Preventing replay-type attacks on a vehicle communications system

[0011]The method described herein can be used by a vehicle to prevent replay-type attacks on a vehicle communications system that communicates with SMS messages. SMS messaging is generally premised on a one-way transmission architecture (i.e. does not use response messages) and lacks some of the security features found in other forms of data communication, such as messaging over a TCP / IP network which is based on a two-way architecture. Therefore, it can be desirable to provide additional security features above and beyond those inherent to the SMS protocol. For example, if a telematics-equipped vehicle is designed to receive SMS messages from an affiliated call center, then it can be desirable to ensure that an incoming SMS message is in fact from the call center and not some unauthorized third party. The method described below uses sequence counters and other techniques to help prevent or at least minimize the effects of unauthorized third party interference; most notably, it is de