> A rolling code system in keyless entry systems is to prevent replay attack. More specifically: rolling codes are used to prevent replay attack while allowing

> A rolling code system in keyless entry systems is to prevent replay attack. More specifically: rolling codes are used to prevent replay attack while allowing the remote fob to be only a transmitter, not a receiver, which saves on costs. If there was bi-directional communication there are obviously better ways to secure the fob/car (like regular challenge/response).