X-Git-Url: https://git.distorted.org.uk/~mdw/catacomb/blobdiff_plain/6687eff59d78369e4d19fb0b3a9a0bb6035d1031..285bf989997b8dc94a0783e260fe73787c7ae767:/math/strongprime.c?ds=sidebyside

diff --git a/math/strongprime.c b/math/strongprime.c
index a2dd4385..a82bfad0 100644
--- a/math/strongprime.c
+++ b/math/strongprime.c
@@ -63,6 +63,7 @@ mp *strongprime_setup(const char *name, mp *d, pfilt *f, unsigned nbits,
 {
   mp *s, *t, *q;
   dstr dn = DSTR_INIT;
+  size_t nb;
 
   mp *rr = d;
   pgen_filterctx c;
@@ -81,20 +82,20 @@ mp *strongprime_setup(const char *name, mp *d, pfilt *f, unsigned nbits,
 
   /* --- Choose two primes %$s$% and %$t$% of half the required size --- */
 
-  assert(((void)"nbits too small in strongprime_setup", nbits/2 > BITSLOP));
-  nbits = nbits/2 - BITSLOP;
+  if (nbits/2 <= BITSLOP) return (0);
+  nb = nbits/2 - BITSLOP;
   c.step = 1;
 
-  rr = mprand(rr, nbits, r, 1);
+  rr = mprand(rr, nb, r, 1);
   DRESET(&dn); dstr_putf(&dn, "%s [s]", name);
   if ((s = pgen(dn.buf, MP_NEWSEC, rr, event, ectx, n, pgen_filter, &c,
-		rabin_iters(nbits), pgen_test, &rb)) == 0)
+		rabin_iters(nb), pgen_test, &rb)) == 0)
     goto fail_s;
 
-  rr = mprand(rr, nbits, r, 1);
+  rr = mprand(rr, nb, r, 1);
   DRESET(&dn); dstr_putf(&dn, "%s [t]", name);
   if ((t = pgen(dn.buf, MP_NEWSEC, rr, event, ectx, n, pgen_filter, &c,
-		rabin_iters(nbits), pgen_test, &rb)) == 0)
+		rabin_iters(nb), pgen_test, &rb)) == 0)
     goto fail_t;
 
   /* --- Choose a suitable value for %$r = 2it + 1$% for some %$i$% --- */
@@ -105,9 +106,8 @@ mp *strongprime_setup(const char *name, mp *d, pfilt *f, unsigned nbits,
   rr = mp_add(rr, rr, MP_ONE);
   DRESET(&dn); dstr_putf(&dn, "%s [r]", name);
   j.j = &c.f;
-  nbits += BITSLOP;
   q = pgen(dn.buf, MP_NEW, rr, event, ectx, n, pgen_jump, &j,
-	   rabin_iters(nbits), pgen_test, &rb);
+	   rabin_iters(nb + BITSLOP), pgen_test, &rb);
   pfilt_destroy(&c.f);
   if (!q)
     goto fail_r;
@@ -132,13 +132,13 @@ mp *strongprime_setup(const char *name, mp *d, pfilt *f, unsigned nbits,
   /* --- Now find %$p = p_0 + 2jrs$% for some %$j$% --- */
 
   {
-    mp *x;
+    mp *x, *y;
     x = mp_mul(MP_NEW, q, s);
     x = mp_lsl(x, x, 1);
     pfilt_create(f, x);
-    x = mp_lsl(x, x, BITSLOP - 1);
-    rr = mp_add(rr, rr, x);
-    mp_drop(x);
+    y = mp_lsl(MP_NEW, MP_ONE, nbits - 1);
+    rr = mp_leastcongruent(rr, y, rr, x);
+    mp_drop(x); mp_drop(y);
   }
 
   /* --- Return the result --- */
@@ -188,16 +188,20 @@ fail_s:
 mp *strongprime(const char *name, mp *d, unsigned nbits, grand *r,
 		unsigned n, pgen_proc *event, void *ectx)
 {
+  mp *p;
   pfilt f;
   pgen_jumpctx j;
   rabin rb;
 
-  d = strongprime_setup(name, d, &f, nbits, r, n, event, ectx);
+  if (d) mp_copy(d);
+  p = strongprime_setup(name, d, &f, nbits, r, n, event, ectx);
+  if (!p) { mp_drop(d); return (0); }
   j.j = &f;
-  d = pgen(name, d, d, event, ectx, n, pgen_jump, &j,
+  p = pgen(name, p, p, event, ectx, n, pgen_jump, &j,
 	   rabin_iters(nbits), pgen_test, &rb);
   pfilt_destroy(&f);
-  return (d);
+  mp_drop(d);
+  return (p);
 }
 
 /*----- That's all, folks -------------------------------------------------*/