Secure Keypad with Tearable Circuit Board for Tamper Detection
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Solution Overview
Problem
Current secure keypad devices lack effective anti-tamper functionality to prevent unauthorized access and tampering, as existing solutions do not adequately detect key extraction attempts.
Innovation Solution
A secure data entry device is designed with a flexible, tearable circuit board substrate integrated into the keypad, which breaks when a key is forcibly extracted, triggering a tampering alarm indication. This includes key actuation protrusions, cutting elements, and locking washers to enhance security features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional rigid circuit board is used in the keypad, then structural stability is maintained, but anti-tamper functionality is insufficient
Solution Approach 1:
The patent employs a flexible circuit board substrate instead of a traditional rigid circuit board. This flexible substrate can be designed to tear or break when keys are forcibly extracted, providing inherent anti-tamper functionality. The flexibility allows the circuit board to integrate seamlessly with the keypad structure while maintaining the ability to detect tampering attempts through physical degradation.
Solution Approach 2:
The flexible circuit board is designed with segmented conductive traces that are strategically positioned near key actuation points. When a key is forcibly removed, these segmented traces break, creating open circuits that trigger tamper detection. This segmentation approach divides the circuit board into functional zones that can independently respond to tampering attempts.
2Reliability
If the circuit board is made tearable for anti-tamper detection, then tampering detection capability is improved, but structural strength is reduced
Solution Approach 1:
The flexible circuit board employs local quality variations in its construction. The substrate material and trace thickness are optimized to provide sufficient strength for normal operation while containing predetermined weak points or tear lines that will fail under forced extraction. This localized vulnerability approach ensures the board remains strong enough for regular use but fails reliably when tampering occurs.
Solution Approach 2:
The circuit board is pre-designed with predetermined failure paths and weak points during manufacturing. These preliminary structural features ensure that when tampering attempts occur, the board will break in predictable locations that reliably trigger the tamper detection circuitry, rather than failing unpredictably during the tampering event.
3Reliability
If key extraction is prevented through mechanical means, then security is improved, but ease of legitimate key replacement is reduced
Solution Approach 1:
The flexible circuit board acts as an intermediary between the key and the security system. During legitimate key replacement, the flexible substrate can be carefully manipulated or temporarily displaced to allow key removal without breaking the circuit. However, during forced extraction attempts, the same flexible board breaks due to excessive force, triggering tamper detection. This intermediary approach differentiates between authorized and unauthorized operations.
Data Source
AI summary
A secure data entry device including a housing, a keypad mounted in the housing and including a plurality of selectably depressible keys, tampering alarm indication circuitry and at least one electrical conductor located in the housing in operative association with the keypad, the at least one electrical conductor being coupled to the tampering alarm indication circuitry and being arranged such that extraction of at least one of the plurality of selectably depressible keys results in at least one break in the at least one electrical conductor, which causes the tampering alarm indication circuitry to provide a tampering alarm indication.