System Time Trust Scoring Against Drift and Time Attacks
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Solution Overview
Problem
Automotive and computing systems face challenges in maintaining accurate and secure system time, which is crucial for safety-critical functions like ADAS and digital certificate validity, due to potential drift and malicious attacks.
Innovation Solution
A method is introduced to determine a cumulative trustworthiness score from multiple time sources, updating the system time based on the most trustworthy sources, and using secure storage for default and recovery times to protect against attacks and ensure accurate timekeeping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If system time is updated from external time sources, then time accuracy is improved, but system time becomes vulnerable to malicious attacks and drift
Solution Approach 1:
A trustworthiness scoring mechanism is introduced as an intermediary between external time sources and the system time update process. Each time source is assigned a trustworthiness score that mediates whether its time data should be used for updating, thereby filtering out malicious or drifted time sources while maintaining accuracy from reliable sources
Solution Approach 2:
The system implements a feedback mechanism where the trustworthiness of time sources is continuously evaluated and scored based on their historical performance and consistency. This feedback loop allows the system to adaptively adjust which time sources are used for updates, improving accuracy while preventing attacks through learned trust patterns
2Reliability
If multiple time sources are used to determine system time, then time accuracy and reliability are improved, but system complexity increases
Solution Approach 1:
The system transforms the complex problem of multiple time source management into a simpler parameter-based decision process. By converting time source evaluation into a quantitative trustworthiness score parameter, the system can automatically select appropriate time sources based on score thresholds, reducing complexity while maintaining reliability
Solution Approach 2:
The time source evaluation process is segmented into distinct components: individual time source assessment, trustworthiness scoring, cumulative score calculation, and update decision-making. This segmentation allows each component to be independently optimized and managed, reducing overall system complexity while improving reliability
Data Source
AI summary
Techniques are disclosed for the protection and accuracy of system time used in systems, such as automotive systems, from attacks. In some embodiments, a cumulative trustworthiness score is determined for available time sources, other than a real time clock, by adding together trustworthiness scores associated with the available time sources after a system time is initialized to time of the real time clock during booting. The cumulative trustworthiness score is then used to determine an appropriate technique for updating the system time based on time from one of the available time sources, depending on whether the cumulative trustworthiness score is greater than a maximum threshold, between a minimum threshold and the maximum threshold, or less than the minimum threshold.