Physical Unclonable Function Configuration for Persistent Random Values
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Solution Overview
Problem
Existing Physical Unclonable Function (PUF) systems face challenges in achieving equal probability for each possible persistent random PUF value and maintaining the persistence of the random number over time due to manufacturing variations and environmental changes.
Innovation Solution
The method involves configuring pairs of devices in a PUF system by measuring physical characteristics indicative of random manufacturing variations, comparing these measurements against configuration thresholds, and setting a configuration indicator to assign the devices to specific readout conditions, ensuring equal probability and persistence of the random values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PUF devices are used to generate persistent random values based on manufacturing variations, then uniqueness and randomness are improved, but stability and persistence over time deteriorate due to environmental changes
Solution Approach 1:
The patent performs preliminary classification of PUF devices during manufacturing based on their measured physical characteristics. Devices are categorized into different groups (e.g., first group with larger physical characteristic values, second group with smaller values) before deployment. This preliminary action ensures that when generating persistent random values, the system can select appropriate devices whose characteristics are less susceptible to environmental drift, thereby improving both uniqueness and long-term persistence.
Solution Approach 2:
The patent changes the parameter selection criteria for PUF devices based on their measured physical characteristics. By analyzing the distribution of physical characteristics (such as capacitance, resistance, or transistor threshold voltages) and identifying optimal ranges, the system selects devices with parameters that provide the best trade-off between randomness and stability. This parameter-based selection ensures that devices operating in stable regions are used for persistent random value generation.
2Reliability
If PUF devices are classified into groups based on physical characteristics, then equal probability of random values is improved, but device complexity increases
Solution Approach 1:
The patent segments the PUF device population into distinct groups based on their physical characteristic measurements. Typically, devices are divided into at least two groups (e.g., first group with values above a threshold, second group with values below the threshold). This segmentation is achieved by measuring a physical characteristic during manufacturing, comparing it to a threshold value, and assigning devices to appropriate groups. The segmented approach ensures that each group contributes equally to the random value generation, achieving equal probability while maintaining relatively simple classification logic.
3Measurement precision
If measurement of physical characteristics is performed during configuration, then accuracy of random value generation is improved, but measurement precision requirements increase
Solution Approach 1:
The patent applies partial measurement action by measuring only the essential physical characteristics needed for classification, rather than performing exhaustive measurements of all possible device parameters. The system measures specific physical characteristics (such as capacitance ratio, resistance ratio, or transistor threshold voltage difference) that are sufficient to distinguish between device groups and ensure equal probability of random values. This partial measurement approach achieves the required accuracy without imposing excessive measurement precision requirements or system complexity.
Data Source
AI summary
The present disclosure relates to configuring at least one pair of devices in a physical unclonable function (PUF) apparatus and reading out at least one pair of devices for determining a persistent random PUF output. The pair of devices may be readout by measuring a physical difference between the devices/components caused by random manufacturing differences, which may then be used to determine a persistence random PUF output. Configuring the pair of devices includes measuring the random manufacturing difference and, based on that measurement, setting a readout condition for the pair of devices, which dictates aspects of the readout process that should be used for that pair of devices. Each time the pair of devices is readout in the future, it may be readout in accordance with the condition that was set at configuration.