Counter-Based ECU Encryption for Confidential CAN Packets
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Solution Overview
Problem
Existing CAN bus communication protocols in vehicles are vulnerable to eavesdropping and replay attacks, with current security mechanisms like SecOC in AUTOSAR failing to prevent packet eavesdropping.
Innovation Solution
Implementing encryption and integrity protection methods using a keystream generated from a shared key and a fresh value to encrypt and authenticate packets, ensuring confidentiality and integrity of communication between ECUs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If encryption protection is implemented using keystream generation, then packet confidentiality is improved, but device complexity increases
Solution Approach 1:
The encryption function is segmented into independent modular components: a keystream generation module that takes a key and counter as inputs, and an XOR encryption module that combines the keystream with plaintext packets. This segmentation allows each module to be optimized independently and facilitates easier implementation and maintenance while maintaining confidentiality.
Solution Approach 2:
The encryption system uses self-generated counters at both transmitting and receiving ends to produce synchronized keystreams without requiring external key distribution or complex synchronization protocols. The counters automatically increment with each packet, enabling the system to service its own encryption needs using only locally stored keys and packet sequence information.
2Reliability
If integrity protection is added to encryption, then security against tampering is improved, but communication overhead increases
Solution Approach 1:
The integrity protection mechanism is merged with the existing encryption framework by using the same counter and key materials to generate both the keystream for encryption and the authentication tag for integrity verification. This combining approach ensures that integrity protection is achieved without requiring separate communication channels or additional key distribution infrastructure.
Solution Approach 2:
The system dynamically adjusts the authentication tag length and verification strictness based on the security requirements of different packet types and communication contexts. For less critical packets, shorter tags are used to reduce overhead, while more critical packets receive longer tags for enhanced integrity protection, optimizing the balance between security and overhead.
Data Source
AI summary
A first ECU performs an operation using a first key and a first fresh value to generate a keystream; performs an exclusive OR operation using the keystream and a to-be-transmitted first plaintext packet to generate a first ciphertext packet; and sends the first ciphertext packet to a second ECU. The first fresh value is a value generated by a counter in the first ECU when the first ECU transmits a packet, and the counter is configured to record a quantity of packets transmitted by the first ECU. The first ECU transmits the first ciphertext packet to the second ECU. This can prevent the first packet transmitted by the first ECU from being eavesdropped on, and help improve confidentiality of the packet transmitted by the first ECU.