Abstract: The authenticity of a program executed by a processor is determined by a security element that computes a hash code over re-ordered segments of a known-to-be-authentic copy of a program executed by the processor. The authenticity of the same segments are re-ordered by and provided by the processor to the security element, which computes a second hash code for the re-ordered segments received from the processor. If the hash values for the segments are identical, the program segments are identical. If the hash values for any segment are different, the two programs are different. When a processor's program is determined to be different from a known good copy, the processor can be stopped or an alarm signal generated.

Abstract: The authenticity of a program executed by a processor is determined by a security element that computes a hash code over re-ordered segments of a known-to-be-authentic copy of a program executed by the processor. The authenticity of the same segments are re-ordered by and provided by the processor to the security element, which computes a second hash code for the re-ordered segments received from the processor. If the hash values for the segments are identical, the program segments are identical. If the hash values for any segment are different, the two programs are different. When a processor's program is determined to be different from a known good copy, the processor can be stopped or an alarm signal generated.

Abstract: An example base station assembly includes a transmitter configured to communicate a challenge signal and at least one timing signal to a plurality of fobs. The base station initiates a vehicle operation in response to at least one return signal. The return signal is communicated to the base station from at least one of the fobs in response to the timing signal.

Abstract: An example base station assembly includes a transmitter configured to communicate a challenge signal and at least one timing signal to a plurality of fobs. The base station initiates a vehicle operation in response to at least one return signal. The return signal is communicated to the base station from at least one of the fobs in response to the timing signal.

Abstract: A method of controlling fleet vehicles includes the steps of identifying transmitter signals from a select group and an entire group to allow selective operation of certain specific vehicle functions. The method also includes the step of reprogramming a secret key and storing the previous secret key such that transmitters that have not already been programmed can be programmed if they include the old secret key.