1 files changed, 39 insertions, 0 deletions
diff --git a/libtommath/bn_mp_invmod.c b/libtommath/bn_mp_invmod.c
new file mode 100644
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--- /dev/null
+++ b/libtommath/bn_mp_invmod.c
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+#include <tommath.h>
+#ifdef BN_MP_INVMOD_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
+ */
+
+/* hac 14.61, pp608 */
+int mp_invmod (mp_int * a, mp_int * b, mp_int * c)
+{
+  /* b cannot be negative */
+  if (b->sign == MP_NEG || mp_iszero(b) == 1) {
+    return MP_VAL;
+  }
+
+#ifdef BN_FAST_MP_INVMOD_C
+  /* if the modulus is odd we can use a faster routine instead */
+  if (mp_isodd (b) == 1) {
+    return fast_mp_invmod (a, b, c);
+  }
+#endif
+
+#ifdef BN_MP_INVMOD_SLOW_C
+  return mp_invmod_slow(a, b, c);
+#endif
+
+  return MP_VAL;
+}
+#endif