ECU Message Authentication Code Length Verification

The patent applies preliminary action by performing MAC length verification before the actual MAC comparison. The receiving ECU checks if the received MAC length matches the expected length derived from the secret key configuration. This preliminary check prevents attackers from exploiting bit-by-bit guessing attacks, as the verification process is terminated early when length mismatches are detected, thereby enhancing security without significantly increasing overall system complexity.

The patent applies parameter changes by dynamically adjusting the MAC length parameter based on the secret key configuration. Different secret keys are associated with different predefined MAC lengths, and the receiving ECU verifies that the received MAC length matches the expected length for the selected key. This parameter binding ensures that truncated MACs cannot be exploited for bit-by-bit guessing attacks, as the length itself becomes a verification criterion that prevents such attacks while still allowing efficient bandwidth-optimized communication.

The patent applies segmentation by dividing the authentication system into distinct key-configured verification paths. Each secret key is associated with a specific predefined MAC length, creating separate verification channels. The receiving ECU selects the appropriate verification path based on the transmitted key identifier, ensuring that each key-MAC length combination is verified independently. This segmentation approach manages complexity by organizing multiple keys into discrete, manageable segments rather than requiring a single complex verification logic.