Reconfigurable PUF via Spin-Orbit Torque Magnetization Switching

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing physical unclonable functions (PUFs) based on non-volatile memory, such as magnetic random access memory (MRAM), lack reconfigurability and have limited challenge-response pairs (CPRs) for encryption, making them difficult to form a strong PUF.

Innovation Solution

A method for configuring a reconfigurable PUF using a device with a spin-orbit torque (SOT) effect, where a write current or external magnetic field is applied to change the magnetization state of ferromagnetic layers, and the anomalous Hall resistance is read to generate random codes, allowing for multiple resistance states and increased CPRs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If PUFs based on non-volatile memory use the randomness of the device during the preparation process to generate random codes, then the PUF can be implemented, but the number of challenge-response pairs is limited and it is difficult to form a strong PUF

Engineering Contradiction:

Improvenumber of challenge-response pairsVSAvoidPUF strength

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies spin-orbit torque to dynamically switch the magnetization state of the ferromagnetic layer between vertical and horizontal orientations. This dynamic control allows the same physical device to generate different resistance states repeatedly, enabling multiple challenge-response pairs from a single device configuration, thereby resolving the contradiction between limited CPRs and PUF strength

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the magnetization orientation parameter of the ferromagnetic layer from fixed to controllable. By applying spin-orbit torque, the magnetization can be switched between vertical and horizontal states, creating different resistance values. This parameter change enables the generation of multiple distinct challenge-response pairs while maintaining device reliability

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the PUF is fabricated with a fixed MgO film thickness, then the device structure is simple, but the PUF cannot be reconfigured because the thickness remains unchanged

Engineering Contradiction:

ImprovereconfigurabilityVSAvoiddevice structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical approach of changing physical thickness with a magnetic field approach using spin-orbit torque. Instead of physically altering the MgO film thickness, the invention uses electrical current to generate spin-orbit torque that switches the magnetization state, achieving reconfigurability without modifying the device structure

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the magnetic parameter (magnetization orientation) rather than the physical dimension (film thickness). By controlling the magnetization angle between the ferromagnetic layer and MgO interface, the device achieves multiple resistance states while maintaining the same physical structure, thus enabling reconfigurability without increasing device complexity

Inventive Principle:

Principle #35Parameter changes

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 provides a reconfigurable and secure PUF with a simple structure, capable of generating a large number of challenge-response pairs, enhancing encryption security and durability.

Implementation Method 1

a write current is applied between a first pair of bottom electrodes of a non-volatile device in the device with the SOT effect, so that the magnetization state of ferromagnetic layer of the non-volatile device changes from a vertical magnetization state to a horizontal magnetization state

Methodology Applied

Scientific EffectSpin-orbit torque (SOT) effect:

Implementation Method 2

A read current is applied between the first pair of bottom electrodes of the non-volatile device. An anomalous Hall resistance of the non-volatile device is read

Methodology Applied

Scientific EffectAnomalous Hall effect: Hall Effect

Data Source

PatentUS11538985B2Method for configuring reconfigurable physical unclonable function based on device with spin-orbit torque effect

Publication Date: 2022.12.27 HUAZHONG UNIV OF SCI & TECH

AI summary

A method for configuring a reconfigurable physical unclonable function (PUF) based on a device with spin-orbit torque (SOT) effect is provided. The disclosure uses SOT or magnetic field to change the magnetic moment. After the current or magnetic field is removed, the magnetic moment returns to the easy axis direction. Under the effect of thermal fluctuation, the magnetic moment is randomly oriented in the easy axis direction. The non-volatile devices are formed into an array, the magnetic moments of all non-volatile devices are randomly distributed after a write operation. The read state can be used as a random code to implement the reconfigurable PUF. The PUF has a simple structure and guarantees security. The random code in the disclosure may be two-state or multi-state, which is related to the number of magnetic domains of the ferromagnetic layer. A large number of challenge response pairs form a strong PUF.