The engine blocking system prevents the car from being stolen.
When the key is inserted into the ignition switch, the transponder chip in the head of the key transmits an electronic signal code to the vehicle. The engine will only start if the electronic code in the chip matches the registered vehicle identification code.
The system is automatically set when the key is removed from the ignition switch. Inserting the registered key into the ignition switch will automatically override the system that starts the engine.
In order for a Toyota dealer to make a new key with a built-in transponder chip, they will need the key number and the master key. But there is a limit to the number of extra keys a Toyota dealer can make for a car owner. If you make a duplicate key yourself, you will not be able to cancel this locking system and start the engine.