1 files changed, 38 insertions, 0 deletions
diff --git a/libtommath/bn_mp_submod.c b/libtommath/bn_mp_submod.c
new file mode 100644
index 0000000..b999c85
--- /dev/null
+++ b/libtommath/bn_mp_submod.c
@@ -0,0 +1,38 @@
+#include <tommath.h>
+#ifdef BN_MP_SUBMOD_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis
+ *
+ * LibTomMath is a library that provides multiple-precision
+ * integer arithmetic as well as number theoretic functionality.
+ *
+ * The library was designed directly after the MPI library by
+ * Michael Fromberger but has been written from scratch with
+ * additional optimizations in place.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org
+ */
+
+/* d = a - b (mod c) */
+int
+mp_submod (mp_int * a, mp_int * b, mp_int * c, mp_int * d)
+{
+  int     res;
+  mp_int  t;
+
+
+  if ((res = mp_init (&t)) != MP_OKAY) {
+    return res;
+  }
+
+  if ((res = mp_sub (a, b, &t)) != MP_OKAY) {
+    mp_clear (&t);
+    return res;
+  }
+  res = mp_mod (&t, c, d);
+  mp_clear (&t);
+  return res;
+}
+#endif