CAN Frame Override Using DLC Bits to Block Spoofed Messages
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Solution Overview
Problem
The CAN standard lacks provisions for authentication, making it vulnerable to cyber-attacks through spoofed messages, and existing authentication methods either increase communication overhead or require significant hardware modifications.
Innovation Solution
The system overrides malicious frames on a CAN bus by determining the arbitration ID of incoming frames and transmitting a predetermined sequence of bits during the data length code field, effectively suppressing malicious transmissions without introducing bus overhead or requiring hardware redesign.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cryptographic Message Authentication Code is added within a CAN message at the Application layer, then CAN message authentication is provided, but communication overhead is significantly increased
Solution Approach 1:
The patent extracts the authentication function from the message payload and implements it at the physical layer through a dedicated authentication bit in the arbitration field. This separates the authentication mechanism from the data transmission, allowing authentication to occur without consuming message data space and thus reducing communication overhead while maintaining security.
Solution Approach 2:
The patent moves the authentication mechanism from the application layer (layer 7) down to the physical layer (layer 1) of the OSI model. By embedding authentication information in the arbitration bit rather than adding it to the message payload, the solution changes the dimensional layer where authentication occurs, eliminating the need for additional communication overhead.
2Reliability
If cryptographic CRC replaces error-detecting code in a CAN message at the link layer, then authentication is provided without significant communication overhead, but complete redesign of hardware elements is required
Solution Approach 1:
The patent makes the arbitration bit multi-functional by using it for both message priority identification and authentication purposes. This single bit serves dual functions: it identifies the message priority level and simultaneously provides authentication through a specific pattern (e.g., all ones or all zeros). This eliminates the need for separate authentication hardware while maintaining security.
Solution Approach 2:
The authentication mechanism uses the existing CAN bus infrastructure and standard arbitration field without requiring any external authentication hardware or message modification. The system authenticates messages using only the bits already present in the CAN frame structure, making the existing hardware serve the authentication function without redesign.
3Adaptability or versatility
If standard CAN controllers are used, then existing CAN network functionality is maintained, but cryptographic CRC processing capability is lacking
Solution Approach 1:
The patent performs authentication in advance by setting the arbitration bit to a specific pattern before message transmission. The authenticating ECU pre-configures the arbitration field with an authentication pattern that indicates the message's authenticity. This preliminary authentication action occurs during message construction, allowing standard controllers to process authenticated messages without requiring cryptographic processing capability.
Data Source
AI summary
The present disclosure relates to suppressing malicious transmissions by overriding frames on a Controller Area Network (CAN) bus. In an embodiment, a method operates by determining when a frame arrives at a CAN bus. A determination of whether to override the frame is made based on an arbitration ID of the frame received from the CAN bus. In response to determining to override the frame, a predetermined sequence of bits is transmitted on the CAN bus during transmission of a data length code (DLC) field in the frame. A message to complete the frame is generated based on the predetermined sequence of bits. Then, the message is transmitted on the CAN bus.