Novel Reconfigurable Silicon Novel Reconfigurable Silicon Physical Unclonable FunctionsPhysical Unclonable Functions

Yingjie Lao and Keshab K. ParhiYingjie Lao and Keshab K. Parhi

Department of Electrical and Computer Department of Electrical and Computer EngineeringEngineering

University of Minnesota, Twin CitiesUniversity of Minnesota, Twin Cities

April 11April 11thth, 2011, 2011

FDSCPS 2011

Outline

Summary and Future Work4.

Experimental Results3.

Solutions2.

Introductions1.

Motivation

“It is estimated that as much as 10% of all high-tech products sold globally are counterfeit which leads to a conservative estimate of $100 billion of revenue loss.”

[Guajardo et al, 2008]

Several invasive and semi-invasive physical tampering methods have been developed, which made it possible to learn the ROM- based keys through attacks and compromise

systems by using counterfeit copies of the secret information.

Introduction

Physical Unclonable Functions(PUFs) -a function which is an innovative circuit primitive that

exploits the unique intrinsic uncontrollable physical features which are introduced by manufacturing process variations.

Physical Objects

Process Variations

Unpredictable Behavior

Easy to Evaluate

Hard to Clone

PUFPUFPUFPUF

Anti-counterfeiting marks for ICs

Previous Work

Ravikanth et. al proposed the first PUF in literature in 2001. After that, several research groups have developed a variety types of PUFs. At the same time, commercialization of the PUFs also has led to some startups.

S-RAM PUF[Guajardo et al., Su et al. 2007]

MUX Silicon PUF[Gassend et al. 2002]

FPGA "butterfly“ PUF[Kumar et al. 2008]

Ring Oscillator Silicon PUF[Edward et al. 2002]

Problem for Static PUF

Reconfigurable PUF: updatable

Challenge-like

Challenge-like

Vulnerable to attacks & Poor performance.

The frequencies of ring oscillators can be evaluated by attackers

Reconfigurable RO Silicon PUF

Hard to implement: lower level design detail, symmetrical routing

FPGA based

Reconfigurability for PUF is desirable:1.To updatable authentication keys2.To improve the security, as we can reconfigure the challenge-response behaviors

Outline

Summary and Future Work4.

Experimental Results3.

Solutions2.

Introductions1.

SolutionsNon-FPGA based methods

1.Reconfigurable Challenge- Response Behaviors

PUFn

(Challenge) Response

2. Reconfigurable PUF Circuits

Method One (I)

LFSR (Linear Feedback

Shift Register)

Hash Function

Pre-process Challenge

- To generate new sets of challenge bits, while ensure the security

Method One (II)

Output Recombination

Similar idea used in prior Ring Oscillator PUF

No correlation amongdifferent outputs

Method Two (I)

Reconfigurable Feed-Forward PUFWhy feed-forward?- Add nonlinearity into PUF, make it hard to model, improve the security

Types of feed-forward?1. Feed-forward Cascade2. Feed-forward Overlap3. Feed-forward Separate

[Lee et al, 2004]

Method Two (I)

Reconfigurable Feed-Forward PUF- Can be configured among the 3 different types of

feed-forward structures

Method Two (II)

MUX and DeMUX PUF- Can choose to skip some stages instead of

propagating the rising edge signal successively

Outline

Summary and Future Work4.

Experimental Results3.

Solutions2.

Introductions1.

Experiment

Methodology-SPICE Simulation-65nm technology-Parameter Model from SSTA

(Statistical Static Timing Analysis)

Measurements: -Security: Inter-Chip Variations -Reliability: Intra-Chip Variations -Reconfigurability

Result I

StructuresInter-chip Variation Intra-chip Variation

Max Min Max Avg

Non-feed-forward

59% 22% 13% 5.8%

Feed-forward Overlap

66% 27% 15% 8.7%

Feed-forward Cascade

64% 25% 20% 10.7%

Feed-forward Separate

65% 26% 17% 9.9%

Reconfigurable Feed-forward

65% 25% 19% 10.3%

MUX and DeMUX 57% 23% 16% 7.1%

*Variation is the Hamming Distance of two digital responses divided by the total bit length ( challenge and response both have 100 bits in our simulation)

Result II

StructuresReconfigurability

Max Avg Min

Challenge LFSR 44% 34.6% 28%

Challenge Hash 42% 28.3% 19%

Output Recombination

57% 38.9% 25%

Reconfigurable Feed-forward

47% 32.4% 22%

MUX and DeMUX 33% 24.7% 13%

*Reconfigurability is the Hamming Distance of two digital responses, which we generated by only altering the configure data but fixing the challenge bits, then divided by the total bit length ( Used to test the randomness )

Outline

Summary and Future Work4.

Experimental Results3.

Solutions2.

Introductions1.

Summary

Problem: reconfigurable PUFNovel non-FPGA based methods: - Reconfigurable CRPs - Reconfigurable PUF circuits

Simulation results validated proposed structures

Also take the reliability and the security into consideration:

- Reconfigurable feed-forward MUX PUF has the best performance!

Future Work

Strong authentication scheme for reconfigurable PUFs

Examine the properties of reconfigurable PUFs by mathematical methods

Improve the reliability and the security of reconfigurable PUFs

LOGO

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