Ring Oscillator PUF Circuit With Phase Feedback for Unique Keys
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Solution Overview
Problem
Existing physically unclonable cryptographic key generators, such as those using ring oscillators, fail to produce unique and repeatable sequences of numbers, leading to inter-class differences that are not sufficiently dispersed, making it possible for different specimens to generate the same sequence even when manufactured similarly.
Innovation Solution
A generator comprising at least two ring oscillators with a phase detector and an adjustable speed ring oscillator, where the phase detector's output controls the frequency of the adjustable speed ring oscillator, creating a chaotic circuit that enhances inter-class dispersion and uniqueness of generated sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ring oscillators are used for key generation, then the circuit structure is simple, but the inter-class dispersion is insufficient making sequences non-unique across specimens
Solution Approach 1:
The patent introduces a dynamic feedback mechanism where the phase detector continuously monitors the phase difference between oscillators and adjusts the control voltage in real-time. This dynamic adjustment ensures that the chaotic oscillation patterns remain stable and unique to each specimen's technological dispersion characteristics, resolving the contradiction between simple structure and sufficient inter-class dispersion.
Solution Approach 2:
A phase detector and feedback loop are implemented to monitor and adjust the oscillation phases. The phase detector compares the phases of multiple oscillators and feeds back control signals to maintain optimal phase relationships. This feedback mechanism amplifies the effects of technological dispersion, ensuring unique sequences for each specimen while maintaining circuit simplicity.
2Reliability
If multiple ring oscillators with feedback are used to create chaotic circuit, then unique sequences are generated, but the circuit complexity increases
Solution Approach 1:
The patent combines multiple ring oscillators into a single integrated chaotic circuit block. The oscillators share common control voltage lines and are coupled through a phase detector that consolidates their outputs. This merging approach maintains sequence uniqueness while reducing overall circuit complexity compared to separate independent oscillator systems.
Solution Approach 2:
The phase detector serves multiple functions simultaneously: it detects phase differences between oscillators, generates control voltages for frequency adjustment, and provides feedback signals for maintaining chaotic oscillation. This multi-functionality reduces the need for separate dedicated circuits, thereby maintaining reliability while controlling complexity.
3Manufacturing precision
If phase detector and control system are added, then inter-class spread is magnified, but the device complexity and energy consumption increase
Solution Approach 1:
The phase detector automatically adjusts the control voltages based on real-time phase measurements without requiring external intervention. The feedback loop self-regulates the oscillation frequencies to maintain optimal chaotic behavior, minimizing energy waste from manual adjustments or external control systems while maximizing inter-class spread.
Solution Approach 2:
The system dynamically changes the control voltage parameters applied to the oscillators based on phase detector measurements. By continuously adjusting these parameters, the system amplifies technological dispersion effects and maintains unique chaotic patterns for each specimen. The energy consumption is optimized by making adjustments only when phase deviations occur, rather than continuous high-energy operation.
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 significantly magnifies inter-class spread and technological dispersion, ensuring that sequences generated are unique to each specimen, making them suitable for cryptographic applications by introducing deterministic chaos specific to each device.
Implementation Method 1
at least one phase detector, having inputs connected to respective outputs of the ring oscillators
Implementation Method 2
the generator is a chaotic circuit, in which occurs the magnification of effects of the technological spread of the elements and connections contributing to the initial conditions
Data Source
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Figure 5~6
AI summary
Generator of physically unclonable cryptographic keys (PUF) has two adjustable speed ring oscillators (GPRS, GPRS'), which outputs (o-GPRS, o-GPRS') are connected to inputs (il-DF, i2-DF) of a phase detector (DF), which output (o-DF) is connected to control inputs of the adjustable speed ring oscillators (s-GPRS, s-GPRS' ) through a control system (US) and is also connected to a output (o-PUF) of the generator of physically unclonable cryptographic keys (PUF) through a sample and compare circuit (URP). Generator has a initializing input (i-UCH) connected to both initializing inputs of the adjustable speed ring oscillators (i-GPRS, i-GPRS' ) and to the first input of the sample and compare circuit (i-URP), which second input (z-URP) is connected to the output (o-GPRS') of one of adjustable speed ring oscillators (GPRS').