Threshold-Voltage PUF Circuit for Temperature-Stable Signatures
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Solution Overview
Problem
Existing physical unclonable function (PUF) technologies, such as delay chain and memory-based PUFs, face challenges in reliability due to temperature effects and size constraints, and require improved methods to generate unique and unclonable signatures for secure computing and communication.
Innovation Solution
The use of integrated circuit (IC) devices with varying voltage threshold (VT) transistors, where HVT transistors are utilized for maximum variation in the difference generator and LVT transistors for consistent amplification, to create a unique signature by leveraging manufacturing process variations, enhancing the performance and reliability of PUF generators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If delay chain or memory-based PUF methods are used, then PUF functionality is achieved, but reliability deteriorates due to temperature effects
Solution Approach 1:
The patent changes the operating parameter from time-based (delay chain) or state-based (memory) to voltage-threshold-based comparison. By using HVT and LVT transistors with distinct threshold voltage characteristics, the PUF generates signatures based on voltage division ratios that are inherently less sensitive to temperature variations, thereby improving reliability under temperature effects.
2Reliability
If manufacturing process variations are utilized for uniqueness, then PUF signature uniqueness is improved, but manufacturing precision deteriorates
Solution Approach 1:
The patent applies local quality by creating intentional asymmetry in the voltage division network through selective placement of HVT and LVT transistors. Each PUF cell contains a specific configuration where HVT transistors are placed in certain branches and LVT transistors in others, creating localized threshold voltage differences that amplify manufacturing variations into unique, reproducible signatures while maintaining overall circuit functionality.
3Reliability
If HVT transistors are used for maximum variation, then signature uniqueness is improved, but device complexity increases
Solution Approach 1:
The patent segments the PUF circuit into multiple identical cells, each containing a simplified voltage division network with a fixed pattern of HVT and LVT transistors. This segmentation allows the complex threshold voltage variation to be achieved through repetition of simple, standardized units, thereby managing device complexity while maintaining signature uniqueness through the cumulative effect of many cells.
Data Source
AI summary
A PUF generator includes a difference generator circuit with first and second transistors having a first predetermined VT. The difference generator circuit is configured to provide a first output signal for generating a PUF signature based on respective turn on times of the first and second transistors. An amplifier includes a plurality of transistors having a second predetermined VT. The amplifier is configured to receive the first output signal and output the PUF signature.