--- hmac.py-orig	2007-11-06 06:32:04.000000000 +0600
+++ hmac.py	2008-04-24 17:49:29.000000000 +0600
@@ -3,10 +3,16 @@
 Implements the HMAC algorithm as described by RFC 2104.
 """
 
+import array
 def _strxor(s1, s2):
     """Utility method. XOR the two strings s1 and s2 (must have same length).
     """
-    return "".join(map(lambda x, y: chr(ord(x) ^ ord(y)), s1, s2))
+    a1 = array.array('B')
+    a1.fromstring(s1)
+    a2 = array.array('B')
+    a2.fromstring(s2)
+    return array.array('B', [x ^ y for x, y in zip(a1, a2)]).tostring()
+
 
 # The size of the digests returned by HMAC depends on the underlying
 # hashing module used.