Abstract: A system for remotely controlling a desired door locking or other function in a vehicle or other protected environment has a transmitter and receiver for communicating a message including a sequence number, the code of a selected function to be performed and an authenticator. An algorithm in the transmitter and in the receiver has a cryptographic key and a seed code. Each algorithm generates the authenticator as a function of both the seed code and the function code; if the authenticators are equal, the message is valid. Upon each transmission the seed code is updated and the sequence number is incremented. The receiver updates its seed code according to the transmitted sequence number to keep the algorithm in synchronism. Upon manufacture the transmitter sends the initial seed code and key to the receiver to program the receiver. This data is sent without delay when the battery is first installed but later a time delay is imposed to prevent sending inadvertent program messages.

Abstract: In a preferred embodiment, an apparatus for extending the receiving range of an RF receiver mounted in a non-metallic housing, including: at least one metallic strip attached to an element of the non-metallic housing; and the metallic strip being disposed so as to receive an RF signal transmitted to the RF receiver and air couple the RF signal into the RF receiver.