== Rolling code vs. fixed code RF remote control ==
Remote controls send signalsa indigital code.Whenword to the sendingreceiver. code isIf the samereceiver asdetermines the code thatcodeword is expected by the receiveracceptable, then the receiver will actuate the relay, unlock the door, or open the barrier. RemoteSimple controlsremote withcontrol systems use a fixed code alwaysword; sendthe code word that opens the samegate fixedtoday codewill also open the gate tomorrow. RemoteAn controlsattacker with an appropriate receiver could discover the code word and use it to gain access sometime later. More sophisticated remote control systems use a rolling code (or hopping code) alwaysthat sendchanges outfor aevery use. An attacker may be able to learn the code word that isopened differentthe fromdoor just now, but the onereceiver previouslywill not accept that code word for the forseeable future. A rolling code system uses encryption methods that allow the remote control and the receiver to share codewords but make it difficult for an attacker to break the sentencryption.
