X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/9f11b970d10c4139e1bfd0be6e817e2dfe982f41..3884054be9261b4607f5f3a2d0b79695f65b851f:/mp-modsqrt.c

diff --git a/mp-modsqrt.c b/mp-modsqrt.c
index a3a6b1f..df60aba 100644
--- a/mp-modsqrt.c
+++ b/mp-modsqrt.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mp-modsqrt.c,v 1.1 2000/06/22 19:01:31 mdw Exp $
+ * $Id: mp-modsqrt.c,v 1.4 2001/06/16 12:56:38 mdw Exp $
  *
  * Compute square roots modulo a prime
  *
@@ -30,6 +30,16 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: mp-modsqrt.c,v $
+ * Revision 1.4  2001/06/16 12:56:38  mdw
+ * Fixes for interface change to @mpmont_expr@ and @mpmont_mexpr@.
+ *
+ * Revision 1.3  2001/02/03 12:00:29  mdw
+ * Now @mp_drop@ checks its argument is non-NULL before attempting to free
+ * it.  Note that the macro version @MP_DROP@ doesn't do this.
+ *
+ * Revision 1.2  2000/10/08 12:02:21  mdw
+ * Use @MP_EQ@ instead of @MP_CMP@.
+ *
  * Revision 1.1  2000/06/22 19:01:31  mdw
  * Compute square roots in a prime field.
  *
@@ -75,8 +85,7 @@ mp *mp_modsqrt(mp *d, mp *a, mp *p)
   /* --- Cope if %$a \not\in Q_p$% --- */
 
   if (mp_jacobi(a, p) != 1) {
-    if (d)
-      mp_drop(d);
+    mp_drop(d);
     return (0);
   }
 
@@ -105,10 +114,13 @@ mp *mp_modsqrt(mp *d, mp *a, mp *p)
   /* --- Now to really get going --- */
 
   mpmont_create(&mm, p);
+  b = mpmont_mul(&mm, b, b, mm.r2);
   c = mpmont_expr(&mm, b, b, t);
   t = mp_add(t, t, MP_ONE);
   t = mp_lsr(t, t, 1);
-  r = mpmont_expr(&mm, t, a, t);
+  dd = mpmont_mul(&mm, MP_NEW, a, mm.r2);
+  r = mpmont_expr(&mm, t, dd, t);
+  mp_drop(dd);
   ainv = mpmont_mul(&mm, ainv, ainv, mm.r2);
 
   mone = mp_sub(MP_NEW, p, mm.r);
@@ -132,7 +144,7 @@ mp *mp_modsqrt(mp *d, mp *a, mp *p)
 
     /* --- Fiddle at the end --- */
 
-    if (MP_CMP(dd, ==, mone))
+    if (MP_EQ(dd, mone))
       r = mpmont_mul(&mm, r, r, c);
     c = mp_sqr(c, c);
     c = mpmont_reduce(&mm, c, c);
@@ -143,8 +155,7 @@ mp *mp_modsqrt(mp *d, mp *a, mp *p)
   d = mpmont_reduce(&mm, d, r);
   mp_drop(ainv);
   mp_drop(r); mp_drop(c);
-  if (dd)
-    mp_drop(dd);
+  mp_drop(dd);
   mp_drop(mone);
   mpmont_destroy(&mm);
 
@@ -167,11 +178,11 @@ static int verify(dstr *v)
 
   if (!r)
     ok = 0;
-  else if (MP_CMP(r, ==, rr))
+  else if (MP_EQ(r, rr))
     ok = 1;
   else {
     r = mp_sub(r, p, r);
-    if (MP_CMP(r, ==, rr))
+    if (MP_EQ(r, rr))
       ok = 1;
   }
 
@@ -191,8 +202,7 @@ static int verify(dstr *v)
 
   mp_drop(a);
   mp_drop(p);
-  if (r)
-    mp_drop(r);
+  mp_drop(r);
   mp_drop(rr);
   assert(mparena_count(MPARENA_GLOBAL) == 0);
   return (ok);