Tamper Detector Wake-Up Circuit for Battery Failure

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Solution Overview

Problem

Tamper detectors in utility meters and similar modules are vulnerable to attacks that disable or remove the rechargeable battery, which can lead to falsification of usage records and compromise security, as they rely solely on a battery-powered real-time clock module for tamper detection.

Innovation Solution

A tamper detector design that includes a processor with both powered and power-off modes, utilizing an external power supply and a rechargeable battery, where the RTC module can wake up the external power supply to maintain operation even when the battery is unavailable or compromised, ensuring continuous tamper detection functionality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the tamper detector relies solely on a battery-powered real-time clock module for tamper detection, then the device can operate independently and continuously, but the system becomes vulnerable to battery removal or discharge attacks that can disable tamper detection

Engineering Contradiction:

Improvetamper detection continuityVSAvoidbattery removal attack vulnerability

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an external power supply as an intermediary power source that can activate the tamper detector through a wake-up circuit when the battery is removed or discharged. The wake-up circuit includes a capacitor that stores energy and can power the detector temporarily, while the external power supply provides continuous operation. This intermediary power source resolves the vulnerability by providing alternative power paths that bypass the battery entirely.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements preliminary action by pre-configuring the wake-up circuit with a capacitor that can store electrical energy. When tamper detection is needed and the battery is unavailable, the capacitor has already been positioned to deliver power immediately. The external power supply is also pre-connected to the wake-up circuit, ready to activate the detector without delay. This preliminary preparation ensures continuous tamper detection capability even when the battery is compromised.

Inventive Principle:

Principle #10Preliminary action

2Duration of action of moving object

If the real-time clock module uses a rechargeable battery to maintain operation during power-off modes, then the system can save power and extend operational duration, but the system loses security when the battery is removed or discharged

Engineering Contradiction:

Improveoperational durationVSAvoidsecurity against battery attacks

Core Design Contradiction:

Duration of action of moving objectVSReliability

Solution Approach 1:

The patent applies universality by designing the power supply system to accept multiple power sources: the battery for normal operation, the external power supply for security-critical operation, and the capacitor for immediate wake-up functionality. The wake-up circuit is designed to work with any of these power sources, making the system universally operable regardless of which power source is available. This multi-functionality ensures that security operations can continue even when the battery is removed or discharged.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent implements beforehand cushioning by incorporating a capacitor in the wake-up circuit that can store electrical energy. This capacitor acts as a cushion or buffer that can provide power immediately when the battery is unavailable, bridging the gap between power loss and external power supply activation. The capacitor ensures that the tamper detector remains operational during the transition period, preventing security vulnerabilities during power source transitions.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Use of energy by moving object

If the tamper detector is designed to shut down completely to save power, then energy consumption is reduced, but the system cannot detect tampering events that occur during power-off periods

Engineering Contradiction:

Improvepower consumptionVSAvoidtamper detection coverage

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent implements periodic action through the wake-up circuit that periodically monitors for tamper conditions even when the main processor is in power-off mode. The circuit uses a capacitor that can be charged during power-off periods and then discharges to activate the tamper detection function. This periodic wake-up mechanism allows the system to maintain low power consumption while still providing periodic security monitoring, resolving the contradiction between energy savings and detection coverage.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS9268972B2Tamper detector power supply with wake-up

Publication Date: 2016.02.23 NXP USA INC

AI summary

A tamper detector has tamper detection logic connected to tamper detection ports through a tamper detection interface. A real-time clock (RTC) provides a clock signal and has a battery. A processor is powered by an external power supply in a powered operational mode and has a power-off mode. In a wake-up configuration, a wake-up signal on a specific I/O port awakens the external power supply from the power-off mode to supply power to the RTC and the tamper detection interface when power from the battery is unavailable. The tamper detection ports continue to function despite removal or discharge of the battery without ESD concerns. The specific I/O port optionally may be configured for passive tamper detection.