/* -*-c-*-
*
- * $Id: strongprime.c,v 1.1 1999/12/22 15:51:22 mdw Exp $
+ * $Id: strongprime.c,v 1.2 2000/02/12 18:21:03 mdw Exp $
*
* Generate `strong' prime numbers
*
/*----- Revision history --------------------------------------------------*
*
* $Log: strongprime.c,v $
+ * Revision 1.2 2000/02/12 18:21:03 mdw
+ * Overhaul of key management (again).
+ *
* Revision 1.1 1999/12/22 15:51:22 mdw
* Find `strong' RSA primes using Gordon's algorithm.
*
/*----- Main code ---------------------------------------------------------*/
-/* --- @strongprime@ --- *
+/* --- @strongprime_setup@ --- *
*
* Arguments: @const char *name@ = pointer to name root
- * @mp *d@ = destination integer
+ * @mp *d@ = destination for search start point
+ * @pfilt *f@ = where to store filter jump context
* @unsigned nbits@ = number of bits wanted
* @grand *r@ = random number source
* @unsigned n@ = number of attempts to make
* @pgen_proc *event@ = event handler function
* @void *ectx@ = argument for the event handler
*
- * Returns: A `strong' prime, or zero.
- *
- * Use: Finds `strong' primes. A strong prime %$p$% is such that
- *
- * * %$p - 1$% has a large prime factor %$r$%,
- * * %$p + 1$% has a large prime factor %$s$%, and
- * * %$r - 1$% has a large prime factor %$t$%.
+ * Returns: A starting point for a `strong' prime search, or zero.
*
- * The numbers produced may be slightly larger than requested,
- * by a few bits.
+ * Use: Sets up for a strong prime search, so that primes with
+ * particular properties can be found. It's probably important
+ * to note that the number left in the filter context @f@ is
+ * congruent to 2 (mod 4).
*/
-mp *strongprime(const char *name, mp *d, unsigned nbits, grand *r,
- unsigned n, pgen_proc *event, void *ectx)
+mp *strongprime_setup(const char *name, mp *d, pfilt *f, unsigned nbits,
+ grand *r, unsigned n, pgen_proc *event, void *ectx)
{
- mp *s, *t, *q, *p = 0;
+ mp *s, *t, *q;
dstr dn = DSTR_INIT;
- mp *rr = MP_NEW;
+ mp *rr = d;
pgen_filterctx c;
- pgen_jumpctx cj;
+ pgen_jumpctx j;
rabin rb;
/* --- The bitslop parameter --- *
* numbers around 10 seem to be good.
*/
-#define BITSLOP 10
+#define BITSLOP 12
/* --- Choose two primes %$s$% and %$t$% of half the required size --- */
rr = mprand(rr, nbits, r, 1);
DRESET(&dn); dstr_putf(&dn, "%s [s]", name);
if ((s = pgen(dn.buf, MP_NEW, rr, event, ectx, n, pgen_filter, &c,
- rabin_iters(nbits), pgen_test, &rb)) == 0)
+ rabin_iters(nbits), pgen_test, &rb)) == 0)
goto fail_s;
mp_burn(s);
rr = mp_lsl(rr, rr, BITSLOP - 1);
rr = mp_add(rr, rr, MP_ONE);
DRESET(&dn); dstr_putf(&dn, "%s [r]", name);
- cj.j = &c.f;
+ j.j = &c.f;
nbits += BITSLOP;
- if ((q = pgen(dn.buf, MP_NEW, rr, event, ectx, n, pgen_jump, &cj,
- rabin_iters(nbits), pgen_test, &rb)) == 0)
- goto fail_r;
+ q = pgen(dn.buf, MP_NEW, rr, event, ectx, n, pgen_jump, &j,
+ rabin_iters(nbits), pgen_test, &rb);
pfilt_destroy(&c.f);
+ if (!q)
+ goto fail_r;
/* --- Select a suitable starting-point for finding %$p$% --- *
*
mp *x;
x = mp_mul(MP_NEW, q, s);
x = mp_lsl(x, x, 1);
- pfilt_create(&c.f, x);
+ pfilt_create(f, x);
x = mp_lsl(x, x, BITSLOP - 1);
rr = mp_add(rr, rr, x);
mp_drop(x);
}
- if ((p = pgen(name, d, rr, event, ectx, n, pgen_jump, &cj,
- rabin_iters(nbits * 2), pgen_test, &rb)) == 0)
- goto fail_p;
+ /* --- Return the result --- */
- /* --- Tidy up because we've finished --- */
+#if 0
+fputs("r = ", stdout); mp_writefile(q, stdout, 10); putchar('\n');
+fputs("s = ", stdout); mp_writefile(s, stdout, 10); putchar('\n');
+fputs("t = ", stdout); mp_writefile(t, stdout, 10); putchar('\n');
+#endif
-fail_p:
mp_drop(q);
+ mp_drop(t);
+ mp_drop(s);
+ dstr_destroy(&dn);
+ return (rr);
+
+ /* --- Tidy up if something failed --- */
+
fail_r:
- pfilt_destroy(&c.f);
mp_drop(t);
fail_t:
mp_drop(s);
fail_s:
mp_drop(rr);
dstr_destroy(&dn);
-
- return (p);
+ return (0);
#undef BITSLOP
}
+/* --- @strongprime@ --- *
+ *
+ * Arguments: @const char *name@ = pointer to name root
+ * @mp *d@ = destination integer
+ * @unsigned nbits@ = number of bits wanted
+ * @grand *r@ = random number source
+ * @unsigned n@ = number of attempts to make
+ * @pgen_proc *event@ = event handler function
+ * @void *ectx@ = argument for the event handler
+ *
+ * Returns: A `strong' prime, or zero.
+ *
+ * Use: Finds `strong' primes. A strong prime %$p$% is such that
+ *
+ * * %$p - 1$% has a large prime factor %$r$%,
+ * * %$p + 1$% has a large prime factor %$s$%, and
+ * * %$r - 1$% has a large prime factor %$t$%.
+ *
+ * The numbers produced may be slightly larger than requested,
+ * by a few bits.
+ */
+
+mp *strongprime(const char *name, mp *d, unsigned nbits, grand *r,
+ unsigned n, pgen_proc *event, void *ectx)
+{
+ pfilt f;
+ pgen_jumpctx j;
+ rabin rb;
+
+ d = strongprime_setup(name, d, &f, nbits, r, n, event, ectx);
+ j.j = &f;
+ d = pgen(name, d, d, event, ectx, n, pgen_jump, &j,
+ rabin_iters(nbits), pgen_test, &rb);
+ pfilt_destroy(&f);
+ return (d);
+}
+
/*----- That's all, folks -------------------------------------------------*/
projects / u / mdw / catacomb / blobdiff