A vehicle includes: receiver(s), a timer counting time, a memory, and processor(s) configured to: receive a timestamped signal from a fob; compare the timestamp to a time window; and reject the timestamp if the timestamp is outside the time window. The processor(s) is configured to expand the time window with the counted time. The processor(s) compute the time window as a trigonometric function of the counted time and a predetermined angle, the predetermined angle being derived from the worst case clock skew present between the timer of the vehicle and a timer in the key fob. If the timestamp is within the time window, the timestamp is valid and the vehicle can be controlled, such as unlocking the doors. The vehicle timer is resynchronized with the fob timer after a successful validation of the timestamped signal. The timestamped signal can include the transmitter ID, the command code, a rolling code and the timestamp. The time window can have an upper limit that can be set via a user interface in the vehicle. The invention is intended to be used to overcome jamming or rolljam attacks in which vehicle control signals are intercepted or captured by a criminal for later use.
Expanding time window for remote commands
2018-03-21
Patent
Electronic Resource
English