A student with a laptop and a radio stopped four high-speed trains. The crypto keys hadn’t been changed in 19 years.

At 23:23 on 5 April, a 23-year-old university student in Taichung transmitted a falsified General Alarm signal into the Taiwan High Speed Rail Corporation’s internal radio system. Four trains travelling at up to 300 km/h received the highest-priority emergency alert and switched to manual braking. …