A treasury system that shifts the password (by a Caesar cipher) each time it's entered correctly. It's connected to an arduino board that blinks when the wrong password is entered and lights up when the correct one is entered.
You have a golden trophy from your last competition and you want to keep it in your safe away from the thieves. Your treasury system is controlled by an arduino board. The arduino is connected to a led. When you enter the correct password, the led is turned ON. When the wrong password is entered the led Blinks. In either case, it resets after 3 seconds and waits for the password again.
There is a catch, you are aware that thieves can spy on you while typing the password. So you decide to enter the password encoded by Caesar Cipher, and each time you enter the password correctly, every character in the password shifts by 1, so every time the password is different but only you know what it is.