Using software protocols to mask CAN bus insecurities

The CAN bus was originally developed by Bosch for reliable low cost serial communication in vehicles, basically to reduce wiring costs. It has now become the standard bus used in cars and trucks and is widely used as a control system bus within products and systems. Unfortunately there is an inherent insecurity in the CAN bus specification which can cause a duplicate sending of messages, this problem only occurs if the last bit of a message is corrupted. Our experience in designing a control system for a tin can making machine has proved beyond all doubt that the problem exists. This machine has a 16 kHz 20000 Amp welder right at its centre with 8 computer nodes surrounding it, connected via the CAN bus. The article describes how the use of the protocol stack presented can be used to mask out duplicated messages and so avoid complexity in the control system protocols and software.