CAN Message Authentication via Segmented MAC and Freshness Fields
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Solution Overview
Problem
Current vehicle data bus protocols, such as CAN and CAN-FD, lack authentication mechanisms to verify the source of messages, allowing unauthorized devices to spoof authorized devices and issue commands to electronic control units, potentially leading to malicious control of vehicle subsystems.
Innovation Solution
Implementing a message authentication method that generates a secured message by calculating a message authentication code, truncating it, and placing portions of the truncated code and freshness value in separate parts of the message, ensuring only authorized devices can communicate by comparing the truncated code with a verification code generated using a stored freshness value and encryption key.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If message authentication is implemented on the vehicle data bus, then security against unauthorized access is improved, but message transmission complexity increases
Solution Approach 1:
The message authentication code is divided into multiple segments that are placed in different fields of the CAN message (arbitration ID field, data field, extended data field). This segmentation allows authentication to be integrated into the existing message structure without adding separate authentication messages, thereby improving security while minimizing additional complexity.
Solution Approach 2:
The authentication mechanism performs preliminary validation by checking the message authentication code segments before processing the message content. The receiving device verifies authenticity by regenerating the MAC segments and comparing them with received segments, rejecting forged messages before they can execute malicious commands.
2Reliability
If message authentication codes are placed in separate fields, then authentication security is improved, but message structure complexity increases
Solution Approach 1:
The authentication mechanism utilizes existing CAN message fields (arbitration ID, data field, extended data field) for multiple purposes: carrying both authentication information (MAC segments) and functional data. This multi-functionality allows secure authentication without requiring dedicated authentication message structures, reducing overall system complexity.
Solution Approach 2:
The patent distributes authentication information across multiple dimensions of the CAN message structure rather than concentrating it in a single field. By placing MAC segments in the arbitration ID field, data field, and extended data field simultaneously, the system achieves robust authentication while maintaining compatibility with existing CAN protocols and message formats.
Data Source
AI summary
Method and apparatus are disclosed for controller area network message authentication. An example disclosed vehicle includes a data bus and a first control unit communicatively coupled to the data bus. The example first control unit generates a secured message by (a) calculating a message authentication code, (b) truncating the message authentication code, (c) truncating a freshness value used to generate the message authentication code, and (d) placing portions of the truncated message authentication code and the truncated freshness value in separate portions of the secured message.