ if (proc && (fail = proc(BBSEV_FAILP, py.m, arg)) != 0)
+ goto fail_0;
+ if (n) {
+ n--;
+ if (!n) {
+ fail = BBSEV_FAILP;
+ goto fail_0;
+ }
+ }
+ }
+ }
+
+ if (rcy != PGEN_COMPOSITE)
+ break;
+ }
+ rcx = pgen_step(&px, 2);
+ rcy = pgen_step(&py, 4);
+ }
+
+ if (proc && (fail = proc(BBSEV_GOODP, py.m, arg)) != 0)
+ goto fail_0;
+
+ /* --- I now have a @p@ (and a %$(p - 1)/2$%) --- */
+
+ pp = MP_COPY(px.m); pgen_destroy(&px);
+ p = MP_COPY(py.m); pgen_destroy(&py);
+
+ /* --- Next trick is to generate @q@ --- *
+ *
+ * I don't care about small factors of %$(q - 1)/2$%, just that it's
+ * relatively prime to %$(p - 1)/2$%.
+ */
+
+ {
+ mp *m = mp_lsl(MP_NEW, q, 1);
+ m->v[0] |= 1;
+ rcx = pgen_create(&px, m);
+ mp_drop(m);
+ }
+
+ if (proc && (fail = proc(BBSEV_FINDQ, 0, arg)) != 0)
+ goto fail_1;
+
+ for (;;) {
+ if (rcx != PGEN_COMPOSITE) {
+ int ok;
+
+ /* --- Ensure that %$(p - 1)/2$% and %$(q - 1)/2$% are coprime --- */
+
+ mp_gcd(&g, 0, 0, pp, q);
+ ok = MP_CMP(g, ==, MP_ONE);
+
+ if (ok && rcx != PGEN_PRIME) {
+ rabin r;
+ int i;
+
+ if (proc && (fail = proc(BBSEV_TRYQ, px.m, arg)) != 0)
+ break;
+ rabin_create(&r, px.m);
+ for (i = 0; i < 5; i++) {
+ g = mprand(g, sz, gr, 1);
+ if ((rcx = rabin_test(&r, g)) == PGEN_COMPOSITE)
+ break;
+ if (proc && (fail = proc(BBSEV_PASSQ, px.m, arg)) != 0)
+ break;
+ }
+ rabin_destroy(&r);
+ if (fail)
+ goto fail_1;
+ if (i < 5) {
+ if (proc && (fail = proc(BBSEV_FAILQ, px.m, arg)) != 0)
+ goto fail_1;
+ if (n) {
+ n--;
+ if (!n) {
+ fail = BBSEV_FAILQ;
+ goto fail_1;
+ }
+ }
+ }
+ }
+
+ if (ok && rcx != PGEN_COMPOSITE)
+ break;
+ }
+
+ q = mp_add(q, q, MP_TWO);
+ rcx = pgen_step(&px, 4);
+ }
+
+ if (proc && (fail = proc(BBSEV_GOODQ, px.m, arg)) != 0)
+ goto fail_1;
+
+ /* --- Done --- */
+
+ mp_drop(g);
+ mp_drop(q);
+ mp_drop(pp);
+ q = MP_COPY(px.m);
+ bp->p = p;
+ bp->q = q;
+ pgen_destroy(&px);
+ bp->n = mp_mul(MP_NEW, p, q);
+ gr->ops->destroy(gr);
+ return (0);
+
+ /* --- Failed --- */
+
+fail_1:
+ pgen_destroy(&px);
+ mp_drop(p);
+ mp_drop(pp);
+ mp_drop(g);
+ gr->ops->destroy(gr);
+ return (fail);
+
+fail_0:
+ if (g)
+ mp_drop(g);
+ pgen_destroy(&px);
+ pgen_destroy(&py);
+ mp_drop(q);
+ gr->ops->destroy(gr);
+ return (fail);
+}
+
+/*----- That's all, folks -------------------------------------------------*/
projects / u / mdw / catacomb / blobdiff