Variable-Interval Security Code Display for Payment Cards
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Solution Overview
Problem
Existing payment cards lack sufficient security measures to prevent reverse-engineering and unauthorized reuse of security codes, particularly in remote transactions.
Innovation Solution
A payment card with a display device that periodically refreshes the security code at calculated time intervals, using a control circuit to switch between two different time periods for displaying security code values, making it difficult to identify the change period through reverse engineering, and ensuring the security code expires rapidly enough to prevent extensive use but remains usable for the cardholder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the security code is displayed with a fixed periodic refresh interval, then the code expires rapidly enough to prevent extensive unauthorized use, but the regular pattern makes it vulnerable to reverse engineering and timing analysis
Solution Approach 1:
The patent applies dynamics by making the security code display interval variable rather than fixed. The control circuit changes the display interval between first and second values, preventing attackers from predicting when the code will change. This dynamic adjustment maintains security while avoiding periodic patterns that could be exploited through timing analysis
Solution Approach 2:
The patent changes the time parameter of the security code display by varying the interval between code changes. The control circuit selects between different display intervals (first interval and second interval) based on stored values, effectively changing the temporal parameter to prevent reverse engineering while maintaining rapid expiration for security
2Reliability
If the security code changes very frequently, then unauthorized reuse is prevented, but the cardholder may not have sufficient time to read and use the code before it expires
Solution Approach 1:
The system dynamically adjusts the display interval between security codes, switching between a first longer interval and a second shorter interval. This allows the code to remain visible long enough for legitimate cardholders to read and use it, while still changing frequently enough to prevent unauthorized reuse. The variability prevents attackers from predicting exactly when changes occur
Solution Approach 2:
The patent uses periodic action with variable periods - the control circuit periodically changes the security code but varies the time interval between changes. This creates an irregular periodic pattern that maintains security through frequent changes while ensuring each code remains displayed long enough for legitimate use by cardholders
3Reliability
If the display interval is made variable to prevent reverse engineering, then security is improved, but the device complexity increases due to additional control circuitry and timing mechanisms
Solution Approach 1:
The patent segments the timing control into discrete stored interval values (first display interval and second display interval) that the control circuit can select from. This segmentation simplifies the control logic compared to implementing a fully dynamic variable timer, as the system only needs to choose between predefined intervals rather than calculate arbitrary timing values
Solution Approach 2:
The control circuit automatically manages the variable display intervals using stored timing values without requiring external intervention or complex synchronization. The system self-regulates the timing by selecting from pre-stored interval values, reducing the need for additional control infrastructure or complex coordination mechanisms
Data Source
AI summary
A payment card comprises a display device arranged on a face of the payment card, the display device comprising a field for displaying a security code for card verification operations carried out by a card verification server. The method comprises the operations of:displaying, in the field of the display device, a first value of the security code during a first time period,displaying, in the field of the display device, a second value of the security code during a second time period that follows the first time period, the first and second time periods being of different durations.