Oscillator-Based Capacitor Ratio PUF for Secure Chip Identification
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Solution Overview
Problem
Existing chip identifiers, such as electronic fuses, are susceptible to theft and misuse due to ease of physical access, necessitating a secure and unique identification method.
Innovation Solution
A capacitor ratio identification system utilizing an oscillator, digital controller, and analog measurement circuitry to determine the capacitance ratio of capacitors, which serves as a physically unclonable function (PUF) for secure chip identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If electronic fuses are used as chip identifiers, then the identification method is simple and easy to implement, but the security is compromised due to ease of physical access and theft
Solution Approach 1:
The patent introduces an oscillator circuit as an intermediary measurement system that indirectly determines capacitor characteristics through frequency measurement. This mediator approach allows secure identification without direct physical access to the capacitor, resolving the security vulnerability of traditional electronic fuses while maintaining implementation feasibility through standard oscillator components
Solution Approach 2:
The patent replaces the direct physical inspection method (mechanical/electrical access to fuses) with an analog measurement system using oscillators and frequency detection. This substitution eliminates the need for physical access to read the identifier, thereby improving security while keeping the system relatively simple to implement
2Ease of operation
If traditional electronic fuses are used for identification, then physical access is easy, but this makes the identifiers susceptible to theft and misuse
Solution Approach 1:
The oscillator circuit serves as an intermediary that measures capacitor characteristics without requiring direct physical access to the identifier. The frequency output acts as a mediator that securely transmits identification information, preventing theft and misuse while maintaining operational functionality
Solution Approach 2:
The patent creates a functional copy of the identifier through frequency measurement rather than directly exposing the physical capacitor characteristics. This copying approach allows the system to read identification information securely through analog measurement without physical access to the actual identifier, preventing theft
3Reliability
If capacitor ratio identification is implemented, then security is improved through physically unclonable functions, but the device complexity increases due to additional circuitry
Solution Approach 1:
The oscillator circuit performs multiple functions: it generates a frequency signal based on capacitor characteristics for identification, provides timing references, and enables measurement without requiring separate dedicated measurement equipment. This multi-functionality reduces overall system complexity while maintaining high security through PUF-based identification
4Reliability
If analog measurement circuitry is used to determine capacitance ratio, then security against theft is improved, but the measurement and detection difficulty increases
Solution Approach 1:
The patent replaces complex direct capacitance measurement with frequency measurement through an oscillator. This substitution simplifies the measurement process by converting a difficult-to-measure electrical parameter (capacitance ratio) into an easily measurable frequency signal, thereby reducing measurement complexity while maintaining security
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 system provides a secure and stable capacitance ratio identifier that is difficult to read or replicate, offering superior security compared to traditional electronic fuses by requiring specific analog measurement circuitry for determination.
Implementation Method 1
determine a capacitance ratio of a pair of capacitors... The oscillator may include a capacitor; a comparator coupled to the capacitor at a node
Data Source
AI summary
A system includes an oscillator comprising a first switch, a current source, a capacitor, and a comparator, the capacitor and the comparator coupled at a node. The system includes one or more delay buffers coupled to the comparator. The system includes a first inverter coupled to the one or more delay buffers. The system includes a first buffer coupled to the one or more delay buffers. The system includes a first coupling capacitor coupled to the first inverter and the first buffer via second and third switches, respectively. The system includes a second inverter coupled to the one or more delay buffers. The system includes a second buffer coupled to the one or more delay buffers. The system includes a second coupling capacitor coupled to the second inverter and the second buffer via fourth and fifth switches, respectively. The first and second coupling capacitors are coupled to the oscillator.