refactor np.bitwise xor to ^ operator

src/user.py

@@ -18,8 +18,8 @@ class User:
 
     def renew_keys(self, set_xor: np.ndarray, prop_xor: np.ndarray):
         self.renew = True
-        self.cipher.set_key = np.bitwise_xor(self.cipher.set_key, set_xor)
-        self.cipher.prop_key = np.bitwise_xor(self.cipher.prop_key, prop_xor)
+        self.cipher.combined_set_key = self.cipher.combined_set_key ^ set_xor
+        self.cipher.prop_key = self.cipher.prop_key ^ prop_xor
 
     def refresh_passcode(self, passcode_prop_idxs: list[int], customer_cipher: CustomerCipher):
         self.cipher = UserCipher.create(