Hash collision security issue

Objects/unicodeobject.c

 /*
 
 Unicode implementation based on original code by Fredrik Lundh,
 modified by Marc-Andre Lemburg <mal@lemburg.com> according to the
 Unicode Integration Proposal (see file Misc/unicode.txt).
 
 Major speed upgrades to the method implementations at the Reykjavik
 NeedForSpeed sprint, by Fredrik Lundh and Andrew Dalke.
 
 Copyright (c) Corporation for National Research Initiatives.
@@ skipping 7326 matching lines @@
 static long
 unicode_hash(PyUnicodeObject *self)
 {
     Py_ssize_t len;
     Py_UNICODE *p;
     long x;
 
     if (self->hash != -1)
         return self->hash;
     len = Py_SIZE(self);
+    /*
+      We make the hash of the empty string be 0, rather than using
+      (prefix ^ suffix), since this slightly obfuscates the hash secret
+    */
+    if (len == 0) {
+        self->hash = 0;
+        return 0;
+    }
     p = self->str;
-    x = *p << 7;
+    x = _Py_HashSecret.prefix;
+    x ^= *p << 7;
     while (--len >= 0)
         x = (1000003*x) ^ *p++;
     x ^= Py_SIZE(self);
+    x ^= _Py_HashSecret.suffix;
     if (x == -1)
         x = -2;
     self->hash = x;
     return x;
 }
 
 PyDoc_STRVAR(index__doc__,
              "S.index(sub[, start[, end]]) -> int\n\
 \n\
 Like S.find() but raise ValueError when the substring is not found.");
@@ skipping 2675 matching lines @@
 }
 #endif
 
 
 /*
   Local variables:
   c-basic-offset: 4
   indent-tabs-mode: nil
   End:
 */