diff --git a/www/conservancy/__init__.py b/www/conservancy/__init__.py
index 648278312b89233be6fc9da08f2b30f24991a0a4..28f44d49592182aca58ca1bb766d3dad3087a5ea 100644
--- a/www/conservancy/__init__.py
+++ b/www/conservancy/__init__.py
@@ -1,6 +1,27 @@
+import hashlib
+
+from django.conf import settings
 from django.shortcuts import render_to_response
 from django.template import RequestContext
 
+HASH_ENCODING = 'utf-8'
+
 def render_template_with_context(request, template_path, context_dict):
     return render_to_response(template_path, context_dict,
                               context_instance=RequestContext(request))
+
+def param_if_valid(params, param_name, hash_param_name, default=None):
+    try:
+        seed = settings.CONSERVANCY_SECRET_KEY
+        param_value = params[param_name]
+        param_bytes = param_value.encode(HASH_ENCODING)
+        given_hash = params[hash_param_name]
+    except (AttributeError, KeyError, UnicodeEncodeError):
+        return default
+    good_hash = hashlib.sha256()
+    good_hash.update(seed)
+    good_hash.update(param_bytes)
+    if given_hash == unicode(good_hash.hexdigest()):
+        return param_value
+    else:
+        return default