use hashes of approximately 80 bit and use all digits and characters (lower case) for the hash

wortschlucker/src/wortschlucker.py

@@ -178,10 +178,22 @@ def get_poll_admin_id(hash_key):
     else:
         return None
 
-def get_new_hash_key():
+def get_new_hash_key(length=16, charset=None):
-    hash_key = uuid.uuid4().get_hex()
+    """ returns a quite random hash key with the specified length """
+    if charset is None:
+        charset = "0123456789abcdefghijklmnopqrstuvwxyz"
+    def get_hash_string(length):
+        base = uuid.uuid4().int
+        result = []
+        while len(result) < length:
+            value = base % len(charset)
+            base //= len(charset)
+            result.append(charset[value])
+        return "".join(result)
+    # repeat the hash generation until a new value is found
+    hash_key = get_hash_string(length)
     while (not get_poll_id(hash_key) is None) or (not get_poll_admin_id(hash_key) is None):
-        hash_key = uuid.uuid4().get_hex()
+        hash_key = get_hash_string(length)
     return hash_key
 
 @bobo.query('/polls/new')