Built-in Self-Test Circuit for PUF Quality Check

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Solution Overview

Problem

The existing methods for checking the quality of Physically Unclonable Function (PUF) pools are inefficient and costly, often requiring external equipment and increasing labor and time due to the need for quality detection of random bits generated by PUFs.

Innovation Solution

A built-in self-test (BIST) circuit and method that utilizes a PUF array with readout and comparing circuits to generate parity check results based on hamming distance between output and parity strings, reducing the need for external equipment and minimizing additional hardware.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If external equipment is used to check PUF quality, then measurement precision is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

ImprovePUF quality detection accuracyVSAvoidtesting equipment requirements

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The PUF array performs self-testing through built-in test circuits that are integrated within the PUF structure itself. The test circuit includes a readout circuit that reads PUF values from multiple PUF units and a comparing circuit that compares these values to determine if the PUF array meets quality standards, eliminating the need for external testing equipment.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The testing function is merged with the PUF array structure by integrating the readout circuit and comparing circuit directly into the PUF array. This combination allows the PUF array to perform quality self-testing without requiring separate external testing equipment, thereby reducing device complexity while maintaining measurement precision.

Inventive Principle:

Principle #5Merging (Combining)

2Measurement precision

If external equipment is used for PUF quality check, then measurement precision is improved, but loss of time increases

Engineering Contradiction:

ImprovePUF quality detection accuracyVSAvoidtesting time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The built-in test circuit is prepared in advance within the PUF array structure, allowing quality testing to be performed immediately during or after manufacturing without requiring external equipment setup. This preliminary preparation of testing capability within the device itself reduces the time loss associated with external testing.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If enrollment is performed on all PUF components, then reliability is improved, but productivity decreases

Engineering Contradiction:

ImprovePUF random bit qualityVSAvoidmanufacturing efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Instead of performing enrollment on all PUF components, the invention uses a sampling approach where only a subset of PUF units (e.g., 100 units) are selected for quality testing. The readout circuit reads PUF values from these selected units, and the comparing circuit determines if the sampled units meet quality standards. This partial action maintains reliability through statistical sampling while significantly improving productivity by reducing the number of enrollment operations required.

Inventive Principle:

Principle #16Partial or excessive action

4Reliability

If quality detection is performed on PUF pool, then reliability is improved, but device complexity increases

Engineering Contradiction:

Improverandom bit quality assuranceVSAvoidhardware overhead

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The built-in test circuit serves multiple functions: it can perform quality testing on the PUF array, verify the authenticity of PUF values, and provide feedback for quality control decisions. This multi-functionality reduces the need for separate dedicated testing hardware, thereby reducing overall device complexity while improving reliability through comprehensive quality detection.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11782090B2Built-in self-test circuit and built-in self-test method for physical unclonable function quality check

Publication Date: 2023.10.10 PUFSECURITY CORP

AI summary

A built-in self-test (BIST) circuit and a BIST method for Physical Unclonable Function (PUF) quality check are provided. The BIST circuit may include a PUF array, a readout circuit coupled to the PUF array, and a first comparing circuit coupled to the readout circuit. The PUF array may include a plurality of PUF units, wherein each of the PUF units includes a first cell and a second cell. The readout circuit may be configured to output an output bit from the first cell and output a parity bit from the second cell. The first comparing circuit may be configured to compare an output string with a parity string to generate a parity check result, wherein the output string includes output bits respectively read from selected PUF units of the PUF units, and the parity string includes parity bits read from the selected PUF units.