removed counter because we cannot reliably guarantee that it is incremented

database.py

@@ -69,9 +69,9 @@ def select_all_users(conn):
 
     return rows
 
-def increment_counter(conn, id):
+def register_access(conn, id):
     """
-    increment the authentication counter in the database for the given id
+    increment the authentication counter in the database for the given id and save time of the last access
     """
     sql = ''' UPDATE users
               SET counter = counter + 1 ,

main.py

@@ -11,23 +11,10 @@ class DoorLock():
     def __init__(self):
         # initialize card reader
         self.reader = SimpleMFRC522()
+        self.key = b'Mellon!'
+        self.key += b' ' * (48 - len(self.key))
 
-    def increment(self, counter):
-        # increment counter and send it to card
-        counter += 1
-        data_new = str(counter)
-
-        self.reader.write(data_new)
-
-        # check if counter was updated successfully
-        _, text = self.reader.read()
-        try:
-            counter_new = int(text)
-        except ValueError:
-            return False
-        return counter == counter_new
-
-    def check_authorization(self, reader_id, counter):
+    def check_authorization(self, reader_id, reader_data):
         # open database
         conn = create_connection(database)
 
@@ -39,15 +26,14 @@ class DoorLock():
                 db_id = user[0]
                 name = user[1]
                 user_card_id = user[2]
-                user_counter = user[3]
+
                 if reader_id == user_card_id:
-                    # check if use counter on the card matches counter in the database
-                    # if counter is different -> assume the card has been cloned
-                    if counter == user_counter:
+                    print("card id match found")
+                    if reader_data.encode() == self.key:
                         print("user {} with card_id {} authorized".format(name, hex(reader_id)))
                         return True, db_id
                     else:
-                        print("error: counter does not match! please investigate!")
+                        print("incorrect key phrase")
 
             # if no match was found in the database: deny entry
             print("You shall not pass!")
@@ -70,33 +56,14 @@ class DoorLock():
                 print("Hold card before reader..")
                 uid, data = self.reader.read()
 
-                print("data = ", data)
-                #counter = int.from_bytes(data, byteorder='big')
-                try:
-                    counter = int(data)
-                except ValueError:
-                    print("error: data on the card could not be converted")
-                    counter = None
-
-                if counter is not None:
-                    print("card read: \n  uid = {}\ncounter = {}\n".format(hex(uid), counter))
-                    authorized, db_id = self.check_authorization(uid, counter)
+                print("card read: \n  uid = {}\ndata = {}\n".format(hex(uid), data))
+                authorized, db_id = self.check_authorization(uid, data)
 
                 if authorized:
-                        # increment use counter on the card
-                        increment_status = self.increment(counter)
-
-                        if increment_status:
-                            # update the counter and the time of last access in the database
-                            # open database
                     conn = create_connection(database)
-                            increment_counter(conn, db_id)
+                    register_access(conn, db_id)
 
                     self.unlock_door()
-                        else:
-                            # if we cannot increment the counter on the card (e.g. because the card was removed too quickly)
-                            # we do not let the user in even though authentication was correct -> try again
-                            print("increment failed!")
                 else:
                     print("authentication failed")
                     self.release_the_kraken()
@@ -117,7 +84,7 @@ if __name__ == "__main__":
     doors_of_durin = DoorLock()
 
     data = bytearray([0]*16)
-    #data  = '0'
+    data  = 'Mellon!'
     #write_success = doors_of_durin.reader.write(data)
     doors_of_durin.run_authorization()
     pass