diff --git a/src/nkode_interface.py b/src/nkode_interface.py
index 59eb105..4f5e5f9 100644
--- a/src/nkode_interface.py
+++ b/src/nkode_interface.py
@@ -37,12 +37,12 @@ class CustomerInterface(BaseModel):
         return secure_fisher_yates_shuffle(list(range(len(self.interface))))
 
     def get_attr_set_val(self, attr: int) -> int:
-        assert(attr in self.interface)
-        attr_idx = self.interface.index(attr)
-        set_idx = attr_idx % self.numb_of_sets
+        assert(attr in self.customer_interface)
+        attr_idx = self.customer_interface.index(attr)
+        set_idx = attr_idx % self.attrs_per_key
         return self.set_vals[set_idx]
 
     def get_set_index(self, set_val: int) -> int:
-        assert(set_val in self.get_set_values())
+        assert(set_val in self.set_vals)
         return self.set_vals.index(set_val)
 
diff --git a/src/pseudo_nkode_api.py b/src/pseudo_nkode_api.py
index e058f17..792e9db 100644
--- a/src/pseudo_nkode_api.py
+++ b/src/pseudo_nkode_api.py
@@ -84,7 +84,6 @@ class PseudoNKodeAPI(BaseModel):
         attrs_per_key = customer.interface.attrs_per_key
         assert(all(0 <= key <= numb_of_keys for key in confirm_key_entry))
         passcode = self._deduce_passcode(session_id, numb_of_keys, attrs_per_key, confirm_key_entry)
-        attrs_per_key = customer.interface.numb_of_sets
         set_values = customer.interface.set_vals
         new_user_keys = UserCipherKeys.new_user_encipher_keys(numb_of_keys, attrs_per_key, set_values)
         enciphered_passcode = new_user_keys.encipher_nkode(passcode, customer.interface)
@@ -92,7 +91,11 @@ class PseudoNKodeAPI(BaseModel):
             username=username,
             enciphered_passcode=enciphered_passcode,
             user_keys=new_user_keys,
-            user_interface=self.sessions[session_id].confirm_interface
+            user_interface=UserInterface(
+                interface_index=self.sessions[session_id].confirm_interface,
+                numb_sets=attrs_per_key,
+                numb_keys=numb_of_keys
+            )
         )
         self.customers[customer_id].users.append(new_user)
         return "success"
diff --git a/src/user_cipher_keys.py b/src/user_cipher_keys.py
index ac45664..9b87c15 100644
--- a/src/user_cipher_keys.py
+++ b/src/user_cipher_keys.py
@@ -47,14 +47,14 @@ class UserCipherKeys(BaseModel):
 
     @staticmethod
     def encode_base64_str(data: list[int]) -> str:
-        return base64.b64encode(data).decode("utf-8")
+        return base64.b64encode(bytes(data)).decode("utf-8")
 
     @staticmethod
     def decode_base64_str(data: str) -> list[int]:
         return list(base64.b64decode(data))
 
     def _hash_passcode(self, passcode: list[int]) -> str:
-        passcode_digest = base64.b64encode(hashlib.sha256(passcode).digest())
+        passcode_digest = base64.b64encode(hashlib.sha256(bytes(passcode)).digest())
         hashed_data = bcrypt.hashpw(passcode_digest, self.salt)
         return hashed_data.decode("utf-8")
 
@@ -65,7 +65,7 @@ class UserCipherKeys(BaseModel):
     ) -> EncipheredNKode:
         max_nkode_len = 10
         passcode_len = len(nkode_attr_index)
-        user_nkode_attrs = [customer_interface.interface[idx] for idx in nkode_attr_index]
+        user_nkode_attrs = [customer_interface.customer_interface[idx] for idx in nkode_attr_index]
         user_nkode_mask = [customer_interface.get_attr_set_val(attr) for attr in user_nkode_attrs]
         mask_cipher = self.pad_user_mask(user_nkode_mask, customer_interface, max_nkode_len)
         passcode_cipher = self.pass_key
@@ -76,11 +76,10 @@ class UserCipherKeys(BaseModel):
             attr_val = user_nkode_attrs[idx]
             passcode_cipher[idx] ^= alpha ^ attr_val
 
-        for idx in range(max_nkode_len):
             set_idx = customer_interface.get_set_index(user_nkode_mask[idx])
             mask_cipher[idx] ^= self.set_key[set_idx] ^ self.mask_key[idx]
 
         return EncipheredNKode(
             code=self._hash_passcode(passcode_cipher),
-            mask=self.base64.b64encode(mask_cipher).decode("utf-8")
+            mask=self.encode_base64_str(mask_cipher)
         )
diff --git a/test/test_pseudo_nkode_api.py b/test/test_pseudo_nkode_api.py
index 2d5b9a9..5564505 100644
--- a/test/test_pseudo_nkode_api.py
+++ b/test/test_pseudo_nkode_api.py
@@ -15,7 +15,7 @@ def test_create_new_user(pseudo_nkode_api, numb_keys, attrs_per_key, user_passco
     customer = pseudo_nkode_api.create_new_customer(numb_keys, attrs_per_key)
     session_id, set_interface = pseudo_nkode_api.generate_index_interface(customer.customer_id)
 
-    key_selection = lambda interface: [interface.index(attr) % attrs_per_key for attr in user_passcode]
+    key_selection = lambda interface: [interface.index(attr) // attrs_per_key for attr in user_passcode]
     set_key_selection = key_selection(set_interface)
 
     confirm_interface = pseudo_nkode_api.set_nkode(username, customer.customer_id, set_key_selection, session_id)