diff -r 7cf3e950211d viff/field.py
--- a/viff/field.py	Sun Sep 21 19:25:14 2008 +0200
+++ b/viff/field.py	Wed Sep 24 16:01:12 2008 +0200
@@ -85,6 +85,7 @@
 #: Maps *(x,y)* to *xy*. See `_generate_tables`.
 _mul_table = {}
 
+_mpz_type = type(mpz(1))
 
 # The class name is slightly wrong since the class instances cannot be
 # said to be represent a field. Instead they represent instances of
@@ -103,6 +104,8 @@
         >>> GF256(1) == GF256(257)
         True
         """
+        if isinstance(value, _mpz_type):
+            value = int(value)
         self.value = value % self.modulus
 
     def __add__(self, other):
@@ -248,6 +251,14 @@
         """
         return self.value != 0
 
+    @classmethod
+    def marshal_representation(cls, value):
+        """Returns a version of this value suitable for
+        serializing with marshal.
+
+        We just return the value, as it is an int."""
+        return value
+
 # We provide the class here to make the construction of new elements
 # easy in a polymorphic context.
 GF256.field = GF256
@@ -337,8 +348,10 @@
     class GFElement(FieldElement):
 
         def __init__(self, value):
-            self.value = value % self.modulus
-
+            if isinstance(value, str):
+                self.value = mpz(value, 256) % self.modulus
+            else:
+                self.value = mpz(value) % self.modulus
         def __add__(self, other):
             """Addition."""
             if not isinstance(other, (GFElement, int, long)):
@@ -508,7 +521,15 @@
             """
             return self.value != 0
 
-    GFElement.modulus = modulus
+        @classmethod
+        def marshal_representation(cls, value):
+            """Returns a version of this value suitable for
+            serializing with marshal.
+
+            We take the string representation of the mpz"""
+            return value.binary()
+
+    GFElement.modulus = mpz(modulus)
     GFElement.field = GFElement
 
     _field_cache[modulus] = GFElement
diff -r 7cf3e950211d viff/runtime.py
--- a/viff/runtime.py	Sun Sep 21 19:25:14 2008 +0200
+++ b/viff/runtime.py	Wed Sep 24 16:01:12 2008 +0200
@@ -320,7 +320,10 @@
         The program counter and the share are marshalled and sent to
         the peer.
         """
-        self.sendData(program_counter, "share", share.value)
+        if share.field is GF256:
+            self.sendData(program_counter, "share", share.value)
+        else:
+            self.sendData(program_counter, "share", share.value.binary())
 
     def loseConnection(self):
         """Disconnect this protocol instance."""