CAN Bus Wireless Gateway with Programmable Logic Message Filtering
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Solution Overview
Problem
Existing vehicle area networks (CAN buses) are vulnerable to unauthorized access via wireless interfaces, allowing third parties to interfere or paralyze the network, while preventing write access also restricts diagnostic and network management functions.
Innovation Solution
A control device with a programmable logic module, such as a CPLD or FPGA, is used to filter messages based on authorized IDs, allowing only authorized messages to be transmitted on the CAN bus, while blocking unauthorized ones, and featuring a CAN transceiver like the TJA1041 for high-speed, low-power communication with electromagnetic compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If write access is prevented via the wireless interface to protect against unauthorized access, then security is improved, but diagnostic and network management functions cannot be executed
Solution Approach 1:
The patent segments the message filtering function into two distinct parts: a receive filter for incoming messages and a transmit filter for outgoing messages. The receive filter allows all messages to be read for diagnostic purposes, while the transmit filter restricts unauthorized transmission. This segmentation resolves the contradiction by enabling both security (through transmit restriction) and diagnostic functionality (through receive access).
Solution Approach 2:
The patent introduces an intermediary filtering mechanism between the wireless interface and the CAN bus. The transmit filter acts as a mediator that intercepts outgoing messages, checks their authorization status, and selectively blocks or permits them. This intermediary layer enables security control without preventing diagnostic access, as the filter can be configured to allow diagnostic messages while blocking malicious ones.
2Reliability
If a receive filter is used to block unauthorized messages, then security is improved, but authorized diagnostic and network management messages are also blocked
Solution Approach 1:
The patent divides the filtering functionality into separate receive and transmit filters with different authorization criteria. The receive filter operates independently from the transmit filter, allowing diagnostic messages to be received and processed even if transmission is restricted. This segmentation ensures that security measures do not inadvertently block legitimate diagnostic operations.
Solution Approach 2:
The patent changes the authorization parameters between the receive and transmit filters. The receive filter uses a set of authorization criteria that permits diagnostic messages, while the transmit filter uses different criteria that restrict unauthorized transmission. By changing the parameter settings between the two filters, the system achieves both security and diagnostic accessibility.
3Reliability
If complex filtering logic is implemented to distinguish authorized from unauthorized messages, then security is improved, but device complexity increases
Solution Approach 1:
The patent segments the complex filtering logic into two separate, simpler filter modules: a receive filter and a transmit filter. Each filter handles a specific direction of communication with relatively simple authorization checks. This segmentation reduces the complexity of individual filter modules while maintaining overall security through the combined operation of both filters.
Data Source
AI summary
A control device and corresponding motor vehicle for connecting a CAN bus to a radio network, having the following features: the control device includes a wireless controller, a microcontroller, a programmable logic module and a CAN transceiver; the microcontroller is connected, on the one hand, to the wireless controller and, on the other hand, to the logic module; the CAN transceiver is connected, on the one hand, to the logic module and, on the other hand, to the CAN bus; a data stream to the microcontroller corresponds to a data stream from the CAN transceiver; and the logic module is configured in such a manner that it monitors a data stream from the microcontroller which is addressed to the CAN transceiver and, on the basis of a data frame contained in the data stream from the microcontroller, suppresses at least this data frame.