X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/b817bfc642225b8c3c0b6a7e42d1fb949b61a606..025c5f4aa5ffbf8948482a4233318db81c2df5d2:/mpbarrett-exp.c

diff --git a/mpbarrett-exp.c b/mpbarrett-exp.c
index 56e7c76..9885e2f 100644
--- a/mpbarrett-exp.c
+++ b/mpbarrett-exp.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mpbarrett-exp.c,v 1.2 2004/04/08 01:36:15 mdw Exp $
+ * $Id$
  *
  * Modular exponentiation using Barrett reduction
  *
@@ -52,14 +52,16 @@ mp *mpbarrett_exp(mpbarrett *mb, mp *d, mp *a, mp *e)
 
   MP_COPY(a);
   MP_SHRINK(e);
-  if (e->f & MP_NEG)
-    a = mp_modinv(a, a, mb->m);
-  if (!MP_LEN(e))
+  if (MP_ZEROP(e))
     ;
-  else if (MP_LEN(e) < EXP_THRESH)
-    EXP_SIMPLE(x, a, e);
-  else
-    EXP_WINDOW(x, a, e);
+  else {
+    if (MP_NEGP(e))
+      a = mp_modinv(a, a, mb->m);
+    if (MP_LEN(e) < EXP_THRESH)
+      EXP_SIMPLE(x, a, e);
+    else
+      EXP_WINDOW(x, a, e);
+  }
   mp_drop(d);
   mp_drop(spare);
   mp_drop(a);