Secure Timekeeping Architecture for Power-Off Mobile Devices
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Solution Overview
Problem
Mobile devices face challenges in maintaining the integrity of time information, particularly during power outages or malicious attacks, which can compromise security-based operations.
Innovation Solution
The electronic device incorporates a nonvolatile memory, a power management integrated circuit, and an application processor to generate and manage time information independently of power supply, using a security timer and system timer to ensure time data integrity, even during system-off states, by storing and updating time information securely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time information is generated using a timer dependent on supply power, then the device can operate normally during powered states, but the time information may be altered or falsified during power outages or system-off states
Solution Approach 1:
The power management system is segmented into multiple independent power domains: a first power domain for the security timer generating first time information, and a second power domain for the application processor generating second time information. This segmentation allows the security timer to operate independently during power outages, ensuring time information integrity without requiring a completely redundant system.
Solution Approach 2:
A power capacitor is introduced as an intermediary energy storage element between the power source and the security timer. This capacitor provides auxiliary power during system-off states, enabling the security timer to continue generating time information independently without direct connection to the main power source, thus maintaining reliability while simplifying the overall power management architecture.
2Reliability
If a read-only timer is used to generate time information during system-off states, then time information integrity is maintained, but the device requires additional power management components
Solution Approach 1:
The power capacitor serves multiple functions: it provides auxiliary power to the security timer during system-off states, maintains voltage levels for continuous timer operation, and acts as an energy buffer between the power source and timer circuitry. This multi-functionality reduces the need for separate dedicated components for each function, thereby reducing the overall quantity of power management components while maintaining security.
3Reliability
If time information is stored in nonvolatile memory with encryption, then tampering is prevented, but the operation complexity increases during power resumption
Solution Approach 1:
Time information is pre-processed and stored in encrypted form in nonvolatile memory before power outages occur. The security timer continuously generates and updates this encrypted time information, which is then stored in a tamper-resistant manner. During power resumption, this pre-stored encrypted data can be quickly retrieved and verified without requiring complex real-time processing, thus maintaining both security and operational simplicity.
Solution Approach 2:
The system implements a feedback mechanism where the security processor verifies the integrity of stored encrypted time information against newly generated time information from the security timer. This feedback loop ensures tampering detection while automating the verification process, reducing manual intervention complexity during power resumption while maintaining strong security protections.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures the integrity and security of time information, preventing tampering and ensuring reliable security operations even when power is interrupted or resumed, thus enhancing the security of mobile devices.
Implementation Method 1
a power capacitor configured to provide auxiliary power based on pre-charged electric charges in response to occurrence of a system-off state
Data Source
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AI summary
Provided are an electronic device and an operating method thereof. The electronic device includes a nonvolatile memory; a power management integrated circuit configured to generate operating power based on supply power received from a power source, and generate first time information independent of the supply power; and an application processor configured to receive the operating power, generate second time information, obtain, based on the generation of the operating power being interrupted, the first time information, and output, to the nonvolatile memory, time data including the first time information and the second time information, a write command, and an address.