Index: mpi-1.8.6/mpi.c
===================================================================
--- mpi-1.8.6.orig/mpi.c	2012-03-04 08:51:51.607484757 -0800
+++ mpi-1.8.6/mpi.c	2012-03-04 11:49:32.456841257 -0800
@@ -1960,6 +1960,34 @@
 
 /* }}} */
 
+unsigned long mp_hash(mp_int *a)
+{
+#if SIZEOF_LONG > MP_DIGIT_SIZE
+  unsigned long hash;
+  int ix;
+
+  if (USED(a) >= 2 * SIZEOF_LONG / MP_DIGIT_SIZE) {
+    mp_digit omega = 0;
+    mp_digit alpha = 0;
+    for (ix = 0; ix < SIZEOF_LONG / MP_DIGIT_SIZE; ix++)
+	omega = (omega << MP_DIGIT_BIT) | DIGIT(a, ix);
+    for (ix = USED(a) - SIZEOF_LONG / MP_DIGIT_SIZE; ix < USED(a); ix++)
+	alpha = (alpha << MP_DIGIT_BIT) | DIGIT(a, ix);
+    hash = alpha + omega;
+  } else {
+    hash = 0;
+
+    for (ix = 0; ix < USED(a); ix++)
+	hash = (hash << MP_DIGIT_BIT) | DIGIT(a, ix);
+  }
+#else
+  mp_digit omega = DIGIT(a, 0);
+  mp_digit alpha = DIGIT(a, USED(a) - 1);
+  unsigned long hash = alpha + omega;
+#endif
+  return SIGN(a) == MP_NEG ? ~hash : hash;
+}
+
 /*------------------------------------------------------------------------*/
 /* {{{ Number theoretic functions */
 
Index: mpi-1.8.6/mpi.h
===================================================================
--- mpi-1.8.6.orig/mpi.h	2012-03-04 08:51:51.607484757 -0800
+++ mpi-1.8.6/mpi.h	2012-03-04 11:49:32.196695007 -0800
@@ -165,6 +165,8 @@
 int    mp_isodd(mp_int *a);
 int    mp_iseven(mp_int *a);
 
+unsigned long mp_hash(mp_int *a);
+
 /*------------------------------------------------------------------------*/
 /* Number theoretic                                                       */