Time synchronization
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Solution Overview
Problem
Access control systems, particularly those with battery-operated locks, face challenges in clock synchronization due to target time deviations, which can be exploited by attackers to gain unauthorized access by resetting the clock to a false time, compromising the validity period of electronic keys.
Innovation Solution
A method involving a first apparatus that obtains and checks temporal information from a second apparatus, synchronizing its clock only if certain conditions are met, such as being in a valid state after startup or battery change, and ensuring the deviation is within a predefined threshold, thereby preventing malicious manipulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the clock of a battery-operated lock is used for access authorization checks, then the system can function with limited power supply, but the target time deviations of several minutes per month compromise the reliability of time-based access control
Solution Approach 1:
The system performs preliminary synchronization of the clock with a reference time source before the access authorization check is performed. This ensures that the time deviation is corrected in advance, allowing the battery-operated lock to maintain accurate time-based access control without requiring continuous power supply for timekeeping.
2Reliability
If the clock is synchronized with communicated temporal information, then time synchronization accuracy is improved, but attackers can exploit this by resetting the clock to a false time to gain unauthorized access
Solution Approach 1:
The system incorporates feedback mechanisms where the access control apparatus verifies the authenticity of communicated temporal information before synchronizing the clock. The apparatus checks whether the received time information matches expected time ranges and validates the synchronization process, preventing attackers from successfully manipulating the clock to unauthorized time values.
3Object-affected harmful factors
If multiple checks are performed before synchronization, then security against manipulation is improved, but the complexity of the synchronization process increases
Solution Approach 1:
The synchronization process is segmented into distinct, modular check steps: initial state verification, time deviation threshold check, and date matching check. Each check is an independent decision point that can be implemented as a separate function or module, making the complex security process more manageable and easier to verify while maintaining comprehensive security.
Data Source
AI summary
A method having the steps of obtaining temporal information communicated to a first device; carrying out one or more of the following tests: a test to determine whether the first device is in a state following an initial operation, a battery replacement or other power outage, or a reset, a test to determine whether a deviation between temporal information of the clock and the communicated temporal information is less than or equal to a threshold which is specified, and a test to determine whether the communicated temporal information has the same date as the temporal information of the clock; and synchronizing the clock using the communicated temporal information if all of one or more defined conditions are satisfied, wherein one of the one or more conditions requires that at least one of the one or more tests carried out has a positive result.