There are many ways to lock a door. You could use a keypad, an RFID card, a fingerprint or retina scan, Wi-Fi, Bluetooth, the list goes on. You could even use a regular old metal key. But none of these may be as secure as [mircemk]’s Arduino-based door lock that employs a smartphone’s flashlight as a pass code.
This is a companion discussion topic for the original entry at https://hackaday.com/2023/12/29/flashlight-door-lock-is-a-bright-idea/