On-board Communication System Unauthorized Message Prevention
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Solution Overview
Problem
Existing on-board communication systems in vehicles face the risk of communication line occupation due to repetitive transmission of unauthorized messages, which can impair the transmission of authorized messages.
Innovation Solution
An on-board communication system with a determination unit to identify authorized messages, a discard unit to discard unauthorized messages before completion, and a reception completion notification unit to signal completion of unauthorized messages, preventing further processing based on such messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an ECU transmits an error frame to prevent unauthorized message transmission, then unauthorized message transmission is stopped, but the unauthorized ECU repeatedly retransmits the message occupying the communication line
Solution Approach 1:
The system uses ACK/NACK feedback signals to communicate reception status between transmitting and receiving ECUs. When an ECU detects an unauthorized message, it sends NACK signals to prevent the transmitting ECU from retransmitting, breaking the repetitive transmission cycle while maintaining communication line availability for authorized messages
Solution Approach 2:
The error frame acts as an intermediary signal that mediates between the detecting ECU and the unauthorized transmitting ECU. The error frame conveys the detection result and triggers the transmitting ECU to stop retransmission without direct intervention, resolving the contradiction between preventing unauthorized transmission and maintaining communication efficiency
2Reliability
If message authentication is performed using MAC codes, then unauthorized messages are detected, but communication overhead increases due to additional authentication processing
Solution Approach 1:
The system performs partial authentication by using CAN-ID and count value verification as a first layer of authentication, and only performs full MAC code verification when necessary. This reduces the overall authentication processing complexity while maintaining security, as not all messages require complete MAC verification
Solution Approach 2:
The authentication process is segmented into multiple stages: initial authentication using CAN-ID and count values, followed by MAC code verification only for suspicious messages. This segmentation reduces the complexity of continuous full authentication while maintaining security
3Reliability
If an ECU monitors all messages on the network, then unauthorized messages can be detected, but processing load on ECUs increases
Solution Approach 1:
Each ECU monitors messages with specific local relevance to its functions rather than all messages on the network. The determination unit in each ECU is configured to identify and process only the CAN-IDs that are relevant to that specific ECU, reducing processing load while maintaining detection capability for unauthorized messages affecting that ECU
Data Source
AI summary
Provided is an on-board communication system that can prevent a communication line from being occupied due to repetitive transmission of an unauthorized message. The on-board communication system includes a plurality of interconnected ECUs and a monitoring device including: a determination processing unit to determine whether a message is an authorized message; a discard processing unit to perform processing for discarding an unauthorized message; a storage unit to store the ID of the discarded message; and a notification processing unit to perform processing for outputting, an ACK signal indicating that the reception of the message is complete. The discard processing unit does not discard a message with the same ID as that stored in the storage unit. Each of the ECUs stores the ID added to a message subjected to the discard processing, and prohibits processing of a message with the same ID as that stored in the storage unit.