Capacitor-Based PUF for Persistent Random Number Generation
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Solution Overview
Problem
Existing physical unclonable function (PUF) technologies face challenges in generating sufficiently random and persistent output values due to manufacturing variations, requiring circuit designs that ensure equal probability of output values and low power consumption, while maintaining stability over time.
Innovation Solution
A PUF apparatus comprising a plurality of PUF cells with matched pairs of capacitors, where the random manufacturing differences between capacitors are detected by determining capacitor difference values through specific biasing conditions and measurements, generating a persistent random number based on these differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If matched pairs of capacitors are used to generate random output based on manufacturing variations, then randomness of output is improved, but noise and mismatch components increase reducing reliability
Solution Approach 1:
The patent extracts and eliminates noise and mismatch components from the capacitor measurements through differential measurement techniques. By measuring the difference between complementary capacitor pairs and subtracting common-mode noise, the circuit isolates the genuine random manufacturing variations while removing spurious noise components that would otherwise degrade output reliability.
Solution Approach 2:
The patent employs a composite measurement approach that combines multiple capacitor pairs with complementary noise characteristics. By integrating measurements from multiple capacitor pairs and processing them through differential techniques, the system creates a composite signal that enhances randomness accuracy while suppressing noise through statistical cancellation of mismatch components.
2Reliability
If circuit designs are implemented to ensure equal probability of output values, then randomness is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple capacitor pairs into a unified measurement structure where complementary capacitors are measured differentially. By combining the measurement of multiple capacitor pairs and processing their differences, the circuit achieves equal probability output values while maintaining a relatively simple structural implementation that leverages the natural symmetry of matched capacitor pairs.
3Measurement precision
If capacitor difference values are determined through specific biasing conditions and measurements, then output accuracy is improved, but power consumption increases
Solution Approach 1:
The patent employs periodic switching of bias conditions to measure capacitor differences. By alternating between different bias states and measuring the differential output during each state, the circuit achieves accurate capacitor difference measurement while limiting power consumption to discrete measurement intervals rather than continuous operation, thereby reducing overall energy usage.
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 achieves a reliably random and persistent output, minimizing noise and mismatch components, thus meeting PUF requirements and improving the stability and accuracy of the generated random number.
Implementation Method 1
at least one capacitor divider comprising a first capacitor and a second capacitor sharing a common node
Implementation Method 2
determine a first nodal measurement that is indicative of a voltage at the common node of the at least one capacitor divider during the first bias condition
Data Source
AI summary
The present disclosure relates to a PUF apparatus for generating a persistent, random number. The random number is determined by selecting one or more PUF cells, each of which comprise a matched pair of capacitors that are of identical design, and determining a value that is accurately and reliably indicative of a random manufacturing difference between them, based in which the random number is generated. The random manufacturing differences between the capacitors creates the randomness in the generated random number. Furthermore, because the random manufacturing difference should be relatively stable over time, the generated random number should be persistent.