Ring Oscillator PUF Phase Comparison for IoT Secret Keys

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Solution Overview

Problem

IoT devices face security vulnerabilities due to easily identifiable encryption keys or IDs, which can be exploited for attacks, and existing PUF technologies require user intervention for generating device-specific security information.

Innovation Solution

A method and apparatus using ring oscillator cells to generate secret information by detecting and comparing phases of clock signals, enabling the creation of physically unclonable function (PUF) information without user-set identification, thereby producing device-specific secret keys.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional encryption keys or IDs are used in IoT devices, then device identification and security functions can be implemented, but security vulnerabilities arise as these keys can be easily identified and exploited for attacks

Engineering Contradiction:

ImprovesecurityVSAvoidsecurity vulnerability

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system enables automatic generation of device-specific secret key information through ring oscillator cells without requiring user intervention or manual configuration. The PUF information generation units autonomously produce unique cryptographic identifiers based on inherent manufacturing variations, eliminating the need for users to manually set security parameters while enhancing device security

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention exploits parameter variations in ring oscillator cells caused by manufacturing process differences. By detecting phase differences in clock signals generated by identical circuit structures, the system converts physical parameter variations into unique secret key information, transforming manufacturing inconsistencies into security assets

Inventive Principle:

Principle #35Parameter changes

2Reliability

If user-set identification information is required for IoT device security, then security functions can be implemented, but ease of operation deteriorates as users must manually configure security parameters

Engineering Contradiction:

Improvesecurity functionVSAvoiduser intervention requirement

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

Inventive Principle:

Principle #25Self-service

3Manufacturing precision

If PUF circuit cells are designed to be identical in structure and manufacturing process, then manufacturing precision is improved, but device complexity increases to extract and utilize the minute differences for fingerprinting

Engineering Contradiction:

Improvecircuit consistencyVSAvoidphase detection and comparison complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention extracts the useful phase difference information from identical ring oscillator cells by comparing their clock signal phases. The phase checking unit isolates and utilizes the minute timing differences caused by manufacturing variations while ignoring the identical circuit structures, effectively separating the signal of interest from the uniform background

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The phase checking unit acts as an intermediary that compares phase information from multiple PUF information generation units and translates the physical phase differences into comparable digital values. This intermediary component simplifies the complexity by providing a standardized comparison mechanism rather than requiring direct analysis of raw oscillator signals

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This approach allows for the generation of a large number of challenge-response pairs, enhancing the security of IoT devices by automatically producing secret key information, thus preventing cloning and improving security without user intervention.

Implementation Method 1

the fact that in spite of the same circuit, wire delay and gate delay slightly vary according to the process variation of implementing the circuit

Methodology Applied

Scientific EffectProcess variation:

Implementation Method 2

a phase checking unit cross-checking phases for the multiple pieces of the PUF information that are output from the multiple PUF information generation units

Methodology Applied

Scientific EffectPhase difference detection:

Data Source

PatentUS11115202B2Apparatus for generating secret information on basis of ring oscillator architecture and method of same

Publication Date: 2021.09.07 ELECTRONICS & TELECOMM RES INST

AI summary

Disclosed is a method of generating secret information on the basis of a ring oscillator. According to an embodiment of the present disclosure, there is provided an apparatus for generating secret information on the basis of a ring oscillator, the apparatus including: multiple PUF information generation units each including at least one ring oscillator cell and generating physically unclonable function (PUF) information generated by the at least one ring oscillator cell; a phase checking unit cross-checking phases for the multiple pieces of the PUF information that are output from the multiple PUF information generation units, respectively; and a secret key generation unit outputting secret key information based on a result of comparing the multiple phases received from the phase checking unit.