The device sat under a dusty sheet on the workbench, its black plastic case scratched from a dozen moves. Mateo had been given it as payment after a night of helping an old locksmith clear out his shop: a ZKTeco keycode generator, a compact rectangle of faded buttons and a small LCD that blinked like a sleeping eye. He didn't know much about access control systems — only that places trusted these boxes to whisper secrets that opened doors.