Vehicle Message Authentication for Abnormal-State Detection

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Solution Overview

Problem

Existing vehicle communication devices fail to differentiate between authentication failures due to communication device issues and failures inherent to the device, leading to potential mistaken determinations of abnormal communication states.

Innovation Solution

A communication device that authenticates messages based on appended authentication information, determining an abnormal-communication state only if authentication fails a specific number of times, and otherwise treats it as a normal state or abnormal encryption key state, thereby suppressing mistaken determinations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If authentication is performed for each message received from communication devices, then security and reliability are improved, but the risk of mistaken determination of abnormal-communication state increases when authentication fails for some messages

Engineering Contradiction:

Improveauthentication reliabilityVSAvoidabnormal state determination accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent segments the authentication evaluation by creating separate determination counters for each communication device (e.g., counter1 for device1, counter2 for device2). This allows independent tracking of authentication failures per device, enabling precise identification of which specific device is causing authentication issues rather than treating all failures uniformly. The segmentation resolves the contradiction by maintaining high security through per-message authentication while improving determination accuracy through device-specific failure tracking.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by making the abnormal state determination threshold and evaluation criteria specific to each communication device. Each device can have its own determination counter and evaluation logic, allowing the system to adapt to device-specific characteristics and failure patterns. This localized approach improves measurement precision by evaluating authentication failures in the context of individual device behavior rather than applying a blanket threshold to all devices.

Inventive Principle:

Principle #3Local quality

2Speed

If authentication failure threshold is set low to detect abnormalities quickly, then response speed is improved, but false positives increase due to normal authentication variations

Engineering Contradiction:

Improveabnormal detection speedVSAvoiddetermination accuracy

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent implements dynamic adjustment of the determination threshold based on the accumulated authentication failure count for each device. The determination counter increments with each authentication failure and is compared against a dynamically evaluated threshold that can adapt to normal variations. This dynamic approach allows quick detection when failures accumulate (maintaining speed) while avoiding false positives by requiring sustained failure patterns rather than single isolated failures (maintaining reliability).

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system uses feedback mechanisms where authentication results are continuously monitored and fed back into the determination counter, which in turn influences future authentication evaluations. The feedback loop allows the system to learn from past authentication outcomes and adjust its determination behavior accordingly, balancing quick detection with accurate distinction between normal variations and genuine abnormalities.

Inventive Principle:

Principle #23Feedback

3Reliability

If authentication is performed on all messages from all communication devices, then security coverage is improved, but system complexity increases

Engineering Contradiction:

Improvesecurity coverageVSAvoidauthentication system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent reduces system complexity through segmentation by organizing authentication tracking into separate, independent counters for each communication device. This modular structure simplifies the management of authentication states compared to a monolithic approach, as each device's authentication failures can be evaluated independently without affecting the analysis of other devices. The segmentation maintains comprehensive security coverage while reducing the computational and structural complexity of the authentication system.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12445423B2Communication device, vehicle, communication method, and recording medium recorded with program

Publication Date: 2025.10.14 TOYOTA JIDOSHA KK

AI summary

A communication device including a reception section to receive from each of other communication devices a message appended with authentication information generated by the other communication device, an authentication section to, for each of the messages received by the reception section, authenticate the message based on the authentication information appended to the message, and a determination section to, for each of the other communication devices or for each type of the message, determine an abnormal-communication state in cases in which authentication has failed less than a specific number of times from among plural authentications performed by the authentication section for a corresponding respective plural of the messages, and determine that there is not the abnormal-communication state in cases in which authentication has failed the specific number of times or greater from among the plural authentications performed by the authentication section for the corresponding respective plural messages.