In-Vehicle CAN Authentication Counter Synchronization
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Solution Overview
Problem
Existing authentication systems for in-vehicle CAN networks, such as those described in PTL 1, fail to correctly verify messages when counter values become asynchronous between devices, making them vulnerable to unauthorized operations and replay attacks.
Innovation Solution
An arithmetic device and authentication system that includes a communication unit, abnormality detection unit, storage units for counters and keys, and a verification information generation unit to generate and verify authentication codes using updated counter values, ensuring message integrity even when counters become asynchronous.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single counter value is used for message authentication, then the authentication process is simple, but the system cannot correctly verify messages when counter values become asynchronous between devices
Solution Approach 1:
The single counter value is segmented into two separate counter values: a first counter value that is updated in response to message reception, and a second counter value that is updated when abnormalities occur. This segmentation allows each counter to serve a specific function, enabling reliable message verification even when asynchrony occurs between devices.
2Reliability
If counter values are updated frequently to prevent replay attacks, then security against replay attacks is improved, but counter asynchrony between devices occurs more frequently
Solution Approach 1:
The system dynamically adjusts counter update behavior based on operational conditions. The first counter updates with each message reception while the second counter updates only when abnormalities are detected. This dynamic update strategy maintains security against replay attacks while reducing unnecessary updates that would cause asynchrony.
Solution Approach 2:
The abnormality detection unit acts as an intermediary that monitors counter updates and triggers the second counter update only when necessary. This intermediary mechanism prevents unnecessary counter updates during normal operation, maintaining synchronization between devices while still providing security when abnormalities occur.
3Stability of the object's composition
If counter values are initialized frequently to maintain synchronization, then counter asynchrony is reduced, but message authentication fails during initialization periods
Solution Approach 1:
The system performs preliminary actions by maintaining both counter values continuously updated according to their respective rules, rather than periodically initializing them. The first counter is preliminarily updated with each message and the second counter is preliminarily updated when abnormalities occur, ensuring both values are ready for authentication without requiring initialization that would cause authentication failures.
Data Source
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AI summary
An arithmetic device includes a communication unit configured to receive a message including a reception authentication code, a storage unit configured to store a key, and a message verification unit configured to generate a generation authentication code, using the key, for data to be verified including data excluding at least the reception authentication code from the message received by the communication unit, a first counter value updated in response to reception of the message and initialized at a time when an abnormality regarding transmission/reception of the message occurs, and a second counter value updated at a time when the abnormality occurs, and to verify the message according to whether the reception authentication code and the generation authentication code match.