RFID Research at Adelaide

18 October 2006 Some aspects of Adelaide Research 11

RFID Research at Adelaide

Peter H. Cole

Professor of RFID Systems at the University of Adelaide and Director of the Auto-ID Laboratory @ Adelaide


Outline

• Data Gathering Readers• Tags for embedding in metal• Small tags in difficult situations• Lightweight cryptography for security

and authentication• Microelectronic turn on circuits• Micromachining turn on circuits


Data Gathering Readers


Objectives

• Development of a new RFID instrument• Collect & record data• Display, analyze and model data• Turn data into information

– Information can be passed to other readers by a network or a host PC.• Keep data as raw

– Pass data to PC for later processing & detailed analysis.• Buffering

– Caching and buffering to prevent blocking.• Firmware upgradeable• USB and Ethernet Interfaces

– Can be used for upgrades, monitoring and data communication.• Would allow to improve

– Efficiency, performance, accuracy, reliability, energy consumption, quality assurance, etc.


Implementation

• Modular design:1.DSP 2.Micro-controller3.ADC & DAC4.RF Front-end5.Host Computer Interface


Experimental Results


Applications for SDLR

• Analysis and development of reader architectures (as a template)

• Analysis and measurement of new forms of reader to tag signalling (pulse shaping, etc)

• Analysis of measuring equipment, i.e. understanding the test regulations with respect to the forms of signalling employed by RFID readers

• Interference studies in high density reader environments

• Electromagnetic propagation studies applicable to European Regulations (LBT)


Small Tags in Difficult Situations


Bode-Fano Limit

VS

RS

ZIN

LOSSLESSMATCHINGNETWORK

RC

RCπ dω 1ln

0

≤Γ∫

∞


Bode-Fano Limit (cont)

• Assume R = 1 kΩ, C = 1 pF

• R = 10 kΩ, C = 1 pF (for less powerconsuming tag chip in practice)


A Simple RFID Tag

• Consists of a circular loop antenna with a matching network naturally built into the antenna

FRONT REAR


Tag for embedding in metal

• Design of an embedded UHF RFID label antenna for a metal structure


Cryptography for Security and Authentication in RFID


Security and Privacy Holes

• Outlines vulnerabilities unique to low cost RFID systems

• Provides a realistic assessment of current low cost RFID technology

• Methodologies for addressing vulnerabilities– A review of methodologies applicable to low cost RFID

• Formulation of a framework within which to address vulnerabilities in low cost systems


Elliptic curve cryptography

• Based on group theory for cyclic additive and multiplicative groups

• Underlying fields can be prime fields and or binary fields

• Different calculations in each case• Calculations faster that RSA• Smaller codes than RSA• Can it be applied to passive RFID?


The PUF solution

• Storage of long term secrets on tags is not possible– Physical attacks– Brute force attacks

• Authentication using keys stored on tags is insecure

• PUFs provide a method for storing secret information on tags without the need for tamper proofing

• Investigating the use of PUF for secure and low cost authentication

• Future research directions


• Use of PUFs on RFID tags to securely store keys

• 800 challenge-response pairs to uniquely identify over 109 chips

c0 c1 c2 c61 c62 c63

01

Switch component

Arbiter

ci=0 c0=1

Switch component operation

0

Arbiter operation as the race between the signal ends as the

arbiter

Arbiter

Arbiter

1

PUF Structure


Addressing eavesdropping

• Need to provide a service for providing confidentiality• Use a PUF to initialize LFSRs• Use a shrinking generator to create a key stream• LFSR – lightweight hardware

PUF Circuit Block

CHALLENGE SET

KStream cipher

constructed using a NFSR

⊕

CIPHERTEXT

PLAINTEXT

LFSR R2

LFSR R1

Output ( )kCE CLK

D QBuffer

Clock


The shrinking function

• Two linear shift registers, A (data) and S (sampling), with different seeds, clocked together.

• Outputs are combined as follows– If S is 1, output is A– If S is 0, there is no output and another clock is applied

• This scheme has been resistant to cryptanalysis for 12 years. No known attacks if feedback polynomials are secret and registers are too long for an exhaustive search.


One time codes: 1

• Have available a set of purely random numbers in the tag and matching tag dependent number in a secure data based

• Some are to authenticate the tag to a reader, some to authenticate a reader to a tag, some might be to permit authenticated change of tag identity to prevent trace of items

• Use certain of these to XOR with tag identities to disguise them from eavesdroppers.


One time codes: 2

• Need a large supply to cater for many authentications

• Options– Reserve a pair for final authentication by end user– Recharge in a secure environment– Assume an eavesdropper cannot be every where and use

old codes for identity change for fresh reader or tag authentications

– Better to use a shrinking function


Micromechanical Turn-on Circuits


Turn-on circuits

• Battery-powered labels must have very low current consumption in order to prolong the life of the battery.

• However due to circuit complexity or the desired range the electronics drain the battery more rapidly than desired.

• Labels require a means of turning “on” and “off” the onboard battery support at the start and at the end of a communication, to conserve power and thus prolong battery life.– Solutions available

• Electroacoustic energy conversion using a MEMS device• Rectifier diode resonance


Outcomes

• Analysis of turn on circuit concepts– Diode resonance– MEMS structures


Thank you


Current Problems

• RFID reliability and accuracy– RFID is not yet 100% reliable. – Current approaches to increasing reliability need to be enhanced.

• Standards• Interference

– Proliferation of wireless devices using shared bandwidth.– Proliferation of RFID readers will also reduce the available bandwidth

(phone, wi-fi.)– Malicious interference must be detected such as RF jamming and

spoofing.

• Security– Readable outside supply chain without your consent at large

distance, difficult to remove.


Microelectronic Turn-on Circuits


A low voltage turn on circuit

• Sensitivity about 5 mV• Power consumption few nA


Transmitter operated systems

• A small voltage or a large is generated from the transmitted power

• A low power consumption circuit, or a zero power consumption circuit, detects that event

• Quality factor and detuning issues arise

Junction capacitance

Bypass and reservoir

capacitance

Resonant circuit

Label antenna

D.C. output line

jXs

jXB

jXl

Rr

Ra

Rl


Experiments on detuning

1MΩ

10kΩ 11.5pF

Rectified voltage to Oscilloscope using a BNC connector

RF IN through an SMA connector


Low and high power sweeps


Elliptic code cryptography

• All parties must agree on domain parameters (p,a,b,G,n,h). These can come from an authority.

• Classes of weak curves are known and avoided as above.

• NIST has published some recommended combinations.

• Keys must be be large enough. A 109 bit key has been broken.

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RFID Research at Adelaide

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