Field Device Time Verification for Trusted Authorization Tickets
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Solution Overview
Problem
Field devices in industrial environments often lack reliable methods to verify the authenticity and timing of asynchronous communication tickets, leading to potential unauthorized access and timing discrepancies due to unreliable internal clocks and variable transmission delays.
Innovation Solution
A method for verifying a first time recording unit of a field device using cryptographically secured information and time stamps from a second, more trustworthy time recording unit, with a trust assessment to detect and correct timing deviations, and generate warning messages for discrepancies exceeding a predetermined factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If field devices use basic time recording units without verification mechanisms, then device complexity is reduced and ease of operation is improved, but reliability of time-based authorization and security is worsened
Solution Approach 1:
The system performs preliminary verification of the time recording unit using tickets obtained through asynchronous communication. The field device receives a ticket containing time information from a higher-level control unit, verifies its validity before use, and stores it for later authorization checks. This preliminary action ensures time-based security reliability without requiring continuous complex verification mechanisms.
Solution Approach 2:
The patent introduces a ticket as an intermediary carrier that transports time information from the control unit to the field device. This ticket serves as a mediator that encapsulates trusted time data, allowing the field device to verify time-based authorization without direct real-time connection to the control unit, thus reducing device complexity while maintaining security reliability.
2Productivity
If field devices implement asynchronous communication with control units, then productivity and ease of operation are improved, but reliability of time synchronization and security is worsened due to lack of verification mechanisms
Solution Approach 1:
The system implements a feedback mechanism where the field device verifies the received ticket's time information against its own time recording unit. The verification result feeds back into the authorization process, ensuring that only valid time-synchronized tickets can grant access. This feedback loop maintains time synchronization reliability while preserving the productivity benefits of asynchronous communication.
Solution Approach 2:
The field device performs preliminary verification of the ticket's time stamp before using it for authorization. This preliminary check ensures time synchronization reliability is established before critical security operations, allowing asynchronous communication to proceed efficiently without compromising synchronization accuracy.
3Adaptability or versatility
If field devices use tickets with time stamps from external sources, then adaptability and ease of operation are improved, but reliability of time interpretation is worsened without verification methods
Solution Approach 1:
The field device performs self-verification of the ticket's time information using its own time recording unit. Instead of relying entirely on external sources, the device autonomously checks the validity and interpretation of the received time stamp, ensuring reliable time interpretation while maintaining the adaptability to receive tickets from various external sources.
Solution Approach 2:
The ticket acts as an intermediary that carries time information from external sources to the field device. The verification mechanism ensures that this intermediary accurately represents trusted time data, allowing the system to adapt to different external time sources while maintaining reliable time interpretation through cryptographic verification.
Data Source
AI summary
A method for verifying a first time recording unit of a field device that supplies the field device with a first date and/or a first time. The method includes receiving a ticket at the field device that comprises cryptographically secured information and a time stamp. The time stamp is obtained from a second time recording unit and contains a second date and/or second time. The method includes carrying out a trust assessment of the time stamp, wherein the trustworthiness of the second time recording unit is checked against the first time recording unit. If the trust assessment shows that the second time recording unit is more trustworthy than the first time recording unit, the method includes comparing the first date or the first time with the second date or the second time, and creating a warning message if a deviation greater than a predetermined factor is determined.