@eal After decades, car manufacturers finally fixed basic replay attacks with a rolling code that ignores previously received codes (n-1).

An interception device needs to jam the signals and receive the first unlock sequence (which may be noticed as you press unlock and nothing happens, although this happens regularly if you're too far away from your car and you press unlock) and when it receives a second unlock, it needs to send the previous unlock - as a result the car will accept code n, the interception device has code n and the remote will send code n+1 next unlock.