diff --git a/nkode_api.py b/nkode_api.py
index 6f6f40c..5d9cd4e 100644
--- a/nkode_api.py
+++ b/nkode_api.py
@@ -53,7 +53,13 @@ class NKodeAPI(BaseModel):
         self.signup_sessions[session_id].set_user_nkode(username, key_selection)
         return self.signup_sessions[session_id].confirm_interface
 
-    def confirm_nkode(self, username: str, customer_id: UUID, confirm_key_entry: list[int], session_id: UUID) -> bool:
+    def confirm_nkode(
+            self,
+            username: str,
+            customer_id: UUID,
+            confirm_key_entry: list[int],
+            session_id: UUID
+    ) -> bool:
         assert (
                 session_id in self.signup_sessions.keys() and
                 customer_id == self.signup_sessions[session_id].customer_id and
diff --git a/src/customer.py b/src/customer.py
index 8ee9afb..bc278bf 100644
--- a/src/customer.py
+++ b/src/customer.py
@@ -20,12 +20,12 @@ class Customer(BaseModel):
 
     def valid_key_entry(self, username, selected_keys) -> bool:
         assert (username in self.users.keys())
-        assert (all(key_idx < self.attributes.keypad_size.numb_of_keys for key_idx in selected_keys))
+        assert (all(0 <= key_idx < self.attributes.keypad_size.numb_of_keys for key_idx in selected_keys))
         passcode_len = len(selected_keys)
         user = self.users[username]
 
         passcode_set_vals = user.user_keys.decipher_mask(
-            user.enciphered_passcode.mask, self.attributes.set_vals, len(selected_keys))
+            user.enciphered_passcode.mask, self.attributes.set_vals, passcode_len)
         set_vals_idx = [self.attributes.get_set_index(set_val) for set_val in passcode_set_vals]
 
         presumed_selected_attributes_idx = []
@@ -54,6 +54,7 @@ class Customer(BaseModel):
         set_xor = xor_lists(new_sets, old_sets)
         for user in self.users.values():
             user.renew_keys(set_xor, attrs_xor)
+            self.users[user.username] = user
         return True
 
     def valid_new_nkode(self, passcode_attr_idx: list[int]) -> bool:
diff --git a/src/models.py b/src/models.py
index 2d4dd7a..475cb0b 100644
--- a/src/models.py
+++ b/src/models.py
@@ -1,11 +1,6 @@
 from pydantic import BaseModel
 
 
-class NKodeAttribute(BaseModel):
-    attr_val: int
-    set_val: int
-
-
 class EncipheredNKode(BaseModel):
     code: str
     mask: str
@@ -17,6 +12,8 @@ class NKodePolicy(BaseModel):
     distinct_sets: int = 0
     distinct_attributes: int = 4
     byte_len: int = 2  # Todo: this should change the total number of bytes an attribute or set value can be
+    lock_out: int = 5
+    expiration: int = -1 # in seconds -1 means never expires
 
 
 class KeypadSize(BaseModel):
diff --git a/src/user_interface.py b/src/user_interface.py
index 223f4b4..673272e 100644
--- a/src/user_interface.py
+++ b/src/user_interface.py
@@ -98,6 +98,7 @@ class UserInterface(BaseModel):
 
     def get_attr_idx_by_keynumb_setidx(self, key_numb: int, set_idx: int) -> int:
         assert (0 <= key_numb < self.keypad_size.numb_of_keys)
+        assert (0 <= set_idx < self.keypad_size.attrs_per_key)
         keypad_attr_idx = self.interface_keypad_matrix()
 
         return keypad_attr_idx[key_numb][set_idx]
diff --git a/test/test_user_interface.py b/test/test_user_interface.py
index b371b1b..d3fd2f3 100644
--- a/test/test_user_interface.py
+++ b/test/test_user_interface.py
@@ -9,11 +9,10 @@ def user_interface():
 
 
 def test_dispersion(user_interface):
-    pre_dispersion_graph = user_interface.attribute_adjacency_graph()
-    user_interface.disperse_interface()
-    post_dispersion_graph = user_interface.attribute_adjacency_graph()
-
     for _ in range(10000):
+        pre_dispersion_graph = user_interface.attribute_adjacency_graph()
+        user_interface.disperse_interface()
+        post_dispersion_graph = user_interface.attribute_adjacency_graph()
         for attr, adj_graph in pre_dispersion_graph.items():
             assert (adj_graph.isdisjoint(post_dispersion_graph[attr]))
 
@@ -28,10 +27,9 @@ def test_shuffle_attrs(user_interface):
     pre_shuffle_interface = user_interface.interface
     user_interface.partial_interface_shuffle()
     post_shuffle_interface = user_interface.interface
-    for i in range(1000):
-        assert (not all(
-            post_shuffle_interface[idx] == pre_shuffle_interface[idx] for idx in range(len(post_shuffle_interface))
-        ))
-        assert (not all(
-            post_shuffle_interface[idx] != pre_shuffle_interface[idx] for idx in range(len(post_shuffle_interface))
-        ))
+    assert (not all(
+        post_shuffle_interface[idx] == pre_shuffle_interface[idx] for idx in range(len(post_shuffle_interface))
+    ))
+    assert (not all(
+        post_shuffle_interface[idx] != pre_shuffle_interface[idx] for idx in range(len(post_shuffle_interface))
+    ))