Resistor-Bridge PUF Cells for Stable Low-Bias Random Readout
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Solution Overview
Problem
Existing PUF apparatus face challenges in achieving equal probability of output values, high cost, and instability of random numbers due to environmental changes, which affect their reliability and efficiency, particularly in IoT device security.
Innovation Solution
A PUF apparatus utilizing a plurality of PUF cells with H-bridge configurations of matched resistors, where random manufacturing differences generate a persistent random number by detecting voltage imbalances across the bridges, minimizing non-resistor components and systematic biases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing PUF apparatus use complex circuit configurations to generate random numbers, then the randomness and uniqueness of PUF values are improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates non-essential components from the PUF cell circuit. By removing unnecessary transistors and complex logic gates, the design retains only the critical resistor bridge structure and minimal readout circuitry, achieving simplicity without sacrificing the random number generation capability
Solution Approach 2:
The patent uses matched resistor pairs in the H-bridge configuration where identical resistor structures are created in parallel. These copied resistor pairs exhibit random manufacturing variations that differ between pairs, providing the necessary randomness while maintaining circuit symmetry and simplicity
2Adaptability or versatility
If existing PUF apparatus use multiple components in PUF cells to enhance functionality, then the versatility of the PUF is improved, but the manufacturing precision and stability of random numbers deteriorate due to systematic biases
Solution Approach 1:
The patent removes non-resistor components from the PUF cell to eliminate sources of systematic bias. By using only passive resistor elements in the H-bridge configuration, the design avoids the variability and bias introduced by active components like transistors, ensuring that random variations dominate the output
Solution Approach 2:
The patent employs matched resistor pairs with identical geometry and material properties in symmetric positions within the H-bridge. This homogeneous design ensures that both sides of the bridge experience the same environmental conditions and manufacturing processes, allowing random variations to be the primary differentiator
3Measurement precision
If existing PUF apparatus use conventional readout circuits to measure PUF values, then the readout capability is improved, but the power consumption and cost increase
Solution Approach 1:
The patent implements a self-biasing readout circuit that automatically establishes the correct operating point without requiring external reference voltages or complex biasing networks. The circuit uses the inherent properties of the resistor bridge to generate its own measurement signals, reducing power consumption and component requirements
Solution Approach 2:
The patent eliminates power-hungry components from the readout circuit, such as high-current amplifiers and complex signal conditioning stages. The design uses minimal circuitry that draws only the necessary current to detect the voltage difference across the H-bridge, significantly reducing overall power consumption
4Measurement precision
If existing PUF apparatus include more components in PUF cells to improve measurement capability, then the measurement precision is improved, but the device complexity and systematic bias increase
Solution Approach 1:
The patent removes unnecessary measurement and control components from the PUF cell. The design relies on direct voltage difference measurement across the H-bridge without intermediate buffering or conditioning stages, achieving adequate measurement precision with minimal components
Solution Approach 2:
The patent designs the H-bridge resistor configuration to serve multiple functions simultaneously: it generates the random signal, provides the measurement interface, and establishes the operating point. This multi-functional design eliminates the need for separate components for each function, reducing overall device complexity
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
The solution ensures random and stable PUF values, reducing cost and power consumption, suitable for IoT device authentication and secure communications by maintaining consistent output over time.
Implementation Method 1
each of said at least one PUF cell comprises a resistor bridge; said determination unit is configured to determine a persistent random physical unclonable function value for said PUF cell based on a random difference between impedance values of said resistor bridge
Data Source
AI summary
A Physical Unclonable Function, PUF, apparatus is disclosed. The apparatus comprises a plurality of PUF cells that each comprise a first potential divider and a second potential divider. The apparatus also comprises a determination unit that comprises a selection unit for selecting at least one of the plurality of PUF cells, and a readout unit coupled to each selected PUF cell. The readout unit is configured to determine a PUF value for the selected PUF cell based on a difference between a first analog voltage at the first potential divider and a second analog voltage at the second potential divider.