Emerging Physical UnclonableFunctions With Nanotechnology

Group3 :周宣呈、周琪、黃筱喻、李承哲

Outline

• State-of-art PUF challenge and advantages of nanotechnology

• How PUF works and its vulnerability

• Development and application of nanotechnology PUF

• Possible application of PUF

State-of-art PUF challenge and advantages of nanotechnology

Definition

A Physical Random Function or Physical Unclonable Function (PUF) is a function that is:• Based on a physical system

• Easy to evaluate (using the physical system)

• Its output looks like a random function

• Unpredictable even for an attacker with physical access

Definition

• Most widely used definition:

• Nanoscience is the study of phenomena and manipulation of materials at atomic, molecular and macromolecular scales, where properties differ significantly from those at a larger scale.

• Nanotechnologies are the design, characterisation, production and application of structures, devices and systems by controlling shape and size at nanometre scale.

Millimetre scale (1 m = 1000 mm)ant and flea

• 5 mm

• 3mm

• 1mm

http://www.nation

alinsectweek.co.u

k/resources/buzz

_ant_06.pdf

www.nanotec.org.uk/report/chapter2.pdf

http://commons.wiki

media.org/wiki/File:D

rosophila_melanoga

ster_-

_front_(aka).jpg

Micrometre scale (1 mm = 1000 µm)eye of a fruit fly and a red blood cell

• 400 µm • 8 µm

http://www.molbio1.princeton.edu/facility/confocal/sem/imagelist1.html

www.mta.ca/dmf/blood.htm

Nanometre scale (1 µm = 1000 nm) – viruses & DNA

• 50 – 100 nm • 2 nm

http://www.gala-instrumente.de/images/deben_CCD_DNA.jpg

www.answers.com/topic/virus

Nanostructures

• Nanoparticles

Nanostructures

• Fullerenes – e.g. carbon nanotubes and buckyballs

Nanostructures

• Quantum dots

http://www.nist.gov/public_affairs/update/quantumdots.htm

http://www.nanopicoftheday.org/2003Pics/QDRainbow.htm

Nanostructures

• Non-carbon nanotubes

• Nanowires

• Biopolymers

• Dendrimers

http://nano.med.umich.edu/projects/dendrimers.html

http://www.nist.gov/public_affairs/05nano_image_gallery.htm

Nanotechnology

What make technology at the nanoscale different from technology at the macroscale?

Volume to surface area ratio

• As objects get smaller they have a much greater surface area to volume ratio

2 cm cube has

a surface area

of 24 cm2 and a

volume of 8 cm3

(ratio = 3:1)

10 cm cube has a

surface area of 600

cm2 and a volume of

1000 cm3 (ratio =

0.6:1)

Physical properties

• At very small sizes physical properties (magnetic, electric and optical) of materials can change dramatically.

http://www.omicron.de/index2.html?/re

sults/spin_polarized_tunneling_induce

d_luminescence_microcopy_sp_tilm/in

dex.html~Omicron

Applications

• Microchips

•http://ion.asu.edu/cool66_IC2/cool66_ic_thumb.htm

How PUF works and its vulnerability

CARBON-NANOTUBE FIELD-EFFECT TRANSISTORS (CNFET) BASED PUF

• Entropy• chirality, which denes the type metallic or semiconducting

• diameter

• growth density

• alignment

• doping concentration

CNFET based PUF design (CNPUF) operation

• CN as gate voltage of the two CNFET in PE

• Because of the different conductance, I1 is different from I2

• Compare the two branch of current to get the response

I2

I1

• Only theoretical work• Performance highly relies on the offset of the comparator

Offset

Phase change memory (PCRAM) Based PUF

time

(Low resistance)(High resistance)

• Entropy• Given the same SET/RESET time, the resistance of different cell are random

• Given the same SET/RESET time, the resistance of the same cell is not the same

STT-MRAM-BASED PUFS

• Current direct into free layer change the orientation

• Parallel state (low resistance) and anti-parallel state (high resistance)

• Entropy• Different program voltage such that cells change states

• Different resistance of different cell in AP/P state

STT-MRAM-BASED PUFS

• Poor efficiency if VPUF is not well

• bit error rate requires majority voting mechanism to solved

Reset all cells

Apply VPUF

Cell state determination

Gray bits White bitsBlack bits

01 discard

STT-MRAM-BASED PUFS

WL[0] WL[2] WL[3]WL[1] WL[4] WL[5]

SL

BL

• Reset all cells to AP state

• Compare the resistance of the chosen cell with the averaged resistance of all the other cell

Small difference -> hard to compare

STT-MRAM-BASED PUFS

Cell 1 Cell 2

Reset/SET two cellsmake both at AP or P state

Compare the two resistance

Lower resistance

Higher resistance

Write to PWrite to APBetter sense margin

Small difference-> hard to compare

ReRAM based PUF

Low resistance state (LRS) high resistance state (HRS)

• Generally wider distribution (of the same state)than MRAM

• Larger difference between high low resistance

• Cycle to cycle variation -> reconfigurable

RRAM based arbiter PUF

• Compared the Write time difference

• The selected one is being written • Compared the two column with

each branch resistance are the average of the total cells on that column

• Which branch first reach the threshold of the arbiter

• Large power consumption for each response to be generated

0

1

1

0

Cells that are being written

Active wordline

RRAM based arbiter PUF

• Reset first -> apply Vpulse(necessarily longer than the duration of VCE)

• VCE ends, Vup and Vdown compare

Vup

Vdown

• Arbiter enters the metastable state if the delay of the two path are too close

• Cycle to cycle resistance variation cause reliability issue

Development and application of nanotechnology PUF

PCM PUF pros and cons

Memristor PUF considerations

Xbar PUF

SHIC CNFET PCM STT Memristor

PCM pros and cons

• Programming variability, resistance drifts, read disturb, thermal cross-talk, and RTN noise in PCM devices cause reliability problems for memory implementations but can be utilized for hardware security applications.

• PCM PUF has Implicit manufacturer variability, same as SRAM PUF, while optical PUF doesn’t.

• Only two PUF are considered mathematically unclonable, PCM PUF and optical PUF.

• Most research efforts have focused on improving memory performance, while few reports have discussed the intentional use of variability for hardware security.

Electroforming

• Electroforming is a metal forming process that forms parts through electrodeposition on a model, and the process involves high current through very clean water.

• In recent years, due to its ability to replicate a mandrel surface very precisely with practically no loss of fidelity, electroforming has taken on new importance in the fabrication of micro and nano-scale metallic devices.

Memristors with electroforming

For the transition oxide memristors. , the electroforming process is a necessary step involving high voltages in enabling reproducible ionic conduction that modulates the device resistance.

Memristors without electroforming

The multiferroic YMO memristorswitches from the HRS to LRS by forming a large number of charged vortices.

The switching mechanism of BFO memristor involves two types of impurities in thin film: Ti atoms (blue circles) and oxygen vacancies that are intrinsically formed during fabrication (red circles).

Future work

• The relationship between low-level behavior of EF-free memristors and the application-level performance.

• Device's operation under natural stress (in harsh environment or under aging).

• Device's operation under malicious attacks (e.g., strong laser or electromagnetic pulses).

First Xbar PUF

• Xbar PUF's primary entropy source is the minimum time it takes for memristors to SET during a write operation.

• Xbar PUF is somewhat a reimagining of the APUF where memristors are essentially used in place of switch boxes.

• Xbar PUF decreases the transistor counts a lot compare with APUF, but its reliability still needs to be tested across a wider range of operating parameters from real memristors.

Follow-up development

• Internet of things (IoT) introduces new security concerns such as encryption and authentication are often resource hungry, solutions are needed that provide reasonable levels of security with minimal area and power consumption.

• It has been found that although a basic Xbar PUF structure is prone to modeling attacks like an APUF, by tweaking this Xbar PUF circuit, only roughly 58% accuracy using machine-learning models may be achieved.

Summary

• PUF designs provide a number of unique properties such as abundance of process variations, bidirectionality, C2C variations and formation process

• Major limitations of currently proposed PUF designs that are based on emerging nanoelelctronics

• PUF designs with nanotechnology will secure future memory and circuit applications with low energy, area overhead, and unique device level properties.

Possible application of PUF

Volatile PUF to protect nonvolatile PUF

scramble

Vo

lati

le P

UF

Non-volatile PUF

challenge R1/C2 a

k

3

0

b6 R2

PUF as process variation measurement

Distribution of entropy

The key to perform a PUF is to find the good entropy and digitalized it

No matter what kind of emerging device needs to have good electrical characteristic to be put into use

No matter what physical mechanism, material, process formula, produce step, of the device will eventually converge to electrical characteristic

PUF as process variation measurement

Reset all cells

Apply VPUF

Cell state determination

Gray bits White bitsBlack bits

01 discard

VPUF

Key parameter to improveWhich may depends on specific process details

formula A

formula B

Mostly set under VPUF if formula A is use

Ref

• https://www.techspot.com/news/65990-phase-change-memory-breakthrough-could-make-1000x-faster.html

• https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.researchgate.net%2Ffigure%2FSchematic-representation-of-the-set-reset-operations-in-the-ReRAM-device-a-In-the-low_fig3_327735694&psig=AOvVaw1mE9_NqllqSgOv4832qfFO&ust=1578650276606000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCKiett2g9uYCFQAAAAAdAAAAABAV

• https://ieeexplore.ieee.org/abstract/document/8854394

• https://link.springer.com/chapter/10.1007/978-981-13-8379-3_3

• http://seneca.eecs.utk.edu/publication/Mesbah-2017-JETC.pdf

• https://ieeexplore.ieee.org/abstract/document/8482515

• http://iopscience.iop.org/13474065/56/4S/04CN03/downloadHRFigure/figure/SS16029fig01b

• https://d3i71xaburhd42.cloudfront.net/21d3d0f1a2b7a2a429f95d5591e62f5332fee8af/2-Figure1-1.png

• https://cn.comsol.com/paper/image/64392/big.png